Macroscopic superposition states and decoherence by quantum telegraph noise
Energy Technology Data Exchange (ETDEWEB)
Abel, Benjamin Simon
2008-12-19
In the first part of the present thesis we address the question about the size of superpositions of macroscopically distinct quantum states. We propose a measure for the ''size'' of a Schroedinger cat state, i.e. a quantum superposition of two many-body states with (supposedly) macroscopically distinct properties, by counting how many single-particle operations are needed to map one state onto the other. We apply our measure to a superconducting three-junction flux qubit put into a superposition of clockwise and counterclockwise circulating supercurrent states and find this Schroedinger cat to be surprisingly small. The unavoidable coupling of any quantum system to many environmental degrees of freedom leads to an irreversible loss of information about an initially prepared superposition of quantum states. This phenomenon, commonly referred to as decoherence or dephasing, is the subject of the second part of the thesis. We have studied the time evolution of the reduced density matrix of a two-level system (qubit) subject to quantum telegraph noise which is the major source of decoherence in Josephson charge qubits. We are able to derive an exact expression for the time evolution of the reduced density matrix. (orig.)
Macroscopic superposition states and decoherence by quantum telegraph noise
International Nuclear Information System (INIS)
Abel, Benjamin Simon
2008-01-01
In the first part of the present thesis we address the question about the size of superpositions of macroscopically distinct quantum states. We propose a measure for the ''size'' of a Schroedinger cat state, i.e. a quantum superposition of two many-body states with (supposedly) macroscopically distinct properties, by counting how many single-particle operations are needed to map one state onto the other. We apply our measure to a superconducting three-junction flux qubit put into a superposition of clockwise and counterclockwise circulating supercurrent states and find this Schroedinger cat to be surprisingly small. The unavoidable coupling of any quantum system to many environmental degrees of freedom leads to an irreversible loss of information about an initially prepared superposition of quantum states. This phenomenon, commonly referred to as decoherence or dephasing, is the subject of the second part of the thesis. We have studied the time evolution of the reduced density matrix of a two-level system (qubit) subject to quantum telegraph noise which is the major source of decoherence in Josephson charge qubits. We are able to derive an exact expression for the time evolution of the reduced density matrix. (orig.)
Decoherence bypass of macroscopic superpositions in quantum measurement
International Nuclear Information System (INIS)
Spehner, Dominique; Haake, Fritz
2008-01-01
We study a class of quantum measurement models. A microscopic object is entangled with a macroscopic pointer such that a distinct pointer position is tied to each eigenvalue of the measured object observable. Those different pointer positions mutually decohere under the influence of an environment. Overcoming limitations of previous approaches we (i) cope with initial correlations between pointer and environment by considering them initially in a metastable local thermal equilibrium, (ii) allow for object-pointer entanglement and environment-induced decoherence of distinct pointer readouts to proceed simultaneously, such that mixtures of macroscopically distinct object-pointer product states arise without intervening macroscopic superpositions, and (iii) go beyond the Markovian treatment of decoherence. (fast track communication)
Superposition and macroscopic observation
International Nuclear Information System (INIS)
Cartwright, N.D.
1976-01-01
The principle of superposition has long plagued the quantum mechanics of macroscopic bodies. In at least one well-known situation - that of measurement - quantum mechanics predicts a superposition. It is customary to try to reconcile macroscopic reality and quantum mechanics by reducing the superposition to a mixture. To establish consistency with quantum mechanics, values for the apparatus after a measurement are to be distributed in the way predicted by the superposition. The distributions observed, however, are those of the mixture. The statistical predictions of quantum mechanics, it appears, are not borne out by observation in macroscopic situations. It has been shown that, insofar as specific ergodic hypotheses apply to the apparatus after the interaction, the superposition which evolves is experimentally indistinguishable from the corresponding mixture. In this paper an idealized model of the measuring situation is presented in which this consistency can be demonstrated. It includes a simplified version of the measurement solution proposed by Daneri, Loinger, and Prosperi (1962). The model should make clear the kind of statistical evidence required to carry of this approach, and the role of the ergodic hypotheses assumed. (Auth.)
International Nuclear Information System (INIS)
De Martini, Francesco; Sciarrino, Fabio; Spagnolo, Nicolo
2009-01-01
The high resilience to decoherence shown by a recently discovered macroscopic quantum superposition (MQS) generated by a quantum-injected optical parametric amplifier and involving a number of photons in excess of 5x10 4 motivates the present theoretical and numerical investigation. The results are analyzed in comparison with the properties of the MQS based on |α> and N-photon maximally entangled states (NOON), in the perspective of the comprehensive theory of the subject by Zurek. In that perspective the concepts of 'pointer state' and 'environment-induced superselection' are applied to the new scheme.
International Nuclear Information System (INIS)
Spagnolo, Nicolo; Sciarrino, Fabio; De Martini, Francesco
2010-01-01
We show that the quantum states generated by universal optimal quantum cloning of a single photon represent a universal set of quantum superpositions resilient to decoherence. We adopt the Bures distance as a tool to investigate the persistence of quantum coherence of these quantum states. According to this analysis, the process of universal cloning realizes a class of quantum superpositions that exhibits a covariance property in lossy configuration over the complete set of polarization states in the Bloch sphere.
International Nuclear Information System (INIS)
Everitt, M.J.; Clark, T.D.; Stiffell, P.B.; Prance, R.J.; Prance, H.; Vourdas, A.; Ralph, J.F.
2004-01-01
In this paper we explore the quantum behavior of a superconducting quantum-interference device (SQUID) ring which has a significant Josephson coupling energy. We show that the eigenfunctions of the Hamiltonian for the ring can be used to create macroscopic quantum superposition states of the ring. We also show that the ring potential may be utilized to squeeze coherent states. With the SQUID ring as a strong contender as a device for manipulating quantum information, such properties may be of great utility in the future. However, as with all candidate systems for quantum technologies, decoherence is a fundamental problem. In this paper we apply an open systems approach to model the effect of coupling a quantum-mechanical SQUID ring to a thermal bath. We use this model to demonstrate the manner in which decoherence affects the quantum states of the ring
Macroscopicity of quantum superpositions on a one-parameter unitary path in Hilbert space
Volkoff, T. J.; Whaley, K. B.
2014-12-01
We analyze quantum states formed as superpositions of an initial pure product state and its image under local unitary evolution, using two measurement-based measures of superposition size: one based on the optimal quantum binary distinguishability of the branches of the superposition and another based on the ratio of the maximal quantum Fisher information of the superposition to that of its branches, i.e., the relative metrological usefulness of the superposition. A general formula for the effective sizes of these states according to the branch-distinguishability measure is obtained and applied to superposition states of N quantum harmonic oscillators composed of Gaussian branches. Considering optimal distinguishability of pure states on a time-evolution path leads naturally to a notion of distinguishability time that generalizes the well-known orthogonalization times of Mandelstam and Tamm and Margolus and Levitin. We further show that the distinguishability time provides a compact operational expression for the superposition size measure based on the relative quantum Fisher information. By restricting the maximization procedure in the definition of this measure to an appropriate algebra of observables, we show that the superposition size of, e.g., NOON states and hierarchical cat states, can scale linearly with the number of elementary particles comprising the superposition state, implying precision scaling inversely with the total number of photons when these states are employed as probes in quantum parameter estimation of a 1-local Hamiltonian in this algebra.
Measurement-Induced Macroscopic Superposition States in Cavity Optomechanics
DEFF Research Database (Denmark)
Hoff, Ulrich Busk; Kollath-Bönig, Johann; Neergaard-Nielsen, Jonas Schou
2016-01-01
A novel protocol for generating quantum superpositions of macroscopically distinct states of a bulk mechanical oscillator is proposed, compatible with existing optomechanical devices operating in the bad-cavity limit. By combining a pulsed optomechanical quantum nondemolition (QND) interaction...
International Nuclear Information System (INIS)
Nakano, Masayoshi; Kishi, Ryohei; Ohta, Suguru; Takahashi, Hideaki; Furukawa, Shin-ichi; Yamaguchi, Kizashi
2005-01-01
We investigate the long-time dynamics of two-component dilute gas Bose-Einstein condensates with relatively different two-body interactions and Josephson couplings between the two components. Although in certain parameter regimes the quantum state of the system is known to evolve into macroscopic superposition, i.e., Schroedinger cat state, of two states with relative atom number differences between the two components, the Schroedinger cat state is also found to repeat the collapse and revival behavior in the long-time region. The dynamical behavior of the Pegg-Barnett phase difference between the two components is shown to be closely connected with the dynamics of the relative atom number difference for different parameters. The variation in the relative magnitude between the Josephson coupling and intra- and inter-component two-body interaction difference turns out to significantly change not only the size of the Schroedinger cat state but also its collapse-revival period, i.e., the lifetime of the Schroedinger cat state
Assessments of macroscopicity for quantum optical states
DEFF Research Database (Denmark)
Laghaout, Amine; Neergaard-Nielsen, Jonas Schou; Andersen, Ulrik Lund
2015-01-01
With the slow but constant progress in the coherent control of quantum systems, it is now possible to create large quantum superpositions. There has therefore been an increased interest in quantifying any claims of macroscopicity. We attempt here to motivate three criteria which we believe should...... enter in the assessment of macroscopic quantumness: The number of quantum fluctuation photons, the purity of the states, and the ease with which the branches making up the state can be distinguished. © 2014....
A superposition principle in quantum logics
International Nuclear Information System (INIS)
Pulmannova, S.
1976-01-01
A new definition of the superposition principle in quantum logics is given which enables us to define the sectors. It is shown that the superposition principle holds only in the irreducible quantum logics. (orig.) [de
Testing the quantum superposition principle: matter waves and beyond
Ulbricht, Hendrik
2015-05-01
New technological developments allow to explore the quantum properties of very complex systems, bringing the question of whether also macroscopic systems share such features, within experimental reach. The interest in this question is increased by the fact that, on the theory side, many suggest that the quantum superposition principle is not exact, departures from it being the larger, the more macroscopic the system. Testing the superposition principle intrinsically also means to test suggested extensions of quantum theory, so-called collapse models. We will report on three new proposals to experimentally test the superposition principle with nanoparticle interferometry, optomechanical devices and by spectroscopic experiments in the frequency domain. We will also report on the status of optical levitation and cooling experiments with nanoparticles in our labs, towards an Earth bound matter-wave interferometer to test the superposition principle for a particle mass of one million amu (atomic mass unit).
Experimental superposition of orders of quantum gates
Procopio, Lorenzo M.; Moqanaki, Amir; Araújo, Mateus; Costa, Fabio; Alonso Calafell, Irati; Dowd, Emma G.; Hamel, Deny R.; Rozema, Lee A.; Brukner, Časlav; Walther, Philip
2015-01-01
Quantum computers achieve a speed-up by placing quantum bits (qubits) in superpositions of different states. However, it has recently been appreciated that quantum mechanics also allows one to ‘superimpose different operations'. Furthermore, it has been shown that using a qubit to coherently control the gate order allows one to accomplish a task—determining if two gates commute or anti-commute—with fewer gate uses than any known quantum algorithm. Here we experimentally demonstrate this advantage, in a photonic context, using a second qubit to control the order in which two gates are applied to a first qubit. We create the required superposition of gate orders by using additional degrees of freedom of the photons encoding our qubits. The new resource we exploit can be interpreted as a superposition of causal orders, and could allow quantum algorithms to be implemented with an efficiency unlikely to be achieved on a fixed-gate-order quantum computer. PMID:26250107
Superconductivity and macroscopic quantum phenomena
International Nuclear Information System (INIS)
Rogovin, D.; Scully, M.
1976-01-01
It is often asserted that superconducting systems are manifestations of quantum mechanics on a macroscopic scale. In this review article it is demonstrated that this quantum assertion is true within the framework of the microscopic theory of superconductivity. (Auth.)
Models for universal reduction of macroscopic quantum fluctuations
International Nuclear Information System (INIS)
Diosi, L.
1988-10-01
If quantum mechanics is universal, then macroscopic bodies would, in principle, possess macroscopic quantum fluctuations (MQF) in their positions, orientations, densities etc. Such MQF, however, are not observed in nature. The hypothesis is adopted that the absence of MQF is due to a certain universal mechanism. Gravitational measures were applied for reducing MQF of the mass density. This model leads to classical trajectories in the macroscopic limit of translational motion. For massive objects, unwanted macroscopic superpositions of quantum states will be destroyed within short times. (R.P.) 34 refs
Quantum equilibria for macroscopic systems
International Nuclear Information System (INIS)
Grib, A; Khrennikov, A; Parfionov, G; Starkov, K
2006-01-01
Nash equilibria are found for some quantum games with particles with spin-1/2 for which two spin projections on different directions in space are measured. Examples of macroscopic games with the same equilibria are given. Mixed strategies for participants of these games are calculated using probability amplitudes according to the rules of quantum mechanics in spite of the macroscopic nature of the game and absence of Planck's constant. A possible role of quantum logical lattices for the existence of macroscopic quantum equilibria is discussed. Some examples for spin-1 cases are also considered
Quantum equilibria for macroscopic systems
Energy Technology Data Exchange (ETDEWEB)
Grib, A [Department of Theoretical Physics and Astronomy, Russian State Pedagogical University, St. Petersburg (Russian Federation); Khrennikov, A [Centre for Mathematical Modelling in Physics and Cognitive Sciences Vaexjoe University (Sweden); Parfionov, G [Department of Mathematics, St. Petersburg State University of Economics and Finances (Russian Federation); Starkov, K [Department of Mathematics, St. Petersburg State University of Economics and Finances (Russian Federation)
2006-06-30
Nash equilibria are found for some quantum games with particles with spin-1/2 for which two spin projections on different directions in space are measured. Examples of macroscopic games with the same equilibria are given. Mixed strategies for participants of these games are calculated using probability amplitudes according to the rules of quantum mechanics in spite of the macroscopic nature of the game and absence of Planck's constant. A possible role of quantum logical lattices for the existence of macroscopic quantum equilibria is discussed. Some examples for spin-1 cases are also considered.
Interpretation of macroscopic quantum phenomena
International Nuclear Information System (INIS)
Baumann, K.
1986-01-01
It is argued that a quantum theory without observer is required for the interpretation of macroscopic quantum tunnelling. Such a theory is obtained by augmenting QED by the actual electric field in the rest system of the universe. An equation of the motion of this field is formulated form which the correct macroscopic behavior of the universe and the validity of the Born interpretation is derived. Care is taken to use mathematically sound concepts only. (Author)
Authentication Protocol using Quantum Superposition States
Energy Technology Data Exchange (ETDEWEB)
Kanamori, Yoshito [University of Alaska; Yoo, Seong-Moo [University of Alabama, Huntsville; Gregory, Don A. [University of Alabama, Huntsville; Sheldon, Frederick T [ORNL
2009-01-01
When it became known that quantum computers could break the RSA (named for its creators - Rivest, Shamir, and Adleman) encryption algorithm within a polynomial-time, quantum cryptography began to be actively studied. Other classical cryptographic algorithms are only secure when malicious users do not have sufficient computational power to break security within a practical amount of time. Recently, many quantum authentication protocols sharing quantum entangled particles between communicators have been proposed, providing unconditional security. An issue caused by sharing quantum entangled particles is that it may not be simple to apply these protocols to authenticate a specific user in a group of many users. An authentication protocol using quantum superposition states instead of quantum entangled particles is proposed. The random number shared between a sender and a receiver can be used for classical encryption after the authentication has succeeded. The proposed protocol can be implemented with the current technologies we introduce in this paper.
Toward quantum superposition of living organisms
International Nuclear Information System (INIS)
Romero-Isart, Oriol; Cirac, J Ignacio; Juan, Mathieu L; Quidant, Romain
2010-01-01
The most striking feature of quantum mechanics is the existence of superposition states, where an object appears to be in different situations at the same time. The existence of such states has been previously tested with small objects, such as atoms, ions, electrons and photons (Zoller et al 2005 Eur. Phys. J. D 36 203-28), and even with molecules (Arndt et al 1999 Nature 401 680-2). More recently, it has been shown that it is possible to create superpositions of collections of photons (Deleglise et al 2008 Nature 455 510-14), atoms (Hammerer et al 2008 arXiv:0807.3358) or Cooper pairs (Friedman et al 2000 Nature 406 43-6). Very recent progress in optomechanical systems may soon allow us to create superpositions of even larger objects, such as micro-sized mirrors or cantilevers (Marshall et al 2003 Phys. Rev. Lett. 91 130401; Kippenberg and Vahala 2008 Science 321 1172-6; Marquardt and Girvin 2009 Physics 2 40; Favero and Karrai 2009 Nature Photon. 3 201-5), and thus to test quantum mechanical phenomena at larger scales. Here we propose a method to cool down and create quantum superpositions of the motion of sub-wavelength, arbitrarily shaped dielectric objects trapped inside a high-finesse cavity at a very low pressure. Our method is ideally suited for the smallest living organisms, such as viruses, which survive under low-vacuum pressures (Rothschild and Mancinelli 2001 Nature 406 1092-101) and optically behave as dielectric objects (Ashkin and Dziedzic 1987 Science 235 1517-20). This opens up the possibility of testing the quantum nature of living organisms by creating quantum superposition states in very much the same spirit as the original Schroedinger's cat 'gedanken' paradigm (Schroedinger 1935 Naturwissenschaften 23 807-12, 823-8, 844-9). We anticipate that our paper will be a starting point for experimentally addressing fundamental questions, such as the role of life and consciousness in quantum mechanics.
Toward quantum superposition of living organisms
Energy Technology Data Exchange (ETDEWEB)
Romero-Isart, Oriol; Cirac, J Ignacio [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748, Garching (Germany); Juan, Mathieu L; Quidant, Romain [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels, Barcelona 08860 (Spain)], E-mail: oriol.romero-isart@mpq.mpg.de
2010-03-15
The most striking feature of quantum mechanics is the existence of superposition states, where an object appears to be in different situations at the same time. The existence of such states has been previously tested with small objects, such as atoms, ions, electrons and photons (Zoller et al 2005 Eur. Phys. J. D 36 203-28), and even with molecules (Arndt et al 1999 Nature 401 680-2). More recently, it has been shown that it is possible to create superpositions of collections of photons (Deleglise et al 2008 Nature 455 510-14), atoms (Hammerer et al 2008 arXiv:0807.3358) or Cooper pairs (Friedman et al 2000 Nature 406 43-6). Very recent progress in optomechanical systems may soon allow us to create superpositions of even larger objects, such as micro-sized mirrors or cantilevers (Marshall et al 2003 Phys. Rev. Lett. 91 130401; Kippenberg and Vahala 2008 Science 321 1172-6; Marquardt and Girvin 2009 Physics 2 40; Favero and Karrai 2009 Nature Photon. 3 201-5), and thus to test quantum mechanical phenomena at larger scales. Here we propose a method to cool down and create quantum superpositions of the motion of sub-wavelength, arbitrarily shaped dielectric objects trapped inside a high-finesse cavity at a very low pressure. Our method is ideally suited for the smallest living organisms, such as viruses, which survive under low-vacuum pressures (Rothschild and Mancinelli 2001 Nature 406 1092-101) and optically behave as dielectric objects (Ashkin and Dziedzic 1987 Science 235 1517-20). This opens up the possibility of testing the quantum nature of living organisms by creating quantum superposition states in very much the same spirit as the original Schroedinger's cat 'gedanken' paradigm (Schroedinger 1935 Naturwissenschaften 23 807-12, 823-8, 844-9). We anticipate that our paper will be a starting point for experimentally addressing fundamental questions, such as the role of life and consciousness in quantum mechanics.
Thermalization as an Invisibility Cloak for Fragile Quantum Superpositions
Hahn, Walter; Fine, Boris V.
2017-01-01
We propose a method for protecting fragile quantum superpositions in many-particle systems from dephasing by external classical noise. We call superpositions "fragile" if dephasing occurs particularly fast, because the noise couples very differently to the superposed states. The method consists of letting a quantum superposition evolve under the internal thermalization dynamics of the system, followed by a time reversal manipulation known as Loschmidt echo. The thermalization dynamics makes t...
Quantum State Engineering Via Coherent-State Superpositions
Janszky, Jozsef; Adam, P.; Szabo, S.; Domokos, P.
1996-01-01
The quantum interference between the two parts of the optical Schrodinger-cat state makes possible to construct a wide class of quantum states via discrete superpositions of coherent states. Even a small number of coherent states can approximate the given quantum states at a high accuracy when the distance between the coherent states is optimized, e. g. nearly perfect Fock state can be constructed by discrete superpositions of n + 1 coherent states lying in the vicinity of the vacuum state.
Entanglement and quantum superposition induced by a single photon
Lü, Xin-You; Zhu, Gui-Lei; Zheng, Li-Li; Wu, Ying
2018-03-01
We predict the occurrence of single-photon-induced entanglement and quantum superposition in a hybrid quantum model, introducing an optomechanical coupling into the Rabi model. Originally, it comes from the photon-dependent quantum property of the ground state featured by the proposed hybrid model. It is associated with a single-photon-induced quantum phase transition, and is immune to the A2 term of the spin-field interaction. Moreover, the obtained quantum superposition state is actually a squeezed cat state, which can significantly enhance precision in quantum metrology. This work offers an approach to manipulate entanglement and quantum superposition with a single photon, which might have potential applications in the engineering of new single-photon quantum devices, and also fundamentally broaden the regime of cavity QED.
Generation of optical coherent state superpositions for quantum information processing
DEFF Research Database (Denmark)
Tipsmark, Anders
2012-01-01
I dette projektarbejde med titlen “Generation of optical coherent state superpositions for quantum information processing” har målet været at generere optiske kat-tilstande. Dette er en kvantemekanisk superpositions tilstand af to koherente tilstande med stor amplitude. Sådan en tilstand er...
Thermalization as an invisibility cloak for fragile quantum superpositions
Hahn, Walter; Fine, Boris V.
2017-07-01
We propose a method for protecting fragile quantum superpositions in many-particle systems from dephasing by external classical noise. We call superpositions "fragile" if dephasing occurs particularly fast, because the noise couples very differently to the superposed states. The method consists of letting a quantum superposition evolve under the internal thermalization dynamics of the system, followed by a time-reversal manipulation known as Loschmidt echo. The thermalization dynamics makes the superposed states almost indistinguishable during most of the above procedure. We validate the method by applying it to a cluster of spins ½.
On quantum mechanics for macroscopic systems
International Nuclear Information System (INIS)
Primas, H.
1992-01-01
The parable of Schroedinger's cat may lead to several up-to date questions: how to treat open systems in quantum theory, how to treat thermodynamically irreversible processes in the quantum mechanics framework, how to explain, following the quantum theory, the existence, phenomenologically evident, of classical observables, what implies the predicted existence by the quantum theory of non localized macroscopic material object ?
Macroscopic quantum waves in non local theories
International Nuclear Information System (INIS)
Ventura, I.
1979-01-01
By means of an expansion in the density, it is shown that Macroscopic Quantum Waves also apear in non local theories. This result reinforces the conjecture that these waves should exist in liquid 4 He. (Author) [pt
Macroscopic quantum waves in non local theories
International Nuclear Information System (INIS)
Ventura, I.
1979-01-01
By means of an expansion in the density, it is shown that Macroscopic Quantum Waves also appear in non local theories. This result reinforces the conjecture that these waves should exist in liquid 4 He [pt
Nuclear fission as a macroscopic quantum tunneling
International Nuclear Information System (INIS)
Takigawa, N.
1995-01-01
We discuss nuclear fission from the point of view of a macroscopic quantum tunneling, one of whose major interests is to study the effects of environments on the tunneling rate of a macroscopic variable. We show that a vibrational excitation of the fissioning nucleus significantly enhances the fission rate. We show this effect by two different methods. The one is to treat the vibrational excitation as an environmental degree of freedom, the other treats the fission as a two dimensional quantum tunneling. (author)
Macroscopic and non-linear quantum games
International Nuclear Information System (INIS)
Aerts, D.; D'Hooghe, A.; Posiewnik, A.; Pykacz, J.
2005-01-01
Full text: We consider two models of quantum games. The first one is Marinatto and Weber's 'restricted' quantum game in which only the identity and the spin-flip operators are used. We show that this quantum game allows macroscopic mechanistic realization with the use of a version of the 'macroscopic quantum machine' described by Aerts already in 1980s. In the second model we use non-linear quantum state transformations which operate on points of spin-1/2 on the Bloch sphere and which can be used to distinguish optimally between two non-orthogonal states. We show that efficiency of these non-linear strategies out-perform any linear ones. Some hints on the possible theory of non-linear quantum games are given. (author)
Coherent inflation for large quantum superpositions of levitated microspheres
Romero-Isart, Oriol
2017-12-01
We show that coherent inflation (CI), namely quantum dynamics generated by inverted conservative potentials acting on the center of mass of a massive object, is an enabling tool to prepare large spatial quantum superpositions in a double-slit experiment. Combined with cryogenic, extreme high vacuum, and low-vibration environments, we argue that it is experimentally feasible to exploit CI to prepare the center of mass of a micrometer-sized object in a spatial quantum superposition comparable to its size. In such a hitherto unexplored parameter regime gravitationally-induced decoherence could be unambiguously falsified. We present a protocol to implement CI in a double-slit experiment by letting a levitated microsphere traverse a static potential landscape. Such a protocol could be experimentally implemented with an all-magnetic scheme using superconducting microspheres.
Pathways toward understanding Macroscopic Quantum Phenomena
International Nuclear Information System (INIS)
Hu, B L; Subaşi, Y
2013-01-01
Macroscopic quantum phenomena refer to quantum features in objects of 'large' sizes, systems with many components or degrees of freedom, organized in some ways where they can be identified as macroscopic objects. This emerging field is ushered in by several categories of definitive experiments in superconductivity, electromechanical systems, Bose-Einstein condensates and others. Yet this new field which is rich in open issues at the foundation of quantum and statistical physics remains little explored theoretically (with the important exception of the work of A J Leggett [1], while touched upon or implied by several groups of authors represented in this conference. Our attitude differs in that we believe in the full validity of quantum mechanics stretching from the testable micro to meso scales, with no need for the introduction of new laws of physics.) This talk summarizes our thoughts in attempting a systematic investigation into some key foundational issues of quantum macroscopic phenomena, with the goal of ultimately revealing or building a viable theoretical framework. Three major themes discussed in three intended essays are the large N expansion [2], the correlation hierarchy [3] and quantum entanglement [4]. We give a sketch of the first two themes and then discuss several key issues in the consideration of macro and quantum, namely, a) recognition that there exist many levels of structure in a composite body and only by judicious choice of an appropriate set of collective variables can one give the best description of the dynamics of a specific level of structure. Capturing the quantum features of a macroscopic object is greatly facilitated by the existence and functioning of these collective variables; b) quantum entanglement, an exclusively quantum feature [5], is known to persist to high temperatures [6] and large scales [7] under certain conditions, and may actually decrease with increased connectivity in a quantum network [8]. We use entanglement as a
Single-Atom Gating of Quantum State Superpositions
Energy Technology Data Exchange (ETDEWEB)
Moon, Christopher
2010-04-28
The ultimate miniaturization of electronic devices will likely require local and coherent control of single electronic wavefunctions. Wavefunctions exist within both physical real space and an abstract state space with a simple geometric interpretation: this state space - or Hilbert space - is spanned by mutually orthogonal state vectors corresponding to the quantized degrees of freedom of the real-space system. Measurement of superpositions is akin to accessing the direction of a vector in Hilbert space, determining an angle of rotation equivalent to quantum phase. Here we show that an individual atom inside a designed quantum corral1 can control this angle, producing arbitrary coherent superpositions of spatial quantum states. Using scanning tunnelling microscopy and nanostructures assembled atom-by-atom we demonstrate how single spins and quantum mirages can be harnessed to image the superposition of two electronic states. We also present a straightforward method to determine the atom path enacting phase rotations between any desired state vectors. A single atom thus becomes a real-space handle for an abstract Hilbert space, providing a simple technique for coherent quantum state manipulation at the spatial limit of condensed matter.
Macroscopic Quantum Resonators (MAQRO): 2015 update
International Nuclear Information System (INIS)
Kaltenbaek, Rainer; Aspelmeyer, Markus; Kiesel, Nikolai; Barker, Peter F.; Bose, Sougato; Bassi, Angelo; Bateman, James; Bongs, Kai; Cruise, Adrian Michael; Braxmaier, Claus; Brukner, Caslav; Christophe, Bruno; Rodrigues, Manuel; Chwalla, Michael; Johann, Ulrich; Cohadon, Pierre-Francois; Heidmann, Antoine; Lambrecht, Astrid; Reynaud, Serge; Curceanu, Catalina; Dholakia, Kishan; Mazilu, Michael; Diosi, Lajos; Doeringshoff, Klaus; Peters, Achim; Ertmer, Wolfgang; Rasel, Ernst M.; Gieseler, Jan; Novotny, Lukas; Rondin, Loic; Guerlebeck, Norman; Herrmann, Sven; Laemmerzahl, Claus; Hechenblaikner, Gerald; Hossenfelder, Sabine; Kim, Myungshik; Milburn, Gerard J.; Mueller, Holger; Paternostro, Mauro; Pikovski, Igor; Pilan Zanoni, Andre; Riedel, Charles Jess; Roura, Albert; Schleich, Wolfgang P.; Schmiedmayer, Joerg; Schuldt, Thilo; Schwab, Keith C.; Tajmar, Martin; Tino, Guglielmo M.; Ulbricht, Hendrik; Ursin, Rupert; Vedral, Vlatko
2016-01-01
Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schroedinger's cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to limited free-fall times and the quality of vacuum and microgravity. The proposed mission Macroscopic Quantum Resonators (MAQRO) may overcome these limitations and allow addressing such fundamental questions. MAQRO harnesses recent developments in quantum optomechanics, high-mass matter-wave interferometry as well as state-of-the-art space technology to push macroscopic quantum experiments towards their ultimate performance limits and to open new horizons for applying quantum technology in space. The main scientific goal is to probe the vastly unexplored 'quantum-classical' transition for increasingly massive objects, testing the predictions of quantum theory for objects in a size and mass regime unachievable in ground-based experiments. The hardware will largely be based on available space technology. Here, we present the MAQRO proposal submitted in response to the 4th Cosmic Vision call for a medium-sized mission (M4) in 2014 of the European Space Agency (ESA) with a possible launch in 2025, and we review the progress with respect to the original MAQRO proposal for the 3rd Cosmic Vision call for a medium-sized mission (M3) in 2010. In particular, the updated proposal overcomes several critical issues of the original proposal by relying on established experimental techniques from high-mass matter-wave interferometry and by introducing novel ideas for particle loading and manipulation. Moreover, the mission design was improved to better fulfill the stringent environmental requirements for macroscopic quantum experiments. (orig.)
Macroscopic Quantum Resonators (MAQRO): 2015 update
Energy Technology Data Exchange (ETDEWEB)
Kaltenbaek, Rainer [University of Vienna, Vienna Center for Quantum Science and Technology, Vienna (Austria); Aspelmeyer, Markus; Kiesel, Nikolai [University of Vienna, Vienna Center for Quantum Science and Technology, Vienna (Austria); Barker, Peter F.; Bose, Sougato [University College London, Department of Physics and Astronomy, London (United Kingdom); Bassi, Angelo [University of Trieste, Department of Physics, Trieste (Italy); INFN - Trieste Section, Trieste (Italy); Bateman, James [University of Swansea, Department of Physics, College of Science, Swansea (United Kingdom); Bongs, Kai; Cruise, Adrian Michael [University of Birmingham, School of Physics and Astronomy, Birmingham (United Kingdom); Braxmaier, Claus [University of Bremen, Center of Applied Space Technology and Micro Gravity (ZARM), Bremen (Germany); Institute of Space Systems, German Aerospace Center (DLR), Bremen (Germany); Brukner, Caslav [University of Vienna, Vienna Center for Quantum Science and Technology, Vienna (Austria); Austrian Academy of Sciences, Institute of Quantum Optics and Quantum Information (IQOQI), Vienna (Austria); Christophe, Bruno; Rodrigues, Manuel [The French Aerospace Lab, ONERA, Chatillon (France); Chwalla, Michael; Johann, Ulrich [Airbus Defence and Space GmbH, Immenstaad (Germany); Cohadon, Pierre-Francois; Heidmann, Antoine; Lambrecht, Astrid; Reynaud, Serge [ENS-PSL Research University, Laboratoire Kastler Brossel, UPMC-Sorbonne Universites, CNRS, College de France, Paris (France); Curceanu, Catalina [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Dholakia, Kishan; Mazilu, Michael [University of St. Andrews, School of Physics and Astronomy, St. Andrews (United Kingdom); Diosi, Lajos [Wigner Research Center for Physics, P.O. Box 49, Budapest (Hungary); Doeringshoff, Klaus; Peters, Achim [Humboldt-Universitaet zu Berlin, Institut fuer Physik, Berlin (Germany); Ertmer, Wolfgang; Rasel, Ernst M. [Leibniz Universitaet Hannover, Institut fuer Quantenoptik, Hannover (Germany); Gieseler, Jan; Novotny, Lukas; Rondin, Loic [ETH Zuerich, Photonics Laboratory, Zuerich (Switzerland); Guerlebeck, Norman; Herrmann, Sven; Laemmerzahl, Claus [University of Bremen, Center of Applied Space Technology and Micro Gravity (ZARM), Bremen (Germany); Hechenblaikner, Gerald [Airbus Defence and Space GmbH, Immenstaad (Germany); European Southern Observatory (ESO), Garching bei Muenchen (Germany); Hossenfelder, Sabine [KTH Royal Institute of Technology and Stockholm University, Nordita, Stockholm (Sweden); Kim, Myungshik [Imperial College London, QOLS, Blackett Laboratory, London (United Kingdom); Milburn, Gerard J. [University of Queensland, ARC Centre for Engineered Quantum Systems, Brisbane (Australia); Mueller, Holger [University of California, Department of Physics, Berkeley, CA (United States); Paternostro, Mauro [Queen' s University, Centre for Theoretical Atomic, Molecular and Optical Physics, School of Mathematics and Physics, Belfast (United Kingdom); Pikovski, Igor [Harvard-Smithsonian Center for Astrophysics, ITAMP, Cambridge, MA (United States); Pilan Zanoni, Andre [Airbus Defence and Space GmbH, Immenstaad (Germany); CERN - European Organization for Nuclear Research, EN-STI-TCD, Geneva (Switzerland); Riedel, Charles Jess [Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); Roura, Albert [Universitaet Ulm, Institut fuer Quantenphysik, Ulm (Germany); Schleich, Wolfgang P. [Universitaet Ulm, Institut fuer Quantenphysik, Ulm (Germany); Texas A and M University Institute for Advanced Study (TIAS), Institute for Quantum Science and Engineering (IQSE), and Department of Physics and Astronomy, College Station, TX (United States); Schmiedmayer, Joerg [Vienna University of Technology, Vienna Center for Quantum Science and Technology, Institute of Atomic and Subatomic Physics, Vienna (Austria); Schuldt, Thilo [Institute of Space Systems, German Aerospace Center (DLR), Bremen (Germany); Schwab, Keith C. [California Institute of Technology, Applied Physics, Pasadena, CA (United States); Tajmar, Martin [Technische Universitaet Dresden, Institut fuer Luft- und Raumfahrttechnik, Dresden (Germany); Tino, Guglielmo M. [Universita di Firenze, Dipartimento di Fisica e Astronomia and LENS, INFN, Sesto Fiorentino, Firenze (Italy); Ulbricht, Hendrik [University of Southampton, Physics and Astronomy, Southampton (United Kingdom); Ursin, Rupert [Austrian Academy of Sciences, Institute of Quantum Optics and Quantum Information (IQOQI), Vienna (Austria); Vedral, Vlatko [University of Oxford, Atomic and Laser Physics, Clarendon Laboratory, Oxford (United Kingdom); National University of Singapore, Center for Quantum Technologies, Singapore (SG)
2016-12-15
Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schroedinger's cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to limited free-fall times and the quality of vacuum and microgravity. The proposed mission Macroscopic Quantum Resonators (MAQRO) may overcome these limitations and allow addressing such fundamental questions. MAQRO harnesses recent developments in quantum optomechanics, high-mass matter-wave interferometry as well as state-of-the-art space technology to push macroscopic quantum experiments towards their ultimate performance limits and to open new horizons for applying quantum technology in space. The main scientific goal is to probe the vastly unexplored 'quantum-classical' transition for increasingly massive objects, testing the predictions of quantum theory for objects in a size and mass regime unachievable in ground-based experiments. The hardware will largely be based on available space technology. Here, we present the MAQRO proposal submitted in response to the 4th Cosmic Vision call for a medium-sized mission (M4) in 2014 of the European Space Agency (ESA) with a possible launch in 2025, and we review the progress with respect to the original MAQRO proposal for the 3rd Cosmic Vision call for a medium-sized mission (M3) in 2010. In particular, the updated proposal overcomes several critical issues of the original proposal by relying on established experimental techniques from high-mass matter-wave interferometry and by introducing novel ideas for particle loading and manipulation. Moreover, the mission design was improved to better fulfill the stringent environmental requirements for macroscopic quantum experiments. (orig.)
Macroscopic quantum tunneling of the magnetic moment
Tejada, J.; Hernandez, J. M.; del Barco, E.
1999-05-01
In this paper we review the work done on magnetic relaxation during the last 10 years on both single-domain particles and magnetic molecules and its contribution to the discovery of quantum tunneling of the magnetic moment (Chudnovsky and Tejada, Macroscopic Quantum tunneling of the Magnetic moment, Cambridge University press, Cambridge, 1998). We present first the theoretical expressions and their connection to quantum relaxation and secondly, we show and discuss the experimental results. Finally, we discuss very recent hysteresis data on Mn 12Ac molecules at extremely large sweeping rate for the external magnetic field which suggest the existence of quantum spin—phonon avalanches.
Testing quantum behaviour at the macroscopic level
International Nuclear Information System (INIS)
Ghirardi, G.C.
1994-07-01
We reconsider recent proposals to test macro realism versus quantum mechanics in experiments involving noninvasive measurement processes on a Squid. In spite of the fact that we are able to prove that the proposed experiments do not represent a test of macro realism but simply of macroscopic quantum coherence we call attention to their extreme conceptual relevance. We also discuss some recent criticisms which have been raised against the considered proposal and we show that they are not relevant. (author). 12 refs
Berkeley Experiments on Superfluid Macroscopic Quantum Effects
International Nuclear Information System (INIS)
Packard, Richard
2006-01-01
This paper provides a brief history of the evolution of the Berkeley experiments on macroscopic quantum effects in superfluid helium. The narrative follows the evolution of the experiments proceeding from the detection of single vortex lines to vortex photography to quantized circulation in 3He to Josephson effects and superfluid gyroscopes in both 4He and 3He
The macroscopic harmonic oscillator and quantum measurements
International Nuclear Information System (INIS)
Hayward, R.W.
1982-01-01
A quantum mechanical description of a one-dimensional macroscopic harmonic oscillator interacting with its environment is given. Quasi-coherent states are introduced to serve as convenient basis states for application of a density matrix formalism to characterize the system. Attention is given to the pertinent quantum limits to the precision of measurement of physical observables that may provide some information on the nature of a weak classical force interacting with the oscillator. A number of ''quantum nondemolition'' schemes proposed by various authors are discussed. (Auth.)
Quantum superposition of massive objects and collapse models
International Nuclear Information System (INIS)
Romero-Isart, Oriol
2011-01-01
We analyze the requirements to test some of the most paradigmatic collapse models with a protocol that prepares quantum superpositions of massive objects. This consists of coherently expanding the wave function of a ground-state-cooled mechanical resonator, performing a squared position measurement that acts as a double slit, and observing interference after further evolution. The analysis is performed in a general framework and takes into account only unavoidable sources of decoherence: blackbody radiation and scattering of environmental particles. We also discuss the limitations imposed by the experimental implementation of this protocol using cavity quantum optomechanics with levitating dielectric nanospheres.
Quantum superposition of massive objects and collapse models
Energy Technology Data Exchange (ETDEWEB)
Romero-Isart, Oriol [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany)
2011-11-15
We analyze the requirements to test some of the most paradigmatic collapse models with a protocol that prepares quantum superpositions of massive objects. This consists of coherently expanding the wave function of a ground-state-cooled mechanical resonator, performing a squared position measurement that acts as a double slit, and observing interference after further evolution. The analysis is performed in a general framework and takes into account only unavoidable sources of decoherence: blackbody radiation and scattering of environmental particles. We also discuss the limitations imposed by the experimental implementation of this protocol using cavity quantum optomechanics with levitating dielectric nanospheres.
Toward a superconducting quantum computer. Harnessing macroscopic quantum coherence.
Tsai, Jaw-Shen
2010-01-01
Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as well as its history, and discusses its future. Although progress has been rapid, the field remains beset with unsolved issues, and there are still many new research opportunities open to physicists and engineers.
Adiabatic rotation, quantum search, and preparation of superposition states
International Nuclear Information System (INIS)
Siu, M. Stewart
2007-01-01
We introduce the idea of using adiabatic rotation to generate superpositions of a large class of quantum states. For quantum computing this is an interesting alternative to the well-studied 'straight line' adiabatic evolution. In ways that complement recent results, we show how to efficiently prepare three types of states: Kitaev's toric code state, the cluster state of the measurement-based computation model, and the history state used in the adiabatic simulation of a quantum circuit. We also show that the method, when adapted for quantum search, provides quadratic speedup as other optimal methods do with the advantages that the problem Hamiltonian is time independent and that the energy gap above the ground state is strictly nondecreasing with time. Likewise the method can be used for optimization as an alternative to the standard adiabatic algorithm
Quantum-mechanical Green's functions and nonlinear superposition law
International Nuclear Information System (INIS)
Nassar, A.B.; Bassalo, J.M.F.; Antunes Neto, H.S.; Alencar, P. de T.S.
1986-01-01
The quantum-mechanical Green's function is derived for the problem of a time-dependent variable mass particle subject to a time-dependent forced harmonic oscillator potential by taking direct recourse of the corresponding Schroedinger equation. Through the usage of the nonlinear superposition law of Ray and Reid, it is shown that such a Green's function can be obtained from that for the problem of a particle with unit (constant) mass subject to either a forced harmonic potential with constant frequency or only to a time-dependent linear field. (Author) [pt
Quantum-mechanical Green's function and nonlinear superposition law
International Nuclear Information System (INIS)
Nassar, A.B.; Bassalo, J.M.F.; Antunes Neto, H.S.; Alencar, P.T.S.
1986-01-01
It is derived the quantum-mechanical Green's function for the problem of a time-dependent variable mass particle subject to a time-dependent forced harmonic-oscillator potential by taking direct recourse of the corresponding Schroedinger equation. Through the usage of the nonlinear superposition law of Ray and Reid, it is shown that such a Green's function can be obtained from that for the problem of a particle with unit (constant) mass subject to either a forced harmonic potential with constant frequency or only to a time-dependent linear field
Quantum teleportation between stationary macroscopic objects
Energy Technology Data Exchange (ETDEWEB)
Bao, Xiao-Hui; Yuan, Zhen-Sheng; Pan, Jian-Wei [Physikalisches Institut, Universitaet Heidelberg (Germany); Hefei National Laboratory for Physical Sciences at Microscale, Department of Modern Physics, University of Science and Technology of China, Hefei (China); Xu, Xiao-Fan [Physikalisches Institut, Universitaet Heidelberg (Germany); Li, Che-Ming [Physikalisches Institut, Universitaet Heidelberg (Germany); Department of Physics, National Center for Theoretical Sciences, National Cheng Kung University, Tainan (China)
2010-07-01
Quantum teleportation is a process to transfer a quantum state of an object without transferring the state carrier itself. So far, most of the teleportation experiments realized are within the photonic regime. For the teleportation of stationary states, the largest system reported is a single ion. We are now performing an experiment to teleport the state of an macroscopic atomic cloud which consists about 10{sup 6} single atoms. In our experiment two atomic ensembles are utilized. In the first ensemble A we prepare the collective atomic state to be teleported using the quantum feedback technique. The second ensemble B is utilized to generate entanglement between it collective state with a scattered single-photon. Teleportation is realized by converting the atomic state of A to a single-photon and making a Bell state measurement with the scattered single-photon from ensemble B.
Macroscopic effects of the quantum trace anomaly
International Nuclear Information System (INIS)
Mottola, Emil; Vaulin, Ruslan
2006-01-01
The low energy effective action of gravity in any even dimension generally acquires nonlocal terms associated with the trace anomaly, generated by the quantum fluctuations of massless fields. The local auxiliary field description of this effective action in four dimensions requires two additional scalar fields, not contained in classical general relativity, which remain relevant at macroscopic distance scales. The auxiliary scalar fields depend upon boundary conditions for their complete specification, and therefore carry global information about the geometry and macroscopic quantum state of the gravitational field. The scalar potentials also provide coordinate invariant order parameters describing the conformal behavior and divergences of the stress tensor on event horizons. We compute the stress tensor due to the anomaly in terms of its auxiliary scalar potentials in a number of concrete examples, including the Rindler wedge, the Schwarzschild geometry, and de Sitter spacetime. In all of these cases, a small number of classical order parameters completely determine the divergent behaviors allowed on the horizon, and yield qualitatively correct global approximations to the renormalized expectation value of the quantum stress tensor
Macroscopic quantum tunneling in a dc SQUID
International Nuclear Information System (INIS)
Chen, Y.C.
1986-01-01
The theory of macroscopic quantum tunneling is applied to a current-biased dc SQUID whose dynamics can be described by a two-dimensional mechanical system with a dissipative environment. Based on the phenomenological model proposed by Caldeira and Leggett, the dissipative environment is represented by a set of harmonic oscillators coupling to the system. After integrating out the environmental degrees of freedom, an effective Euclidean action is found for the two-dimensional system. The action is used to provide the quantum tunneling rate formalism for the dc SQUID. Under certain conditions, the tunneling rate reduces to that of a single current-biased Josephson junction with an adjustable effective critical current
Macroscopic quantum tunneling in Mn12-acetat
International Nuclear Information System (INIS)
Beiter, J.; Reissner, M.; Hilscher, G.; Steiner, W.; Pajic, D.; Zadro, K.; Bartel, M.; Linert, W.
2004-01-01
Molecules provide the exciting opportunity to study magnetism on the passage from atomic to macroscopic level. One of the most interesting effects in such mesoscopic systems is the appearance of quantum tunnelling of magnetization (MQT) at low temperatures. In the last decade molecular chemistry has had a large impact in this field by providing new single molecule magnets. They consist of small clusters exhibiting superparamagnetic behavior, similar to that of conventional nanomagnetic particles. The advantage of these new materials is that they form macroscopic samples consisting of regularly arranged small identical high-spin clusters which are widely separated by organic molecules. The lack of distributions in size and shape of the magnetic clusters and the very weak intercluster interaction lead in principle to only one barrier for the spin reversal. We present detailed magnetic investigations on a Mn 12 -ac single crystal. In this compound the tetragonal ordered clusters consist of a central tetrahedron of four Mn 4+ (S = 3/2) atoms surrounded by eight Mn 3+ (S = 2) atoms with antiparallel oriented spins, leading to an overall spin moment of S = 10. In the hysteresis loops nine different jumps at regularly spaced fields are identified in the investigated temperature range (1.5 < T < 3 K). At these fields the relaxation of moment due to thermal activation is superimposed by strong quantum tunnelling. In lowering the temperature the time dependence changes from thermally activated to thermally assisted tunnelling. (author)
Projective measurement onto arbitrary superposition of weak coherent state bases
DEFF Research Database (Denmark)
Izumi, Shuro; Takeoka, Masahiro; Wakui, Kentaro
2018-01-01
One of the peculiar features in quantum mechanics is that a superposition of macroscopically distinct states can exist. In optical system, this is highlighted by a superposition of coherent states (SCS), i.e. a superposition of classical states. Recently this highly nontrivial quantum state and i...
Evolution of superpositions of quantum states through a level crossing
International Nuclear Information System (INIS)
Torosov, B. T.; Vitanov, N. V.
2011-01-01
The Landau-Zener-Stueckelberg-Majorana (LZSM) model is widely used for estimating transition probabilities in the presence of crossing energy levels in quantum physics. This model, however, makes the unphysical assumption of an infinitely long constant interaction, which introduces a divergent phase in the propagator. This divergence remains hidden when estimating output probabilities for a single input state insofar as the divergent phase cancels out. In this paper we show that, because of this divergent phase, the LZSM model is inadequate to describe the evolution of pure or mixed superposition states across a level crossing. The LZSM model can be used only if the system is initially in a single state or in a completely mixed superposition state. To this end, we show that the more realistic Demkov-Kunike model, which assumes a hyperbolic-tangent level crossing and a hyperbolic-secant interaction envelope, is free of divergences and is a much more adequate tool for describing the evolution through a level crossing for an arbitrary input state. For multiple crossing energies which are reducible to one or more effective two-state systems (e.g., by the Majorana and Morris-Shore decompositions), similar conclusions apply: the LZSM model does not produce definite values of the populations and the coherences, and one should use the Demkov-Kunike model instead.
Student Ability to Distinguish between Superposition States and Mixed States in Quantum Mechanics
Passante, Gina; Emigh, Paul J.; Shaffer, Peter S.
2015-01-01
Superposition gives rise to the probabilistic nature of quantum mechanics and is therefore one of the concepts at the heart of quantum mechanics. Although we have found that many students can successfully use the idea of superposition to calculate the probabilities of different measurement outcomes, they are often unable to identify the…
Experimental demonstration of macroscopic quantum coherence in Gaussian states
DEFF Research Database (Denmark)
Marquardt, C.; Andersen, Ulrik Lund; Leuchs, G.
2007-01-01
We witness experimentally the presence of macroscopic coherence in Gaussian quantum states using a recently proposed criterion [E. G. Cavalcanti and M. D. Reid, Phys. Rev. Lett. 97 170405 (2006)]. The macroscopic coherence stems from interference between macroscopically distinct states in phase...
Collapsing a perfect superposition to a chosen quantum state without measurement.
Directory of Open Access Journals (Sweden)
Ahmed Younes
Full Text Available Given a perfect superposition of [Formula: see text] states on a quantum system of [Formula: see text] qubits. We propose a fast quantum algorithm for collapsing the perfect superposition to a chosen quantum state [Formula: see text] without applying any measurements. The basic idea is to use a phase destruction mechanism. Two operators are used, the first operator applies a phase shift and a temporary entanglement to mark [Formula: see text] in the superposition, and the second operator applies selective phase shifts on the states in the superposition according to their Hamming distance with [Formula: see text]. The generated state can be used as an excellent input state for testing quantum memories and linear optics quantum computers. We make no assumptions about the used operators and applied quantum gates, but our result implies that for this purpose the number of qubits in the quantum register offers no advantage, in principle, over the obvious measurement-based feedback protocol.
Macroscopic quantum tunnelling in a current biased Josephson junction
International Nuclear Information System (INIS)
Martinis, J.M.; Devoret, M.H.; Clarke, J.; Urbina, C.
1984-11-01
We discuss in this work an attempt to answer experimentally the question: do macroscopic variables obey quantum mechanics. More precisely, this experiment deals with the question of quantum-mechanical tunnelling of a macroscopic variable, a subject related to the famous Schrodinger's cat problem in the theory of measurement
Theory of superfluidity macroscopic quantum waves
International Nuclear Information System (INIS)
Ventura, I.
1978-10-01
A new description of superfluidity is proposed, based upon the fact that Bogoliubov's theory of superfluidity exhibits some so far unsuspected macroscopic quantum waves (MQWs), which have a topological nature and travel within the fluid at subsonic velocities. To quantize the bounded quasi-particles the field theoretic version of the Bohr-Sommerfeld quantization rule, is employed and also resort to a variational computation. In an instantaneous configuration the MQWs cut the condensate into blocks of phase, providing, by analogy with ferromagnetism, a nice explanation of what could be the lambda-transition. A crude estimate of the critical temperature gives T sub(c) approximately equal to 2-4K. An attempt is made to understand Tisza's two-fluid model in terms of the MQWs, and we rise the conjecture that they play an important role in the motion of second. We present also a qualitative prediction concerning to the behavior of the 'phononroton' peak below 1.0K, and propose two experiments to look for MQWs [pt
Classical behaviour of macroscopic bodies and quantum measurements
International Nuclear Information System (INIS)
Ghirardi, G.; Rimini, A.; Weber, T.
1986-01-01
This report describes a recent attempt of giving a consistent and unified description of microscopic and macroscopic phenomena. The model presented in this paper exhibits the nice features of leaving unaltered the quantum description of microsystems and of accounting for the classical behaviour of the macroscopic objects when their dynamical evolution is consistently deduced from the dynamics of their elementary constituents
Macroscopic quantum mechanics: theory and experimental concepts of optomechanics
International Nuclear Information System (INIS)
Chen Yanbei
2013-01-01
Rapid experimental progress has recently allowed the use of light to prepare macroscopic mechanical objects into nearly pure quantum states. This research field of quantum optomechanics opens new doors towards testing quantum mechanics, and possibly other laws of physics, in new regimes. In the first part of this article, I will review a set of techniques of quantum measurement theory that are often used to analyse quantum optomechanical systems. Some of these techniques were originally designed to analyse how a classical driving force passes through a quantum system, and can eventually be detected with an optimal signal-to-noise ratio—while others focus more on the quantum-state evolution of a mechanical object under continuous monitoring. In the second part of this article, I will review a set of experimental concepts that will demonstrate quantum mechanical behaviour of macroscopic objects—quantum entanglement, quantum teleportation and the quantum Zeno effect. Taking the interplay between gravity and quantum mechanics as an example, I will review a set of speculations on how quantum mechanics can be modified for macroscopic objects, and how these speculations—and their generalizations—might be tested by optomechanics. (invited review)
Thermal activation and macroscopic quantum tunneling in a DC SQUID
International Nuclear Information System (INIS)
Sharifi, F.; Gavilano, J.L.; VanHarlingen, D.J.
1989-01-01
The authors report measurements of the transition rate from metastable minima in the two-dimensional 1 of a dc SQUID as a function of applied flux temperature. The authors observe a crossover from energy-activated escape to macroscopic quantum tunneling at a critical temperature. The macroscopic quantum tunneling rate is substantially reduced by damping, and also broadens the crossover region. Most interestingly, the authors observe thermal rates that are suppressed from those predicted by the two-dimensional thermal activation model. The authors discuss possible explanations for this based on the interaction of the macroscopic degree of freedom in the device and energy level effects
International Nuclear Information System (INIS)
Daoud, M.; Ahl Laamara, R.
2012-01-01
We give the explicit expressions of the pairwise quantum correlations present in superpositions of multipartite coherent states. A special attention is devoted to the evaluation of the geometric quantum discord. The dynamics of quantum correlations under a dephasing channel is analyzed. A comparison of geometric measure of quantum discord with that of concurrence shows that quantum discord in multipartite coherent states is more resilient to dissipative environments than is quantum entanglement. To illustrate our results, we consider some special superpositions of Weyl–Heisenberg, SU(2) and SU(1,1) coherent states which interpolate between Werner and Greenberger–Horne–Zeilinger states. -- Highlights: ► Pairwise quantum correlations multipartite coherent states. ► Explicit expression of geometric quantum discord. ► Entanglement sudden death and quantum discord robustness. ► Generalized coherent states interpolating between Werner and Greenberger–Horne–Zeilinger states
Energy Technology Data Exchange (ETDEWEB)
Daoud, M., E-mail: m_daoud@hotmail.com [Department of Physics, Faculty of Sciences, University Ibnou Zohr, Agadir (Morocco); Ahl Laamara, R., E-mail: ahllaamara@gmail.com [LPHE-Modeling and Simulation, Faculty of Sciences, University Mohammed V, Rabat (Morocco); Centre of Physics and Mathematics, CPM, CNESTEN, Rabat (Morocco)
2012-07-16
We give the explicit expressions of the pairwise quantum correlations present in superpositions of multipartite coherent states. A special attention is devoted to the evaluation of the geometric quantum discord. The dynamics of quantum correlations under a dephasing channel is analyzed. A comparison of geometric measure of quantum discord with that of concurrence shows that quantum discord in multipartite coherent states is more resilient to dissipative environments than is quantum entanglement. To illustrate our results, we consider some special superpositions of Weyl–Heisenberg, SU(2) and SU(1,1) coherent states which interpolate between Werner and Greenberger–Horne–Zeilinger states. -- Highlights: ► Pairwise quantum correlations multipartite coherent states. ► Explicit expression of geometric quantum discord. ► Entanglement sudden death and quantum discord robustness. ► Generalized coherent states interpolating between Werner and Greenberger–Horne–Zeilinger states.
Kobayashi, Tsunehiro
1996-01-01
Quantum macroscopic motions are investigated in the scheme consisting of N-number of harmonic oscillators in terms of ultra-power representations of nonstandard analysis. Decoherence is derived from the large internal degrees of freedom of macroscopic matters.
Macroscopic quantum phenomena from the large N perspective
International Nuclear Information System (INIS)
Chou, C H; Hu, B L; Subasi, Y
2011-01-01
Macroscopic quantum phenomena (MQP) is a relatively new research venue, with exciting ongoing experiments and bright prospects, yet with surprisingly little theoretical activity. What makes MQP intellectually stimulating is because it is counterpoised against the traditional view that macroscopic means classical. This simplistic and hitherto rarely challenged view need be scrutinized anew, perhaps with much of the conventional wisdoms repealed. In this series of papers we report on a systematic investigation into some key foundational issues of MQP, with the hope of constructing a viable theoretical framework for this new endeavour. The three major themes discussed in these three essays are the large N expansion, the correlation hierarchy and quantum entanglement for systems of 'large' sizes, with many components or degrees of freedom. In this paper we use different theories in a variety of contexts to examine the conditions or criteria whereby a macroscopic quantum system may take on classical attributes, and, more interestingly, that it keeps some of its quantum features. The theories we consider here are, the O(N) quantum mechanical model, semiclassical stochastic gravity and gauge / string theories; the contexts include that of a 'quantum roll' in inflationary cosmology, entropy generation in quantum Vlasov equation for plasmas, the leading order and next-to-leading order large N behaviour, and hydrodynamic / thermodynamic limits. The criteria for classicality in our consideration include the use of uncertainty relations, the correlation between classical canonical variables, randomization of quantum phase, environment-induced decoherence, decoherent history of hydrodynamic variables, etc. All this exercise is to ask only one simple question: Is it really so surprising that quantum features can appear in macroscopic objects? By examining different representative systems where detailed theoretical analysis has been carried out, we find that there is no a priori
Macroscopic quantum systems and gravitational phenomena
International Nuclear Information System (INIS)
Pikovski, I.
2014-01-01
Low-energy quantum systems are studied theoretically in light of possible experiments to test the interplay between quantum theory and general relativity. The research focus in this thesis is on quantum systems which can be controlled with very high precision and which allow for tests of quantum theory at novel scales in terms of mass and size. The pulsed regime of opto-mechanics is explored and it is shown how short optical pulses can be used to prepare and characterize quantum states of a massive mechanical resonator, and how some phenomenological models of quantum gravity can be probed. In addition, quantum interferometry with photons and matter-waves in the presence of gravitational time dilation is considered. It is shown that time dilation causes entanglement between internal states and the center-of-mass position and that it leads to decoherence of all composite quantum systems. The results of the thesis show that the interplay between quantum theory and general relativity affects even low-energy quantum systems and that it offers novel phenomena which can be probed in experiments. (author) [de
Macroscopic realism and quantum measurement: measurers as a natural kind
International Nuclear Information System (INIS)
Jaeger, Gregg
2014-01-01
The notion of macroscopic realism has been used in attempts to achieve consistency between physics and everyday experience and to locate some boundary between the realms of classical mechanics and quantum meachanics. Its ostensibly underlying conceptual components, realism and macroscopicity, have most often appeared in the foundations of physics in relation to quantum measurement: reality became a prominent topic of discussion in quantum physics after the notion of element of reality was defined and used by Einstein, Podolsky and Rosen in that context, and macroscopicity is often explicitly assumed to be an essential property of any measuring apparatus. However, macroscopicity turns out to be a rather vaguer and less consistently understood notion than typically assumed by physicists who have not explicitly explored the notion themselves. For this reason, it behooves those investigating the foundations of quantum mechanics from a realist perspective to look for alternative notions for grounding quantum measurement. Here, the merits of treating the measuring instrument as a ‘natural kind’ as a means of avoiding anthropocentrism in the foundations of quantum measurement are pointed out as a means of advancing quantum measurement theory. (paper)
The superposition of the states and the logic approach to quantum mechanics
International Nuclear Information System (INIS)
Zecca, A.
1981-01-01
An axiomatic approach to quantum mechanics is proposed in terms of a 'logic' scheme satisfying a suitable set of axioms. In this context the notion of pure, maximal, and characteristic state as well as the superposition relation and the superposition principle for the states are studied. The role the superposition relation plays in the reversible and in the irreversible dynamics is investigated and its connection with the tensor product is studied. Throughout the paper, the W*-algebra model, is used to exemplify results and properties of the general scheme. (author)
Macroscopic quantum effects in nonlinear optical patterns
International Nuclear Information System (INIS)
Gatti, A.; Lugiato, L.A.; Oppo, G.L.; Barnett, S.M.; Marzoli, I.
1998-01-01
We display the results of the numerical simulations of a set of Langevin equations, which describe the dynamics of a degenerate optical parametric oscillator in the Wigner representation. The scan of the threshold region shows the gradual transformation of a quantum image into a classical roll pattern. Thus the quantum image behaves as a precursor of the roll pattern which appear above threshold. In the fax field, suitable spatial correlation functions of intensity and field quadratures show unambiguously the quantum nature of fluctuations that generate the image, leading to effects of quantum noise reduction below the shot noise level and to the formulation of an EPR paradox. (author)
Towards quantum superposition of a levitated nanodiamond with a NV center
Li, Tongcang
2015-05-01
Creating large Schrödinger's cat states with massive objects is one of the most challenging goals in quantum mechanics. We have previously achieved an important step of this goal by cooling the center-of-mass motion of a levitated microsphere from room temperature to millikelvin temperatures with feedback cooling. To generate spatial quantum superposition states with an optical cavity, however, requires a very strong quadratic coupling that is difficult to achieve. We proposed to optically trap a nanodiamond with a nitrogen-vacancy (NV) center in vacuum, and generate large spatial superposition states using the NV spin-optomechanical coupling in a strong magnetic gradient field. The large spatial superposition states can be used to study objective collapse theories of quantum mechanics. We have optically trapped nanodiamonds in air and are working towards this goal.
Quantum fluctuations in mesoscopic and macroscopic systems
International Nuclear Information System (INIS)
Cerdeira, H.A.; Guinea Lopez, F.; Weiss, U.
1991-01-01
The conference presentations have been grouped in three chapters; Quantum Transport (4 papers), Dissipation in Discrete Systems (7 papers) and Mesoscopic Junction, Rings and Arrays (6 papers). A separate abstract was prepared for each paper. Refs and figs
Proposed test of macroscopic quantum contextuality
International Nuclear Information System (INIS)
Cabello, Adan
2010-01-01
We show that, for any system with a number of levels which can be identified with n qubits, there is an inequality for the correlations between three compatible dichotomic measurements which must be satisfied by any noncontextual theory, but is violated by any quantum state. Remarkably, the violation grows exponentially with n, and the tolerated error per correlation also increases with n, showing that state-independent quantum contextuality is experimentally observable in complex systems.
The origins of macroscopic quantum coherence in high temperature superconductivity
International Nuclear Information System (INIS)
Turner, Philip; Nottale, Laurent
2015-01-01
Highlights: • We propose a new theoretical approach to superconductivity in p-type cuprates. • Electron pairing mechanisms in the superconducting and pseudogap phases are proposed. • A scale free network of dopants is key to macroscopic quantum coherence. - Abstract: A new, theoretical approach to macroscopic quantum coherence and superconductivity in the p-type (hole doped) cuprates is proposed. The theory includes mechanisms to account for e-pair coupling in the superconducting and pseudogap phases and their inter relations observed in these materials. Electron pair coupling in the superconducting phase is facilitated by local quantum potentials created by static dopants in a mechanism which explains experimentally observed optimal doping levels and the associated peak in critical temperature. By contrast, evidence suggests that electrons contributing to the pseudogap are predominantly coupled by fractal spin waves (fractons) induced by the fractal arrangement of dopants. On another level, the theory offers new insights into the emergence of a macroscopic quantum potential generated by a fractal distribution of dopants. This, in turn, leads to the emergence of coherent, macroscopic spin waves and a second associated macroscopic quantum potential, possibly supported by charge order. These quantum potentials play two key roles. The first involves the transition of an expected diffusive process (normally associated with Anderson localization) in fractal networks, into e-pair coherence. The second involves the facilitation of tunnelling between localized e-pairs. These combined effects lead to the merger of the super conducting and pseudo gap phases into a single coherent condensate at optimal doping. The underlying theory relating to the diffusion to quantum transition is supported by Coherent Random Lasing, which can be explained using an analogous approach. As a final step, an experimental program is outlined to validate the theory and suggests a new
Guérin, Philippe Allard; Feix, Adrien; Araújo, Mateus; Brukner, Časlav
2016-09-01
In communication complexity, a number of distant parties have the task of calculating a distributed function of their inputs, while minimizing the amount of communication between them. It is known that with quantum resources, such as entanglement and quantum channels, one can obtain significant reductions in the communication complexity of some tasks. In this work, we study the role of the quantum superposition of the direction of communication as a resource for communication complexity. We present a tripartite communication task for which such a superposition allows for an exponential saving in communication, compared to one-way quantum (or classical) communication; the advantage also holds when we allow for protocols with bounded error probability.
Quantum-limited heat conduction over macroscopic distances
Partanen, Matti; Tan, Kuan Yen; Govenius, Joonas; Lake, Russell E.; Mäkelä, Miika K.; Tanttu, Tuomo; Möttönen, Mikko
2016-05-01
The emerging quantum technological apparatuses, such as the quantum computer, call for extreme performance in thermal engineering. Cold distant heat sinks are needed for the quantized electric degrees of freedom owing to the increasing packaging density and heat dissipation. Importantly, quantum mechanics sets a fundamental upper limit for the flow of information and heat, which is quantified by the quantum of thermal conductance. However, the short distance between the heat-exchanging bodies in the previous experiments hinders their applicability in quantum technology. Here, we present experimental observations of quantum-limited heat conduction over macroscopic distances extending to a metre. We achieved this improvement of four orders of magnitude in the distance by utilizing microwave photons travelling in superconducting transmission lines. Thus, it seems that quantum-limited heat conduction has no fundamental distance cutoff. This work establishes the integration of normal-metal components into the framework of circuit quantum electrodynamics, which provides a basis for the superconducting quantum computer. Especially, our results facilitate remote cooling of nanoelectronic devices using faraway in situ-tunable heat sinks. Furthermore, quantum-limited heat conduction is important in contemporary thermodynamics. Here, the long distance may lead to ultimately efficient mesoscopic heat engines with promising practical applications.
Quantum tele-amplification with a continuous-variable superposition state
DEFF Research Database (Denmark)
Neergaard-Nielsen, Jonas S.; Eto, Yujiro; Lee, Chang-Woo
2013-01-01
-enhanced functions such as coherent-state quantum computing (CSQC), quantum metrology and a quantum repeater could be realized in the networks. Optical cat states are now routinely generated in laboratories. An important next challenge is to use them for implementing the aforementioned functions. Here, we......Optical coherent states are classical light fields with high purity, and are essential carriers of information in optical networks. If these states could be controlled in the quantum regime, allowing for their quantum superposition (referred to as a Schrödinger-cat state), then novel quantum...... demonstrate a basic CSQC protocol, where a cat state is used as an entanglement resource for teleporting a coherent state with an amplitude gain. We also show how this can be extended to a loss-tolerant quantum relay of multi-ary phase-shift keyed coherent states. These protocols could be useful in both...
International Nuclear Information System (INIS)
Martini, F. de; Giuseppe, G. di
2001-01-01
A multiparticle quantum superposition state has been generated by a novel phase-selective parametric amplifier of an entangled two-photon state. This realization is expected to open a new field of investigations on the persistence of the validity of the standard quantum theory for systems of increasing complexity, in a quasi decoherence-free environment. Because of its nonlocal structure the new system is expected to play a relevant role in the modern endeavor on quantum information and in the basic physics of entanglement. (orig.)
Macroscopic quantum electrodynamics of high-Q cavities
International Nuclear Information System (INIS)
Khanbekyan, Mikayel
2009-01-01
In this thesis macroscopic quantum electrodynamics in linear media was applied in order to develop an universally valid quantum theory for the description of the interaction of the electromagnetic field with atomic sources in high-Q cavities. In this theory a complete description of the characteristics of the emitted radiation is given. The theory allows to show the limits of the applicability of the usually applied theory. In order to establish an as possible generally valid theory first the atom-field interaction was studied in the framework of macroscopic quantum electrodynamics in dispersive and absorptive media. In order to describe the electromagnetic field from Maxwell's equations was started, whereby the noise-current densities, which are connected with the absorption of the medium, were included. The solution of these equations expresses the electromagnetic field variables by the noise-current densities by means of Green's tensor of the macroscopic Maxwell equations. The explicit quantization is performed by means of the noise-current densities, whereby a diagonal Hamiltonian is introduced, which then guarantees the time development according to Maxwell's equation and the fulfillment of the fundamental simultaneous commutation relations of the field variables. In the case of the interaction of the medium-supported field with atoms the Hamiltonian must be extended by atom-field interactions energies, whereby the canonical coupling schemes of the minimal or multipolar coupling can be used. The dieelectric properties of the material bodies as well as their shape are coded in the Green tensor of the macroscopic Maxwell equations. As preparing step first the Green tensor was specified in order to derive three-dimensional input-output relations for the electromagnetic field operators on a plane multilayer structure. Such a general dewscription of the electromagnetic field allows the inclusion both of dispersion and absorption of the media and the possible
Wu, Kaifeng; Lim, Jaehoon; Klimov, Victor I
2017-08-22
Application of colloidal semiconductor quantum dots (QDs) in optical and optoelectronic devices is often complicated by unintentional generation of extra charges, which opens fast nonradiative Auger recombination pathways whereby the recombination energy of an exciton is quickly transferred to the extra carrier(s) and ultimately dissipated as heat. Previous studies of Auger recombination have primarily focused on neutral and, more recently, negatively charged multicarrier states. Auger dynamics of positively charged species remains more poorly explored due to difficulties in creating, stabilizing, and detecting excess holes in the QDs. Here we apply photochemical doping to prepare both negatively and positively charged CdSe/CdS QDs with two distinct core/shell interfacial profiles ("sharp" versus "smooth"). Using neutral and charged QD samples we evaluate Auger lifetimes of biexcitons, negative and positive trions (an exciton with an extra electron or a hole, respectively), and multiply negatively charged excitons. Using these measurements, we demonstrate that Auger decay of both neutral and charged multicarrier states can be presented as a superposition of independent elementary three-particle Auger events. As one of the manifestations of the superposition principle, we observe that the biexciton Auger decay rate can be presented as a sum of the Auger rates for independent negative and positive trion pathways. By comparing the measurements on the QDs with the "sharp" versus "smooth" interfaces, we also find that while affecting the absolute values of Auger lifetimes, manipulation of the shape of the confinement potential does not lead to violation of the superposition principle, which still allows us to accurately predict the biexciton Auger lifetimes based on the measured negative and positive trion dynamics. These findings indicate considerable robustness of the superposition principle as applied to Auger decay of charged and neutral multicarrier states
Quantum mechanics versus macroscopic realism: Is the flux there when nobody looks
International Nuclear Information System (INIS)
Leggett, A.J.; Garg, A.
1985-01-01
It is shown that, in the contect of an idealized ''macroscopic quantum coherence'' experiment, the prediction of quantum mechanics are incompattible with the conjunction of two general assimptions which are designated ''macroscopic realism'' and ''noninvasive measurability at the macroscopiclevel.'' The conditions under which quantum mechanics can be tested against these assumptions in a realistic experiment are discussed
Chang, Li-Na; Luo, Shun-Long; Sun, Yuan
2017-11-01
The principle of superposition is universal and lies at the heart of quantum theory. Although ever since the inception of quantum mechanics a century ago, superposition has occupied a central and pivotal place, rigorous and systematic studies of the quantification issue have attracted significant interests only in recent years, and many related problems remain to be investigated. In this work we introduce a figure of merit which quantifies superposition from an intuitive and direct perspective, investigate its fundamental properties, connect it to some coherence measures, illustrate it through several examples, and apply it to analyze wave-particle duality. Supported by Science Challenge Project under Grant No. TZ2016002, Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing, Key Laboratory of Random Complex Structures and Data Science, Chinese Academy of Sciences, Grant under No. 2008DP173182
Yin, H-L; Cao, W-F; Fu, Y; Tang, Y-L; Liu, Y; Chen, T-Y; Chen, Z-B
2014-09-15
Measurement-device-independent quantum key distribution (MDI-QKD) with decoy-state method is believed to be securely applied to defeat various hacking attacks in practical quantum key distribution systems. Recently, the coherent-state superpositions (CSS) have emerged as an alternative to single-photon qubits for quantum information processing and metrology. Here, in this Letter, CSS are exploited as the source in MDI-QKD. We present an analytical method that gives two tight formulas to estimate the lower bound of yield and the upper bound of bit error rate. We exploit the standard statistical analysis and Chernoff bound to perform the parameter estimation. Chernoff bound can provide good bounds in the long-distance MDI-QKD. Our results show that with CSS, both the security transmission distance and secure key rate are significantly improved compared with those of the weak coherent states in the finite-data case.
The universe as an ultimate macroscopic quantum phenomenon?
International Nuclear Information System (INIS)
Hu, Bei-Lok
2005-01-01
Full text: We explore two unconventional proposals on the meaning of quantum gravity and the quantum properties of spacetime. The first is an older proposal of mine that general relativity is the hydrodynamic limit of some fundamental theories of the microscopic structure of spacetime and matter, a more specific derivative of the idea of Sakharov. The latter is a more recent thought of mine on the possibility that spacetime is a condensate (Bose or Fermi). These proposals have implications radically different from the conventional views. For the former, spacetime described by a differentiable manifold is regarded as an emergent entity and the metric or connection forms are collective variables valid only at the low energy, long wavelength limit of the micro-theories of spacetime and matter. This view would render irrelevant the traditional efforts to find ways to quantize general relativity, because it would only give us the equivalent of phonon physics, not a theory of electrons or photons, QED. In the second proposal, even without the knowledge of what the 'atom of spacetime' is, the mere thought that spacetime at all energies below the Planck scale, including today's, is quantum rather than classical, has many challenging consequences. We discuss the implications of this view pertaining to issues in gravitation and cosmology, as well as to macroscopic quantum coherence phenomena. (author)
International Nuclear Information System (INIS)
Streltsov, Alexej I.; Alon, Ofir E.; Cederbaum, Lorenz S.
2009-01-01
Scattering in one dimension of an attractive ultracold bosonic cloud from a barrier can lead to the formation of two nonoverlapping clouds. Once formed, the clouds travel with constant velocity, in general different in magnitude from that of the incoming cloud, and do not disperse. The phenomenon and its mechanism - transformation of kinetic energy to internal energy of the scattered cloud - are obtained by solving the time-dependent many-boson Schroedinger equation. The analysis of the wave function shows that the object formed corresponds to a quantum superposition state of two distinct wave packets traveling through real space.
Quantum Experiments and Graphs: Multiparty States as Coherent Superpositions of Perfect Matchings
Krenn, Mario; Gu, Xuemei; Zeilinger, Anton
2017-12-01
We show a surprising link between experimental setups to realize high-dimensional multipartite quantum states and graph theory. In these setups, the paths of photons are identified such that the photon-source information is never created. We find that each of these setups corresponds to an undirected graph, and every undirected graph corresponds to an experimental setup. Every term in the emerging quantum superposition corresponds to a perfect matching in the graph. Calculating the final quantum state is in the #P-complete complexity class, thus it cannot be done efficiently. To strengthen the link further, theorems from graph theory—such as Hall's marriage problem—are rephrased in the language of pair creation in quantum experiments. We show explicitly how this link allows one to answer questions about quantum experiments (such as which classes of entangled states can be created) with graph theoretical methods, and how to potentially simulate properties of graphs and networks with quantum experiments (such as critical exponents and phase transitions).
Quantum Experiments and Graphs: Multiparty States as Coherent Superpositions of Perfect Matchings.
Krenn, Mario; Gu, Xuemei; Zeilinger, Anton
2017-12-15
We show a surprising link between experimental setups to realize high-dimensional multipartite quantum states and graph theory. In these setups, the paths of photons are identified such that the photon-source information is never created. We find that each of these setups corresponds to an undirected graph, and every undirected graph corresponds to an experimental setup. Every term in the emerging quantum superposition corresponds to a perfect matching in the graph. Calculating the final quantum state is in the #P-complete complexity class, thus it cannot be done efficiently. To strengthen the link further, theorems from graph theory-such as Hall's marriage problem-are rephrased in the language of pair creation in quantum experiments. We show explicitly how this link allows one to answer questions about quantum experiments (such as which classes of entangled states can be created) with graph theoretical methods, and how to potentially simulate properties of graphs and networks with quantum experiments (such as critical exponents and phase transitions).
On quantum effects in the dynamics of macroscopic test masses
International Nuclear Information System (INIS)
Mueller-Ebhardt, Helge
2009-01-01
This thesis provides theoretically a link between the increase of the sensitivity of gravitational-wave detectors and the possibility of preparing macroscopic quantum states in such detectors. In the first part of this thesis, we theoretically explore the quantum measurement noise of an optical speed meter topology, the Sagnac interferometer, equipped with an additional detuned cavity at the output port. This detuned signal-recycling technique was already investigated when applying it to a Michelson interferometer and is used in the gravitational-wave detector GEO600. Together with the quantum noise analysis of the simple Sagnac interferometer, it is the basis of our study: we optimize the Sagnac interferometer's sensitivity towards the detection of a certain gravitational-wave source in the vicinity of a realistic classical noise environment. Motivated by the fact that the Michelson interferometer, as a position meter, with detuned signal-recycling can transduce the gravitational-wave strain into real mirror motion, we compare the transducer effect in a speed and in a position meter. Furthermore, we theoretically investigate the conditional output squeezing of a cavity which is detuned with respect to its carrier and its subcarrier. Therewith we pursue the theoretical analysis of the ponderomotive squeezer. With the knowledge gained in the first part about the quantum measurement process in laser interferometers, the second part of this thesis comprises a theoretical analysis of the conditonal state in positon and momentum of the interferometer's test masses. We motivate not to obtain the conditional states from a stochastic master equation but with the help of the so-called Wiener filtering method. Using this method, we calculate the most general expression for the conditional covariance matrix of the Gaussian state of a test mass under any linear Markovian measurement process. Then we specify to the interferometry and theoretically show under which circumstances
Macroscopic quantum electrodynamics of high-Q cavities
Energy Technology Data Exchange (ETDEWEB)
Khanbekyan, Mikayel
2009-10-27
In this thesis macroscopic quantum electrodynamics in linear media was applied in order to develop an universally valid quantum theory for the description of the interaction of the electromagnetic field with atomic sources in high-Q cavities. In this theory a complete description of the characteristics of the emitted radiation is given. The theory allows to show the limits of the applicability of the usually applied theory. In order to establish an as possible generally valid theory first the atom-field interaction was studied in the framework of macroscopic quantum electrodynamics in dispersive and absorptive media. In order to describe the electromagnetic field from Maxwell's equations was started, whereby the noise-current densities, which are connected with the absorption of the medium, were included. The solution of these equations expresses the electromagnetic field variables by the noise-current densities by means of Green's tensor of the macroscopic Maxwell equations. The explicit quantization is performed by means of the noise-current densities, whereby a diagonal Hamiltonian is introduced, which then guarantees the time development according to Maxwell's equation and the fulfillment of the fundamental simultaneous commutation relations of the field variables. In the case of the interaction of the medium-supported field with atoms the Hamiltonian must be extended by atom-field interactions energies, whereby the canonical coupling schemes of the minimal or multipolar coupling can be used. The dieelectric properties of the material bodies as well as their shape are coded in the Green tensor of the macroscopic Maxwell equations. As preparing step first the Green tensor was specified in order to derive three-dimensional input-output relations for the electromagnetic field operators on a plane multilayer structure. Such a general dewscription of the electromagnetic field allows the inclusion both of dispersion and absorption of the media and the
Gravitational wave echoes from macroscopic quantum gravity effects
Energy Technology Data Exchange (ETDEWEB)
Barceló, Carlos [Instituto de Astrofísica de Andalucía (IAA-CSIC),Glorieta de la Astronomía, 18008 Granada (Spain); Carballo-Rubio, Raúl [The Cosmology & Gravity Group and the Laboratory for Quantum Gravity & Strings,Department of Mathematics & Applied Mathematics, University of Cape Town,Private Bag, Rondebosch 7701 (South Africa); Garay, Luis J. [Departamento de Física Teórica II,Universidad Complutense de Madrid, 28040 Madrid (Spain); Instituto de Estructura de la Materia (IEM-CSIC),Serrano 121, 28006 Madrid (Spain)
2017-05-10
New theoretical approaches developed in the last years predict that macroscopic quantum gravity effects in black holes should lead to modifications of the gravitational wave signals expected in the framework of classical general relativity, with these modifications being characterized in certain scenarios by the existence of dampened repetitions of the primary signal. Here we use the fact that non-perturbative corrections to the near-horizon external geometry of black holes are necessary for these modifications to exist, in order to classify different proposals and paradigms with respect to this criterion and study in a neat and systematic way their phenomenology. Proposals that lead naturally to the existence of echoes in the late-time ringdown of gravitational wave signals from black hole mergers must share the replacement of black holes by horizonless configurations with a physical surface showing reflective properties in the relevant range of frequencies. On the other hand, proposals or paradigms that restrict quantum gravity effects on the external geometry to be perturbative, such as black hole complementarity or the closely related firewall proposal, do not display echoes. For the sake of completeness we exploit the interplay between the timescales associated with the formation of firewalls and the mechanism behind the existence of echoes in order to conclude that even unconventional distortions of the firewall concept (such as naked firewalls) do not lead to this phenomenon.
Energy Technology Data Exchange (ETDEWEB)
Lee, Su-Yong; Kim, Ho-Joon [Department of Physics, Texas A and M University at Qatar, P.O. Box 23874, Doha (Qatar); Ji, Se-Wan [School of Computational Sciences, Korea Institute for Advanced Study, Seoul 130-012 (Korea, Republic of); Nha, Hyunchul [Department of Physics, Texas A and M University at Qatar, P.O. Box 23874, Doha (Qatar); Institute fuer Quantenphysik, Universitaet Ulm, D-89069 Ulm (Germany)
2011-07-15
We investigate how the entanglement properties of a two-mode state can be improved by performing a coherent superposition operation ta+ra{sup {dagger}} of photon subtraction and addition, proposed by Lee and Nha [Phys. Rev. A 82, 053812 (2010)], on each mode. We show that the degree of entanglement, the Einstein-Podolsky-Rosen-type correlation, and the performance of quantum teleportation can be all enhanced for the output state when the coherent operation is applied to a two-mode squeezed state. The effects of the coherent operation are more prominent than those of the mere photon subtraction a and the addition a{sup {dagger}} particularly in the small-squeezing regime, whereas the optimal operation becomes the photon subtraction (case of r=0) in the large-squeezing regime.
Testing quantum mechanics against macroscopic realism using the output of χ(2) nonlinearity
International Nuclear Information System (INIS)
Podoshvedov, Sergey A.; Kim, Jaewan
2006-01-01
We suggest an all-optical scheme to generate entangled superposition of a single photon with macroscopic entangled states for testing macroscopic realism. The scheme consists of source of single photons, a Mach-Zehnder interferometer in routes of which a system of coupled-down converters with type-I phase matching is inserted, and a beam splitter for the other auxiliary modes of the scheme. We use quantization of the pumping modes, depletion of the coherent states passing through the system, and interference effect in the pumping modes in the process of erasing which-path information of the single-photon on exit from the Mach-Zehnder interferometer. We show the macroscopic fields of the output superposition are distinguishable states. This scheme generates macroscopic entangled state that violates Bell's inequality. Moreover, the detailed analysis concerning change of amplitudes of entangled superposition by means of repeating this process many times is accomplished. We show our scheme works without photon number resolving detection and it is robust to detector inefficiency
International Nuclear Information System (INIS)
Schlegel, R.
1975-01-01
With the interaction interpretation, the Lorentz transformation of a system arises with selection from a superposition of its states in an observation-interaction. Integration of momentum states of a mass over all possible velocities gives the rest-mass energy. Static electrical and magnetic fields are not found to form such a superposition and are to be taken as irreducible elements. The external superposition consists of those states that are reached only by change of state of motion, whereas the internal superposition contains all the states available to an observer in a single inertial coordinate system. The conjecture is advanced that states of superposition may only be those related by space-time transformations (Lorentz transformations plus space inversion and charge conjugation). The continuum of external and internal superpositions is examined for various masses, and an argument for the unity of the superpositions is presented
Generation of a superposition of odd photon number states for quantum information networks
DEFF Research Database (Denmark)
Neergaard-Nielsen, Jonas Schou; Nielsen, B.; Hettich, C.
2006-01-01
Quantum information networks, quantum memories, quantum repeaters, linear optics quantum computers Udgivelsesdato: 25 August......Quantum information networks, quantum memories, quantum repeaters, linear optics quantum computers Udgivelsesdato: 25 August...
Observation of squeezed light and quantum description of the macroscopical body movement
International Nuclear Information System (INIS)
Bykov, V.P.
1992-01-01
The possibility of a nondemolition measurement (observation) of macroscopical objects in widely distributed quantum mechanical states arises from the fact of the squezzed light observation. Macroscopical bodies -bodies of classical mechanics - are usually in states with narrow wave packets. It is shown that the absence of macroscopical bodies in widely distributed states is due to the focusing influence of the body's gravity field on its wave packet. An evidence that the gravity is essential in the classic limit of quantum mechanics is given. (author). 14 refs, 7 figs
Quantum teleportation from light beams to vibrational states of a macroscopic diamond
Hou, P.-Y.; Huang, Y.-Y.; Yuan, X.-X.; Chang, X.-Y.; Zu, C.; He, L.; Duan, L.-M.
2016-01-01
With the recent development of optomechanics, the vibration in solids, involving collective motion of trillions of atoms, gradually enters into the realm of quantum control. Here, building on the recent remarkable progress in optical control of motional states of diamonds, we report an experimental demonstration of quantum teleportation from light beams to vibrational states of a macroscopic diamond under ambient conditions. Through quantum process tomography, we demonstrate average teleportation fidelity (90.6±1.0)%, clearly exceeding the classical limit of 2/3. The experiment pushes the target of quantum teleportation to the biggest object so far, with interesting implications for optomechanical quantum control and quantum information science. PMID:27240553
Macroscopic Quantum States and Quantum Phase Transition in the Dicke Model
International Nuclear Information System (INIS)
Lian Jin-Ling; Zhang Yuan-Wei; Liang Jiu-Qing
2012-01-01
The energy spectrum of Dicke Hamiltonians with and without the rotating wave approximation for an arbitrary atom number is obtained analytically by means of the variational method, in which the effective pseudo-spin Hamiltonian resulting from the expectation value in the boson-field coherent state is diagonalized by the spin-coherent-state transformation. In addition to the ground-state energy, an excited macroscopic quantum-state is found corresponding to the south- and north-pole gauges of the spin-coherent states, respectively. Our results of ground-state energies in exact agreement with various approaches show that these models exhibit a zero-temperature quantum phase transition of the second order for any number of atoms, which was commonly considered as a phenomenon of the thermodynamic limit with the atom number tending to infinity. The critical behavior of the geometric phase is analyzed. (general)
Experimental observation of the quantum behavior of a macroscopic degree of freedom
International Nuclear Information System (INIS)
Devoret, M.H.; Martinis, J.M.; Esteve, D.
1986-08-01
At Berkeley a series of experiments have been performed, that demonstrates the quantum behavior of one macroscopic degree of freedom, namely the phase difference across a current biased Josephson junction. Here we will focus on the praticalities involved in such a demonstration. The emphasis is put on the particular procedures used to solve the two problems of noise shielding and parameter determination. To begin, a short description of the macroscopic system investigated, the current biased Josephson junction is given
Bell inequalities and experiments on quantum correlations for macroscopic distances
International Nuclear Information System (INIS)
Grib, A.A.
1984-01-01
Recently in different laboratories experiments checking the validity of Bell's inequalities were made. These inequalities give the answer to the qUestion which interpretation of quantum mechanics is correct: either Einstein's interpretation according to which properties of quantum system exist as elements of physical reality independently from their observation or Copenhagen's interpretation due to Bohr and Fock according to which quantUm properties described by noncommuting operators don't exist independently from measurement. Experiments are classified on three groups: Those with optical photons with γ-quanta and with nucleons. The experiments undoubtedly show that Bell's inequalities are not satisfied, so the Copenhagen's interpretation of quantum mehanics and the principle of relativity to the means of measurement of properties of the microsystem give the only non-contradicting-to-experiment description of quantum phenomena
Berube-Lauziere, Yves
The measurement-based quantum feedback scheme developed and implemented by Haroche and collaborators to actively prepare and stabilize specific photon number states in cavity quantum electrodynamics (CQED) is a milestone achievement in the active protection of quantum states from decoherence. This feat was achieved by injecting, after each weak dispersive measurement of the cavity state via Rydberg atoms serving as cavity sensors, a low average number classical field (coherent state) to steer the cavity towards the targeted number state. This talk will present the generalization of the theory developed for targeting number states in order to prepare and stabilize desired superpositions of two cavity photon number states. Results from realistic simulations taking into account decoherence and imperfections in a CQED set-up will be presented. These demonstrate the validity of the generalized theory and points to the experimental feasibility of preparing and stabilizing such superpositions. This is a further step towards the active protection of more complex quantum states than number states. This work, cast in the context of CQED, is also almost readily applicable to circuit QED. YBL acknowledges financial support from the Institut Quantique through a Canada First Research Excellence Fund.
Macroscopic influence on the spontaneous symmetry breaking in quantum field
International Nuclear Information System (INIS)
Kirzhnitz, D.A.
1977-01-01
Major results of investigations concerning macroscopic influence (heating, compression, external field and current) on elementary particle systems with spontaneous symmetry breaking are briefly reviewed. The study of this problem has been stimulated by recent progress in the unified renormalizable theory of elementary particles. Typically it appears that at some values of external parameters a phase transition with symmetry restoration takes place. There exists a profound and far going analogy with phase transition in many-body physics especially with superconductivity phenomenon. Some applications to cosmology are also considered
On Macroscopic Quantum Phenomena in Biomolecules and Cells: From Levinthal to Hopfield
Directory of Open Access Journals (Sweden)
Dejan Raković
2014-01-01
Full Text Available In the context of the macroscopic quantum phenomena of the second kind, we hereby seek for a solution-in-principle of the long standing problem of the polymer folding, which was considered by Levinthal as (semiclassically intractable. To illuminate it, we applied quantum-chemical and quantum decoherence approaches to conformational transitions. Our analyses imply the existence of novel macroscopic quantum biomolecular phenomena, with biomolecular chain folding in an open environment considered as a subtle interplay between energy and conformation eigenstates of this biomolecule, governed by quantum-chemical and quantum decoherence laws. On the other hand, within an open biological cell, a system of all identical (noninteracting and dynamically noncoupled biomolecular proteins might be considered as corresponding spatial quantum ensemble of these identical biomolecular processors, providing spatially distributed quantum solution to a single corresponding biomolecular chain folding, whose density of conformational states might be represented as Hopfield-like quantum-holographic associative neural network too (providing an equivalent global quantum-informational alternative to standard molecular-biology local biochemical approach in biomolecules and cells and higher hierarchical levels of organism, as well.
Macroscopic quantum phenomena in strongly correlated fermionic systems
International Nuclear Information System (INIS)
Rech, J.
2006-06-01
It took several years after the idea of a zero-temperature phase transition emerged to realize the impact of such a quantum critical point over a large region of the phase diagram. Observed in many experimental examples, this quantum critical regime is not yet understood in details theoretically, and one needs to develop new approaches. In the first part, we focused on the ferromagnetic quantum critical point. After constructing a controlled approach allowing us to describe the quantum critical regime, we show through the computation of the static spin susceptibility that the ferromagnetic quantum critical point is unstable, destroyed internally by an effective dynamic long-range interaction generated by the Landau damping. In the second part, we revisit the exactly screened single impurity Kondo model, using a bosonic representation of the local spin and treating it in the limit of large spin degeneracy N. We show that, in this regime, the ground-state is a non-trivial Fermi liquid, unlike what was advocated by previous similar studies. We then extend our method to encompass the physics of two coupled impurities, for which our results are qualitatively comparable to the ones obtained from various approaches carried out in the past. We also develop a Luttinger-Ward formalism, enabling us to cure some of the drawbacks of the original method used to describe the single impurity physics. Finally, we present the main ideas and the first results for an extension of the method towards the description of a Kondo lattice, relevant for the understanding of the quantum critical regime of heavy fermion materials. (authors)
Quantum description of microscopic and macroscopic systems: Old problems and recent investigations
International Nuclear Information System (INIS)
Ghirardi, G.C.
1986-04-01
We review some open problems and some proposed solutions which are encountered in the quantum description of the microscopic systems, of the macroscopic ones, and of the interactions between these two types of objects. We describe a recent attempt allowing a unified description of all phenomena, reproducing the quantum mechanical situation for microscopic systems and inducing in a completely consistent way the classical behaviour of macro object and the phenomena of wave packet reduction in the system-apparatus interaction. (author)
Macroscopic quantum coherence in a magnetic nanoparticle above the surface of a superconductor
Chudnovsky; Friedman
2000-12-11
We study macroscopic quantum tunneling of the magnetic moment in a single-domain particle placed above the surface of a superconductor. Such a setup allows one to manipulate the height of the energy barrier, preserving the degeneracy of the ground state. The tunneling amplitude and the effect of the dissipation in the superconductor are computed.
Macroscopic Quantum Coherence in a Magnetic Nanoparticle Above the Surface of a Superconductor
Energy Technology Data Exchange (ETDEWEB)
Chudnovsky, Eugene M.; Friedman, Jonathan R.
2000-12-11
We study macroscopic quantum tunneling of the magnetic moment in a single-domain particle placed above the surface of a superconductor. Such a setup allows one to manipulate the height of the energy barrier, preserving the degeneracy of the ground state. The tunneling amplitude and the effect of the dissipation in the superconductor are computed.
Macroscopic Quantum Coherence in a Magnetic Nanoparticle Above the Surface of a Superconductor
International Nuclear Information System (INIS)
Chudnovsky, Eugene M.; Friedman, Jonathan R.
2000-01-01
We study macroscopic quantum tunneling of the magnetic moment in a single-domain particle placed above the surface of a superconductor. Such a setup allows one to manipulate the height of the energy barrier, preserving the degeneracy of the ground state. The tunneling amplitude and the effect of the dissipation in the superconductor are computed
Macroscopic Quantum-Type Potentials in Theoretical Systems Biology
Directory of Open Access Journals (Sweden)
Laurent Nottale
2013-12-01
Full Text Available We review in this paper the use of the theory of scale relativity and fractal space-time as a tool particularly well adapted to the possible development of a future genuine systems theoretical biology. We emphasize in particular the concept of quantum-type potentials, since, in many situations, the effect of the fractality of space—or of the underlying medium—can be reduced to the addition of such a potential energy to the classical equations of motion. Various equivalent representations—geodesic, quantum-like, fluid mechanical, stochastic—of these equations are given, as well as several forms of generalized quantum potentials. Examples of their possible intervention in high critical temperature superconductivity and in turbulence are also described, since some biological processes may be similar in some aspects to these physical phenomena. These potential extra energy contributions could have emerged in biology from the very fractal nature of the medium, or from an evolutive advantage, since they involve spontaneous properties of self-organization, morphogenesis, structuration and multi-scale integration. Finally, some examples of applications of the theory to actual biological-like processes and functions are also provided.
Macroscopic objects in quantum mechanics: A combinatorial approach
International Nuclear Information System (INIS)
Pitowsky, Itamar
2004-01-01
Why do we not see large macroscopic objects in entangled states? There are two ways to approach this question. The first is dynamic. The coupling of a large object to its environment cause any entanglement to decrease considerably. The second approach, which is discussed in this paper, puts the stress on the difficulty of observing a large-scale entanglement. As the number of particles n grows we need an ever more precise knowledge of the state and an ever more carefully designed experiment, in order to recognize entanglement. To develop this point we consider a family of observables, called witnesses, which are designed to detect entanglement. A witness W distinguishes all the separable (unentangled) states from some entangled states. If we normalize the witness W to satisfy tr(Wρ)≤1 for all separable states ρ, then the efficiency of W depends on the size of its maximal eigenvalue in absolute value; that is, its operator norm parallel W parallel . It is known that there are witnesses on the space of n qubits for which parallel W parallel is exponential in n. However, we conjecture that for a large majority of n-qubit witnesses parallel W parallel ≤O(√(n log n)). Thus, in a nonideal measurement, which includes errors, the largest eigenvalue of a typical witness lies below the threshold of detection. We prove this conjecture for the family of extremal witnesses introduced by Werner and Wolf [Phys. Rev. A 64, 032112 (2001)
Evolution of Quantum Systems from Microscopic to Macroscopic Scales
International Nuclear Information System (INIS)
Ovchinnikov, Sergey Y.; Macek, Joseph H.; Sternberg, James S.; Lee, Teck-Ghee; Schultz, David R.
2009-01-01
Even though the static properties of quantum systems have been known since the early days of quantum mechanics, accurate simulation of the dynamical break-up or ionization remains a theoretical challenge despite our complete knowledge of the relevant interactions. Simulations are challenging because of highly oscillatory exponential phase factors in the electronic wave function and the infinitesimally small values of the continuum components of electronic probability density at large times after the collision. The approach we recently developed, the regularized time-dependent Schroedinger equation method, has addressed these difficulties by removing the diverging phase factors and transforming the time-dependent Schroedinger equation to an expanding space. The evolution of the electronic wave function was followed to internuclear distances of R = 100,000 a.u. or 5 microns, which is of the order of the diameter of a human hair. Our calculations also revealed unexpected presence of free vortices in the electronic wave function. The discovered vortices also bring new light on the mechanism of transferring of the angular momentum from an external to internal motion. The connection between the observable momentum distribution and the time-dependent wave function implies that vortices in the wave function at large times are imaged in the momentum distribution.
A dualism in entanglement and testing quantum identicity of macroscopic objects
International Nuclear Information System (INIS)
Bose, S.; Home, D.
2005-01-01
Full text: Identical quantum objects are known to behave very differently from their classical counterparts by exhibiting bosonic/fermionic statistics. We present another consequence of the impossibility of distinguishing identical quantum objects through their superselected innate attributes. If two quantum objects distinguished through a dynamical variable A are entangled in another dynamical variable B, then (under certain conditions) they are also entangled in variable A when distinguished from each other by variable B. This dualism is independent of and more general than quantum statistics. We formulate a general scheme to test this dualism through polarization entangled photons. The dualism enables one to use prior entanglement to avoid scattering while probing the identicity of two mutually interacting, even macroscopic objects. It thus opens the way for studying the quantum to classical transition of identicity. (author)
Quantum hologram of macroscopically entangled light via the mechanism of diffuse light storage
International Nuclear Information System (INIS)
Gerasimov, L V; Sokolov, I M; Kupriyanov, D V; Havey, M D
2012-01-01
In this paper, we consider a quantum memory scheme for light diffusely propagating through a spatially disordered atomic gas. A unique characteristic is enhanced trapping of the signal light pulse by quantum multiple scattering, which can be naturally integrated with the mechanism of stimulated Raman conversion into a long-lived spin coherence. Then, the quantum state of the light can be mapped onto the disordered atomic spin subsystem and can be stored in it for a relatively long time. The proposed memory scheme can be applicable for storage of the macroscopic analogue of the Ψ (−) Bell state and the prepared entangled atomic state performs its quantum hologram, which suggests the possibility of further quantum information processing. (paper)
Experimental study of macroscopic quantum tunnelling in Bi2212 intrinsic Josephson junctions
International Nuclear Information System (INIS)
Matsumoto, Tetsuro; Kashiwaya, Hiromi; Shibata, Hajime; Kashiwaya, Satoshi; Kawabata, Shiro; Eisaki, Hiroshi; Yoshida, Yoshiyuki; Tanaka, Yukio
2007-01-01
The quantum dynamics of Bi 2 Sr 2 CaCu 2 O 8+δ intrinsic Josephson junctions (IJJs) is studied based on escape rate measurements. The saturations observed in the escape temperature and in the width of the switching current below 0.5 K (= T * ) indicate the transition of the switching mechanism from thermal activation to macroscopic quantum tunnelling. It is shown that the switching properties are consistently explained in terms of the underdamped Josephson junction with a quality factor of 70 ± 20 in spite of possible damping due to the nodal quasiparticles of d-wave superconductivity. The present result gives the upper limit of the damping of IJJs
Quantum properties of a superposition of squeezed displaced two-mode vacuum and single-photon states
International Nuclear Information System (INIS)
El-Orany, Faisal A A; Obada, A-S F; M Asker, Zafer; Perina, J
2009-01-01
In this paper, we study some quantum properties of a superposition of displaced squeezed two-mode vacuum and single-photon states, such as the second-order correlation function, the Cauchy-Schwarz inequality, quadrature squeezing, quasiprobability distribution functions and purity. These type of states include two mechanisms, namely interference in phase space and entanglement. We show that these states can exhibit sub-Poissonian statistics, squeezing and deviate from the classical Cauchy-Schwarz inequality. Moreover, the amount of entanglement in the system can be increased by increasing the squeezing mechanism. In the framework of the quasiprobability distribution functions, we show that the single-mode state can tend to the thermal state based on the correlation mechanism. A generation scheme for such states is given.
Can We Advance Macroscopic Quantum Systems Outside the Framework of Complex Decoherence Theory?
Brezinski, Mark E; Rupnick, Maria
2016-01-01
Macroscopic quantum systems (MQS) are macroscopic systems driven by quantum rather than classical mechanics, a long studied area with minimal success till recently. Harnessing the benefits of quantum mechanics on a macroscopic level would revolutionize fields ranging from telecommunication to biology, the latter focused on here for reasons discussed. Contrary to misconceptions, there are no known physical laws that prevent the development of MQS. Instead, they are generally believed universally lost in complex systems from environmental entanglements (decoherence). But we argue success is achievable MQS with decoherence compensation developed, naturally or artificially, from top-down rather current reductionist approaches. This paper advances the MQS field by a complex systems approach to decoherence. First, why complex system decoherence approaches (top-down) are needed is discussed. Specifically, complex adaptive systems (CAS) are not amenable to reductionist models (and their master equations) because of emergent behaviour, approximation failures, not accounting for quantum compensatory mechanisms, ignoring path integrals, and the subentity problem. In addition, since MQS must exist within the context of the classical world, where rapid decoherence and prolonged coherence are both needed. Nature has already demonstrated this for quantum subsystems such as photosynthesis and magnetoreception. Second, we perform a preliminary study that illustrates a top-down approach to potential MQS. In summary, reductionist arguments against MQS are not justifiable. It is more likely they are not easily detectable in large intact classical systems or have been destroyed by reductionist experimental set-ups. This complex systems decoherence approach, using top down investigations, is critical to paradigm shifts in MQS research both in biological and non-biological systems. PMID:29200743
International Nuclear Information System (INIS)
Ghirardi, G.C.; Rimini, A.; Weber, T.
1987-06-01
It is shown that the assumption of a stochastic localization process for the quantum wave function is essentially different from the suppression of coherence over macroscopic distances arising from the interaction with the environment and allows for a conceptually complete derivation of the classical behaviour of macroscopic bodies. (author). 4 refs
Gunji, Yukio-Pegio; Shinohara, Shuji; Haruna, Taichi; Basios, Vasileios
2017-02-01
To overcome the dualism between mind and matter and to implement consciousness in science, a physical entity has to be embedded with a measurement process. Although quantum mechanics have been regarded as a candidate for implementing consciousness, nature at its macroscopic level is inconsistent with quantum mechanics. We propose a measurement-oriented inference system comprising Bayesian and inverse Bayesian inferences. While Bayesian inference contracts probability space, the newly defined inverse one relaxes the space. These two inferences allow an agent to make a decision corresponding to an immediate change in their environment. They generate a particular pattern of joint probability for data and hypotheses, comprising multiple diagonal and noisy matrices. This is expressed as a nondistributive orthomodular lattice equivalent to quantum logic. We also show that an orthomodular lattice can reveal information generated by inverse syllogism as well as the solutions to the frame and symbol-grounding problems. Our model is the first to connect macroscopic cognitive processes with the mathematical structure of quantum mechanics with no additional assumptions. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
Macroscopic quantum tunneling of a Bose-Einstein condensate through double Gaussian barriers
Maeda, Kenji; Urban, Gregor; Weidemüller, Matthias; Carr, Lincoln D.
2015-05-01
Macroscopic quantum tunneling is one of the great manifestations of quantum physics, not only showing passage through a potential barrier but also emerging in a many-body wave function. We study a quasi-1D Bose-Einstein condensate of Lithium, confined by two Gaussian barriers, and show that in an experimentally realistic potential tens of thousands of atoms tunnel on time scales of 10 to 100 ms. Using a combination of variational and WKB approximations based on the Gross-Pitaevskii or nonlinear Schrödinger equation, we show that many unusual tunneling features appear due to the nonlinearity, including the number of trapped atoms exhibiting non-exponential decay, severe distortion of the barriers by the mean field, and even formation of a triple barrier in certain regimes. In the first 10ms, nonlinear many-body effects make the tunneling rates significantly larger than background loss rates, from 10 to 70 Hz. Thus we conclude that macroscopic quantum tunneling can be observed on experimental time scales. Funded by NSF, AFOSR, the Alexander von Humboldt foundation, and the Heidelberg Center for Quantum Dynamics.
Explaining electric conductivity using the particle-in-a-box model: quantum superposition is the key
Sivanesan, Umaseh; Tsang, Kin; Izmaylov, Artur F.
2017-12-01
Most of the textbooks explaining electric conductivity in the context of quantum mechanics provide either incomplete or semi-classical explanations that are not connected with the elementary concepts of quantum mechanics. We illustrate the conduction phenomena using the simplest model system in quantum dynamics, a particle in a box (PIB). To induce the particle dynamics, a linear potential tilting the bottom of the box is introduced, which is equivalent to imposing a constant electric field for a charged particle. Although the PIB model represents a closed system that cannot have a flow of electrons through the system, we consider the oscillatory dynamics of the particle probability density as the analogue of the electric current. Relating the amplitude and other parameters of the particle oscillatory dynamics with the gap between the ground and excited states of the PIB model allows us to demonstrate one of the most basic dependencies of electric conductivity on the valence-conduction band gap of the material.
Macroscopic quantum tunneling in 1 μm Nb junctions below 100mK
International Nuclear Information System (INIS)
Voss, R.F.; Webb, R.A.
1981-01-01
The transition probabilities out of the superconducting state of low current density 1 μm Nb Josephson junctions with capacitance < 0.15 pF have been measured as a function of temperature T down to 3 mK. Below 100 mK the distribution widths become independent of T. Junctions with critical currents that differ by an order of magnitude have the same dependence of relative width on T. The low T results are interpreted in terms of quantum tunneling of the (macroscopic) junction phase. The observed low temperature widths are smaller than expected indicating the necessity of corrections to the simple WKB tunneling rates. (orig.)
Quantum laws of the microworld and the wealth of macroscopic structures
International Nuclear Information System (INIS)
Noga, M.
2000-01-01
The reasons are highlighted why classical physics was unable to explain the formation of any collective self-organized arrangement such as magnetism and how the wealth of macroscopic self-organized structures emerges spontaneously from quantum theory applied to the given physical system. This is demonstrated on the simplest multi-electron system, viz. the model of a metal as electron gas with Coulomb interaction with a background of homogeneously distributed positive charge possessing a constant density so as to ensure charge neutrality of the system
Kim, Jihwan; Kim, Bum-Kyu; Kim, Hong-Seok; Hwang, Ahreum; Kim, Bongsoo; Doh, Yong-Joo
2017-11-08
We report on the fabrication and electrical transport properties of superconducting junctions made of β-Ag 2 Se topological insulator (TI) nanowires in contact with Al superconducting electrodes. The temperature dependence of the critical current indicates that the superconducting junction belongs to a short and diffusive junction regime. As a characteristic feature of the narrow junction, the critical current decreases monotonously with increasing magnetic field. The stochastic distribution of the switching current exhibits the macroscopic quantum tunneling behavior, which is robust up to T = 0.8 K. Our observations indicate that the TI nanowire-based Josephson junctions can be a promising building block for the development of nanohybrid superconducting quantum bits.
Hernández Velázquez, J D; Barroso-Flores, J; Gama Goicochea, A
2016-11-23
Two of the most commonly encountered friction-reducing agents used in plastic sheet production are the amides known as erucamide and behenamide, which despite being almost identical chemically, lead to markedly different values of the friction coefficient. To understand the origin of this contrasting behavior, in this work we model brushes made of these two types of linear-chain molecules using quantum mechanical numerical simulations under the density functional theory at the B97D/6-31G(d,p) level of theory. Four chains of erucamide and behenamide were linked to a 2 × 10 zigzag graphene sheet and optimized both in vacuum and in continuous solvent using the SMD implicit solvation model. We find that erucamide chains tend to remain closer together through π-π stacking interactions arising from the double bonds located at C13-C14, a feature behenamide lacks, and thus a more spread configuration is obtained with the latter. It is argued that this arrangement of the erucamide chains is responsible for the lower friction coefficient of erucamide brushes, compared with behenamide brushes, which is a macroscopic consequence of cooperative quantum mechanical interactions. While only quantum level interactions are modeled here, we show that behenamide chains are more spread out in the brush than erucamide chains as a consequence of those interactions. The spread-out configuration allows more solvent particles to penetrate the brush, leading in turn to more friction, in agreement with macroscopic measurements and mesoscale simulations of the friction coefficient reported in the literature.
Macroscopic nonclassical-state preparation via postselection
Montenegro, Víctor; Coto, Raúl; Eremeev, Vitalie; Orszag, Miguel
2017-11-01
Macroscopic quantum superposition states are fundamental to test the classical-quantum boundary and present suitable candidates for quantum technologies. Although the preparation of such states has already been realized, the existing setups commonly consider external driving and resonant interactions, predominantly by considering Jaynes-Cummings-like and beam-splitter-like interactions, as well as the nonlinear radiation pressure interaction in cavity optomechanics. In contrast to previous works on the matter, we propose a feasible probabilistic scheme to generate a macroscopic mechanical qubit, as well as phononic Schrödinger's cat states with no need of any energy exchange with the macroscopic mechanical oscillator. Essentially, we investigate an open dispersive spin-mechanical system in the absence of any external driving under nonideal conditions, such as the detrimental effects due to the oscillator and spin energy losses in a thermal bath at nonzero temperature. In our work, we show that the procedure to generate the mechanical qubit state is solely based on spin postselection in the weak to moderate coupling regime. Finally, we demonstrate that the mechanical superposition is related to the amplification of the mean values of the mechanical quadratures as they maximize the quantum coherence.
Energy Technology Data Exchange (ETDEWEB)
Asai, Hidehiro, E-mail: hd-asai@aist.go.jp [Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Ota, Yukihiro [CCSE, Japan Atomic Energy Agency, Kashiwa, Chiba 277-8587 (Japan); Kawabata, Shiro [Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Nori, Franco [CEMS, RIKEN, Wako-shi, Saitama 351-0198 (Japan); Physics Department, University of Michigan, Ann Arbor, MI 48109-1040 (United States)
2014-09-15
Highlights: • We study MQT in Josephson junctions composed of multi-gap superconductors. • We derive a formula of the MQT escape rate for multiple phase differences. • We investigate the effect of inter-band phase fluctuation on MQT. • The MQT escape rate is significantly enhanced by the inter-band phase fluctuation. - Abstract: We theoretically investigate macroscopic quantum tunneling (MQT) in a hetero Josephson junction formed by a conventional single-gap superconductor and a multi-gap superconductor. In such Josephson junctions, phase differences for each tunneling channel are defined, and the fluctuation of the relative phase differences appear which is referred to as Josephson–Leggett’s mode. We take into account the effect of the fluctuation in the tunneling process and calculate the MQT escape rate for various junction parameters. We show that the fluctuation of relative phase differences drastically enhances the escape rate.
International Nuclear Information System (INIS)
Asai, Hidehiro; Ota, Yukihiro; Kawabata, Shiro; Nori, Franco
2014-01-01
Highlights: • We study MQT in Josephson junctions composed of multi-gap superconductors. • We derive a formula of the MQT escape rate for multiple phase differences. • We investigate the effect of inter-band phase fluctuation on MQT. • The MQT escape rate is significantly enhanced by the inter-band phase fluctuation. - Abstract: We theoretically investigate macroscopic quantum tunneling (MQT) in a hetero Josephson junction formed by a conventional single-gap superconductor and a multi-gap superconductor. In such Josephson junctions, phase differences for each tunneling channel are defined, and the fluctuation of the relative phase differences appear which is referred to as Josephson–Leggett’s mode. We take into account the effect of the fluctuation in the tunneling process and calculate the MQT escape rate for various junction parameters. We show that the fluctuation of relative phase differences drastically enhances the escape rate
Two-dimensional macroscopic quantum tunneling in multi-gap superconductor Josephson junctions
International Nuclear Information System (INIS)
Asai, Hidehiro; Kawabata, Shiro; Ota, Yukihiro; Machida, Masahiko
2014-01-01
Low-temperature characters of superconducting devices yield definite probes for different superconducting phenomena. We study the macroscopic quantum tunneling (MQT) in a Josephson junction, composed of a single-gap superconductor and a two-gap superconductor. Since this junction has two kinds to the superconducting phase differences, calculating the MQT escape rate requires the analysis of quantum tunneling in a multi-dimensional configuration space. Our approach is the semi-classical approximation along a 1D curve in a 2D potential- energy landscape, connecting two adjacent potential (local) minimums through a saddle point. We find that this system has two plausible tunneling paths; an in-phase path and an out-of-phase path. The former is characterized by the Josephson-plasma frequency, whereas the latter is by the frequency of the characteristic collective mode in a two-band superconductor, Josephson- Leggett mode. Depending on external bias current and inter-band Josephson-coupling energy, one of them mainly contributes to the MQT. Our numerical calculations show that the difference between the in-phase path and the out-of-phase path is manifest, with respect to the bias- current-dependence of the MQT escape rate. This result suggests that our MQT setting be an indicator of the Josephson-Leggett mode
International Nuclear Information System (INIS)
Cleland, A.N.
1991-01-01
Experiments investigated the process of macroscopic quantum tunneling in a moderately-damped, resistively shunted, Josephson junction are described, followed by a discussion of experiments performed on very-small-capacitance normal-metal tunnel junctions. The experiments on the resistively-shunted Josephson junction were designed to investigate a quantum process, that of the tunneling of the Josephson-phase variable under a potential barrier, in a system in which dissipation plays a major role in the dynamics of motion. All the parameters of the junction were measured using the classical phenomena of thermal activation and resonant activation. Theoretical predictions are compared with the experimental results, showing good agreement with no adjustable parameters. The experiments on small-capacitance tunnel junctions extend the measurements on the large-area Josephson junctions from the region in which the phase variable has a fairly well-defined value, i.e. its wave function has a narrow width, to the region where its value is almost completely unknown. The charge on the junction becomes well-defined and is predicted to quantize the current through the junction, giving rise to the Coulomb blockade at low bias
Theory of macroscopic quantum tunneling in high-T c cuprate
International Nuclear Information System (INIS)
Kawabata, Shiro; Tanaka, Yukio; Kashiwaya, Satoshi; Asano, Yasuhiro
2006-01-01
To reveal macroscopic quantum tunneling (MQT) in high-T c superconductor Josephson junctions is an important issue since there is a possibility to fabricate a superconducting quantum bit by use of high T c junctions. Using the functional integral and the instanton theory, we analytically obtain the MQT rate (the inverse lifetime of the metastable state) for the c-axis twist Josephson junctions. In the case of the zero twist angle, the system shows the super-Ohmic dissipation due to the presence of the nodal quasiparticle tunneling. Therefore, the MQT rate is suppressed compared with the finite twist angle cases. Furthermore, the effect of the zero energy bound states (ZES) on the MQT in the in-plane junctions is theoretically investigated. We obtained the analytical formula of the MQT rate and showed that the presence of the ZES at the normal/superconductor interface leads to a strong Ohmic quasiparticle dissipation. Therefore, the MQT rate is noticeably inhibited compared with the c-axis junctions in which the ZES are completely absent
Martín-Pacheco, Ana; Del Río Castillo, Antonio Esaú; Martín, Cristina; Herrero, María Antonia; Merino, Sonia; García Fierro, José Luis; Díez-Barra, Enrique; Vázquez, Ester
2018-05-17
Fluorescence based on quantum confinement is a property restricted to the nanoscopic range. The incorporation of nanoparticles in a three-dimensional polymeric network could afford macroscopic scaffolds that show nanoscopic properties. Moreover, if these scaffolds are based on strong bonds, the stability of the resulting materials can be preserved, thus enhancing their final applications. We report for the first time the preparation of a graphene quantum dot (GQD) composite based on a cationic covalent network. This new material has unusual features: (i) the final composite remains stable after several swelling-deswelling cycles, thus demonstrating strong interactions between GQDs and the polymeric material, and therefore it could be used as a portable system. (ii) Fluorescence emission in the composite and in solution is quasi-independent to the excitation wavelength. (iii) However, and in contrast to the behavior observed in GQD solutions, the fluorescence of the composite remains unaltered over a wide pH range and in the presence of different ions commonly found in tap water. (iv) Fluorescence quenching is only observed as a consequence of molecules that bear aromatic systems, and this could be applied to the preparation of in situ water sensors.
International Nuclear Information System (INIS)
Cleland, A.N.
1991-04-01
Experiments investigating the process of macroscopic quantum tunneling in a moderately-damped, resistively shunted, Josephson junction are described, followed by a discussion of experiments performed on very small capacitance normal-metal tunnel junctions. The experiments on the resistively-shunted Josephson junction were designed to investigate a quantum process, that of the tunneling of the Josephson phase variable under a potential barrier, in a system in which dissipation plays a major role in the dynamics of motion. All the parameters of the junction were measured using the classical phenomena of thermal activation and resonant activation. Theoretical predictions are compared with the experimental results, showing good agreement with no adjustable parameters; the tunneling rate in the moderately damped (Q ∼ 1) junction is seen to be reduced by a factor of 300 from that predicted for an undamped junction. The phase is seen to be a good quantum-mechanical variable. The experiments on small capacitance tunnel junctions extend the measurements on the larger-area Josephson junctions from the region in which the phase variable has a fairly well-defined value, i.e. its wavefunction has a narrow width, to the region where its value is almost completely unknown. The charge on the junction becomes well-defined and is predicted to quantize the current through the junction, giving rise to the Coulomb blockade at low bias. I present the first clear observation of the Coulomb blockade in single junctions. The electrical environment of the tunnel junction, however, strongly affects the behavior of the junction: higher resistance leads are observed to greatly sharpen the Coulomb blockade over that seen with lower resistance leads. I present theoretical descriptions of how the environment influences the junctions; comparisons with the experimental results are in reasonable agreement
International Nuclear Information System (INIS)
Handel, P.H.
1998-01-01
The author's recent application of the new Quantum Information Theory Approach (QIT) to Infra Quantum Physics (IQP) explains for the first time the apparent lack of unitarity caused by the entropy increase in the Quantum 1/f Effect (Q1/fE). This allows for a better understanding of the quantum 1/f effect in this paper, showing no resultant entropy increase and therefore no violation of unitarity. This new interpretation involves the concept of von Neumann Quantum Entropy, including the new negative conditional entropy concept for quantum entangled states introduced by QIT. The Q1/fE was applied to many high-tech systems, in particular to ultra small electronic devices. The present paper explains how the additional entropy implied by the Q1/fE arises in spite of the entropy-conserving evolution of the system. On this basis, a general derivation of the conventional and coherent quantum 1/f effect is given. (author)
A strict experimental test of macroscopic realism in a superconducting flux qubit.
Knee, George C; Kakuyanagi, Kosuke; Yeh, Mao-Chuang; Matsuzaki, Yuichiro; Toida, Hiraku; Yamaguchi, Hiroshi; Saito, Shiro; Leggett, Anthony J; Munro, William J
2016-11-04
Macroscopic realism is the name for a class of modifications to quantum theory that allow macroscopic objects to be described in a measurement-independent manner, while largely preserving a fully quantum mechanical description of the microscopic world. Objective collapse theories are examples which aim to solve the quantum measurement problem through modified dynamical laws. Whether such theories describe nature, however, is not known. Here we describe and implement an experimental protocol capable of constraining theories of this class, that is more noise tolerant and conceptually transparent than the original Leggett-Garg test. We implement the protocol in a superconducting flux qubit, and rule out (by ∼84 s.d.) those theories which would deny coherent superpositions of 170 nA currents over a ∼10 ns timescale. Further, we address the 'clumsiness loophole' by determining classical disturbance with control experiments. Our results constitute strong evidence for the superposition of states of nontrivial macroscopic distinctness.
Directory of Open Access Journals (Sweden)
Vladimir I. Volchikhin
2017-12-01
Full Text Available Introduction: The aim of the study is to accelerate the solution of neural network biometrics inverse problem on an ordinary desktop computer. Materials and Methods: To speed up the calculations, the artificial neural network is introduced into the dynamic mode of “jittering” of the states of all 256 output bits. At the same time, too many output states of the neural network are logarithmically folded by transitioning to the Hamming distance space between the code of the image “Own” and the codes of the images “Alien”. From the database of images of “Alien” 2.5 % of the most similar images are selected. In the next generation, 97.5 % of the discarded images are restored with GOST R 52633.2-2010 procedures by crossing parent images and obtaining descendant images from them. Results: Over a period of about 10 minutes, 60 generations of directed search for the solution of the inverse problem can be realized that allows inversing matrices of neural network functionals of dimension 416 inputs to 256 outputs with restoration of up to 97 % information on unknown biometric parameters of the image “Own”. Discussion and Conclusions: Supporting for 10 minutes of computer time the 256 qubit quantum superposition allows on a conventional computer to bypass the actual infinity of analyzed states in 5050 (50 to 50 times more than the same computer could process realizing the usual calculations. The increase in the length of the supported quantum superposition by 40 qubits is equivalent to increasing the processor clock speed by about a billion times. It is for this reason that it is more profitable to increase the number of quantum superpositions supported by the software emulator in comparison with the creation of a more powerful processor.
Energy Technology Data Exchange (ETDEWEB)
Vega, H.J. de [Sorbonne Universites, Universite Pierre et Marie Curie UPMC Paris VI, LPTHE CNRS UMR 7589, Paris Cedex 05 (France); Sanchez, N.G. [Observatoire de Paris PSL Research University, Sorbonne Universites UPMC Paris VI, Observatoire de Paris, LERMA CNRS UMR 8112, Paris (France)
2017-02-15
The Thomas-Fermi approach to galaxy structure determines self-consistently and non-linearly the gravitational potential of the fermionic warm dark matter (WDM) particles given their quantum distribution function f(E). This semiclassical framework accounts for the quantum nature and high number of DM particles, properly describing gravitational bounded and quantum macroscopic systems as neutron stars, white dwarfs and WDM galaxies. We express the main galaxy magnitudes as the halo radius r{sub h}, mass M{sub h}, velocity dispersion and phase space density in terms of the surface density which is important to confront to observations. From these expressions we derive the general equation of state for galaxies, i.e., the relation between pressure and density, and provide its analytic expression. Two regimes clearly show up: (1) Large diluted galaxies for M{sub h} >or similar 2.3 x 10{sup 6} M {sub CircleDot} and effective temperatures T{sub 0} > 0.017 K described by the classical self-gravitating WDM Boltzman gas with a space-dependent perfect gas equation of state, and (2) Compact dwarf galaxies for 1.6 x 10{sup 6} M {sub CircleDot} >or similar M{sub h} >or similar M{sub h,min} ≅ 3.10 x 10{sup 4} (2 keV/m){sup (16)/(5)} M {sub CircleDot}, T{sub 0} < 0.011 K described by the quantum fermionic WDM regime with a steeper equation of state close to the degenerate state. In particular, the T{sub 0} = 0 degenerate or extreme quantum limit yields the most compact and smallest galaxy. In the diluted regime, the halo radius r{sub h}, the squared velocity v{sup 2}(r{sub h}) and the temperature T{sub 0} turn to exhibit square-root of M{sub h} scaling laws. The normalized density profiles ρ(r)/ρ(0) and the normalized velocity profiles v{sup 2}(r)/v{sup 2}(0) are universal functions of r/r{sub h} reflecting the WDM perfect gas behavior in this regime. These theoretical results contrasted to robust and independent sets of galaxy data remarkably reproduce the observations. For
Beating the macroscopic quantum tunneling limit by man-made magnetic dead layers
Ma, Ji; Chen, Kezheng
2018-05-01
Magnetic dead layers (MDLs) are always undesirable in practical applications due to their highly frustrated spin configurations and severe degradation of host magnetism. Here we provide new insights in MDLs and unravel their attractive prospect for ferrimagnetic hybrid of Fe3O4 and γ-Fe2O3 (denoted as Fe3O4@γ-Fe2O3 in the main text) to exhibit macroscopic quantum tunneling (MQT) phenomena in measureable kelvin range. The 3 nm-sized negatively-charged Fe3O4@γ-Fe2O3 nanoparticles were immersed in various metal chloride solutions containing Mn2+, Co2+, Ni2+, Fe3+, and Fe2+ cations to form cationic MDLs via electrostatic attraction. These man-made MDLs, if being of positive enough zeta potentials, greatly disordered the magnetic dipole interactions among Fe3O4@γ-Fe2O3 nanoparticles and induce extra energy barrier to yield pronounced MQT effect in Fe3O4@γ-Fe2O3 nanoparticles even though they were dispersed neither in water nor in oil. Their crossover temperatures dividing MQT and purely thermal relaxation were found to be one order of magnitude higher than reported values in other MQT systems, and more strikingly, they could be tailored by altering the soak period in our facile and scalable route.
Scale relativity theory and integrative systems biology: 2. Macroscopic quantum-type mechanics.
Nottale, Laurent; Auffray, Charles
2008-05-01
In these two companion papers, we provide an overview and a brief history of the multiple roots, current developments and recent advances of integrative systems biology and identify multiscale integration as its grand challenge. Then we introduce the fundamental principles and the successive steps that have been followed in the construction of the scale relativity theory, which aims at describing the effects of a non-differentiable and fractal (i.e., explicitly scale dependent) geometry of space-time. The first paper of this series was devoted, in this new framework, to the construction from first principles of scale laws of increasing complexity, and to the discussion of some tentative applications of these laws to biological systems. In this second review and perspective paper, we describe the effects induced by the internal fractal structures of trajectories on motion in standard space. Their main consequence is the transformation of classical dynamics into a generalized, quantum-like self-organized dynamics. A Schrödinger-type equation is derived as an integral of the geodesic equation in a fractal space. We then indicate how gauge fields can be constructed from a geometric re-interpretation of gauge transformations as scale transformations in fractal space-time. Finally, we introduce a new tentative development of the theory, in which quantum laws would hold also in scale space, introducing complexergy as a measure of organizational complexity. Initial possible applications of this extended framework to the processes of morphogenesis and the emergence of prokaryotic and eukaryotic cellular structures are discussed. Having founded elements of the evolutionary, developmental, biochemical and cellular theories on the first principles of scale relativity theory, we introduce proposals for the construction of an integrative theory of life and for the design and implementation of novel macroscopic quantum-type experiments and devices, and discuss their potential
Furusawa, Akira
2015-01-01
This book explains what quantum states of light look like. Of special interest, a single photon state is explained by using a wave picture, showing that it corresponds to the complementarity of a quantum. Also explained is how light waves are created by photons, again corresponding to the complementarity of a quantum. The author shows how an optical wave is created by superposition of a "vacuum" and a single photon as a typical example. Moreover, squeezed states of light are explained as "longitudinal" waves of light and Schrödinger's cat states as macroscopic superposition states.
Quantum Biology at the Cellular Level - elements of the research program
Bordonaro, Michael; Ogryzko, Vasily
2013-01-01
Quantum Biology is emerging as a new field at the intersection between fundamental physics and biology, promising novel insights into the nature and origin of biological order. We discuss several elements of QBCL (Quantum Biology at Cellular Level), a research program designed to extend the reach of quantum concepts to higher than molecular levels of biological organization. Key words. decoherence, macroscopic superpositions, basis-dependence, formal superposition, non-classical correlations,...
International Nuclear Information System (INIS)
Uribe-Patarroyo, Nestor; Alvarez-Herrero, Alberto; Belenguer, Tomas
2010-01-01
We propose the use of a phase-diversity technique to estimate the orbital angular momentum (OAM) superposition state of an ensemble of photons that passes through an optical system, proceeding from an extended object. The phase-diversity technique permits the estimation of the optical transfer function (OTF) of an imaging optical system. As the OTF is derived directly from the wave-front characteristics of the observed light, we redefine the phase-diversity technique in terms of a superposition of OAM states. We test this new technique experimentally and find coherent results among different tests, which gives us confidence in the estimation of the photon ensemble state. We find that this technique not only allows us to estimate the square of the amplitude of each OAM state, but also the relative phases among all states, thus providing complete information about the quantum state of the photons. This technique could be used to measure the OAM spectrum of extended objects in astronomy or in an optical communication scheme using OAM states. In this sense, the use of extended images could lead to new techniques in which the communication is further multiplexed along the field.
Superposition Attacks on Cryptographic Protocols
DEFF Research Database (Denmark)
Damgård, Ivan Bjerre; Funder, Jakob Løvstad; Nielsen, Jesper Buus
2011-01-01
of information. In this paper, we introduce a fundamentally new model of quantum attacks on classical cryptographic protocols, where the adversary is allowed to ask several classical queries in quantum superposition. This is a strictly stronger attack than the standard one, and we consider the security......Attacks on classical cryptographic protocols are usually modeled by allowing an adversary to ask queries from an oracle. Security is then defined by requiring that as long as the queries satisfy some constraint, there is some problem the adversary cannot solve, such as compute a certain piece...... of several primitives in this model. We show that a secret-sharing scheme that is secure with threshold $t$ in the standard model is secure against superposition attacks if and only if the threshold is lowered to $t/2$. We use this result to give zero-knowledge proofs for all of NP in the common reference...
Teleportation of Unknown Superpositions of Collective Atomic Coherent States
Institute of Scientific and Technical Information of China (English)
ZHENG ShiBiao
2001-01-01
We propose a scheme to teleport an unknown superposition of two atomic coherent states with different phases. Our scheme is based on resonant and dispersive atom-field interaction. Our scheme provides a possibility of teleporting macroscopic superposition states of many atoms first time.``
Levitation of Bose-Einstein condensates induced by macroscopic non-adiabatic quantum tunneling
Nakamura, Katsuhiro; Kohi, Akihisa; Yamasaki, Hisatsugu; Perez-Garcia, Victor M.
2006-01-01
We study the dynamics of two-component Bose-Einstein condensates trapped in different vertical positions in the presence of an oscillating magnetic field. It is shown here how tuning appropriately the oscillation frequency of the magnetic field leads to the levitation of the system against gravity. This phenomenon is a manifestation of a macroscopic non-adiabatic tunneling in a system with internal degrees of freedom.
Atoms, cavities and ''Schroedinger's cats''. The monsters and wonders of quantum mechanics
International Nuclear Information System (INIS)
Raimond, J.M.
1997-01-01
The decoherence effect appears at the border between quantum world and macroscopic reality when the superposition of quantum states collapses into one particular state. This article deals with an experiment made to study for the first time the decoherence phenomenon. Circular Rydberg atoms of rubidium and superconducting cavity are the tools used to seize the very moment when the quantum superposition vanishes. This experimental proof of decoherence allows to perceive the limitations of the applications of quantum physics to fields such as quantum computing. This kind of experiment could be used to test other properties of quantum systems. (A.C.)
Directory of Open Access Journals (Sweden)
Vladimir I. Volchikhin
2017-06-01
Full Text Available Introduction: The study promotes to decrease a number of errors of calculating the correlation coefficient in small test samples. Materials and Methods: We used simulation tool for the distribution functions of the density values of the correlation coefficient in small samples. A method for quantization of the data, allows obtaining a discrete spectrum states of one of the varieties of correlation functional. This allows us to consider the proposed structure as a mathematical correlation molecule, described by some analogue continuous-quantum Schrödinger equation. Results: The chi-squared Pearson’s molecule on small samples allows enhancing power of classical chi-squared test to 20 times. A mathematical correlation molecule described in the article has similar properties. It allows in the future reducing calculation errors of the classical correlation coefficients in small samples. Discussion and Conclusions: The authors suggest that there are infinitely many mathematical molecules are similar in their properties to the actual physical molecules. Schrödinger equations are not unique, their analogues can be constructed for each mathematical molecule. You can expect a mathematical synthesis of molecules for a large number of known statistical tests and statistical moments. All this should make it possible to reduce calculation errors due to quantum effects that occur in small test samples.
Stochastic space interval as a link between quantum randomness and macroscopic randomness?
Haug, Espen Gaarder; Hoff, Harald
2018-03-01
For many stochastic phenomena, we observe statistical distributions that have fat-tails and high-peaks compared to the Gaussian distribution. In this paper, we will explain how observable statistical distributions in the macroscopic world could be related to the randomness in the subatomic world. We show that fat-tailed (leptokurtic) phenomena in our everyday macroscopic world are ultimately rooted in Gaussian - or very close to Gaussian-distributed subatomic particle randomness, but they are not, in a strict sense, Gaussian distributions. By running a truly random experiment over a three and a half-year period, we observed a type of random behavior in trillions of photons. Combining our results with simple logic, we find that fat-tailed and high-peaked statistical distributions are exactly what we would expect to observe if the subatomic world is quantized and not continuously divisible. We extend our analysis to the fact that one typically observes fat-tails and high-peaks relative to the Gaussian distribution in stocks and commodity prices and many aspects of the natural world; these instances are all observable and documentable macro phenomena that strongly suggest that the ultimate building blocks of nature are discrete (e.g. they appear in quanta).
International Nuclear Information System (INIS)
Raghavan, S.; Fantoni, S.; Shenoy, S.R.; Smerzi, A.
1997-07-01
We consider coherent atomic tunneling between two weakly coupled Bose-Einstein condensates (BEC) at T = 0 in (possibly asymmetric) double-well trap. The condensate dynamics of the macroscopic amplitudes in the two wells is modeled by two Gross-Pitaevskii equations (GPE) coupled by a tunneling matrix element. The evolution of the inter-well fractional population imbalance (related to the condensate phase difference) is obtained in terms of elliptic functions, generalizing well-known Josephson effects such as the 'ac' effect, the 'plasma oscillations', and the resonant Shapiro effect, to the nonsiusoidal regimes. We also present exact solutions for a novel 'macroscopic quantum self-trapping' effect arising from nonlinear atomic self-interaction in the GPE. The coherent BEC tunneling signatures are obtained in terms of the oscillations periods and the Fourier spectrum of the imbalance oscillations, as a function of the initial values of GPE parameters. Experimental procedures are suggested to make contact with theoretical predictions. (author). 44 refs, 8 figs
Phase-Covariant Cloning and EPR Correlations in Entangled Macroscopic Quantum Systems
de Martini, Francesco; Sciarrino, Fabio
2007-03-01
Theoretical and experimental results on the Quantum Injected Optical Parametric Amplification (QI-OPA) of optical qubits in the high gain regime are reported. The large size of the gain parameter in the collinear configuration, g = 4.5, allows the generation of EPR nonlocally correlated bunches containing about 4000 photons. The entanglement of the related Schroedinger Cat-State (SCS) is demonstrated as well as the establishment of Phase-Covariant quantum cloning. The cloning ``fidelity'' has been found to match the theoretical results. According to the original 1935 definition of the SCS, the overall apparatus establishes for the first time the nonlocal correlations between a microcopic spin (qubit) and a high J angular momentum i.e. a mesoscopic multiparticle system close to the classical limit. The results of the first experimental realization of the Herbert proposal for superluminal communication via nonlocality will be presented.
Creation of Two-Particle Entanglement in Open Macroscopic Quantum Systems
Directory of Open Access Journals (Sweden)
M. Merkli
2012-01-01
Full Text Available We consider an open quantum system of N not directly interacting spins (qubits in contact with both local and collective thermal environments. The qubit-environment interactions are energy conserving. We trace out the variables of the thermal environments and N−2 qubits to obtain the time-dependent reduced density matrix for two arbitrary qubits. We numerically simulate the reduced dynamics and the creation of entanglement (concurrence as a function of the parameters of the thermal environments and the number of qubits, N. Our results demonstrate that the two-qubit entanglement generally decreases as N increases. We show analytically that, in the limit N→∞, no entanglement can be created. This indicates that collective thermal environments cannot create two-qubit entanglement when many qubits are located within a region of the size of the environment coherence length. We discuss possible relevance of our consideration to recent quantum information devices and biosystems.
International Nuclear Information System (INIS)
Julia-Diaz, B.; Dagnino, D.; Martorell, J.; Polls, A.; Lewenstein, M.
2010-01-01
We consider a Bose-Einstein condensate in a double-well potential undergoing a dynamical transition from the regime of Josephson oscillations to the regime of self-trapping. We analyze the statistical properties of the ground state (or the highest excited state) of the Hamiltonian in these two regimes for attractive (repulsive) interactions. We demonstrate that it is impossible to describe the transition within the mean-field theory. In contrast, the transition proceeds through a strongly correlated delocalized state, with large quantum fluctuations, and spontaneous breaking of the symmetry.
Engineering mesoscopic superpositions of superfluid flow
International Nuclear Information System (INIS)
Hallwood, D. W.; Brand, J.
2011-01-01
Modeling strongly correlated atoms demonstrates the possibility to prepare quantum superpositions that are robust against experimental imperfections and temperature. Such superpositions of vortex states are formed by adiabatic manipulation of interacting ultracold atoms confined to a one-dimensional ring trapping potential when stirred by a barrier. Here, we discuss the influence of nonideal experimental procedures and finite temperature. Adiabaticity conditions for changing the stirring rate reveal that superpositions of many atoms are most easily accessed in the strongly interacting, Tonks-Girardeau, regime, which is also the most robust at finite temperature. NOON-type superpositions of weakly interacting atoms are most easily created by adiabatically decreasing the interaction strength by means of a Feshbach resonance. The quantum dynamics of small numbers of particles is simulated and the size of the superpositions is calculated based on their ability to make precision measurements. The experimental creation of strongly correlated and NOON-type superpositions with about 100 atoms seems feasible in the near future.
Thermally Assisted Macroscopic Quantum Resonance on a Single-Crystal of Mn12-ac
Lionti, F.; Thomas, L.; Ballou, R.; Wernsdorfer, W.; Barbara, B.; Sulpice, A.; Sessoli, R.; Gatteschi, D.
1997-03-01
Magnetization measurements have been performed on a single mono-crystal of the molecule Mn12-acetate (L. Thomas, F. Lionti, R. Ballou, R. Sessoli, D. Gatteschi and B. Barbara, Nature, 383, 145 (1996).). Steps were observed in the hysteresis loop for values of the applied field at which level crossings of the collective spin states of each manganese clusters take place. The influence of quartic terms is taken into account. At these fields, the magnetization relaxes at short time scales, being otherwise essentially blocked. This novel behavior is interpreted in terms of resonant quantum tunneling of the magnetization from thermally activated energy levels. Hysteresis loop measurements performed for different field orientations and ac-susceptibility experiments, confirm general trends of this picture.
Dolomatov, M. Yu.; Kovaleva, E. A.; Khamidullina, D. A.
2018-05-01
An approach that allows the calculation of dynamic viscosity for liquid hydrocarbons from quantum (ionization energies) and molecular (Wiener topological indices) parameters is proposed. A physical relationship is revealed between ionization and the energies of viscous flow activation. This relationship is due to the contribution from the dispersion component of Van der Waals forces to intermolecular interaction. A two-parameter dependence of the energy of viscous flow activation, energy of ionization, and Wiener topological indices is obtained. The dynamic viscosities of liquid hydrocarbons can be calculated from the kinetic compensation effect of dynamic viscosity, which indicates a relationship between the energy of activation and the Arrhenius pre-exponental factor of the Frenkel-Eyring hole model. Calculation results are confirmed through statistical processing of the experimental data.
Qin, Wei; Wang, Xin; Miranowicz, Adam; Zhong, Zhirong; Nori, Franco
2017-07-01
Heralded near-deterministic multiqubit controlled-phase gates with integrated error detection have recently been proposed by Borregaard et al. [Phys. Rev. Lett. 114, 110502 (2015), 10.1103/PhysRevLett.114.110502]. This protocol is based on a single four-level atom (a heralding quartit) and N three-level atoms (operational qutrits) coupled to a single-resonator mode acting as a cavity bus. Here we generalize this method for two distant resonators without the cavity bus between the heralding and operational atoms. Specifically, we analyze the two-qubit controlled-Z gate and its multiqubit-controlled generalization (i.e., a Toffoli-like gate) acting on the two-lowest levels of N qutrits inside one resonator, with their successful actions being heralded by an auxiliary microwave-driven quartit inside the other resonator. Moreover, we propose a circuit-quantum-electrodynamics realization of the protocol with flux and phase qudits in linearly coupled transmission-line resonators with dissipation. These methods offer a quadratic fidelity improvement compared to cavity-assisted deterministic gates.
International Nuclear Information System (INIS)
Raghavan, S.; Smerzi, A.; Fantoni, S.; Shenoy, S.R.
2001-03-01
We discuss the coherent atomic oscillations between two weakly coupled Bose-Einstein condensates. The weak link is provided by a laser barrier in a (possibly asymmetric) double-well trap or by Raman coupling between two condensates in different hyperfine levels. The boson Josephson junction (BJJ) dynamics is described by the two-mode nonlinear Gross-Pitaevskii equation that is solved analytically in terms of elliptic functions. The BJJ, being a neutral, isolated system, allows the investigations of dynamical regimes for the phase difference across the junction and for the population imbalance that are not accessible with superconductor Josephson junctions (SJJ's). These include oscillations with either or both of the following properties: (i) the time-averaged value of the phase is equal to π (π-phase oscillations); (ii) the average population imbalance is nonzero, in states with macroscopic quantum self-trapping. The (nonsinusoidal) generalization of the SJJ ac and plasma oscillations and the Shapiro resonance can also be observed. We predict the collapse of experimental data (corresponding to different trap geometries and the total number of condensate atoms) onto a single universal curve for the inverse period of oscillations. Analogies with Josephson oscillations between two weakly coupled reservoirs of 3 He-B and the internal Josephson effect in 3 He-A are also discussed. (author)
Bathed, Strained, Attenuated, Annihilated: Towards Quantum Optomechanics
Pepper, Brian Jeffrey
The field of optomechanics studies tiny devices that can be pushed mechanically by light. It is an extremely promising avenue towards tests of quantum mechanics on a macroscopic scale, by transferring quantum states of light to nano- or micromechanical objects. This dissertation concerns a long term research program to create quantum superpositions of a macroscopic mirror in an optomechanical cavity. This dissertation has two broad thrusts. The first focuses on microfabrication of a new type of device called optomechanical trampoline resonators, consisting of a small mirror on a cross-shaped tensed silicon nitride membrane. Devices have been fabricated with high mechanical and optical quality, including a 300 kHz device with quality factor 480,000, as well as a device of optical finesse 107,000. These devices are well into the sideband-resolved regime and suitable for optical cooling to the quantum ground state. One such device has been optically cooled to approximately 10 phonons. The second major thrust is theoretical. Creating a macroscopic superposition is a challenging problem, requiring optical cooling to the ground state, strong coupling, extremely high optical finesse and extremely low frequency. A realistic assessment of achievable parameters indicates that it is possible to achieve ground state cooling or strong coupling, but not both. This dissertation proposes a new technique using postselection to achieve macroscopic superpositions with only weak coupling. This relaxes some of the required parameters by orders of magnitude. Prospects for observing hypothetical novel decoherence mechanisms are also discussed.
Geneva University - Superconducting flux quantum bits: fabricated quantum objects
2007-01-01
Ecole de physique Département de physique nucléaire et corspusculaire 24, Quai Ernest-Ansermet 1211 GENEVE 4 Tél: (022) 379 62 73 Fax: (022) 379 69 92 Lundi 29 janvier 2007 COLLOQUE DE LA SECTION DE PHYSIQUE 17 heures - Auditoire Stueckelberg Superconducting flux quantum bits: fabricated quantum objects Prof. Hans Mooij / Kavli Institute of Nanoscience, Delft University of Technology The quantum conjugate variables of a superconductor are the charge or number of Cooper pairs, and the phase of the order parameter. In circuits that contain small Josephson junctions, these quantum properties can be brought forward. In Delft we study so-called flux qubits, superconducting rings that contain three small Josephson junctions. When a magnetic flux of half a flux quantum is applied to the loop, there are two states with opposite circulating current. For suitable junction parameters, a quantum superposition of those macroscopic states is possible. Transitions can be driven with resonant microwaves. These quantum ...
Superposition Enhanced Nested Sampling
Directory of Open Access Journals (Sweden)
Stefano Martiniani
2014-08-01
Full Text Available The theoretical analysis of many problems in physics, astronomy, and applied mathematics requires an efficient numerical exploration of multimodal parameter spaces that exhibit broken ergodicity. Monte Carlo methods are widely used to deal with these classes of problems, but such simulations suffer from a ubiquitous sampling problem: The probability of sampling a particular state is proportional to its entropic weight. Devising an algorithm capable of sampling efficiently the full phase space is a long-standing problem. Here, we report a new hybrid method for the exploration of multimodal parameter spaces exhibiting broken ergodicity. Superposition enhanced nested sampling combines the strengths of global optimization with the unbiased or athermal sampling of nested sampling, greatly enhancing its efficiency with no additional parameters. We report extensive tests of this new approach for atomic clusters that are known to have energy landscapes for which conventional sampling schemes suffer from broken ergodicity. We also introduce a novel parallelization algorithm for nested sampling.
Macroscopic constraints on string unification
International Nuclear Information System (INIS)
Taylor, T.R.
1989-03-01
The comparison of sting theory with experiment requires a huge extrapolation from the microscopic distances, of order of the Planck length, up to the macroscopic laboratory distances. The quantum effects give rise to large corrections to the macroscopic predictions of sting unification. I discus the model-independent constraints on the gravitational sector of string theory due to the inevitable existence of universal Fradkin-Tseytlin dilatons. 9 refs
Energy Technology Data Exchange (ETDEWEB)
Rech, J
2006-06-15
It took several years after the idea of a zero-temperature phase transition emerged to realize the impact of such a quantum critical point over a large region of the phase diagram. Observed in many experimental examples, this quantum critical regime is not yet understood in details theoretically, and one needs to develop new approaches. In the first part, we focused on the ferromagnetic quantum critical point. After constructing a controlled approach allowing us to describe the quantum critical regime, we show through the computation of the static spin susceptibility that the ferromagnetic quantum critical point is unstable, destroyed internally by an effective dynamic long-range interaction generated by the Landau damping. In the second part, we revisit the exactly screened single impurity Kondo model, using a bosonic representation of the local spin and treating it in the limit of large spin degeneracy N. We show that, in this regime, the ground-state is a non-trivial Fermi liquid, unlike what was advocated by previous similar studies. We then extend our method to encompass the physics of two coupled impurities, for which our results are qualitatively comparable to the ones obtained from various approaches carried out in the past. We also develop a Luttinger-Ward formalism, enabling us to cure some of the drawbacks of the original method used to describe the single impurity physics. Finally, we present the main ideas and the first results for an extension of the method towards the description of a Kondo lattice, relevant for the understanding of the quantum critical regime of heavy fermion materials. (authors)
Network class superposition analyses.
Directory of Open Access Journals (Sweden)
Carl A B Pearson
Full Text Available Networks are often used to understand a whole system by modeling the interactions among its pieces. Examples include biomolecules in a cell interacting to provide some primary function, or species in an environment forming a stable community. However, these interactions are often unknown; instead, the pieces' dynamic states are known, and network structure must be inferred. Because observed function may be explained by many different networks (e.g., ≈ 10(30 for the yeast cell cycle process, considering dynamics beyond this primary function means picking a single network or suitable sample: measuring over all networks exhibiting the primary function is computationally infeasible. We circumvent that obstacle by calculating the network class ensemble. We represent the ensemble by a stochastic matrix T, which is a transition-by-transition superposition of the system dynamics for each member of the class. We present concrete results for T derived from boolean time series dynamics on networks obeying the Strong Inhibition rule, by applying T to several traditional questions about network dynamics. We show that the distribution of the number of point attractors can be accurately estimated with T. We show how to generate Derrida plots based on T. We show that T-based Shannon entropy outperforms other methods at selecting experiments to further narrow the network structure. We also outline an experimental test of predictions based on T. We motivate all of these results in terms of a popular molecular biology boolean network model for the yeast cell cycle, but the methods and analyses we introduce are general. We conclude with open questions for T, for example, application to other models, computational considerations when scaling up to larger systems, and other potential analyses.
International Nuclear Information System (INIS)
Papp, E.; Micu, C.; Racolta, D.
2013-01-01
In this paper one deals with the theoretical derivation of energy bands and of related wavefunctions characterizing quasi 1D semiconductor heterostructures, such as InAs quantum wire models. Such models get characterized this time by equal coupling strength superpositions of Rashba and Dresselhaus spin-orbit interactions of dimensionless magnitude a under the influence of in-plane magnetic fields of magnitude B. We found that the orientations of the field can be selected by virtue of symmetry requirements. For this purpose one resorts to spin conservations, but alternative conditions providing sensible simplifications of the energy-band formula can be reasonably accounted for. Besides the wavenumber k relying on the 1D electron, one deals with the spin-like s=±1 factors in the front of the square root term of the energy. Having obtained the spinorial wavefunction, opens the way to the derivation of spin precession effects. For this purpose one resorts to the projections of the wavenumber operator on complementary spin states. Such projections are responsible for related displacements proceeding along the Ox-axis. This results in a 2D rotation matrix providing both the precession angle as well as the precession axis
Creating cat states in one-dimensional quantum walks using delocalized initial states
International Nuclear Information System (INIS)
Zhang, Wei-Wei; Gao, Fei; Goyal, Sandeep K; Sanders, Barry C; Simon, Christoph
2016-01-01
Cat states are coherent quantum superpositions of macroscopically distinct states and are useful for understanding the boundary between the classical and the quantum world. Due to their macroscopic nature, cat states are difficult to prepare in physical systems. We propose a method to create cat states in one-dimensional quantum walks using delocalized initial states of the walker. Since the quantum walks can be performed on any quantum system, our proposal enables a platform-independent realization of the cat states. We further show that the linear dispersion relation of the effective quantum walk Hamiltonian, which governs the dynamics of the delocalized states, is responsible for the formation of the cat states. We analyze the robustness of these states against environmental interactions and present methods to control and manipulate the cat states in the photonic implementation of quantum walks. (paper)
International Nuclear Information System (INIS)
Martinez-Linares, Jesus; Vargas-Medina, Julio
2004-01-01
A scheme for an atomic beam quantum self-eraser is presented. The proposal is based on time reversal invariance on a quantum optical Ramsey fringe experiment, where a realization of complementarity for atomic coherence can be achieved. It consists of two high-finesse resonators that are pumped and probed by the same atom. This property relates quantum erasing to time reversal symmetry, allowing for a full quantum erasing of the which-way information stored in the cavity fields. The outlined scheme also prepares and observes a non-local state in the fields of the resonators: a coherent superposition between correlated states of macroscopically separated quantum systems. The proposed scheme emphasizes the role of entanglement swapping in delayed-choice experiments
International Nuclear Information System (INIS)
Abramov, D V; Antipov, A A; Arakelian, S M; Khor’kov, K S; Kucherik, A O; Kutrovskaya, S V; Prokoshev, V G
2014-01-01
The main goal of our work is the laser fabrication of nanostructured materials including the nano- and microclusters for control of electrical, optical and other properties of obtained structures. First, we took an opportunity to select nanoparticles in various sizes and weights and also in topology distribution for some materials (carbon, Ni, PbTe, etc). Second, for a deposited extended array of nanoparticles we used a method of laser-induced nanoparticle fabrication in colloid and deposition metal (and/or oxide) nanoparticles from colloidal systems (LDPCS) to obtain the multilayered nanostructures with controlled topology, including the fractal cluster structures (for Ni, Pb Te et al). Electrophysical properties are analyzed for such nanocluster systems as well. A brief analogy of the obtained nanocluster structures with a quantum correlated state evidence is carried out. (paper)
Energy Technology Data Exchange (ETDEWEB)
Fillaux, François, E-mail: francois.fillaux@upmc.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 8233, MONARIS, F-7505 Paris (France); Cousson, Alain, E-mail: alain-f.cousson@cea.fr [Laboratoire Léon Brillouin (CEA-CNRS), C.E. Saclay, 91191 Gif-sur-Yvette cedex (France)
2016-11-10
Highlights: • Proton transfer and tautomerism are revisited from quantum viewpoint. • Neutron-diffraction gives evidence for long-range correlations for protons. • We introduce a decoherence-free macroscopic-scale crystal-state. • All observations accord with the principle of complementarity. • Computational-chemistry models are inappropriate. - Abstract: Measurements via different techniques of the crystal of benzoic acid have led to conflicting conceptions of tautomerism: statistical disorder for diffraction; semiclassical jumps for relaxometry; quantum states for vibrational spectroscopy. We argue that these conflicts follow from the prejudice that nuclear positions and eigenstates are pre-existing to measurements, what is at variance with the principle of complementarity. We propose a self-contained quantum theory. First of all, new single-crystal neutron-diffraction data accord with long-range correlation for proton-site occupancies. Then we introduce a macroscopic-scale quantum-state emerging from phonon condensation, for which nuclear positions and eigenstates are indefinite. As to quantum-measurements, an incoming wave (neutron or photon) entangled with the condensate realizes a transitory state, either in the space of static nuclear-coordinates (diffraction), or in that of the symmetry coordinates (spectroscopy and relaxometry). We derive temperature-laws for proton-site occupancies and for the relaxation rate, which compare favorably with measurements.
Breakdown of the equivalence between active gravitational mass and energy for a quantum body
International Nuclear Information System (INIS)
Lebed, Andrei G.
2016-01-01
We determine active gravitational mass operator of the simplest composite quantum body - a hydrogen atom - within the semiclassical approach to the Einstein equation for a gravitational field. We show that the expectation value of the mass is equivalent to energy for stationary quantum states. On the other hand, it occurs that, for quantum superpositions of stationary states with constant expectation values of energy, the expectation values of the gravitational mass exhibit time-dependent oscillations. This breaks the equivalence between active gravitational mass and energy and can be observed as a macroscopic effect for a macroscopic ensemble of coherent quantum states of the atoms. The corresponding experiment could be the first direct observation of quantum effects in General Relativity. (paper)
Quantum biology at the cellular level--elements of the research program.
Bordonaro, Michael; Ogryzko, Vasily
2013-04-01
Quantum biology is emerging as a new field at the intersection between fundamental physics and biology, promising novel insights into the nature and origin of biological order. We discuss several elements of QBCL (quantum biology at cellular level) - a research program designed to extend the reach of quantum concepts to higher than molecular levels of biological organization. We propose a new general way to address the issue of environmentally induced decoherence and macroscopic superpositions in biological systems, emphasizing the 'basis-dependent' nature of these concepts. We introduce the notion of 'formal superposition' and distinguish it from that of Schroedinger's cat (i.e., a superposition of macroscopically distinct states). Whereas the latter notion presents a genuine foundational problem, the former one contradicts neither common sense nor observation, and may be used to describe cellular 'decision-making' and adaptation. We stress that the interpretation of the notion of 'formal superposition' should involve non-classical correlations between molecular events in a cell. Further, we describe how better understanding of the physics of Life can shed new light on the mechanism driving evolutionary adaptation (viz., 'Basis-Dependent Selection', BDS). Experimental tests of BDS and the potential role of synthetic biology in closing the 'evolvability mechanism' loophole are also discussed. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
Interplay of gravitation and linear superposition of different mass eigenstates
International Nuclear Information System (INIS)
Ahluwalia, D.V.
1998-01-01
The interplay of gravitation and the quantum-mechanical principle of linear superposition induces a new set of neutrino oscillation phases. These ensure that the flavor-oscillation clocks, inherent in the phenomenon of neutrino oscillations, redshift precisely as required by Einstein close-quote s theory of gravitation. The physical observability of these phases in the context of the solar neutrino anomaly, type-II supernova, and certain atomic systems is briefly discussed. copyright 1998 The American Physical Society
Quantum Computer Games: Quantum Minesweeper
Gordon, Michal; Gordon, Goren
2010-01-01
The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…
I, Quantum Robot: Quantum Mind control on a Quantum Computer
Zizzi, Paola
2008-01-01
The logic which describes quantum robots is not orthodox quantum logic, but a deductive calculus which reproduces the quantum tasks (computational processes, and actions) taking into account quantum superposition and quantum entanglement. A way toward the realization of intelligent quantum robots is to adopt a quantum metalanguage to control quantum robots. A physical implementation of a quantum metalanguage might be the use of coherent states in brain signals.
Linear superposition solutions to nonlinear wave equations
International Nuclear Information System (INIS)
Liu Yu
2012-01-01
The solutions to a linear wave equation can satisfy the principle of superposition, i.e., the linear superposition of two or more known solutions is still a solution of the linear wave equation. We show in this article that many nonlinear wave equations possess exact traveling wave solutions involving hyperbolic, triangle, and exponential functions, and the suitable linear combinations of these known solutions can also constitute linear superposition solutions to some nonlinear wave equations with special structural characteristics. The linear superposition solutions to the generalized KdV equation K(2,2,1), the Oliver water wave equation, and the k(n, n) equation are given. The structure characteristic of the nonlinear wave equations having linear superposition solutions is analyzed, and the reason why the solutions with the forms of hyperbolic, triangle, and exponential functions can form the linear superposition solutions is also discussed
Superposition as a logical glue
Directory of Open Access Journals (Sweden)
Andrea Asperti
2011-03-01
Full Text Available The typical mathematical language systematically exploits notational and logical abuses whose resolution requires not just the knowledge of domain specific notation and conventions, but not trivial skills in the given mathematical discipline. A large part of this background knowledge is expressed in form of equalities and isomorphisms, allowing mathematicians to freely move between different incarnations of the same entity without even mentioning the transformation. Providing ITP-systems with similar capabilities seems to be a major way to improve their intelligence, and to ease the communication between the user and the machine. The present paper discusses our experience of integration of a superposition calculus within the Matita interactive prover, providing in particular a very flexible, "smart" application tactic, and a simple, innovative approach to automation.
International Nuclear Information System (INIS)
Fillaux, Francois; Cousson, Alain; Gutmann, Matthias J
2008-01-01
We utilize single-crystal neutron diffraction to study the C 2/m structure of potassium hydrogen carbonate (KHCO 3 ) and macroscopic quantum entanglement above the phase transition at T c = 318 K. Whereas split atom sites could be due to disorder, the diffraction pattern at 340 K evidences macroscopic proton states identical to those previously observed below T c by Fillaux et al (2006 J. Phys.: Condens. Matter 18 3229). We propose a theoretical framework for decoherence-free proton states and the calculated differential cross-section accords with observations. The structural transition occurs from one ordered P 2 1 /a structure (T c ) to another ordered C 2/m structure. There is no breakdown of the quantum regime. It is suggested that the crystal is a macroscopic quantum object which can be represented by a state vector. Raman spectroscopy and quasi-elastic neutron scattering suggest that the |C2/m> state vector is a superposition of the state vectors for two P 2 1 /a-like structures symmetric with respect to (a,c) planes
Multiphoton quantum optics and quantum state engineering
Energy Technology Data Exchange (ETDEWEB)
Dell' Anno, Fabio [Dipartimento di Fisica ' E. R. Caianiello' , Universita degli Studi di Salerno, CNISM and CNR-INFM Coherentia, and INFN Sezione di Napoli, Gruppo Collegato di Salerno, Via S. Allende, I-84081 Baronissi (Saudi Arabia) (Italy)]. E-mail: dellanno@sa.infn.it; De Siena, Silvio [Dipartimento di Fisica ' E. R. Caianiello' , Universita degli Studi di Salerno, CNISM and CNR-INFM Coherentia, and INFN Sezione di Napoli, Gruppo Collegato di Salerno, Via S. Allende, I-84081 Baronissi (SA) (Italy)]. E-mail: desiena@sa.infn.it; Illuminati, Fabrizio [Dipartimento di Fisica ' E. R. Caianiello' , Universita degli Studi di Salerno, CNISM and CNR-INFM Coherentia, and INFN Sezione di Napoli, Gruppo Collegato di Salerno, Via S. Allende, I-84081 Baronissi (SA) (Italy)]. E-mail: illuminati@sa.infn.it
2006-05-15
We present a review of theoretical and experimental aspects of multiphoton quantum optics. Multiphoton processes occur and are important for many aspects of matter-radiation interactions that include the efficient ionization of atoms and molecules, and, more generally, atomic transition mechanisms; system-environment couplings and dissipative quantum dynamics; laser physics, optical parametric processes, and interferometry. A single review cannot account for all aspects of such an enormously vast subject. Here we choose to concentrate our attention on parametric processes in nonlinear media, with special emphasis on the engineering of nonclassical states of photons and atoms that are relevant for the conceptual investigations as well as for the practical applications of forefront aspects of modern quantum mechanics. We present a detailed analysis of the methods and techniques for the production of genuinely quantum multiphoton processes in nonlinear media, and the corresponding models of multiphoton effective interactions. We review existing proposals for the classification, engineering, and manipulation of nonclassical states, including Fock states, macroscopic superposition states, and multiphoton generalized coherent states. We introduce and discuss the structure of canonical multiphoton quantum optics and the associated one- and two-mode canonical multiphoton squeezed states. This framework provides a consistent multiphoton generalization of two-photon quantum optics and a consistent Hamiltonian description of multiphoton processes associated to higher-order nonlinearities. Finally, we discuss very recent advances that by combining linear and nonlinear optical devices allow to realize multiphoton entangled states of the electromagnetic field, either in discrete or in continuous variables, that are relevant for applications to efficient quantum computation, quantum teleportation, and related problems in quantum communication and information.
Multiphoton quantum optics and quantum state engineering
International Nuclear Information System (INIS)
Dell'Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio
2006-01-01
We present a review of theoretical and experimental aspects of multiphoton quantum optics. Multiphoton processes occur and are important for many aspects of matter-radiation interactions that include the efficient ionization of atoms and molecules, and, more generally, atomic transition mechanisms; system-environment couplings and dissipative quantum dynamics; laser physics, optical parametric processes, and interferometry. A single review cannot account for all aspects of such an enormously vast subject. Here we choose to concentrate our attention on parametric processes in nonlinear media, with special emphasis on the engineering of nonclassical states of photons and atoms that are relevant for the conceptual investigations as well as for the practical applications of forefront aspects of modern quantum mechanics. We present a detailed analysis of the methods and techniques for the production of genuinely quantum multiphoton processes in nonlinear media, and the corresponding models of multiphoton effective interactions. We review existing proposals for the classification, engineering, and manipulation of nonclassical states, including Fock states, macroscopic superposition states, and multiphoton generalized coherent states. We introduce and discuss the structure of canonical multiphoton quantum optics and the associated one- and two-mode canonical multiphoton squeezed states. This framework provides a consistent multiphoton generalization of two-photon quantum optics and a consistent Hamiltonian description of multiphoton processes associated to higher-order nonlinearities. Finally, we discuss very recent advances that by combining linear and nonlinear optical devices allow to realize multiphoton entangled states of the electromagnetic field, either in discrete or in continuous variables, that are relevant for applications to efficient quantum computation, quantum teleportation, and related problems in quantum communication and information
The emergent Copenhagen interpretation of quantum mechanics
Hollowood, Timothy J.
2014-05-01
We introduce a new and conceptually simple interpretation of quantum mechanics based on reduced density matrices of sub-systems from which the standard Copenhagen interpretation emerges as an effective description of macroscopically large systems. This interpretation describes a world in which definite measurement results are obtained with probabilities that reproduce the Born rule. Wave function collapse is seen to be a useful but fundamentally unnecessary piece of prudent book keeping which is only valid for macro-systems. The new interpretation lies in a class of modal interpretations in that it applies to quantum systems that interact with a much larger environment. However, we show that it does not suffer from the problems that have plagued similar modal interpretations like macroscopic superpositions and rapid flipping between macroscopically distinct states. We describe how the interpretation fits neatly together with fully quantum formulations of statistical mechanics and that a measurement process can be viewed as a process of ergodicity breaking analogous to a phase transition. The key feature of the new interpretation is that joint probabilities for the ergodic subsets of states of disjoint macro-systems only arise as emergent quantities. Finally we give an account of the EPR-Bohm thought experiment and show that the interpretation implies the violation of the Bell inequality characteristic of quantum mechanics but in a way that is rather novel. The final conclusion is that the Copenhagen interpretation gives a completely satisfactory phenomenology of macro-systems interacting with micro-systems.
The emergent Copenhagen interpretation of quantum mechanics
International Nuclear Information System (INIS)
Hollowood, Timothy J
2014-01-01
We introduce a new and conceptually simple interpretation of quantum mechanics based on reduced density matrices of sub-systems from which the standard Copenhagen interpretation emerges as an effective description of macroscopically large systems. This interpretation describes a world in which definite measurement results are obtained with probabilities that reproduce the Born rule. Wave function collapse is seen to be a useful but fundamentally unnecessary piece of prudent book keeping which is only valid for macro-systems. The new interpretation lies in a class of modal interpretations in that it applies to quantum systems that interact with a much larger environment. However, we show that it does not suffer from the problems that have plagued similar modal interpretations like macroscopic superpositions and rapid flipping between macroscopically distinct states. We describe how the interpretation fits neatly together with fully quantum formulations of statistical mechanics and that a measurement process can be viewed as a process of ergodicity breaking analogous to a phase transition. The key feature of the new interpretation is that joint probabilities for the ergodic subsets of states of disjoint macro-systems only arise as emergent quantities. Finally we give an account of the EPR–Bohm thought experiment and show that the interpretation implies the violation of the Bell inequality characteristic of quantum mechanics but in a way that is rather novel. The final conclusion is that the Copenhagen interpretation gives a completely satisfactory phenomenology of macro-systems interacting with micro-systems. (paper)
Macroscopic averages in Qed in material media
International Nuclear Information System (INIS)
Dutra, S.M.; Furuya, K.
1997-01-01
The starting point of macroscopic theories of quantum electrodynamics in material media is usually the classical macroscopic Maxwell equations that are then quantized. Such approach however, is based on the assumption that a macroscopic description is attainable, i.e., it assumes that we can describe the effect of the atoms of material on the field only in terms of a dielectric constant in the regime where the field has to be treated quantum mechanically. The problem we address is whether this assumption is valid at all and if so, under what conditions. We have chosen a simple model, which allows us to start from first principles and determine the validity of these approximations, without simply taking them for granted as in previous papers
Unveiling the curtain of superposition: Recent gedanken and laboratory experiments
Cohen, E.; Elitzur, A. C.
2017-08-01
What is the true meaning of quantum superposition? Can a particle genuinely reside in several places simultaneously? These questions lie at the heart of this paper which presents an updated survey of some important stages in the evolution of the three-boxes paradox, as well as novel conclusions drawn from it. We begin with the original thought experiment of Aharonov and Vaidman, and proceed to its non-counterfactual version. The latter was recently realized by Okamoto and Takeuchi using a quantum router. We then outline a dynamic version of this experiment, where a particle is shown to “disappear” and “re-appear” during the time evolution of the system. This surprising prediction based on self-cancellation of weak values is directly related to our notion of Quantum Oblivion. Finally, we present the non-counterfactual version of this disappearing-reappearing experiment. Within the near future, this last version of the experiment is likely to be realized in the lab, proving the existence of exotic hitherto unknown forms of superposition. With the aid of Bell’s theorem, we prove the inherent nonlocality and nontemporality underlying such pre- and post-selected systems, rendering anomalous weak values ontologically real.
Quantum mechanics: new experiments, new applications, and new formulations of old questions
International Nuclear Information System (INIS)
Menskii, Mikhail B
2000-01-01
Some of the quantum mechanical conceptual problems, their current status, and related theoretical developments are reviewed. The characteristics of the entangled quantum states are analyzed, and new experiments and quantum information applications involving such states are discussed. The well-known paradox of Schroedinger's cat (the impossibility of observing superpositions of macroscopically distinct states that are predicted by quantum mechanics) is discussed. It is shown that decoherence (arising when a quantum system is measured in such a way that some information about its state is recorded in its environment) prevents the distinguishing of a superposition and the corresponding mixture. This overcomes the difficulties associated with the paradoxical nature of quantum measurement provided we remain within the framework of the theory of open systems. Other conceptual difficulties, while actually lying outside physics, are now the subject of much research and have already led to new interesting interpretations of quantum mechanics. The suggestion of Wigner and others that the observer's consciousness be included in the theory of quantum measurement is discussed in this context. A hypothesis is put forward which might enable the functioning of consciousness to be described in quantum measurement terms. (reviews of topical problems)
Decoherence of superposition states in trapped ions
CSIR Research Space (South Africa)
Uys, H
2010-09-01
Full Text Available This paper investigates the decoherence of superpositions of hyperfine states of 9Be+ ions due to spontaneous scattering of off-resonant light. It was found that, contrary to conventional wisdom, elastic Raleigh scattering can have major...
Quasicrystals and Quantum Computing
Berezin, Alexander A.
1997-03-01
In Quantum (Q) Computing qubits form Q-superpositions for macroscopic times. One scheme for ultra-fast (Q) computing can be based on quasicrystals. Ultrafast processing in Q-coherent structures (and the very existence of durable Q-superpositions) may be 'consequence' of presence of entire manifold of integer arithmetic (A0, aleph-naught of Georg Cantor) at any 4-point of space-time, furthermore, at any point of any multidimensional phase space of (any) N-particle Q-system. The latter, apart from quasicrystals, can include dispersed and/or diluted systems (Berezin, 1994). In such systems such alleged centrepieces of Q-Computing as ability for fast factorization of long integers can be processed by sheer virtue of the fact that entire infinite pattern of prime numbers is instantaneously available as 'free lunch' at any instant/point. Infinitely rich pattern of A0 (including pattern of primes and almost primes) acts as 'independent' physical effect which directly generates Q-dynamics (and physical world) 'out of nothing'. Thus Q-nonlocality can be ultimately based on instantaneous interconnectedness through ever- the-same structure of A0 ('Platonic field' of integers).
Exclusion of identification by negative superposition
Directory of Open Access Journals (Sweden)
Takač Šandor
2012-01-01
Full Text Available The paper represents the first report of negative superposition in our country. Photo of randomly selected young, living woman was superimposed on the previously discovered female skull. Computer program Adobe Photoshop 7.0 was used in work. Digitilized photographs of the skull and face, after uploaded to computer, were superimposed on each other and displayed on the monitor in order to assess their possible similarities or differences. Special attention was payed to matching the same anthropometrical points of the skull and face, as well as following their contours. The process of fitting the skull and the photograph is usually started by setting eyes in correct position relative to the orbits. In this case, lower jaw gonions go beyond the face contour and gnathion is highly placed. By positioning the chin, mouth and nose their correct anatomical position cannot be achieved. All the difficulties associated with the superposition were recorded, with special emphasis on critical evaluation of work results in a negative superposition. Negative superposition has greater probative value (exclusion of identification than positive (possible identification. 100% negative superposition is easily achieved, but 100% positive - almost never. 'Each skull is unique and viewed from different perspectives is always a new challenge'. From this point of view, identification can be negative or of high probability.
Macroscopic theory of superconductors
International Nuclear Information System (INIS)
Carr, W.J. Jr.
1981-01-01
A macroscopic theory for bulk superconductors is developed in the framework of the theory for other magnetic materials, where ''magnetization'' current is separated from ''free'' current on the basis of scale. This contrasts with the usual separation into equilibrium and nonequilibrium currents. In the present approach magnetization, on a large macroscopic scale, results from the vortex current, while the Meissner current and other surface currents are surface contributions to the Maxwell j. The results are important for the development of thermodynamics in type-II superconductors. The advantage of the description developed here is that magnetization becomes a local concept and its associated magnetic field can be given physical meaning
Faithful conversion of propagating quantum information to mechanical motion
Reed, A. P.; Mayer, K. H.; Teufel, J. D.; Burkhart, L. D.; Pfaff, W.; Reagor, M.; Sletten, L.; Ma, X.; Schoelkopf, R. J.; Knill, E.; Lehnert, K. W.
2017-12-01
The motion of micrometre-sized mechanical resonators can now be controlled and measured at the fundamental limits imposed by quantum mechanics. These resonators have been prepared in their motional ground state or in squeezed states, measured with quantum-limited precision, and even entangled with microwave fields. Such advances make it possible to process quantum information using the motion of a macroscopic object. In particular, recent experiments have combined mechanical resonators with superconducting quantum circuits to frequency-convert, store and amplify propagating microwave fields. But these systems have not been used to manipulate states that encode quantum bits (qubits), which are required for quantum communication and modular quantum computation. Here we demonstrate the conversion of propagating qubits encoded as superpositions of zero and one photons to the motion of a micromechanical resonator with a fidelity in excess of the classical bound. This ability is necessary for mechanical resonators to convert quantum information between the microwave and optical domains or to act as storage elements in a modular quantum information processor. Additionally, these results are an important step towards testing speculative notions that quantum theory may not be valid for sufficiently massive systems.
Macroscopic magnetic Self assembly
Löthman, Per Arvid
2018-01-01
Exploring the macroscopic scale's similarities to the microscale is part and parcel of this thesis as reflected in the research question: what can we learn about the microscopic scale by studying the macroscale? Investigations of the environment in which the self-assembly takes place, and the
International Nuclear Information System (INIS)
Jack, B.; Leach, J.; Franke-Arnold, S.; Ireland, D. G.; Padgett, M. J.; Yao, A. M.; Barnett, S. M.; Romero, J.
2010-01-01
We use spatial light modulators (SLMs) to measure correlations between arbitrary superpositions of orbital angular momentum (OAM) states generated by spontaneous parametric down-conversion. Our technique allows us to fully access a two-dimensional OAM subspace described by a Bloch sphere, within the higher-dimensional OAM Hilbert space. We quantify the entanglement through violations of a Bell-type inequality for pairs of modal superpositions that lie on equatorial, polar, and arbitrary great circles of the Bloch sphere. Our work shows that SLMs can be used to measure arbitrary spatial states with a fidelity sufficient for appropriate quantum information processing systems.
Diamond NV centers for quantum computing and quantum networks
Childress, L.; Hanson, R.
2013-01-01
The exotic features of quantum mechanics have the potential to revolutionize information technologies. Using superposition and entanglement, a quantum processor could efficiently tackle problems inaccessible to current-day computers. Nonlocal correlations may be exploited for intrinsically secure
Noise-based logic hyperspace with the superposition of 2N states in a single wire
International Nuclear Information System (INIS)
Kish, Laszlo B.; Khatri, Sunil; Sethuraman, Swaminathan
2009-01-01
In the introductory paper [L.B. Kish, Phys. Lett. A 373 (2009) 911], about noise-based logic, we showed how simple superpositions of single logic basis vectors can be achieved in a single wire. The superposition components were the N orthogonal logic basis vectors. Supposing that the different logic values have 'on/off' states only, the resultant discrete superposition state represents a single number with N bit accuracy in a single wire, where N is the number of orthogonal logic vectors in the base. In the present Letter, we show that the logic hyperspace (product) vectors defined in the introductory paper can be generalized to provide the discrete superposition of 2 N orthogonal system states. This is equivalent to a multi-valued logic system with 2 2 N logic values per wire. This is a similar situation to quantum informatics with N qubits, and hence we introduce the notion of noise-bit. This system has major differences compared to quantum informatics. The noise-based logic system is deterministic and each superposition element is instantly accessible with the high digital accuracy, via a real hardware parallelism, without decoherence and error correction, and without the requirement of repeating the logic operation many times to extract the probabilistic information. Moreover, the states in noise-based logic do not have to be normalized, and non-unitary operations can also be used. As an example, we introduce a string search algorithm which is O(√(M)) times faster than Grover's quantum algorithm (where M is the number of string entries), while it has the same hardware complexity class as the quantum algorithm.
Noise-based logic hyperspace with the superposition of 2 states in a single wire
Kish, Laszlo B.; Khatri, Sunil; Sethuraman, Swaminathan
2009-05-01
In the introductory paper [L.B. Kish, Phys. Lett. A 373 (2009) 911], about noise-based logic, we showed how simple superpositions of single logic basis vectors can be achieved in a single wire. The superposition components were the N orthogonal logic basis vectors. Supposing that the different logic values have “on/off” states only, the resultant discrete superposition state represents a single number with N bit accuracy in a single wire, where N is the number of orthogonal logic vectors in the base. In the present Letter, we show that the logic hyperspace (product) vectors defined in the introductory paper can be generalized to provide the discrete superposition of 2 orthogonal system states. This is equivalent to a multi-valued logic system with 2 logic values per wire. This is a similar situation to quantum informatics with N qubits, and hence we introduce the notion of noise-bit. This system has major differences compared to quantum informatics. The noise-based logic system is deterministic and each superposition element is instantly accessible with the high digital accuracy, via a real hardware parallelism, without decoherence and error correction, and without the requirement of repeating the logic operation many times to extract the probabilistic information. Moreover, the states in noise-based logic do not have to be normalized, and non-unitary operations can also be used. As an example, we introduce a string search algorithm which is O(√{M}) times faster than Grover's quantum algorithm (where M is the number of string entries), while it has the same hardware complexity class as the quantum algorithm.
The principle of superposition in human prehension.
Zatsiorsky, Vladimir M; Latash, Mark L; Gao, Fan; Shim, Jae Kun
2004-03-01
The experimental evidence supports the validity of the principle of superposition for multi-finger prehension in humans. Forces and moments of individual digits are defined by two independent commands: "Grasp the object stronger/weaker to prevent slipping" and "Maintain the rotational equilibrium of the object". The effects of the two commands are summed up.
Generation of picosecond pulsed coherent state superpositions
DEFF Research Database (Denmark)
Dong, Ruifang; Tipsmark, Anders; Laghaout, Amine
2014-01-01
We present the generation of approximated coherent state superpositions-referred to as Schrodinger cat states-by the process of subtracting single photons from picosecond pulsed squeezed states of light. The squeezed vacuum states are produced by spontaneous parametric down-conversion (SPDC...... which exhibit non-Gaussian behavior. (C) 2014 Optical Society of America...
Macroscopic Optomechanically Induced Transparency
Pate, Jacob; Castelli, Alessandro; Martinez, Luis; Thompson, Johnathon; Chiao, Ray; Sharping, Jay
Optomechanically induced transparency (OMIT) is an effect wherein the spectrum of a cavity resonance is modified through interference between coupled excitation pathways. In this work we investigate a macroscopic, 3D microwave, superconducting radio frequency (SRF) cavity incorporating a niobium-coated, silicon-nitride membrane as the flexible boundary. The boundary supports acoustic vibrational resonances, which lead to coupling with the microwave resonances of the SRF cavity. The theoretical development and physical understanding of OMIT for our macroscopic SRF cavity is the same as that for other recently-reported OMIT systems despite vastly different optomechanical coupling factors and device sizes. Our mechanical oscillator has a coupling factor of g0 = 2 π . 1 ×10-5 Hz and is roughly 38 mm in diameter. The Q = 5 ×107 for the SRF cavity allows probing of optomechanical effects in the resolved sideband regime.
Experimental motivation and empirical consistency in minimal no-collapse quantum mechanics
International Nuclear Information System (INIS)
Schlosshauer, Maximilian
2006-01-01
We analyze three important experimental domains (SQUIDs, molecular interferometry, and Bose-Einstein condensation) as well as quantum-biophysical studies of the neuronal apparatus to argue that (i) the universal validity of unitary dynamics and the superposition principle has been confirmed far into the mesoscopic and macroscopic realm in all experiments conducted thus far; (ii) all observed 'restrictions' can be correctly and completely accounted for by taking into account environmental decoherence effects; (iii) no positive experimental evidence exists for physical state-vector collapse; (iv) the perception of single 'outcomes' is likely to be explainable through decoherence effects in the neuronal apparatus. We also discuss recent progress in the understanding of the emergence of quantum probabilities and the objectification of observables. We conclude that it is not only viable, but moreover compelling to regard a minimal no-collapse quantum theory as a leading candidate for a physically motivated and empirically consistent interpretation of quantum mechanics
Characterization of quantum logics
International Nuclear Information System (INIS)
Lahti, P.J.
1980-01-01
The quantum logic approach to axiomatic quantum mechanics is used to analyze the conceptual foundations of the traditional quantum theory. The universal quantum of action h>0 is incorporated into the theory by introducing the uncertainty principle, the complementarity principle, and the superposition principle into the framework. A characterization of those quantum logics (L,S) which may provide quantum descriptions is then given. (author)
International Nuclear Information System (INIS)
Kiefer, C.
2004-01-01
The following topics are dealt with: Particles and waves, the superposition principle and probability interpretation, the uncertainty relation, spin, the Schroedinger equation, wave functions, symmetries, the hydrogen atom, atoms with many electrons, Schroedinger's cat and the Einstein-podolsky-Rosen problem, the Bell inequalities, the classical limit, quantum systems in the electromagnetic field, solids and quantum liquids, quantum information, quantum field theory, quantum theory and gravitation, the mathematical formalism of quantum theory. (HSI)
Quantum computer games: quantum minesweeper
Gordon, Michal; Gordon, Goren
2010-07-01
The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical minesweeper the goal of the game is to discover all the mines laid out on a board without triggering them, in the quantum version there are several classical boards in superposition. The goal is to know the exact quantum state, i.e. the precise layout of all the mines in all the superposed classical boards. The player can perform three types of measurement: a classical measurement that probabilistically collapses the superposition; a quantum interaction-free measurement that can detect a mine without triggering it; and an entanglement measurement that provides non-local information. The application of the concepts taught by quantum minesweeper to one-way quantum computing are also presented.
Finite-time quantum-to-classical transition for a Schroedinger-cat state
International Nuclear Information System (INIS)
Paavola, Janika; Hall, Michael J. W.; Paris, Matteo G. A.; Maniscalco, Sabrina
2011-01-01
The transition from quantum to classical, in the case of a quantum harmonic oscillator, is typically identified with the transition from a quantum superposition of macroscopically distinguishable states, such as the Schroedinger-cat state, into the corresponding statistical mixture. This transition is commonly characterized by the asymptotic loss of the interference term in the Wigner representation of the cat state. In this paper we show that the quantum-to-classical transition has different dynamical features depending on the measure for nonclassicality used. Measures based on an operatorial definition have well-defined physical meaning and allow a deeper understanding of the quantum-to-classical transition. Our analysis shows that, for most nonclassicality measures, the Schroedinger-cat state becomes classical after a finite time. Moreover, our results challenge the prevailing idea that more macroscopic states are more susceptible to decoherence in the sense that the transition from quantum to classical occurs faster. Since nonclassicality is a prerequisite for entanglement generation our results also bridge the gap between decoherence, which is lost only asymptotically, and entanglement, which may show a ''sudden death''. In fact, whereas the loss of coherences still remains asymptotic, we emphasize that the transition from quantum to classical can indeed occur at a finite time.
Neutron interferometric tests of quantum mechanics
International Nuclear Information System (INIS)
Rauch, H.
1986-01-01
Since the invention of perfect crystal neutron interferometry this technique has become an important tool in the realization of many textbook experiments in quantum mechanics. Widely separated coherent beams of thermal neutrons are produced and superposed by dynamical Bragg diffraction from a properly shaped perfect crystal. The observed interference patterns show the characteristic coherence properties of matter waves which are influenced by the individual particle and by the properties of the experimental device. The verification of the 4π-periodicity of spinor wavefunctions and the realization of the spin-superposition experiment on a macroscopic scale has become feasible by this technique. A new kind of a quantum beat effect with an energy sensitivity of 2.7 x 20 19 eV has been observed in a double coil resonance experiment. The influence of gravity and of the Earth's rotation on the wavefunction become visible at a level of an elementary particle with non-zero mass. All the results are in agreement with the formulation of quantum mechanics but, nevertheless, they stimulate discussion about its interpretation. The particle-wave dualism becomes obvious on a macroscopic scale and with a beam of massive particles. (author)
On the superposition principle and its physics content
International Nuclear Information System (INIS)
Roos, M.
1984-01-01
What is commonly denoted the superposition principle is shown to consist of three different physical assumptions: conservation of probability, completeness, and some phase conditions. The latter conditions form the physical assumptions of the superposition principle. These phase conditions are exemplified by the Kobayashi-Maskawa matrix. Some suggestions for testing the superposition principle are given. (Auth.)
Quantum interference experiments with complex organic molecules
International Nuclear Information System (INIS)
Eibenberger, S. I.
2015-01-01
measure absolute absorption cross sections in very dilute beams without the need of knowing the vapor pressure. In the future this technique can be extended to a variety of biological molecules. The experiments presented in this thesis define the currently most stringent bound of the experimental macroscopicity parameter for quantum superpositions. (author) [de
Nuclear physics: Macroscopic aspects
International Nuclear Information System (INIS)
Swiatecki, W.J.
1993-12-01
A systematic macroscopic, leptodermous approach to nuclear statics and dynamics is described, based formally on the assumptions ℎ → 0 and b/R << 1, where b is the surface diffuseness and R the nuclear radius. The resulting static model of shell-corrected nuclear binding energies and deformabilities is accurate to better than 1 part in a thousand and yields a firm determination of the principal properties of the nuclear fluid. As regards dynamics, the above approach suggests that nuclear shape evolutions will often be dominated by dissipation, but quantitative comparisons with experimental data are more difficult than in the case of statics. In its simplest liquid drop version the model exhibits interesting formal connections to the classic astronomical problem of rotating gravitating masses
QUANTUM COMPUTING: Quantum Entangled Bits Step Closer to IT.
Zeilinger, A
2000-07-21
In contrast to today's computers, quantum computers and information technologies may in future be able to store and transmit information not only in the state "0" or "1," but also in superpositions of the two; information will then be stored and transmitted in entangled quantum states. Zeilinger discusses recent advances toward using this principle for quantum cryptography and highlights studies into the entanglement (or controlled superposition) of several photons, atoms, or ions.
Measurement contextuality is implied by macroscopic realism
International Nuclear Information System (INIS)
Chen Zeqian; Montina, A.
2011-01-01
Ontological theories of quantum mechanics provide a realistic description of single systems by means of well-defined quantities conditioning the measurement outcomes. In order to be complete, they should also fulfill the minimal condition of macroscopic realism. Under the assumption of outcome determinism and for Hilbert space dimension greater than 2, they were all proved to be contextual for projective measurements. In recent years a generalized concept of noncontextuality was introduced that applies also to the case of outcome indeterminism and unsharp measurements. It was pointed out that the Beltrametti-Bugajski model is an example of measurement noncontextual indeterminist theory. Here we provide a simple proof that this model is the only one with such a feature for projective measurements and Hilbert space dimension greater than 2. In other words, there is no extension of quantum theory providing more accurate predictions of outcomes and simultaneously preserving the minimal labeling of events through projective operators. As a corollary, noncontextuality for projective measurements implies noncontextuality for unsharp measurements. By noting that the condition of macroscopic realism requires an extension of quantum theory, unless a breaking of unitarity is invoked, we arrive at the conclusion that the only way to solve the measurement problem in the framework of an ontological theory is by relaxing the hypothesis of measurement noncontextuality in its generalized sense.
Towards testing quantum physics in deep space
Kaltenbaek, Rainer
2016-07-01
MAQRO is a proposal for a medium-sized space mission to use the unique environment of deep space in combination with novel developments in space technology and quantum technology to test the foundations of physics. The goal is to perform matter-wave interferometry with dielectric particles of up to 10^{11} atomic mass units and testing for deviations from the predictions of quantum theory. Novel techniques from quantum optomechanics with optically trapped particles are to be used for preparing the test particles for these experiments. The core elements of the instrument are placed outside the spacecraft and insulated from the hot spacecraft via multiple thermal shields allowing to achieve cryogenic temperatures via passive cooling and ultra-high vacuum levels by venting to deep space. In combination with low force-noise microthrusters and inertial sensors, this allows realizing an environment well suited for long coherence times of macroscopic quantum superpositions and long integration times. Since the original proposal in 2010, significant progress has been made in terms of technology development and in refining the instrument design. Based on these new developments, we submitted/will submit updated versions of the MAQRO proposal in 2015 and 2016 in response to Cosmic-Vision calls of ESA for a medium-sized mission. A central goal has been to address and overcome potentially critical issues regarding the readiness of core technologies and to provide realistic concepts for further technology development. We present the progress on the road towards realizing this ground-breaking mission harnessing deep space in novel ways for testing the foundations of physics, a technology pathfinder for macroscopic quantum technology and quantum optomechanics in space.
Quantum Statistics and Entanglement Problems
Trainor, L. E. H.; Lumsden, Charles J.
2002-01-01
Interpretations of quantum measurement theory have been plagued by two questions, one concerning the role of observer consciousness and the other the entanglement phenomenon arising from the superposition of quantum states. We emphasize here the remarkable role of quantum statistics in describing the entanglement problem correctly and discuss the relationship to issues arising from current discussions of intelligent observers in entangled, decohering quantum worlds.
Extended superposed quantum-state initialization using disjoint prime implicants
International Nuclear Information System (INIS)
Rosenbaum, David; Perkowski, Marek
2009-01-01
Extended superposed quantum-state initialization using disjoint prime implicants is an algorithm for generating quantum arrays for the purpose of initializing a desired quantum superposition. The quantum arrays generated by this algorithm almost always use fewer gates than other algorithms and in the worst case use the same number of gates. These improvements are achieved by allowing certain parts of the quantum superposition that cannot be initialized directly by the algorithm to be initialized using special circuits. This allows more terms in the quantum superposition to be initialized at the same time which decreases the number of gates required by the generated quantum array.
Energy Technology Data Exchange (ETDEWEB)
Abram, I [Centre National d' Etudes des Telecommunications (CNET), 196 Avenue Henri Ravera, F-92220 Bagneux (France)
1999-02-01
results in an improvement in the bit-error rate of the transmission. The fact that squeezing does not survive attenuation does not matter in this case, since it is alive during the nonlinear interaction when it is needed. Another possible application of squeezed solitons would be in switching devices and logic gates based on soliton interactions, such as the fibre-end devices for signal processing in telecommunications developed by Mohamed Islam at AT and T in the US in the early 1990s. The use of number-squeezing would allow collisions between solitons to be controlled to high precision, thus significantly reducing the error rate of these devices. Solitons and quantum information It might also be possible to use solitons in the processing of quantum information. Quantum information is an emerging field of physics that takes advantage of phenomena that are particular to quantum mechanics such as uncertainty, superposition and entanglement to code, transmit or process information (see Physics World March 1998). Recent highlights in this field include quantum cryptography (which can be used to achieve unconditionally secure key distribution) and quantum computing, which considerably speeds up the solution of problems that are exponentially difficult. These problems include the factorization of large numbers and searches of large databases. Although most proposals for processing quantum information to date concentrate on single-photon or single-spin implementations, optical solitons may offer an alternative that is easier to handle experimentally, yet still provides many of the basic quantum features that are displayed by single quanta. This could lead to new paradigms for computation and communications. In particular, the existence of quantum correlations in the fluctuations of the spectral and temporal sidebands of the solitons turns them into macroscopic quantum objects with internal entanglement. If these internal quantum correlations can be tailored into prescribed
Microscopic and macroscopic bell inequalities
International Nuclear Information System (INIS)
Santos, E.
1984-01-01
The Bell inequalities, being derived for micro-systems, cannot be tested by (macroscopic) experiments without additional assumptions. A macroscopic definition of local realism is proposed which might be the starting point for deriving Bell inequalities testable without auxiliary assumptions. (orig.)
Atomic quantum superposition state generation via optical probing
DEFF Research Database (Denmark)
Nielsen, Anne E. B.; Poulsen, Uffe Vestergaard; Negretti, Antonio
2009-01-01
investigate cavity enhanced probing with continuous beams of both coherent and squeezed light. The stochastic master equations used in the analysis are expressed in terms of the Hamiltonian of the probed system and the interaction between the probed system and the probe field and are thus quite generally...
Quantum teleportation of an arbitrary superposition of atomic states
Institute of Scientific and Technical Information of China (English)
Chen Qiong; Fang Xi-Ming
2008-01-01
This paper proposes a scheme to teleport an arbitrary multi-particle two-level atomic state between two parties or an arbitrary zero- and one-photon entangled state of multi-mode between two high-Q cavities in cavity QED.This scheme is based on the resonant interaction between atom and cavity and does not involve Bell-state measurement.It investigates the fidelity of this scheme and find out the case of this unity fidelity of this teleportation.Considering the practical case of the cavity decay,this paper finds that the condition of the unity fidelity is also valid and obtains the effect of the decay of the cavity on the successful probability of the teleportation.
Bell-inequality tests with macroscopic entangled states of light
Energy Technology Data Exchange (ETDEWEB)
Stobinska, M. [Max Planck Institute for the Science of Light, Erlangen (Germany); Institute for Theoretical Physics II, Erlangen-Nuernberg University, Erlangen (Germany); Sekatski, P.; Gisin, N. [Group of Applied Physics, University of Geneva, Geneva (Switzerland); Buraczewski, A. [Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw (Poland); Leuchs, G. [Max Planck Institute for the Science of Light, Erlangen (Germany); Institute for Optics, Information and Photonics, Erlangen-Nuernberg University, Erlangen (Germany)
2011-09-15
Quantum correlations may violate the Bell inequalities. Most experimental schemes confirming this prediction have been realized in all-optical Bell tests suffering from the detection loophole. Experiments which simultaneously close this loophole and the locality loophole are highly desirable and remain challenging. An approach to loophole-free Bell tests is based on amplification of the entangled photons (i.e., on macroscopic entanglement), for which an optical signal should be easy to detect. However, the macroscopic states are partially indistinguishable by classical detectors. An interesting idea to overcome these limitations is to replace the postselection by an appropriate preselection immediately after the amplification. This is in the spirit of state preprocessing revealing hidden nonlocality. Here, we examine one of the possible preselections, but the presented tools can be used for analysis of other schemes. Filtering methods making the macroscopic entanglement useful for Bell tests and quantum protocols are the subject of an intensive study in the field nowadays.
Macroscopic charge quantization in single-electron devices
Burmistrov, I.S.; Pruisken, A.M.M.
2010-01-01
In a recent paper by the authors [I. S. Burmistrov and A. M. M. Pruisken, Phys. Rev. Lett. 101, 056801 (2008)] it was shown that single-electron devices (single-electron transistor or SET) display "macroscopic charge quantization" which is completely analogous to the quantum Hall effect observed on
On the superposition principle in interference experiments.
Sinha, Aninda; H Vijay, Aravind; Sinha, Urbasi
2015-05-14
The superposition principle is usually incorrectly applied in interference experiments. This has recently been investigated through numerics based on Finite Difference Time Domain (FDTD) methods as well as the Feynman path integral formalism. In the current work, we have derived an analytic formula for the Sorkin parameter which can be used to determine the deviation from the application of the principle. We have found excellent agreement between the analytic distribution and those that have been earlier estimated by numerical integration as well as resource intensive FDTD simulations. The analytic handle would be useful for comparing theory with future experiments. It is applicable both to physics based on classical wave equations as well as the non-relativistic Schrödinger equation.
Quantum phase-space analysis of the pendular cavity
International Nuclear Information System (INIS)
Olsen, M.K.; Melo, A.B.; Dechoum, K.; Khoury, A.Z.
2004-01-01
We perform a quantum-mechanical analysis of the pendular cavity, using the positive-P representation, showing that the quantum state of the moving mirror, a macroscopic object, has noticeable effects on the dynamics. This system has previously been proposed as a candidate for the quantum-limited measurement of small displacements of the mirror due to radiation pressure, for the production of states with entanglement between the mirror and the field, and even for superposition states of the mirror. However, when we treat the oscillating mirror quantum mechanically, we find that it always oscillates, has no stationary steady state, and exhibits uncertainties in position and momentum which are typically larger than the mean values. This means that previous linearized fluctuation analyses which have been used to predict these highly quantum states are of limited use. We find that the achievable accuracy in measurement is far worse than the standard quantum limit due to thermal noise, which, for typical experimental parameters, is overwhelming even at 2 mK
Kholmetskii, A. L.; Missevitch, O. V.; Yarman, T.
2018-05-01
We point out that the known quantum phases for an electric/magnetic dipole moving in an electromagnetic (EM) field must be presented as the superposition of more fundamental quantum phases emerging for elementary charges. Using this idea, we find two new fundamental quantum phases for point-like charges, next to the known electric and magnetic Aharonov-Bohm (A-B) phases, named by us as the complementary electric and magnetic phases, correspondingly. We further demonstrate that these new phases can indeed be derived via the Schrödinger equation for a particle in an EM field, where however the operator of momentum is re-defined via the replacement of the canonical momentum of particle by the sum of its mechanical momentum and interactional field momentum for a system "charged particle and a macroscopic source of EM field". The implications of the obtained results are discussed.
Noise-based logic hyperspace with the superposition of 2{sup N} states in a single wire
Energy Technology Data Exchange (ETDEWEB)
Kish, Laszlo B. [Texas A and M University, Department of Electrical and Computer Engineering, College Station, TX 77843-3128 (United States)], E-mail: laszlo.kish@ece.tamu.edu; Khatri, Sunil; Sethuraman, Swaminathan [Texas A and M University, Department of Electrical and Computer Engineering, College Station, TX 77843-3128 (United States)
2009-05-11
In the introductory paper [L.B. Kish, Phys. Lett. A 373 (2009) 911], about noise-based logic, we showed how simple superpositions of single logic basis vectors can be achieved in a single wire. The superposition components were the N orthogonal logic basis vectors. Supposing that the different logic values have 'on/off' states only, the resultant discrete superposition state represents a single number with N bit accuracy in a single wire, where N is the number of orthogonal logic vectors in the base. In the present Letter, we show that the logic hyperspace (product) vectors defined in the introductory paper can be generalized to provide the discrete superposition of 2{sup N} orthogonal system states. This is equivalent to a multi-valued logic system with 2{sup 2{sup N}} logic values per wire. This is a similar situation to quantum informatics with N qubits, and hence we introduce the notion of noise-bit. This system has major differences compared to quantum informatics. The noise-based logic system is deterministic and each superposition element is instantly accessible with the high digital accuracy, via a real hardware parallelism, without decoherence and error correction, and without the requirement of repeating the logic operation many times to extract the probabilistic information. Moreover, the states in noise-based logic do not have to be normalized, and non-unitary operations can also be used. As an example, we introduce a string search algorithm which is O({radical}(M)) times faster than Grover's quantum algorithm (where M is the number of string entries), while it has the same hardware complexity class as the quantum algorithm.
Quantum Information Processing
Leuchs, Gerd
2005-01-01
Quantum processing and communication is emerging as a challenging technique at the beginning of the new millennium. This is an up-to-date insight into the current research of quantum superposition, entanglement, and the quantum measurement process - the key ingredients of quantum information processing. The authors further address quantum protocols and algorithms. Complementary to similar programmes in other countries and at the European level, the German Research Foundation (DFG) started a focused research program on quantum information in 1999. The contributions - written by leading experts - bring together the latest results in quantum information as well as addressing all the relevant questions
THESEUS: maximum likelihood superpositioning and analysis of macromolecular structures.
Theobald, Douglas L; Wuttke, Deborah S
2006-09-01
THESEUS is a command line program for performing maximum likelihood (ML) superpositions and analysis of macromolecular structures. While conventional superpositioning methods use ordinary least-squares (LS) as the optimization criterion, ML superpositions provide substantially improved accuracy by down-weighting variable structural regions and by correcting for correlations among atoms. ML superpositioning is robust and insensitive to the specific atoms included in the analysis, and thus it does not require subjective pruning of selected variable atomic coordinates. Output includes both likelihood-based and frequentist statistics for accurate evaluation of the adequacy of a superposition and for reliable analysis of structural similarities and differences. THESEUS performs principal components analysis for analyzing the complex correlations found among atoms within a structural ensemble. ANSI C source code and selected binaries for various computing platforms are available under the GNU open source license from http://monkshood.colorado.edu/theseus/ or http://www.theseus3d.org.
Quantum memory for images: A quantum hologram
International Nuclear Information System (INIS)
Vasilyev, Denis V.; Sokolov, Ivan V.; Polzik, Eugene S.
2008-01-01
Matter-light quantum interface and quantum memory for light are important ingredients of quantum information protocols, such as quantum networks, distributed quantum computation, etc. [P. Zoller et al., Eur. Phys. J. D 36, 203 (2005)]. In this paper we present a spatially multimode scheme for quantum memory for light, which we call a quantum hologram. Our approach uses a multiatom ensemble which has been shown to be efficient for a single spatial mode quantum memory. Due to the multiatom nature of the ensemble and to the optical parallelism it is capable of storing many spatial modes, a feature critical for the present proposal. A quantum hologram with the fidelity exceeding that of classical hologram will be able to store quantum features of an image, such as multimode superposition and entangled quantum states, something that a standard hologram is unable to achieve
Statistical thermodynamics understanding the properties of macroscopic systems
Fai, Lukong Cornelius
2012-01-01
Basic Principles of Statistical PhysicsMicroscopic and Macroscopic Description of StatesBasic PostulatesGibbs Ergodic AssumptionGibbsian EnsemblesExperimental Basis of Statistical MechanicsDefinition of Expectation ValuesErgodic Principle and Expectation ValuesProperties of Distribution FunctionRelative Fluctuation of an Additive Macroscopic ParameterLiouville TheoremGibbs Microcanonical EnsembleMicrocanonical Distribution in Quantum MechanicsDensity MatrixDensity Matrix in Energy RepresentationEntropyThermodynamic FunctionsTemperatureAdiabatic ProcessesPressureThermodynamic IdentityLaws of Th
Fermionic entanglement via quantum walks in quantum dots
Melnikov, Alexey A.; Fedichkin, Leonid E.
2018-02-01
Quantum walks are fundamentally different from random walks due to the quantum superposition property of quantum objects. Quantum walk process was found to be very useful for quantum information and quantum computation applications. In this paper we demonstrate how to use quantum walks as a tool to generate high-dimensional two-particle fermionic entanglement. The generated entanglement can survive longer in the presence of depolorazing noise due to the periodicity of quantum walk dynamics. The possibility to create two distinguishable qudits in a system of tunnel-coupled semiconductor quantum dots is discussed.
Weak measurements and quantum weak values for NOON states
Rosales-Zárate, L.; Opanchuk, B.; Reid, M. D.
2018-03-01
Quantum weak values arise when the mean outcome of a weak measurement made on certain preselected and postselected quantum systems goes beyond the eigenvalue range for a quantum observable. Here, we propose how to determine quantum weak values for superpositions of states with a macroscopically or mesoscopically distinct mode number, that might be realized as two-mode Bose-Einstein condensate or photonic NOON states. Specifically, we give a model for a weak measurement of the Schwinger spin of a two-mode NOON state, for arbitrary N . The weak measurement arises from a nondestructive measurement of the two-mode occupation number difference, which for atomic NOON states might be realized via phase contrast imaging and the ac Stark effect using an optical meter prepared in a coherent state. The meter-system coupling results in an entangled cat-state. By subsequently evolving the system under the action of a nonlinear Josephson Hamiltonian, we show how postselection leads to quantum weak values, for arbitrary N . Since the weak measurement can be shown to be minimally invasive, the weak values provide a useful strategy for a Leggett-Garg test of N -scopic realism.
Optimal simultaneous superpositioning of multiple structures with missing data.
Theobald, Douglas L; Steindel, Phillip A
2012-08-01
Superpositioning is an essential technique in structural biology that facilitates the comparison and analysis of conformational differences among topologically similar structures. Performing a superposition requires a one-to-one correspondence, or alignment, of the point sets in the different structures. However, in practice, some points are usually 'missing' from several structures, for example, when the alignment contains gaps. Current superposition methods deal with missing data simply by superpositioning a subset of points that are shared among all the structures. This practice is inefficient, as it ignores important data, and it fails to satisfy the common least-squares criterion. In the extreme, disregarding missing positions prohibits the calculation of a superposition altogether. Here, we present a general solution for determining an optimal superposition when some of the data are missing. We use the expectation-maximization algorithm, a classic statistical technique for dealing with incomplete data, to find both maximum-likelihood solutions and the optimal least-squares solution as a special case. The methods presented here are implemented in THESEUS 2.0, a program for superpositioning macromolecular structures. ANSI C source code and selected compiled binaries for various computing platforms are freely available under the GNU open source license from http://www.theseus3d.org. dtheobald@brandeis.edu Supplementary data are available at Bioinformatics online.
Macroscopic reality and the dynamical reduction program
International Nuclear Information System (INIS)
Ghirardi, G.C.
1995-10-01
With reference to recently proposed theoretical models accounting for reduction in terms of a unified dynamics governing all physical processes, we analyze the problem of working out a worldview accommodating our knowledge about natural phenomena. We stress the relevant conceptual differences between the considered models and standard quantum mechanics. In spite of the fact that both theories describe individual physical systems within a genuine Hilbert space framework, the nice features of spontaneous reduction theories drastically limit the class of states which are dynamically stable. This allows one to work out a description of the world in terms of a mass density function in ordinary configuration space. A topology based on this function and differing radically from the one characterizing the Hilbert space is introduced and in terms of it the idea of similarity of macroscopic situations is made precise. Finally it is shown how the formalism and the proposed interpretation yield a natural criterion for establishing the psychophysical parallelism. The conclusion is that, within the considered theoretical models and at the nonrelativistic level, one can satisfy all sensible requirements for a consistent, unified, and objective description of reality at the macroscopic level. (author). 16 refs
Macroscopic reality and the dynamical reduction program
Energy Technology Data Exchange (ETDEWEB)
Ghirardi, G C
1995-10-01
With reference to recently proposed theoretical models accounting for reduction in terms of a unified dynamics governing all physical processes, we analyze the problem of working out a worldview accommodating our knowledge about natural phenomena. We stress the relevant conceptual differences between the considered models and standard quantum mechanics. In spite of the fact that both theories describe individual physical systems within a genuine Hilbert space framework, the nice features of spontaneous reduction theories drastically limit the class of states which are dynamically stable. This allows one to work out a description of the world in terms of a mass density function in ordinary configuration space. A topology based on this function and differing radically from the one characterizing the Hilbert space is introduced and in terms of it the idea of similarity of macroscopic situations is made precise. Finally it is shown how the formalism and the proposed interpretation yield a natural criterion for establishing the psychophysical parallelism. The conclusion is that, within the considered theoretical models and at the nonrelativistic level, one can satisfy all sensible requirements for a consistent, unified, and objective description of reality at the macroscopic level. (author). 16 refs.
Does the Equivalence between Gravitational Mass and Energy Survive for a Composite Quantum Body?
Directory of Open Access Journals (Sweden)
A. G. Lebed
2014-01-01
Full Text Available We define passive and active gravitational mass operators of the simplest composite quantum body—a hydrogen atom. Although they do not commute with its energy operator, the equivalence between the expectation values of passive and active gravitational masses and energy is shown to survive for stationary quantum states. In our calculations of passive gravitational mass operator, we take into account not only kinetic and Coulomb potential energies but also the so-called relativistic corrections to electron motion in a hydrogen atom. Inequivalence between passive and active gravitational masses and energy at a macroscopic level is demonstrated to reveal itself as time-dependent oscillations of the expectation values of the gravitational masses for superpositions of stationary quantum states. Breakdown of the equivalence between passive gravitational mass and energy at a microscopic level reveals itself as unusual electromagnetic radiation, emitted by macroscopic ensemble of hydrogen atoms, moved by small spacecraft with constant velocity in the Earth’s gravitational field. We suggest the corresponding experiment on the Earth’s orbit to detect this radiation, which would be the first direct experiment where quantum effects in general relativity are observed.
International Nuclear Information System (INIS)
Chernichenko, Yu.D.
2005-01-01
Within the relativistic quasipotential approach to quantum field theory, the relativistic inverse scattering problem is solved for the case where the total quasipotential describing the interaction of two relativistic spinless particles having different masses is a superposition of a nonlocal separable and a local quasipotential. It is assumed that the local component of the total quasipotential is known and that there exist bound states in this local component. It is shown that the nonlocal separable component of the total interaction can be reconstructed provided that the local component, an increment of the phase shift, and the energies of bound states are known
Entanglement and discord of the superposition of Greenberger-Horne-Zeilinger states
International Nuclear Information System (INIS)
Parashar, Preeti; Rana, Swapan
2011-01-01
We calculate the analytic expression for geometric measure of entanglement for arbitrary superposition of two N-qubit canonical orthonormal Greenberger-Horne-Zeilinger (GHZ) states and the same for two W states. In the course of characterizing all kinds of nonclassical correlations, an explicit formula for quantum discord (via relative entropy) for the former class of states has been presented. Contrary to the GHZ state, the closest separable state to the W state is not classical. Therefore, in this case, the discord is different from the relative entropy of entanglement. We conjecture that the discord for the N-qubit W state is log 2 N.
Empirical Evaluation of Superposition Coded Multicasting for Scalable Video
Chun Pong Lau
2013-03-01
In this paper we investigate cross-layer superposition coded multicast (SCM). Previous studies have proven its effectiveness in exploiting better channel capacity and service granularities via both analytical and simulation approaches. However, it has never been practically implemented using a commercial 4G system. This paper demonstrates our prototype in achieving the SCM using a standard 802.16 based testbed for scalable video transmissions. In particular, to implement the superposition coded (SPC) modulation, we take advantage a novel software approach, namely logical SPC (L-SPC), which aims to mimic the physical layer superposition coded modulation. The emulation results show improved throughput comparing with generic multicast method.
Al-Khalili, Jim
2003-01-01
In this lively look at quantum science, a physicist takes you on an entertaining and enlightening journey through the basics of subatomic physics. Along the way, he examines the paradox of quantum mechanics--beautifully mathematical in theory but confoundingly unpredictable in the real world. Marvel at the Dual Slit experiment as a tiny atom passes through two separate openings at the same time. Ponder the peculiar communication of quantum particles, which can remain in touch no matter how far apart. Join the genius jewel thief as he carries out a quantum measurement on a diamond without ever touching the object in question. Baffle yourself with the bizzareness of quantum tunneling, the equivalent of traveling partway up a hill, only to disappear then reappear traveling down the opposite side. With its clean, colorful layout and conversational tone, this text will hook you into the conundrum that is quantum mechanics.
Generating superpositions of higher order bessel beams [Conference paper
CSIR Research Space (South Africa)
Vasilyeu, R
2009-10-01
Full Text Available An experimental setup to generate a superposition of higher-order Bessel beams by means of a spatial light modulator and ring aperture is presented. The experimentally produced fields are in good agreement with those calculated theoretically....
Empirical Evaluation of Superposition Coded Multicasting for Scalable Video
Chun Pong Lau; Shihada, Basem; Pin-Han Ho
2013-01-01
In this paper we investigate cross-layer superposition coded multicast (SCM). Previous studies have proven its effectiveness in exploiting better channel capacity and service granularities via both analytical and simulation approaches. However
Macroscopic models for traffic safety.
Oppe, S.
1988-01-01
Recently there has been an increased interest in the application of macroscopic models for the description of developments in traffic safety. A discussion was started on the causes of the sudden decrease in the number of fatal and injury accidents after 1974. Before that time these numbers had
International Nuclear Information System (INIS)
Roa, Luis; Retamal, Juan Carlos; Saavedra, Carlos
2002-01-01
A proposal for a physical implementation of a quantum-state discrimination protocol using an ion in a linear trap is studied, where two nonorthogonal quantum states are codified using two electronic states of the ion. In addition, a protocol is given for discriminating superpositions of nonorthogonal entangled states between ions inside widely separated optical cavities. The discrimination protocol is extended to the case of N linearly independent nonorthogonal quantum states lying in a space of 2N-1 dimensions
Pseudo-Goldstone bosons and new macroscopic forces
International Nuclear Information System (INIS)
Hill, C.T.; Ross, G.G.
1988-01-01
Pseudoscalar Goldstone bosons may readily be associated with weakly, explicitly broken symmetries giving them mixed CP quantum numbers. In general this leads to scalar couplings to nucleons and leptons, which produces coherent long range forces. This can naturally accommodate detectable long range macroscopic forces mediated by bosons completely consistent with conventional cosmological limits, e.g., new interactions with the range of present 'fifth force' searches which probe a scale of new physics of f ≅ 10 14 GeV. (orig.)
International Nuclear Information System (INIS)
Zhang Aixia; Xue Jukui
2012-01-01
We propose a scheme to reveal the interplay between dipole–dipole interaction (DDI), inter-level coupling and macroscopic phase transitions in dipolar condensates. By considering a macroscopic sample of dipolar bosons in triple-well potentials, DDI-induced coupling between the inter-level physics and the macroscopic phase transitions is presented. When the DDI exceeds certain thresholds, the degeneracy of the two lowest energy levels and the excitation of new eigenstates occur, respectively. Interestingly, these thresholds give the boundaries of various quantum phase transitions. That is, the quantum phase transitions are the consequence of the levels' degeneracy and the new eigenstates' excitation. Furthermore, DDI-induced long-range macroscopic Josephson oscillations are observed and long-range coherent quantum transportation is achieved. Our results give clear proof of the interplay between the multi-level physics and quantum phase transitions, and also provide a way for designing the long-range coherent quantum transportation. (paper)
The Two-Time Interpretation and Macroscopic Time-Reversibility
Directory of Open Access Journals (Sweden)
Yakir Aharonov
2017-03-01
Full Text Available The two-state vector formalism motivates a time-symmetric interpretation of quantum mechanics that entails a resolution of the measurement problem. We revisit a post-selection-assisted collapse model previously suggested by us, claiming that unlike the thermodynamic arrow of time, it can lead to reversible dynamics at the macroscopic level. In addition, the proposed scheme enables us to characterize the classical-quantum boundary. We discuss the limitations of this approach and its broad implications for other areas of physics.
Searching for the nanoscopic–macroscopic boundary
Energy Technology Data Exchange (ETDEWEB)
Velásquez, E.A. [GICM and GES Groups, Instituto de Física-FCEN, Universidad de Antioquia UdeA, Calle 70 No. 52-21 Medellín (Colombia); Grupo de Investigación en Modelamiento y Simulación Computacional, Universidad de San Buenaventura Sec. Medellín, A.A. 5222, Medellín (Colombia); Altbir, D. [Departamento de Física, Universidad de Santiago de Chile (USACH), CEDENNA, Santiago (Chile); Mazo-Zuluaga, J. [GICM and GES Groups, Instituto de Física-FCEN, Universidad de Antioquia UdeA, Calle 70 No. 52-21 Medellín (Colombia); Duque, L.F. [GICM and GES Groups, Instituto de Física-FCEN, Universidad de Antioquia UdeA, Calle 70 No. 52-21 Medellín (Colombia); Grupo de Física Teórica, Aplicada y Didáctica, Facultad de Ciencias Exactas y Aplicadas Instituto Tecnológico Metropolitano, Medellín (Colombia); Mejía-López, J., E-mail: jmejia@puc.cl [Facultad de Física, Pontificia Universidad Católica de Chile, CEDENNA, Santiago (Chile)
2013-12-15
Several studies have focused on the size-dependent properties of elements, looking for a unique definition of the nanoscopic–macroscopic boundary. By using a novel approach consisting of an energy variational method combined with a quantum Heisenberg model, here we address the size at which the ordering temperature of a magnetic nanoparticle reaches its bulk value. We consider samples with sizes in the range 1–500 nm, as well as several geometries and crystalline lattices and observe that, contrarily to what is commonly argued, the nanoscopic-microscopic boundary depends on both factors: shape and crystalline structure. This suggests that the surface-to-volume ratio is not the unique parameter that defines the behavior of a nanometric sample whenever its size increases reaching the bulk dimension. Comparisons reveal very good agreement with experimental evidence with differences less than 2%. Our results have broad implications for practical issues in measurements on systems at the nanometric scale. - Highlights: • A novel quantum-Heisenberg variational energy method is implemented. • The asymptotic behavior toward the thermodynamic limit is explored. • An important dependence of the nano-bulk boundary on the geometry is found. • And also an important dependence on the crystalline lattice. • We obtain a very good agreement with experimental evidence with differences <2%.
A quantum computer only needs one universe
Steane, A. M.
2000-01-01
The nature of quantum computation is discussed. It is argued that, in terms of the amount of information manipulated in a given time, quantum and classical computation are equally efficient. Quantum superposition does not permit quantum computers to ``perform many computations simultaneously'' except in a highly qualified and to some extent misleading sense. Quantum computation is therefore not well described by interpretations of quantum mechanics which invoke the concept of vast numbers of ...
Quantum Chess: Making Quantum Phenomena Accessible
Cantwell, Christopher
Quantum phenomena have remained largely inaccessible to the general public. There tends to be a scare factor associated with the word ``Quantum''. This is in large part due to the alien nature of phenomena such as superposition and entanglement. However, Quantum Computing is a very active area of research and one day we will have games that run on those quantum computers. Quantum phenomena such as superposition and entanglement will seem as normal as gravity. Is it possible to create such games today? Can we make games that are built on top of a realistic quantum simulation and introduce players of any background to quantum concepts in a fun and mentally stimulating way? One of the difficulties with any quantum simulation run on a classical computer is that the Hilbert space grows exponentially, making simulations of an appreciable size physically impossible due largely to memory restrictions. Here we will discuss the conception and development of Quantum Chess, and how to overcome some of the difficulties faced. We can then ask the question, ``What's next?'' What are some of the difficulties Quantum Chess still faces, and what is the future of quantum games?
Quantum measurement and entanglement of spin quantum bits in diamond
Pfaff, W.
2013-01-01
This thesis presents a set of experiments that explore the possible realisation of a macroscopic quantum network based on solid-state quantum bits. Such a quantum network would allow for studying quantum mechanics on large scales (meters, or even kilometers), and can open new possibilities for
Non-coaxial superposition of vector vortex beams.
Aadhi, A; Vaity, Pravin; Chithrabhanu, P; Reddy, Salla Gangi; Prabakar, Shashi; Singh, R P
2016-02-10
Vector vortex beams are classified into four types depending upon spatial variation in their polarization vector. We have generated all four of these types of vector vortex beams by using a modified polarization Sagnac interferometer with a vortex lens. Further, we have studied the non-coaxial superposition of two vector vortex beams. It is observed that the superposition of two vector vortex beams with same polarization singularity leads to a beam with another kind of polarization singularity in their interaction region. The results may be of importance in ultrahigh security of the polarization-encrypted data that utilizes vector vortex beams and multiple optical trapping with non-coaxial superposition of vector vortex beams. We verified our experimental results with theory.
Robust mesoscopic superposition of strongly correlated ultracold atoms
International Nuclear Information System (INIS)
Hallwood, David W.; Ernst, Thomas; Brand, Joachim
2010-01-01
We propose a scheme to create coherent superpositions of annular flow of strongly interacting bosonic atoms in a one-dimensional ring trap. The nonrotating ground state is coupled to a vortex state with mesoscopic angular momentum by means of a narrow potential barrier and an applied phase that originates from either rotation or a synthetic magnetic field. We show that superposition states in the Tonks-Girardeau regime are robust against single-particle loss due to the effects of strong correlations. The coupling between the mesoscopically distinct states scales much more favorably with particle number than in schemes relying on weak interactions, thus making particle numbers of hundreds or thousands feasible. Coherent oscillations induced by time variation of parameters may serve as a 'smoking gun' signature for detecting superposition states.
International Nuclear Information System (INIS)
Rodgers, P.
1998-01-01
There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)
Energy Technology Data Exchange (ETDEWEB)
Rodgers, P
1998-03-01
There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)
International Nuclear Information System (INIS)
Khrennikov, Andrei; Klein, Moshe; Mor, Tal
2010-01-01
In number theory, a partition of a positive integer n is a way of writing n as a sum of positive integers. The number of partitions of n is given by the partition function p(n). Inspired by quantum information processing, we extend the concept of partitions in number theory as follows: for an integer n, we treat each partition as a basis state of a quantum system representing that number n, so that the Hilbert-space that corresponds to that integer n is of dimension p(n); the 'classical integer' n can thus be generalized into a (pure) quantum state ||ψ(n) > which is a superposition of the partitions of n, in the same way that a quantum bit (qubit) is a generalization of a classical bit. More generally, ρ(n) is a density matrix in that same Hilbert-space (a probability distribution over pure states). Inspired by the notion of quantum numbers in quantum theory (such as in Bohr's model of the atom), we then try to go beyond the partitions, by defining (via recursion) the notion of 'sub-partitions' in number theory. Combining the two notions mentioned above, sub-partitions and quantum integers, we finally provide an alternative definition of the quantum integers [the pure-state |ψ'(n)> and the mixed-state ρ'(n),] this time using the sub-partitions as the basis states instead of the partitions, for describing the quantum number that corresponds to the integer n.
Energy Technology Data Exchange (ETDEWEB)
Rodgers, P
1998-03-01
There is more to information than a string of ones and zeroes the ability of ''quantum bits'' to be in two states at the same time could revolutionize information technology. In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry one of the biggest industries in the world today. Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers? Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed. (author)
Quantum mechanics & the big world
Wezel, Jasper van
2007-01-01
Quantum Mechanics is one of the most successful physical theories of the last century. It explains physical phenomena from the smallest to the largest lengthscales. Despite this triumph, quantum mechanics is often perceived as a mysterious theory, involving superposition states that are alien to our
Superposition of helical beams by using a Michelson interferometer.
Gao, Chunqing; Qi, Xiaoqing; Liu, Yidong; Weber, Horst
2010-01-04
Orbital angular momentum (OAM) of a helical beam is of great interests in the high density optical communication due to its infinite number of eigen-states. In this paper, an experimental setup is realized to the information encoding and decoding on the OAM eigen-states. A hologram designed by the iterative method is used to generate the helical beams, and a Michelson interferometer with two Porro prisms is used for the superposition of two helical beams. The experimental results of the collinear superposition of helical beams and their OAM eigen-states detection are presented.
Quantum Computer Games: Schrodinger Cat and Hounds
Gordon, Michal; Gordon, Goren
2012-01-01
The quantum computer game "Schrodinger cat and hounds" is the quantum extension of the well-known classical game fox and hounds. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. "Schrodinger cat and hounds" demonstrates the effects of superposition, destructive and constructive interference, measurements and…
Nori, Franco
2008-03-01
Superconducting (SC) circuits can behave like atoms making transitions between a few energy levels. Such circuits can test quantum mechanics at macroscopic scales and be used to conduct atomic-physics experiments on a silicon chip. This talk overviews a few of our theoretical studies on SC circuits and quantum information processing (QIP) including: SC qubits for single photon generation and for lasing; controllable couplings among qubits; how to increase the coherence time of qubits using a capacitor in parallel to one of the qubit junctions; hybrid circuits involving both charge and flux qubits; testing Bell's inequality in SC circuits; generation of GHZ states; quantum tomography in SC circuits; preparation of macroscopic quantum superposition states of a cavity field via coupling to a SC qubit; generation of nonclassical photon states using a SC qubit in a microcavity; scalable quantum computing with SC qubits; and information processing with SC qubits in a microwave field. Controllable couplings between qubits can be achieved either directly or indirectly. This can be done with and without coupler circuits, and with and without data-buses like EM fields in cavities (e.g., we will describe both the variable-frequency magnetic flux approach and also a generalized double-resonance approach that we introduced). It is also possible to ``turn a quantum bug into a feature'' by using microscopic defects as qubits, and the macroscopic junction as a controller of it. We have also studied ways to implement radically different approaches to QIP by using ``cluster states'' in SC circuits. For a general overview of this field, see, J.Q. You and F. Nori, Phys. Today 58 (11), 42 (2005)
Blutner, Reinhard
2009-03-01
Recently, Gerd Niestegge developed a new approach to quantum mechanics via conditional probabilities developing the well-known proposal to consider the Lüders-von Neumann measurement as a non-classical extension of probability conditionalization. I will apply his powerful and rigorous approach to the treatment of concepts using a geometrical model of meaning. In this model, instances are treated as vectors of a Hilbert space H. In the present approach there are at least two possibilities to form categories. The first possibility sees categories as a mixture of its instances (described by a density matrix). In the simplest case we get the classical probability theory including the Bayesian formula. The second possibility sees categories formed by a distinctive prototype which is the superposition of the (weighted) instances. The construction of prototypes can be seen as transferring a mixed quantum state into a pure quantum state freezing the probabilistic characteristics of the superposed instances into the structure of the formed prototype. Closely related to the idea of forming concepts by prototypes is the existence of interference effects. Such inference effects are typically found in macroscopic quantum systems and I will discuss them in connection with several puzzles of bounded rationality. The present approach nicely generalizes earlier proposals made by authors such as Diederik Aerts, Andrei Khrennikov, Ricardo Franco, and Jerome Busemeyer. Concluding, I will suggest that an active dialogue between cognitive approaches to logic and semantics and the modern approach of quantum information science is mandatory.
Investigation of dissipative forces near macroscopic media
International Nuclear Information System (INIS)
Becker, R.S.
1982-12-01
The interaction of classical charged particles with the fields they induce in macroscopic dielectric media is investigated. For 10- to 1000-eV electrons, the angular perturbation of the trajectory by the image potential for surface impact parameters of 50 to 100 A is shown to be of the order of 0.001 rads over a distance of 100 A. The energy loss incurred by low-energy particles due to collective excitations such as surface plasmons is shown to be observable with a transition probability of 0.01 to 0.001 (Becker, et al., 1981b). The dispersion of real surface plasmon modes in planar and cylindrical geometries is discussed and is derived for pinhole geometry described in terms of a single-sheeted hyperboloid of revolution. An experimental apparatus for the measurement of collective losses for medium-energy electrons translating close to a dielectric surface is described and discussed. Data showing such losses at electron energies of 500 to 900 eV in silver foils containing many small apertures are presented and shown to be in good agreement with classical stopping power calculations and quantum mechanical calculations carried out in the low-velocity limit. The data and calculations are compared and contrasted with earlier transmission and reflection measurements, and the course of further investigation is discussed
Linear Plasma Oscillation Described by Superposition of Normal Modes
DEFF Research Database (Denmark)
Pécseli, Hans
1974-01-01
The existence of steady‐state solutions to the linearized ion and electron Vlasov equation is demonstrated for longitudinal waves in an initially stable plasma. The evolution of an arbitrary initial perturbation can be described by superposition of these solutions. Some common approximations...
Generating superpositions of higher–order Bessel beams [Journal article
CSIR Research Space (South Africa)
Vasilyeu, R
2009-12-01
Full Text Available The authors report the first experimental generation of the superposition of higher-order Bessel beams, by means of a spatial light modulator (SLM) and a ring slit aperture. They present illuminating a ring slit aperture with light which has...
Spectral properties of superpositions of Ornstein-Uhlenbeck type processes
DEFF Research Database (Denmark)
Barndorff-Nielsen, Ole Eiler; Leonenko, N.N.
2005-01-01
Stationary processes with prescribed one-dimensional marginal laws and long-range dependence are constructed. The asymptotic properties of the spectral densities are studied. The possibility of Mittag-Leffler decay in the autocorrelation function of superpositions of Ornstein-Uhlenbeck type...... processes is proved....
On some properties of the superposition operator on topological manifolds
Directory of Open Access Journals (Sweden)
Janusz Dronka
2010-01-01
Full Text Available In this paper the superposition operator in the space of vector-valued, bounded and continuous functions on a topological manifold is considered. The acting conditions and criteria of continuity and compactness are established. As an application, an existence result for the nonlinear Hammerstein integral equation is obtained.
Quantum-like microeconomics: Statistical model of distribution of investments and production
Khrennikov, Andrei
2008-10-01
In this paper we demonstrate that the probabilistic quantum-like (QL) behavior-the Born’s rule, interference of probabilities, violation of Bell’s inequality, representation of variables by in general noncommutative self-adjoint operators, Schrödinger’s dynamics-can be exhibited not only by processes in the micro world, but also in economics. In our approach the QL-behavior is induced not by properties of systems. Here systems (commodities) are macroscopic. They could not be superpositions of two different states. In our approach the QL-behavior of economical statistics is a consequence of the organization of the process of production as well as investments. In particular, Hamiltonian (“financial energy”) is determined by rate of return.
Drummond, P. D.; Chaturvedi, S.; Dechoum, K.; Comey, J.
2001-02-01
We investigate the theory of quantum fluctuations in non-equilibrium systems having large critical fluctuations. This allows us to treat the limits imposed by nonlinearities to quantum squeezing and noise reduction, and also to envisage future tests of quantum theory in regions of macroscopic quantum fluctuations. A long-term objective of this research is to identify suitable physical systems in which macroscopic 'Schrödinger cat'-like behaviour may be observed. We investigate two systems in particular of much current experimental interest, namely the degenerate parametric oscillator near threshold, and the evaporatively cooled (BEC). We compare the results obtained in the positive-P representation, as a fully quantum mechanical calculation, with the truncated Wigner phase space equation, also known as semi-classical theory. We show when these results agree and differ in calculations taken beyond the linearized approximation. In the region where the largest quantum fluctuations and Schrödinger cat-like behaviour might be expected, we find that the quantum predictions correspond very closely to the semi-classical theory. Nature abhors observing a Schrödinger cat. -Pacs: 03.65.Bz
Seismic scanning tunneling macroscope - Theory
Schuster, Gerard T.
2012-09-01
We propose a seismic scanning tunneling macroscope (SSTM) that can detect the presence of sub-wavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the point scatterer is in the near-field region; if the sub-wavelength scatterer is a spherical impedance discontinuity then the resolution will also be limited by the radius of the sphere. Therefore, superresolution imaging can be achieved as the scatterer approaches the source. This is analogous to an optical scanning tunneling microscope that has sub-wavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by imaging of near-field seismic energy.
Seismic scanning tunneling macroscope - Theory
Schuster, Gerard T.; Hanafy, Sherif M.; Huang, Yunsong
2012-01-01
We propose a seismic scanning tunneling macroscope (SSTM) that can detect the presence of sub-wavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the point scatterer is in the near-field region; if the sub-wavelength scatterer is a spherical impedance discontinuity then the resolution will also be limited by the radius of the sphere. Therefore, superresolution imaging can be achieved as the scatterer approaches the source. This is analogous to an optical scanning tunneling microscope that has sub-wavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by imaging of near-field seismic energy.
Le Gouët, Jean-Louis; Moiseev, Sergey
2012-06-01
quest for higher efficiency, better fidelity, broader bandwidth, multimode capacity and longer storage lifetime is pursued in all those approaches, as shown in this special issue. The improvement of quantum memory operation specifically requires in-depth study and control of numerous physical processes leading to atomic decoherence. The present issue reflects the development of rare earth ion doped matrices offering long lifetime superposition states, either as bulk crystals or as optical waveguides. The need for quantum sources and high efficiency detectors at the single photon level is also illustrated. Several papers address the networking of quantum memories either in long-haul cryptography or in the prospect of quantum processing. In this context, much attention has been paid recently to interfacing quantum light with superconducting qubits and with nitrogen-vacancy centers in diamond. Finally, the quantum interfacing of light with matter raises questions on entanglement. The last two papers are devoted to the generation of entanglement by dissipative processes. It is shown that long lifetime entanglement may be built in this way. We hope this special issue will help readers to become familiar with the exciting field of ensemble-based quantum memories and will stimulate them to bring deeper insights and new ideas to this area.
Strong-field effects in Rabi oscillations between a single state and a superposition of states
International Nuclear Information System (INIS)
Zhdanovich, S.; Milner, V.; Hepburn, J. W.
2011-01-01
Rabi oscillations of quantum population are known to occur in two-level systems driven by spectrally narrow laser fields. In this work we study Rabi oscillations induced by shaped broadband femtosecond laser pulses. Due to the broad spectral width of the driving field, the oscillations are initiated between a ground state and a coherent superposition of excited states, or a ''wave packet,'' rather than a single excited state. Our experiments reveal an intricate dependence of the wave-packet phase on the intensity of the laser field. We confirm numerically that the effect is associated with the strong-field nature of the interaction and provide a qualitative picture by invoking a simple theoretical model.
Are Quantum Models for Order Effects Quantum?
Moreira, Catarina; Wichert, Andreas
2017-12-01
The application of principles of Quantum Mechanics in areas outside of physics has been getting increasing attention in the scientific community in an emergent disciplined called Quantum Cognition. These principles have been applied to explain paradoxical situations that cannot be easily explained through classical theory. In quantum probability, events are characterised by a superposition state, which is represented by a state vector in a N-dimensional vector space. The probability of an event is given by the squared magnitude of the projection of this superposition state into the desired subspace. This geometric approach is very useful to explain paradoxical findings that involve order effects, but do we really need quantum principles for models that only involve projections? This work has two main goals. First, it is still not clear in the literature if a quantum projection model has any advantage towards a classical projection. We compared both models and concluded that the Quantum Projection model achieves the same results as its classical counterpart, because the quantum interference effects play no role in the computation of the probabilities. Second, it intends to propose an alternative relativistic interpretation for rotation parameters that are involved in both classical and quantum models. In the end, instead of interpreting these parameters as a similarity measure between questions, we propose that they emerge due to the lack of knowledge concerned with a personal basis state and also due to uncertainties towards the state of world and towards the context of the questions.
Transfer of an unknown quantum state, quantum networks, and memory
International Nuclear Information System (INIS)
Biswas, Asoka; Agarwal, G.S.
2004-01-01
We present a protocol for transfer of an unknown quantum state. The protocol is based on a two-mode cavity interacting dispersively in a sequential manner with three-level atoms in the Λ configuration. We propose a scheme for quantum networking using an atomic channel. We investigate the effect of cavity decoherence in the entire process. Further, we demonstrate the possibility of an efficient quantum memory for arbitrary superposition of two modes of a cavity containing one photon
Macroscopic polarization in crystalline dielectrics: the geometric phase approach
International Nuclear Information System (INIS)
Resta, R.
1994-01-01
The macroscopic electric polarization of a crystal is often defined as the dipole of a unit cell. In fact, such a dipole moment is ill defined, and the above definition is incorrect. Looking more closely, the quantity generally measured is differential polarization, defined with respect to a ''reference state'' of the same material. Such differential polarizations include either derivatives of the polarization (dielectric permittivity, Born effective charges, piezoelectricity, pyroelectricity) or finite differences (ferroelectricity). On the theoretical side, the differential concept is basic as well. Owing to continuity, a polarization difference is equivalent to a macroscopic current, which is directly accessible to the theory as a bulk property. Polarization is a quantum phenomenon and cannot be treated with a classical model, particularly whenever delocalized valence electrons are present in the dielectric. In a quantum picture, the current is basically a property of the phase of the wave functions, as opposed to the charge, which is a property of their modulus. An elegant and complete theory has recently been developed by King-Smith and Vanderbilt, in which the polarization difference between any two crystal states--in a null electric field--takes the form of a geometric quantum phase. This gives a comprehensive account of this theory, which is relevant for dealing with transverse-optic phonons, piezoelectricity, and ferroelectricity. Its relation to the established concepts of linear-response theory is also discussed. Within the geometric phase approach, the relevant polarization difference occurs as the circuit integral of a Berry connection (or ''vector potential''), while the corresponding curvature (or ''magnetic field'') provides the macroscopic linear response
Transforming spatial point processes into Poisson processes using random superposition
DEFF Research Database (Denmark)
Møller, Jesper; Berthelsen, Kasper Klitgaaard
with a complementary spatial point process Y to obtain a Poisson process X∪Y with intensity function β. Underlying this is a bivariate spatial birth-death process (Xt,Yt) which converges towards the distribution of (X,Y). We study the joint distribution of X and Y, and their marginal and conditional distributions....... In particular, we introduce a fast and easy simulation procedure for Y conditional on X. This may be used for model checking: given a model for the Papangelou intensity of the original spatial point process, this model is used to generate the complementary process, and the resulting superposition is a Poisson...... process with intensity function β if and only if the true Papangelou intensity is used. Whether the superposition is actually such a Poisson process can easily be examined using well known results and fast simulation procedures for Poisson processes. We illustrate this approach to model checking...
Improved superposition schemes for approximate multi-caloron configurations
International Nuclear Information System (INIS)
Gerhold, P.; Ilgenfritz, E.-M.; Mueller-Preussker, M.
2007-01-01
Two improved superposition schemes for the construction of approximate multi-caloron-anti-caloron configurations, using exact single (anti-)caloron gauge fields as underlying building blocks, are introduced in this paper. The first improvement deals with possible monopole-Dirac string interactions between different calorons with non-trivial holonomy. The second one, based on the ADHM formalism, improves the (anti-)selfduality in the case of small caloron separations. It conforms with Shuryak's well-known ratio-ansatz when applied to instantons. Both superposition techniques provide a higher degree of (anti-)selfduality than the widely used sum-ansatz, which simply adds the (anti)caloron vector potentials in an appropriate gauge. Furthermore, the improved configurations (when discretized onto a lattice) are characterized by a higher stability when they are exposed to lattice cooling techniques
EDITORIAL: CAMOP: Quantum Non-Stationary Systems CAMOP: Quantum Non-Stationary Systems
Dodonov, Victor V.; Man'ko, Margarita A.
2010-09-01
Although time-dependent quantum systems have been studied since the very beginning of quantum mechanics, they continue to attract the attention of many researchers, and almost every decade new important discoveries or new fields of application are made. Among the impressive results or by-products of these studies, one should note the discovery of the path integral method in the 1940s, coherent and squeezed states in the 1960-70s, quantum tunneling in Josephson contacts and SQUIDs in the 1960s, the theory of time-dependent quantum invariants in the 1960-70s, different forms of quantum master equations in the 1960-70s, the Zeno effect in the 1970s, the concept of geometric phase in the 1980s, decoherence of macroscopic superpositions in the 1980s, quantum non-demolition measurements in the 1980s, dynamics of particles in quantum traps and cavity QED in the 1980-90s, and time-dependent processes in mesoscopic quantum devices in the 1990s. All these topics continue to be the subject of many publications. Now we are witnessing a new wave of interest in quantum non-stationary systems in different areas, from cosmology (the very first moments of the Universe) and quantum field theory (particle pair creation in ultra-strong fields) to elementary particle physics (neutrino oscillations). A rapid increase in the number of theoretical and experimental works on time-dependent phenomena is also observed in quantum optics, quantum information theory and condensed matter physics. Time-dependent tunneling and time-dependent transport in nano-structures are examples of such phenomena. Another emerging direction of study, stimulated by impressive progress in experimental techniques, is related to attempts to observe the quantum behavior of macroscopic objects, such as mirrors interacting with quantum fields in nano-resonators. Quantum effects manifest themselves in the dynamics of nano-electromechanical systems; they are dominant in the quite new and very promising field of circuit
Generation of macroscopic singlet states in atomic ensembles
Tóth, Géza; Mitchell, Morgan W.
2010-05-01
We study squeezing of the spin uncertainties by quantum non-demolition (QND) measurement in non-polarized spin ensembles. Unlike the case of polarized ensembles, the QND measurements can be performed with negligible back-action, which allows, in principle, perfect spin squeezing as quantified by Tóth et al (2007 Phys. Rev. Lett. 99 250405). The generated spin states approach many-body singlet states and contain a macroscopic number of entangled particles even when individual spin is large. We introduce the Gaussian treatment of unpolarized spin states and use it to estimate the achievable spin squeezing for realistic experimental parameters. Our proposal might have applications for magnetometry with a high spatial resolution or quantum memories storing information in decoherence free subspaces.
Non-Poissonian photon statistics from macroscopic photon cutting materials.
de Jong, Mathijs; Meijerink, Andries; Rabouw, Freddy T
2017-05-24
In optical materials energy is usually extracted only from the lowest excited state, resulting in fundamental energy-efficiency limits such as the Shockley-Queisser limit for single-junction solar cells. Photon-cutting materials provide a way around such limits by absorbing high-energy photons and 'cutting' them into multiple low-energy excitations that can subsequently be extracted. The occurrence of photon cutting or quantum cutting has been demonstrated in a variety of materials, including semiconductor quantum dots, lanthanides and organic dyes. Here we show that photon cutting results in bunched photon emission on the timescale of the excited-state lifetime, even when observing a macroscopic number of optical centres. Our theoretical derivation matches well with experimental data on NaLaF 4 :Pr 3+ , a material that can cut deep-ultraviolet photons into two visible photons. This signature of photon cutting can be used to identify and characterize new photon-cutting materials unambiguously.
Quantum Darwinism, Decoherence, and the Randomness of Quantum Jumps
Energy Technology Data Exchange (ETDEWEB)
Zurek, Wojciech H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2014-06-05
Tracing flows of information in our quantum Universe explains why we see the world as classical. Quantum principle of superposition decrees every combination of quantum states a legal quantum state. This is at odds with our experience. Decoherence selects preferred pointer states that survive interaction with the environment. They are localized and effectively classical. They persist while their superpositions decohere. Here we consider emergence of `the classical' starting at a more fundamental pre-decoherence level, tracing the origin of preferred pointer states and deducing their probabilities from the core quantum postulates. We also explore role of the environment as medium through which observers acquire information. This mode of information transfer leads to perception of objective classical reality.
Realizing Controllable Quantum States
Takayanagi, Hideaki; Nitta, Junsaku
1. Entanglement in solid states. Orbital entanglement and violation of bell inequalities in mesoscopic conductors / M. Büttiker, P. Samuelsson and E. V. Sukhoruk. Teleportation of electron spins with normal and superconducting dots / O. Sauret, D. Feinberg and T. Martin. Entangled state analysis for one-dimensional quantum spin system: singularity at critical point / A. Kawaguchi and K. Shimizu. Detecting crossed Andreev reflection by cross-current correlations / G. Bignon et al. Current correlations and transmission probabilities for a Y-shaped diffusive conductor / S. K. Yip -- 2. Mesoscopic electronics. Quantum bistability, structural transformation, and spontaneous persistent currents in mesoscopic Aharonov-Bohm loops / I. O. Kulik. Many-body effects on tunneling of electrons in magnetic-field-induced quasi one-dimensional systems in quantum wells / T. Kubo and Y. Tokura. Electron transport in 2DEG narrow channel under gradient magnetic field / M. Hara et al. Transport properties of a quantum wire with a side-coupled quantum dot / M. Yamaguchi et al. Photoconductivity- and magneto-transport studies of single InAs quantum wires / A. Wirthmann et al. Thermoelectric transports in charge-density-wave systems / H. Yoshimoto and S. Kurihara -- 3. Mesoscopic superconductivity. Parity-restricted persistent currents in SNS nanorings / A. D. Zaikin and S. V. Sharov. Large energy dependence of current noise in superconductingh/normal metal junctions / F. Pistolesi and M. Houzet. Generation of photon number states and their superpositions using a superconducting qubit in a microcavity / Yu-Xi Liu, L. F. Wei and F. Nori. Andreev interferometry for pumped currents / F. Taddei, M. Governale and R. Fazio. Suppression of Cooper-pair breaking against high magnetic fields in carbon nanotubes / J. Haruyama et al. Impact of the transport supercurrent on the Josephson effect / S. N. Shevchenko. Josephson current through spin-polarized Luttinger liquid / N. Yokoshi and S. Kurihara
Quantum physics meets biology.
Arndt, Markus; Juffmann, Thomas; Vedral, Vlatko
2009-12-01
Quantum physics and biology have long been regarded as unrelated disciplines, describing nature at the inanimate microlevel on the one hand and living species on the other hand. Over the past decades the life sciences have succeeded in providing ever more and refined explanations of macroscopic phenomena that were based on an improved understanding of molecular structures and mechanisms. Simultaneously, quantum physics, originally rooted in a world-view of quantum coherences, entanglement, and other nonclassical effects, has been heading toward systems of increasing complexity. The present perspective article shall serve as a "pedestrian guide" to the growing interconnections between the two fields. We recapitulate the generic and sometimes unintuitive characteristics of quantum physics and point to a number of applications in the life sciences. We discuss our criteria for a future "quantum biology," its current status, recent experimental progress, and also the restrictions that nature imposes on bold extrapolations of quantum theory to macroscopic phenomena.
Quantum Mechanical Earth: Where Orbitals Become Orbits
Keeports, David
2012-01-01
Macroscopic objects, although quantum mechanical by nature, conform to Newtonian mechanics under normal observation. According to the quantum mechanical correspondence principle, quantum behavior is indistinguishable from classical behavior in the limit of very large quantum numbers. The purpose of this paper is to provide an example of the…
Quantum logic: is it necessarily orthocomplemented
International Nuclear Information System (INIS)
Mielnik, B.
1976-01-01
There exist conservative arguments supporting the necessity of the present day form of quantum theory, which are found in the axiomatics of quantum logic. In this paper the axioms of quantum logic are critically reexamined. The lattice macroscopic measurements, the motivation of the Hilbert space formalism and the convex scheme of quantum mechanics are among the topics discussed. (B.R.H.)
International Nuclear Information System (INIS)
Cejnar, P.
2007-01-01
Chaos is a name given in physics to a branch which, within classical mechanics, studies the consequences of sensitive dependences of the behavior of physical systems on the starting conditions, i.e., the 'butterfly wing effect'. However, how to describe chaotic behavior in the world of quantum particles? It appears that quantum mechanics does not admit the sensitive dependence on the starting conditions, and moreover, predicts a substantial suppression of chaos also at the macroscopic level. Still, the quantum properties of systems that are chaotic in terms of classical mechanics differ basically from the properties of classically arranged systems. This topic is studied by a field of physics referred to as quantum chaos. (author)
Rank distributions: A panoramic macroscopic outlook
Eliazar, Iddo I.; Cohen, Morrel H.
2014-01-01
This paper presents a panoramic macroscopic outlook of rank distributions. We establish a general framework for the analysis of rank distributions, which classifies them into five macroscopic "socioeconomic" states: monarchy, oligarchy-feudalism, criticality, socialism-capitalism, and communism. Oligarchy-feudalism is shown to be characterized by discrete macroscopic rank distributions, and socialism-capitalism is shown to be characterized by continuous macroscopic size distributions. Criticality is a transition state between oligarchy-feudalism and socialism-capitalism, which can manifest allometric scaling with multifractal spectra. Monarchy and communism are extreme forms of oligarchy-feudalism and socialism-capitalism, respectively, in which the intrinsic randomness vanishes. The general framework is applied to three different models of rank distributions—top-down, bottom-up, and global—and unveils each model's macroscopic universality and versatility. The global model yields a macroscopic classification of the generalized Zipf law, an omnipresent form of rank distributions observed across the sciences. An amalgamation of the three models establishes a universal rank-distribution explanation for the macroscopic emergence of a prevalent class of continuous size distributions, ones governed by unimodal densities with both Pareto and inverse-Pareto power-law tails.
Giovannetti, Vittorio; Lloyd, Seth; Maccone, Lorenzo
2007-01-01
A random access memory (RAM) uses n bits to randomly address N=2^n distinct memory cells. A quantum random access memory (qRAM) uses n qubits to address any quantum superposition of N memory cells. We present an architecture that exponentially reduces the requirements for a memory call: O(log N) switches need be thrown instead of the N used in conventional (classical or quantum) RAM designs. This yields a more robust qRAM algorithm, as it in general requires entanglement among exponentially l...
Quantum Computation and Algorithms
International Nuclear Information System (INIS)
Biham, O.; Biron, D.; Biham, E.; Grassi, M.; Lidar, D.A.
1999-01-01
It is now firmly established that quantum algorithms provide a substantial speedup over classical algorithms for a variety of problems, including the factorization of large numbers and the search for a marked element in an unsorted database. In this talk I will review the principles of quantum algorithms, the basic quantum gates and their operation. The combination of superposition and interference, that makes these algorithms efficient, will be discussed. In particular, Grover's search algorithm will be presented as an example. I will show that the time evolution of the amplitudes in Grover's algorithm can be found exactly using recursion equations, for any initial amplitude distribution
Projection quantum mechanics and neutrino mixing
Energy Technology Data Exchange (ETDEWEB)
Góźdź, A., E-mail: andrzej.gozdz@umcs.lublin.pl; Góźdź, M., E-mail: mgozdz@kft.umcs.lublin.pl [University of Maria Curie–Skłodowska, Faculty of Mathematics, Physics and Computer Science (Poland)
2017-03-15
The theory of neutrino oscillations rests on the assumption, that the interaction basis and the physical (mass) basis of neutrino states are different. Therefore neutrino is produced in a certain welldefined superposition of three mass eigenstates, which propagate separately and may be detected as a different superposition. This is called flavor oscillations. It is, however, not clear why neutrinos behave this way, i.e., what is the underlying mechanism which leads to the production of a superposition of physical states in a single reaction. In this paper we argue, that one of the reasons may be connected with the temporal structure of the process. In order to discuss the role of time in processes on the quantum level, we use a special formulation of the quantum mechanics, which is based on the projection time evolution. We arrive at the conclusion, that for short reaction times the formation of a superposition of states of similar masses is natural.
Quantum Mechanics with a Little Less Mystery
Cropper, William H.
1969-01-01
Suggests the "route of the inquiring mind in presenting the esoteric quantum mechanical postulates and concepts in an understandable form. Explains that the quantum mechanical postulates are but useful mathematical forms to express thebroader principles of superposition and correspondence. Briefly describes some of the features which makes the…
Entanglement in non-Hermitian quantum theory
Indian Academy of Sciences (India)
hope that the entanglement in PT -symmetric quantum theory may provide new ways of processing information in the quantum world. We conclude our .... Similarly, if we have a two-level atom, then an arbitrary superposition of the ground state ...
Efficient Power Allocation for Video over Superposition Coding
Lau, Chun Pong
2013-03-01
In this paper we consider a wireless multimedia system by mapping scalable video coded (SVC) bit stream upon superposition coded (SPC) signals, referred to as (SVC-SPC) architecture. Empirical experiments using a software-defined radio(SDR) emulator are conducted to gain a better understanding of its efficiency, specifically, the impact of the received signal due to different power allocation ratios. Our experimental results show that to maintain high video quality, the power allocated to the base layer should be approximately four times higher than the power allocated to the enhancement layer.
On Kolmogorov's superpositions and Boolean functions
Energy Technology Data Exchange (ETDEWEB)
Beiu, V.
1998-12-31
The paper overviews results dealing with the approximation capabilities of neural networks, as well as bounds on the size of threshold gate circuits. Based on an explicit numerical (i.e., constructive) algorithm for Kolmogorov's superpositions they will show that for obtaining minimum size neutral networks for implementing any Boolean function, the activation function of the neurons is the identity function. Because classical AND-OR implementations, as well as threshold gate implementations require exponential size (in the worst case), it will follow that size-optimal solutions for implementing arbitrary Boolean functions require analog circuitry. Conclusions and several comments on the required precision are ending the paper.
Push-pull optical pumping of pure superposition states
International Nuclear Information System (INIS)
Jau, Y.-Y.; Miron, E.; Post, A.B.; Kuzma, N.N.; Happer, W.
2004-01-01
A new optical pumping method, 'push-pull pumping', can produce very nearly pure, coherent superposition states between the initial and the final sublevels of the important field-independent 0-0 clock resonance of alkali-metal atoms. The key requirement for push-pull pumping is the use of D1 resonant light which alternates between left and right circular polarization at the Bohr frequency of the state. The new pumping method works for a wide range of conditions, including atomic beams with almost no collisions, and atoms in buffer gases with pressures of many atmospheres
Quantum Darwinism in Quantum Brownian Motion
Blume-Kohout, Robin; Zurek, Wojciech H.
2008-12-01
Quantum Darwinism—the redundant encoding of information about a decohering system in its environment—was proposed to reconcile the quantum nature of our Universe with apparent classicality. We report the first study of the dynamics of quantum Darwinism in a realistic model of decoherence, quantum Brownian motion. Prepared in a highly squeezed state—a macroscopic superposition—the system leaves records whose redundancy increases rapidly with initial delocalization. Redundancy appears rapidly (on the decoherence time scale) and persists for a long time.
Macroscopic transport by synthetic molecular machines
Berna, J; Leigh, DA; Lubomska, M; Mendoza, SM; Perez, EM; Rudolf, P; Teobaldi, G; Zerbetto, F
Nature uses molecular motors and machines in virtually every significant biological process, but demonstrating that simpler artificial structures operating through the same gross mechanisms can be interfaced with - and perform physical tasks in - the macroscopic world represents a significant hurdle
Quantum voting and violation of Arrow's impossibility theorem
Bao, Ning; Yunger Halpern, Nicole
2017-06-01
We propose a quantum voting system in the spirit of quantum games such as the quantum prisoner's dilemma. Our scheme enables a constitution to violate a quantum analog of Arrow's impossibility theorem. Arrow's theorem is a claim proved deductively in economics: Every (classical) constitution endowed with three innocuous-seeming properties is a dictatorship. We construct quantum analogs of constitutions, of the properties, and of Arrow's theorem. A quantum version of majority rule, we show, violates this quantum Arrow conjecture. Our voting system allows for tactical-voting strategies reliant on entanglement, interference, and superpositions. This contribution to quantum game theory helps elucidate how quantum phenomena can be harnessed for strategic advantage.
SUPERPOSITION OF STOCHASTIC PROCESSES AND THE RESULTING PARTICLE DISTRIBUTIONS
International Nuclear Information System (INIS)
Schwadron, N. A.; Dayeh, M. A.; Desai, M.; Fahr, H.; Jokipii, J. R.; Lee, M. A.
2010-01-01
Many observations of suprathermal and energetic particles in the solar wind and the inner heliosheath show that distribution functions scale approximately with the inverse of particle speed (v) to the fifth power. Although there are exceptions to this behavior, there is a growing need to understand why this type of distribution function appears so frequently. This paper develops the concept that a superposition of exponential and Gaussian distributions with different characteristic speeds and temperatures show power-law tails. The particular type of distribution function, f ∝ v -5 , appears in a number of different ways: (1) a series of Poisson-like processes where entropy is maximized with the rates of individual processes inversely proportional to the characteristic exponential speed, (2) a series of Gaussian distributions where the entropy is maximized with the rates of individual processes inversely proportional to temperature and the density of individual Gaussian distributions proportional to temperature, and (3) a series of different diffusively accelerated energetic particle spectra with individual spectra derived from observations (1997-2002) of a multiplicity of different shocks. Thus, we develop a proof-of-concept for the superposition of stochastic processes that give rise to power-law distribution functions.
Quantum computing with four-particle decoherence-free states in ion trap
Feng, Mang; Wang, Xiaoguang
2001-01-01
Quantum computing gates are proposed to apply on trapped ions in decoherence-free states. As phase changes due to time evolution of components with different eigenenergies of quantum superposition are completely frozen, quantum computing based on this model would be perfect. Possible application of our scheme in future ion-trap quantum computer is discussed.
Quantum walks in brain microtubules--a biomolecular basis for quantum cognition?
Hameroff, Stuart
2014-01-01
Cognitive decisions are best described by quantum mathematics. Do quantum information devices operate in the brain? What would they look like? Fuss and Navarro () describe quantum lattice registers in which quantum superpositioned pathways interact (compute/integrate) as 'quantum walks' akin to Feynman's path integral in a lattice (e.g. the 'Feynman quantum chessboard'). Simultaneous alternate pathways eventually reduce (collapse), selecting one particular pathway in a cognitive decision, or choice. This paper describes how quantum walks in a Feynman chessboard are conceptually identical to 'topological qubits' in brain neuronal microtubules, as described in the Penrose-Hameroff 'Orch OR' theory of consciousness. Copyright © 2013 Cognitive Science Society, Inc.
International Nuclear Information System (INIS)
Basdevant, J.L.; Dalibart, J.
1997-01-01
This pedagogical book gives an initiation to the principles and practice of quantum mechanics. A large part is devoted to experimental facts and to their analysis: concrete facts, phenomena and applications related to fundamental physics, elementary particles, astrophysics, high-technology, semi-conductors, micro-electronics and lasers. The book is divided in 22 chapters dealing with: quantum phenomena, wave function and Schroedinger equation, physical units and measurements, energy quantification of some simple systems, Hilbert space, Dirac formalism and quantum mechanics postulates, two-state systems and ammonia Maser principle, bands theory and crystals conductibility, commutation of observables, Stern and Gerlach experiment, approximation methods, kinetic momentum in quantum mechanics, first description of atoms, 1/2 spin formalism and magnetic resonance, Lagrangian, Hamiltonian and Lorentz force in quantum mechanics, addition of kinetic momenta and fine and hyper-fine structure of atomic lines, identical particle systems and Pauli principle, qualitative physics and scale of size of some microscopic and macroscopic phenomena, systems evolution, collisions and cross sections, invariance and conservation laws, quantum mechanics and astrophysics, and historical aspects of quantum mechanics. (J.S.)
Fundamental principles of quantum theory
International Nuclear Information System (INIS)
Bugajski, S.
1980-01-01
After introducing general versions of three fundamental quantum postulates - the superposition principle, the uncertainty principle and the complementarity principle - the question of whether the three principles are sufficiently strong to restrict the general Mackey description of quantum systems to the standard Hilbert-space quantum theory is discussed. An example which shows that the answer must be negative is constructed. An abstract version of the projection postulate is introduced and it is demonstrated that it could serve as the missing physical link between the general Mackey description and the standard quantum theory. (author)
Reactive probing of macroscopically quantum mechanical SQUID rings
International Nuclear Information System (INIS)
Prance, R.J.; Clark, T.D.; Whiteman, R.; Diggins, J.; Ralph, J.F.; Prance, H.; Spiller, T.P.; Widom, A.; Srivastava, Y.
1994-01-01
In this paper we demonstrate that the energy level structure of ultra small capacitance SQUID rings can be probed adiabatically at radio frequency using both dynamical and quasistatic reactive techniques. ((orig.))
Capacity-Approaching Superposition Coding for Optical Fiber Links
DEFF Research Database (Denmark)
Estaran Tolosa, Jose Manuel; Zibar, Darko; Tafur Monroy, Idelfonso
2014-01-01
We report on the first experimental demonstration of superposition coded modulation (SCM) for polarization-multiplexed coherent-detection optical fiber links. The proposed coded modulation scheme is combined with phase-shifted bit-to-symbol mapping (PSM) in order to achieve geometric and passive......-SCM) is employed in the framework of bit-interleaved coded modulation with iterative decoding (BICM-ID) for forward error correction. The fiber transmission system is characterized in terms of signal-to-noise ratio for back-to-back case and correlated with simulated results for ideal transmission over additive...... white Gaussian noise channel. Thereafter, successful demodulation and decoding after dispersion-unmanaged transmission over 240-km standard single mode fiber of dual-polarization 6-Gbaud 16-, 32- and 64-ary SCM-PSM is experimentally demonstrated....
Superposition of Stress Fields in Diametrically Compressed Cylinders
Directory of Open Access Journals (Sweden)
João Augusto de Lima Rocha
Full Text Available Abstract The theoretical analysis for the Brazilian test is a classical plane stress problem of elasticity theory, where a vertical force is applied to a horizontal plane, the boundary of a semi-infinite medium. Hypothesizing a normal radial stress field, the results of that model are correct. Nevertheless, the superposition of three stress fields, with two being based on prior results and the third based on a hydrostatic stress field, is incorrect. Indeed, this work shows that the Cauchy vectors (tractions are non-vanishing in the parallel planes in which the two opposing vertical forces are applied. The aim of this work is to detail the process used in the construction of the theoretical model for the three stress fields used, with the objective being to demonstrate the inconsistency often stated in the literature.
Simulation Analysis of DC and Switching Impulse Superposition Circuit
Zhang, Chenmeng; Xie, Shijun; Zhang, Yu; Mao, Yuxiang
2018-03-01
Surge capacitors running between the natural bus and the ground are affected by DC and impulse superposition voltage during operation in the converter station. This paper analyses the simulation aging circuit of surge capacitors by PSCAD electromagnetic transient simulation software. This paper also analyses the effect of the DC voltage to the waveform of the impulse voltage generation. The effect of coupling capacitor to the test voltage waveform is also studied. Testing results prove that the DC voltage has little effect on the waveform of the output of the surge voltage generator, and the value of the coupling capacitor has little effect on the voltage waveform of the sample. Simulation results show that surge capacitor DC and impulse superimposed aging test is feasible.
Quantum equivalence principle without mass superselection
International Nuclear Information System (INIS)
Hernandez-Coronado, H.; Okon, E.
2013-01-01
The standard argument for the validity of Einstein's equivalence principle in a non-relativistic quantum context involves the application of a mass superselection rule. The objective of this work is to show that, contrary to widespread opinion, the compatibility between the equivalence principle and quantum mechanics does not depend on the introduction of such a restriction. For this purpose, we develop a formalism based on the extended Galileo group, which allows for a consistent handling of superpositions of different masses, and show that, within such scheme, mass superpositions behave as they should in order to obey the equivalence principle. - Highlights: • We propose a formalism for consistently handling, within a non-relativistic quantum context, superpositions of states with different masses. • The formalism utilizes the extended Galileo group, in which mass is a generator. • The proposed formalism allows for the equivalence principle to be satisfied without the need of imposing a mass superselection rule
Polyphony: superposition independent methods for ensemble-based drug discovery.
Pitt, William R; Montalvão, Rinaldo W; Blundell, Tom L
2014-09-30
Structure-based drug design is an iterative process, following cycles of structural biology, computer-aided design, synthetic chemistry and bioassay. In favorable circumstances, this process can lead to the structures of hundreds of protein-ligand crystal structures. In addition, molecular dynamics simulations are increasingly being used to further explore the conformational landscape of these complexes. Currently, methods capable of the analysis of ensembles of crystal structures and MD trajectories are limited and usually rely upon least squares superposition of coordinates. Novel methodologies are described for the analysis of multiple structures of a protein. Statistical approaches that rely upon residue equivalence, but not superposition, are developed. Tasks that can be performed include the identification of hinge regions, allosteric conformational changes and transient binding sites. The approaches are tested on crystal structures of CDK2 and other CMGC protein kinases and a simulation of p38α. Known interaction - conformational change relationships are highlighted but also new ones are revealed. A transient but druggable allosteric pocket in CDK2 is predicted to occur under the CMGC insert. Furthermore, an evolutionarily-conserved conformational link from the location of this pocket, via the αEF-αF loop, to phosphorylation sites on the activation loop is discovered. New methodologies are described and validated for the superimposition independent conformational analysis of large collections of structures or simulation snapshots of the same protein. The methodologies are encoded in a Python package called Polyphony, which is released as open source to accompany this paper [http://wrpitt.bitbucket.org/polyphony/].
Point kernels and superposition methods for scatter dose calculations in brachytherapy
International Nuclear Information System (INIS)
Carlsson, A.K.
2000-01-01
Point kernels have been generated and applied for calculation of scatter dose distributions around monoenergetic point sources for photon energies ranging from 28 to 662 keV. Three different approaches for dose calculations have been compared: a single-kernel superposition method, a single-kernel superposition method where the point kernels are approximated as isotropic and a novel 'successive-scattering' superposition method for improved modelling of the dose from multiply scattered photons. An extended version of the EGS4 Monte Carlo code was used for generating the kernels and for benchmarking the absorbed dose distributions calculated with the superposition methods. It is shown that dose calculation by superposition at and below 100 keV can be simplified by using isotropic point kernels. Compared to the assumption of full in-scattering made by algorithms currently in clinical use, the single-kernel superposition method improves dose calculations in a half-phantom consisting of air and water. Further improvements are obtained using the successive-scattering superposition method, which reduces the overestimates of dose close to the phantom surface usually associated with kernel superposition methods at brachytherapy photon energies. It is also shown that scatter dose point kernels can be parametrized to biexponential functions, making them suitable for use with an effective implementation of the collapsed cone superposition algorithm. (author)
Conversion of light into macroscopic helical motion
Iamsaard, Supitchaya; Aßhoff, Sarah J.; Matt, Benjamin; Kudernac, Tibor; Cornelissen, Jeroen J. L. M.; Fletcher, Stephen P.; Katsonis, Nathalie
2014-03-01
A key goal of nanotechnology is the development of artificial machines capable of converting molecular movement into macroscopic work. Although conversion of light into shape changes has been reported and compared to artificial muscles, real applications require work against an external load. Here, we describe the design, synthesis and operation of spring-like materials capable of converting light energy into mechanical work at the macroscopic scale. These versatile materials consist of molecular switches embedded in liquid-crystalline polymer springs. In these springs, molecular movement is converted and amplified into controlled and reversible twisting motions. The springs display complex motion, which includes winding, unwinding and helix inversion, as dictated by their initial shape. Importantly, they can produce work by moving a macroscopic object and mimicking mechanical movements, such as those used by plant tendrils to help the plant access sunlight. These functional materials have potential applications in micromechanical systems, soft robotics and artificial muscles.
Nonequilibrium work relation in a macroscopic system
International Nuclear Information System (INIS)
Sughiyama, Yuki; Ohzeki, Masayuki
2013-01-01
We reconsider a well-known relationship between the fluctuation theorem and the second law of thermodynamics by evaluating stochastic evolution of the density field (probability measure valued process). In order to establish a bridge between microscopic and macroscopic behaviors, we must take the thermodynamic limit of a stochastic dynamical system following the standard procedure in statistical mechanics. The thermodynamic path characterizing a dynamical behavior in the macroscopic scale can be formulated as an infimum of the action functional for the stochastic evolution of the density field. In our formulation, the second law of thermodynamics can be derived only by symmetry of the action functional without recourse to the Jarzynski equality. Our formulation leads to a nontrivial nonequilibrium work relation for metastable (quasi-stationary) states, which are peculiar in the macroscopic system. We propose a prescription for computing the free energy for metastable states based on the resultant work relation. (paper)
Hybrid methods for witnessing entanglement in a microscopic-macroscopic system
International Nuclear Information System (INIS)
Spagnolo, Nicolo; Vitelli, Chiara; Paternostro, Mauro; De Martini, Francesco; Sciarrino, Fabio
2011-01-01
We propose a hybrid approach to the experimental assessment of the genuine quantum features of a general system consisting of microscopic and macroscopic parts. We infer entanglement by combining dichotomic measurements on a bidimensional system and phase-space inference through the Wigner distribution associated with the macroscopic component of the state. As a benchmark, we investigate the feasibility of our proposal in a bipartite-entangled state composed of a single-photon and a multiphoton field. Our analysis shows that, under ideal conditions, maximal violation of a Clauser-Horne-Shimony-Holt-based inequality is achievable regardless of the number of photons in the macroscopic part of the state. The difficulty in observing entanglement when losses and detection inefficiency are included can be overcome by using a hybrid entanglement witness that allows efficient correction for losses in the few-photon regime.
Hybrid methods for witnessing entanglement in a microscopic-macroscopic system
Energy Technology Data Exchange (ETDEWEB)
Spagnolo, Nicolo [Dipartimento di Fisica, Sapienza Universita di Roma, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Vitelli, Chiara [Dipartimento di Fisica, Sapienza Universita di Roma, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Paternostro, Mauro [School of Mathematics and Physics, Queen' s University, BT 7 1NN Belfast (United Kingdom); De Martini, Francesco [Dipartimento di Fisica, Sapienza Universita di Roma, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Accademia Nazionale dei Lincei, via della Lungara 10, I-00165 Roma (Italy); Sciarrino, Fabio [Dipartimento di Fisica, Sapienza Universita di Roma, Piazzale Aldo Moro 5, I-00185 Roma (Italy); Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche (INO-CNR), largo E. Fermi 6, I-50125 Firenze (Italy)
2011-09-15
We propose a hybrid approach to the experimental assessment of the genuine quantum features of a general system consisting of microscopic and macroscopic parts. We infer entanglement by combining dichotomic measurements on a bidimensional system and phase-space inference through the Wigner distribution associated with the macroscopic component of the state. As a benchmark, we investigate the feasibility of our proposal in a bipartite-entangled state composed of a single-photon and a multiphoton field. Our analysis shows that, under ideal conditions, maximal violation of a Clauser-Horne-Shimony-Holt-based inequality is achievable regardless of the number of photons in the macroscopic part of the state. The difficulty in observing entanglement when losses and detection inefficiency are included can be overcome by using a hybrid entanglement witness that allows efficient correction for losses in the few-photon regime.
A Review on Macroscopic Pedestrian Flow Modelling
Directory of Open Access Journals (Sweden)
Anna Kormanová
2013-12-01
Full Text Available This paper reviews several various approaches to macroscopic pedestrian modelling. It describes hydrodynamic models based on similarity of pedestrian flow with fluids and gases; first-order flow models that use fundamental diagrams and conservation equation; and a model similar to LWR vehicular traffic model, which allows non-classical shocks. At the end of the paper there is stated a comparison of described models, intended to find appropriate macroscopic model to eventually be a part of a hybrid model. The future work of the author is outlined.
Macroscopic effects in attosecond pulse generation
International Nuclear Information System (INIS)
Ruchon, T; Varju, K; Mansten, E; Swoboda, M; L'Huillier, A; Hauri, C P; Lopez-Martens, R
2008-01-01
We examine how the generation and propagation of high-order harmonics in a partly ionized gas medium affect their strength and synchronization. The temporal properties of the resulting attosecond pulses generated in long gas targets can be significantly influenced by macroscopic effects, in particular by the intensity in the medium and the degree of ionization which control the dispersion. Under some conditions, the use of gas targets longer than the absorption length can lead to the generation of compressed attosecond pulses. We show these macroscopic effects experimentally, using a 6 mm-long argon-filled gas cell as the generating medium
Macroscopic effects in attosecond pulse generation
Energy Technology Data Exchange (ETDEWEB)
Ruchon, T; Varju, K; Mansten, E; Swoboda, M; L' Huillier, A [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Hauri, C P; Lopez-Martens, R [Laboratoire d' Optique Appliquee, Ecole Nationale Superieure des Techniques Avancees (ENSTA)-Ecole Polytechnique CNRS UMR 7639, 91761 Palaiseau (France)], E-mail: anne.lhuillier@fysik.lth.se
2008-02-15
We examine how the generation and propagation of high-order harmonics in a partly ionized gas medium affect their strength and synchronization. The temporal properties of the resulting attosecond pulses generated in long gas targets can be significantly influenced by macroscopic effects, in particular by the intensity in the medium and the degree of ionization which control the dispersion. Under some conditions, the use of gas targets longer than the absorption length can lead to the generation of compressed attosecond pulses. We show these macroscopic effects experimentally, using a 6 mm-long argon-filled gas cell as the generating medium.
Macroscopic optical constants of a cloud of randomly oriented nonspherical scatterers
International Nuclear Information System (INIS)
Borghese, F.; Denti, P.; Saija, R.; Toscano, G.; Sindoni, O.I.
1984-01-01
A method to calculate the macroscopic optical constants of a low-density medium consisting of a cloud of identical nonspherical scatterers is presented. The scatterers in the medium are clusters of dielectric spheres and the electromagnetic field scattered by each of the clusters is obtained as a superposition of multipole fields, as previously proposed by the authors. The transformation properties of the spherical multipoles under rotation allow the orientation-dependent terms in the expression for the forward-scattering amplitude of each of the clusters to be factored out. In this way the sum of the scattering amplitudes of the clusters with different orientations, needed to calculate the optical response of the medium, is greatly facilitated and admits a simple analytic expression in the case of randomly oriented clusters. Results of calculations of the optical constants for a few model media are presented
International Nuclear Information System (INIS)
Pozza, Nicola Dalla; Wiseman, Howard M; Huntington, Elanor H
2015-01-01
The preparation stage of optical qubits is an essential task in all the experimental setups employed for the test and demonstration of quantum optics principles. We consider a deterministic protocol for the preparation of qubits as a superposition of vacuum and one photon number states, which has the advantage to reduce the amount of resources required via phase-sensitive measurements using a local oscillator (‘dyne detection’). We investigate the performances of the protocol using different phase measurement schemes: homodyne, heterodyne, and adaptive dyne detection (involving a feedback loop). First, we define a suitable figure of merit for the prepared state and we obtain an analytical expression for that in terms of the phase measurement considered. Further, we study limitations that the phase measurement can exhibit, such as delay or limited resources in the feedback strategy. Finally, we evaluate the figure of merit of the protocol for different mode-shapes handily available in an experimental setup. We show that even in the presence of such limitations simple feedback algorithms can perform surprisingly well, outperforming the protocols when simple homodyne or heterodyne schemes are employed. (paper)
A Bethe ansatz solvable model for superpositions of Cooper pairs and condensed molecular bosons
International Nuclear Information System (INIS)
Hibberd, K.E.; Dunning, C.; Links, J.
2006-01-01
We introduce a general Hamiltonian describing coherent superpositions of Cooper pairs and condensed molecular bosons. For particular choices of the coupling parameters, the model is integrable. One integrable manifold, as well as the Bethe ansatz solution, was found by Dukelsky et al. [J. Dukelsky, G.G. Dussel, C. Esebbag, S. Pittel, Phys. Rev. Lett. 93 (2004) 050403]. Here we show that there is a second integrable manifold, established using the boundary quantum inverse scattering method. In this manner we obtain the exact solution by means of the algebraic Bethe ansatz. In the case where the Cooper pair energies are degenerate we examine the relationship between the spectrum of these integrable Hamiltonians and the quasi-exactly solvable spectrum of particular Schrodinger operators. For the solution we derive here the potential of the Schrodinger operator is given in terms of hyperbolic functions. For the solution derived by Dukelsky et al., loc. cit. the potential is sextic and the wavefunctions obey PT-symmetric boundary conditions. This latter case provides a novel example of an integrable Hermitian Hamiltonian acting on a Fock space whose states map into a Hilbert space of PT-symmetric wavefunctions defined on a contour in the complex plane
Probing the conductance superposition law in single-molecule circuits with parallel paths.
Vazquez, H; Skouta, R; Schneebeli, S; Kamenetska, M; Breslow, R; Venkataraman, L; Hybertsen, M S
2012-10-01
According to Kirchhoff's circuit laws, the net conductance of two parallel components in an electronic circuit is the sum of the individual conductances. However, when the circuit dimensions are comparable to the electronic phase coherence length, quantum interference effects play a critical role, as exemplified by the Aharonov-Bohm effect in metal rings. At the molecular scale, interference effects dramatically reduce the electron transfer rate through a meta-connected benzene ring when compared with a para-connected benzene ring. For longer conjugated and cross-conjugated molecules, destructive interference effects have been observed in the tunnelling conductance through molecular junctions. Here, we investigate the conductance superposition law for parallel components in single-molecule circuits, particularly the role of interference. We synthesize a series of molecular systems that contain either one backbone or two backbones in parallel, bonded together cofacially by a common linker on each end. Single-molecule conductance measurements and transport calculations based on density functional theory show that the conductance of a double-backbone molecular junction can be more than twice that of a single-backbone junction, providing clear evidence for constructive interference.
Intermediate statistics in quantum maps
Energy Technology Data Exchange (ETDEWEB)
Giraud, Olivier [H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Marklof, Jens [School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW (United Kingdom); O' Keefe, Stephen [School of Mathematics, University of Bristol, University Walk, Bristol BS8 1TW (United Kingdom)
2004-07-16
We present a one-parameter family of quantum maps whose spectral statistics are of the same intermediate type as observed in polygonal quantum billiards. Our central result is the evaluation of the spectral two-point correlation form factor at small argument, which in turn yields the asymptotic level compressibility for macroscopic correlation lengths. (letter to the editor)
Continuous quantum measurement and the quantum to classical transition
International Nuclear Information System (INIS)
Bhattacharya, Tanmoy; Habib, Salman; Jacobs, Kurt
2003-01-01
While ultimately they are described by quantum mechanics, macroscopic mechanical systems are nevertheless observed to follow the trajectories predicted by classical mechanics. Hence, in the regime defining macroscopic physics, the trajectories of the correct classical motion must emerge from quantum mechanics, a process referred to as the quantum to classical transition. Extending previous work [Bhattacharya, Habib, and Jacobs, Phys. Rev. Lett. 85, 4852 (2000)], here we elucidate this transition in some detail, showing that once the measurement processes that affect all macroscopic systems are taken into account, quantum mechanics indeed predicts the emergence of classical motion. We derive inequalities that describe the parameter regime in which classical motion is obtained, and provide numerical examples. We also demonstrate two further important properties of the classical limit: first, that multiple observers all agree on the motion of an object, and second, that classical statistical inference may be used to correctly track the classical motion
Microscopic approaches to quantum nonequilibriumthermodynamics and information
2018-02-09
perspective on quantum thermalization for Science [8]. Wrote a joint experiment- theory paper on studying connections between quantum and classical chaos in...on the random matrix theory (eigenstate thermalization) and macroscopic phenomena (both equilibrium and non-equilibrium). Understanding thermodynamics...information. Specific questions to be addressed: connections of microscopic description of quantum chaotic systems based on the random matrix theory
Equivalence principle and quantum mechanics: quantum simulation with entangled photons.
Longhi, S
2018-01-15
Einstein's equivalence principle (EP) states the complete physical equivalence of a gravitational field and corresponding inertial field in an accelerated reference frame. However, to what extent the EP remains valid in non-relativistic quantum mechanics is a controversial issue. To avoid violation of the EP, Bargmann's superselection rule forbids a coherent superposition of states with different masses. Here we suggest a quantum simulation of non-relativistic Schrödinger particle dynamics in non-inertial reference frames, which is based on the propagation of polarization-entangled photon pairs in curved and birefringent optical waveguides and Hong-Ou-Mandel quantum interference measurement. The photonic simulator can emulate superposition of mass states, which would lead to violation of the EP.
Macroscopic optical response and photonic bands
International Nuclear Information System (INIS)
Pérez-Huerta, J S; Luis Mochán, W; Ortiz, Guillermo P; Mendoza, Bernardo S
2013-01-01
We develop a formalism for the calculation of the macroscopic dielectric response of composite systems made of particles of one material embedded periodically within a matrix of another material, each of which is characterized by a well-defined dielectric function. The nature of these dielectric functions is arbitrary, and could correspond to dielectric or conducting, transparent or opaque, absorptive and dispersive materials. The geometry of the particles and the Bravais lattice of the composite are also arbitrary. Our formalism goes beyond the long-wavelength approximation as it fully incorporates retardation effects. We test our formalism through the study of the propagation of electromagnetic waves in two-dimensional photonic crystals made of periodic arrays of cylindrical holes in a dispersionless dielectric host. Our macroscopic theory yields a spatially dispersive macroscopic response which allows the calculation of the full photonic band structure of the system, as well as the characterization of its normal modes, upon substitution into the macroscopic field equations. We can also account approximately for the spatial dispersion through a local magnetic permeability and analyze the resulting dispersion relation, obtaining a region of left handedness. (paper)
Macroscopic sizes of field of superrelativistic charges
International Nuclear Information System (INIS)
Strel'tsov, V.N.
1995-01-01
Based on the equation of Lienard-Wiechert equipotentials, it is shown that the field of superrelativistic charges reaches macroscopic sizes (e.g., R || = 2 m at E e = 50 GeV). This phenomenon serves an initial cause of the known considerable growth of formation length at high energies. 3 refs., 1 tab
He, Q. Y.; Reid, M. D.
2013-06-01
Experiments have reported the entanglement of two spatially separated macroscopic atomic ensembles at room temperature (Krauter et al 2011 Phys. Rev. Lett. 107 080503; Julsgaard et al 2001 Nature 413 400). We show how an Einstein-Podolsky-Rosen (EPR) paradox is realizable with this experiment. Our proposed test involves violation of an inferred Heisenberg uncertainty principle, which is a sufficient condition for an EPR paradox. This is a stronger test of nonlocality than entanglement. Our proposal would enable the first definitive confirmation of quantum EPR paradox correlations between two macroscopic objects at room temperature. This is a necessary intermediate step towards a nonlocal experiment with causal measurement separations. As well as having fundamental significance, the realization of an atomic EPR paradox could provide a resource for novel applications in quantum technology.
International Nuclear Information System (INIS)
He, Q Y; Reid, M D
2013-01-01
Experiments have reported the entanglement of two spatially separated macroscopic atomic ensembles at room temperature (Krauter et al 2011 Phys. Rev. Lett. 107 080503; Julsgaard et al 2001 Nature 413 400). We show how an Einstein–Podolsky–Rosen (EPR) paradox is realizable with this experiment. Our proposed test involves violation of an inferred Heisenberg uncertainty principle, which is a sufficient condition for an EPR paradox. This is a stronger test of nonlocality than entanglement. Our proposal would enable the first definitive confirmation of quantum EPR paradox correlations between two macroscopic objects at room temperature. This is a necessary intermediate step towards a nonlocal experiment with causal measurement separations. As well as having fundamental significance, the realization of an atomic EPR paradox could provide a resource for novel applications in quantum technology. (paper)
Fluctuations in quantum devices
Directory of Open Access Journals (Sweden)
H.Haken
2004-01-01
Full Text Available Logical gates can be formalized by Boolean algebra whose elementary operations can be realized by devices that employ the interactions of macroscopic numbers of elementary excitations such as electrons, holes, photons etc. With increasing miniaturization to the nano scale and below, quantum fluctuations become important and can no longer be ignored. Based on Heisenberg equations of motion for the creation and annihilation operators of elementary excitations, I determine the noise sources of composite quantum systems.
Intra-cavity generation of superpositions of Laguerre-Gaussian beams
CSIR Research Space (South Africa)
Naidoo, Darryl
2012-01-01
Full Text Available In this paper we demonstrate experimentally the intra-cavity generation of a coherent superposition of Laguerre–Gaussian modes of zero radial order but opposite azimuthal order. The superposition is created with a simple intra-cavity stop...
Energy Technology Data Exchange (ETDEWEB)
Alexeyev, Alexander A [Laboratory of Computer Physics and Mathematical Simulation, Research Division, Room 247, Faculty of Phys.-Math. and Natural Sciences, Peoples' Friendship University of Russia, 6 Miklukho-Maklaya street, Moscow 117198 (Russian Federation) and Department of Mathematics 1, Faculty of Cybernetics, Moscow State Institute of Radio Engineering, Electronics and Automatics, 78 Vernadskogo Avenue, Moscow 117454 (Russian Federation)
2004-11-26
In the framework of a multidimensional superposition principle a series of computer experiments with integrable and nonintegrable models are carried out with the goal of verifying the existence of switching effect and superposition in soliton-perturbation interactions for a wide class of nonlinear PDEs. (letter to the editor)
Thermodynamical quantum information sharing
International Nuclear Information System (INIS)
Wiesniak, M.; Vedral, V.; Brukner, C.
2005-01-01
Full text: Thermodynamical properties fully originate from classical physics and can be easily measured for macroscopic systems. On the other hand, entanglement is a widely spoken feature of quantum physics, which allows to perform certain task with efficiency unavailable with any classical resource. Therefore an interesting question is whether we can witness entanglement in a state of a macroscopic sample. We show, that some macroscopic properties, in particular magnetic susceptibility, can serve as an entanglement witnesses. We also study a mutual relation between magnetic susceptibility and magnetisation. Such a complementarity exhibits quantum information sharing between these two thermodynamical quantities. Magnetization expresses properties of individual spins, while susceptibility might reveal non-classical correlations as a witness. Therefore, a rapid change of one of these two quantities may mean a phase transition also in terms of entanglement. The complementarity relation is demonstrated by an analytical solution of an exemplary model. (author)
Quantum computational finance: Monte Carlo pricing of financial derivatives
Rebentrost, Patrick; Gupt, Brajesh; Bromley, Thomas R.
2018-01-01
Financial derivatives are contracts that can have a complex payoff dependent upon underlying benchmark assets. In this work, we present a quantum algorithm for the Monte Carlo pricing of financial derivatives. We show how the relevant probability distributions can be prepared in quantum superposition, the payoff functions can be implemented via quantum circuits, and the price of financial derivatives can be extracted via quantum measurements. We show how the amplitude estimation algorithm can...
Ma, Yue; Hoang, Thai M.; Gong, Ming; Li, Tongcang; Yin, Zhang-qi
2017-08-01
Hybrid spin-mechanical systems have great potential in sensing, macroscopic quantum mechanics, and quantum information science. In order to induce strong coupling between an electron spin and the center-of-mass motion of a mechanical oscillator, a large magnetic gradient usually is required, which is difficult to achieve. Here we show that strong coupling between the electron spin of a nitrogen-vacancy (NV) center and the torsional vibration of an optically levitated nanodiamond can be achieved in a uniform magnetic field. Thanks to the uniform magnetic field, multiple spins can strongly couple to the torsional vibration at the same time. We propose utilizing this coupling mechanism to realize the Lipkin-Meshkov-Glick (LMG) model by an ensemble of NV centers in a levitated nanodiamond. The quantum phase transition in the LMG model and finite number effects can be observed with this system. We also propose generating torsional superposition states and realizing torsional matter-wave interferometry with spin-torsional coupling.
The European quantum technologies flagship programme
Riedel, Max F.; Binosi, Daniele; Thew, Rob; Calarco, Tommaso
2017-09-01
Quantum technologies, such as quantum communication, computation, simulation as well as sensors and metrology, address and manipulate individual quantum states and make use of superposition and entanglement. Both companies and governments have realised the high disruptive potential of this technology. Consequently, the European Commission has announced an ambitious flagship programme to start in 2018. Here, we sum up the history leading to the quantum technologies flagship programme and outline its envisioned goals and structure. We also give an overview of the strategic research agenda for quantum communication, which the flagship will pursue during its 10-year runtime.
Thermodynamics of Weakly Measured Quantum Systems.
Alonso, Jose Joaquin; Lutz, Eric; Romito, Alessandro
2016-02-26
We consider continuously monitored quantum systems and introduce definitions of work and heat along individual quantum trajectories that are valid for coherent superposition of energy eigenstates. We use these quantities to extend the first and second laws of stochastic thermodynamics to the quantum domain. We illustrate our results with the case of a weakly measured driven two-level system and show how to distinguish between quantum work and heat contributions. We finally employ quantum feedback control to suppress detector backaction and determine the work statistics.
Quantum information processing with atoms and photons
International Nuclear Information System (INIS)
Monroe, C.
2003-01-01
Quantum information processors exploit the quantum features of superposition and entanglement for applications not possible in classical devices, offering the potential for significant improvements in the communication and processing of information. Experimental realization of large-scale quantum information processors remains a long term vision, as the required nearly pure quantum behaviour is observed only in exotic hardware such as individual laser-cooled atoms and isolated photons. But recent theoretical and experimental advances suggest that cold atoms and individual photons may lead the way towards bigger and better quantum information processors, effectively building mesoscopic versions of Schroedinger's cat' from the bottom up. (author)
Classical system boundaries cannot be determined within quantum Darwinism
Fields, Chris
Multiple observers who interact with environmental encodings of the states of a macroscopic quantum system S as required by quantum Darwinism cannot demonstrate that they are jointly observing S without a joint a priori assumption of a classical boundary separating S from its environment E. Quantum Darwinism cannot, therefore, be regarded as providing a purely quantum-mechanical explanation of the "emergence" of classicality.
Stapp, Henry P.
2012-05-01
Robert Griffiths has recently addressed, within the framework of a `consistent quantum theory' that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues that the putative proofs of this property that involve hidden variables include in their premises some essentially classical-physics-type assumptions that are not entailed by the precepts of quantum mechanics. Thus whatever is proved is not a feature of quantum mechanics, but is a property of a theory that tries to combine quantum theory with quasi-classical features that go beyond what is entailed by quantum theory itself. One cannot logically prove properties of a system by establishing, instead, properties of a system modified by adding properties alien to the original system. Hence Griffiths' rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence for nonlocal influences. But he did not examine the particular proof that he cites. An examination of that particular proof by the method specified by his `consistent quantum theory' shows that the cited proof is valid within that restrictive version of quantum theory. An added section responds to Griffiths' reply, which cites general possibilities of ambiguities that might make what is to be proved ill-defined, and hence render the pertinent `consistent framework' ill defined. But the vagaries that he cites do not upset the proof in question, which, both by its physical formulation and by explicit identification, specify the framework to be used. Griffiths confirms the validity of the proof insofar as that pertinent framework is used. The section also shows
The weirdness barrier what keeps us from the craziness of the quantum world?
Sample, I
2002-01-01
Tiny particles such as photons can easily be put into a quantum superposition - existing in two different states simultaneously. Keith Schwab has designed an experiment to discover what prevents this happening in larger objects (1 page).
Fundamentals of quantum mechanics
Erkoc, Sakir
2006-01-01
HISTORICAL EXPERIMENTS AND THEORIESDates of Important Discoveries and Events Blackbody RadiationPhotoelectrice Effect Quantum Theory of Spectra TheComptone Effect Matterwaves, the de Broglie HypothesisThe Davisson -Germer Experiment Heisenberg's Uncertainity PrincipleDifference Between Particles and Waves Interpretation of the Wavefunction AXIOMATIC STRUCTURE OF QUANTUM MECHANICSThe Necessity of Quantum TheoryFunction Spaces Postulates of Quantum Mechanics The Kronecker Delta and the Dirac Delta Function Dirac Notation OBSERVABLES AND SUPERPOSITIONFree Particle Particle In A Box Ensemble Average Hilbert -Space Interpretation The Initial Square Wave Particle Beam Superposition and Uncertainty Degeneracy of States Commutators and Uncertainty TIME DEVELOPMENT AND CONSERVATION THEOREMSTime Development of State Functions, The Discrete Case The Continuous Case, Wave Packets Particle Beam Gaussian Wave Packet Free Particle Propagator The Limiting Cases of the Gaussian Wave Packets Time Development of Expectation Val...
Biswas, Rupak
2018-01-01
Quantum computing promises an unprecedented ability to solve intractable problems by harnessing quantum mechanical effects such as tunneling, superposition, and entanglement. The Quantum Artificial Intelligence Laboratory (QuAIL) at NASA Ames Research Center is the space agency's primary facility for conducting research and development in quantum information sciences. QuAIL conducts fundamental research in quantum physics but also explores how best to exploit and apply this disruptive technology to enable NASA missions in aeronautics, Earth and space sciences, and space exploration. At the same time, machine learning has become a major focus in computer science and captured the imagination of the public as a panacea to myriad big data problems. In this talk, we will discuss how classical machine learning can take advantage of quantum computing to significantly improve its effectiveness. Although we illustrate this concept on a quantum annealer, other quantum platforms could be used as well. If explored fully and implemented efficiently, quantum machine learning could greatly accelerate a wide range of tasks leading to new technologies and discoveries that will significantly change the way we solve real-world problems.
Bimodality in macroscopic dynamics of nuclear fission
International Nuclear Information System (INIS)
Bastrukov, S.I.; Salamatin, V.S.; Strteltsova, O.I.; Molodtsova, I.V.; Podgainy, D.V.; )
2000-01-01
The elastodynamic collective model of nuclear fission is outlined whose underlying idea is that the stiff structure of nuclear shells imparts to nucleus properties typical of a small piece of an elastic solid. Emphasis is placed on the macroscopic dynamics of nuclear deformations resulting in fission by two energetically different modes. The low-energy S-mode is the fission due to disruption of elongated quadrupole spheroidal shape. The characteristic features of the high-energy T-mode of division by means of torsional shear deformations is the compact scission configuration. Analytic and numerical estimates for the macroscopic fission-barrier heights are presented, followed by discussion of fingerprints of the above dynamical bimodality in the available data [ru
Special relativity - the foundation of macroscopic physics
International Nuclear Information System (INIS)
Dixon, W.G.
1978-01-01
This book aims to show that an understanding of the basic laws of macroscopic systems can be gained more easily within relativistic physics than within Newtonian physics. The unity of dynamics, thermodynamics and electromagnetism under the umbrella of special relativity is examined under chapter headings entitled: the physics of space and time, affine spaces in mathematics and physics, foundations of dynamics, relativistic simple fluids, and, electrodynamics of polarizable fluids. (U.K.)
Microscopic and macroscopic models for pedestrian crowds
Makmul, Juntima
2016-01-01
This thesis is concerned with microscopic and macroscopic models for pedes- trian crowds. In the first chapter, we consider pedestrians exit choices and model human behaviour in an evacuation process. Two microscopic models, discrete and continuous, are studied in this chapter. The former is a cellular automaton model and the latter is a social force model. Different numerical test cases are investigated and their results are compared. In chapter 2, a hierarchy of models for...
Macroscopic acoustoelectric charge transport in graphene
Bandhu, L.; Lawton, L. M.; Nash, G. R.
2013-09-01
We demonstrate macroscopic acoustoelectric transport in graphene, transferred onto piezoelectric lithium niobate substrates, between electrodes up to 500 μm apart. Using double finger interdigital transducers we have characterised the acoustoelectric current as a function of both surface acoustic wave intensity and frequency. The results are consistent with a relatively simple classical relaxation model, in which the acoustoelectric current is proportional to both the surface acoustic wave intensity and the attenuation of the wave caused by the charge transport.
Thermomechanical macroscopic model of shape memory alloys
International Nuclear Information System (INIS)
Volkov, A.E.; Sakharov, V.Yu.
2003-01-01
The phenomenological macroscopic model of the mechanical behaviour of the titanium nickelide-type shape memory alloys is proposed. The model contains as a parameter the average phase shear deformation accompanying the martensite formation. It makes i possible to describe correctly a number of functional properties of the shape memory alloys, in particular, the pseudoelasticity ferroplasticity, plasticity transformation and shape memory effects in the stressed and unstressed samples [ru
Macroscopic behaviour of a charged Boltzmann gas
International Nuclear Information System (INIS)
Banyai, L.; Gartner, P.; Protopopescu, V.
1980-08-01
We consider a classical charged gas (with self-consistent Coulomb interaction) described by a solvable linearized Boltzman equation with thermaljzation on unifopmly distributed scatterers. It is shown that jf one scales the time t, the reciprocal space coordinate k vector and the Debye length l as lambda 2 t, k vector/lambda, lambda l respectively, in the lambda→infinity limit the charge density is equal to the solution of the corresponding diffusion-conduction (macroscopic) equation. (author)
Some analogies between quantum cloning and quantum deleting
International Nuclear Information System (INIS)
Qiu Daowen
2002-01-01
We further verify the impossibility of deleting an arbitrary unknown quantum state, and also show it is impossible to delete two nonorthogonal quantum states as a consequence of unitarity of quantum mechanics. A quantum approximate (deterministic) deleting machine and a probabilistic (exact) deleting machine are constructed. The estimation for the global fidelity characterizing the efficiency of the quantum approximate deleting is given. We then demonstrate that unknown nonorthogonal states chosen from a set with their multiple copies can evolve into a linear superposition of multiple deletions and failure branches by a unitary process if and only if the states are linearly independent. It is notable that the proof for necessity is somewhat different from Pati's [Phys. Rev. Lett. 83, 2849 (1999)]. Another deleting machine for the input states that are unnecessarily linearly independent is also presented. The bounds on the success probabilities of these deleting machines are derived. So we expound some preliminary analogies between quantum cloning and deleting
Active Polar Two-Fluid Macroscopic Dynamics
Pleiner, Harald; Svensek, Daniel; Brand, Helmut R.
2014-03-01
We study the dynamics of systems with a polar dynamic preferred direction. Examples include the pattern-forming growth of bacteria (in a solvent, shoals of fish (moving in water currents), flocks of birds and migrating insects (flying in windy air). Because the preferred direction only exists dynamically, but not statically, the macroscopic variable of choice is the macroscopic velocity associated with the motion of the active units. We derive the macroscopic equations for such a system and discuss novel static, reversible and irreversible cross-couplings connected to this second velocity. We find a normal mode structure quite different compared to the static descriptions, as well as linear couplings between (active) flow and e.g. densities and concentrations due to the genuine two-fluid transport derivatives. On the other hand, we get, quite similar to the static case, a direct linear relation between the stress tensor and the structure tensor. This prominent ``active'' term is responsible for many active effects, meaning that our approach can describe those effects as well. In addition, we also deal with explicitly chiral systems, which are important for many active systems. In particular, we find an active flow-induced heat current specific for the dynamic chiral polar order.
Scanner-based macroscopic color variation estimation
Kuo, Chunghui; Lai, Di; Zeise, Eric
2006-01-01
Flatbed scanners have been adopted successfully in the measurement of microscopic image artifacts, such as granularity and mottle, in print samples because of their capability of providing full color, high resolution images. Accurate macroscopic color measurement relies on the use of colorimeters or spectrophotometers to provide a surrogate for human vision. The very different color response characteristics of flatbed scanners from any standard colorimetric response limits the utility of a flatbed scanner as a macroscopic color measuring device. This metamerism constraint can be significantly relaxed if our objective is mainly to quantify the color variations within a printed page or between pages where a small bias in measured colors can be tolerated as long as the color distributions relative to the individual mean values is similar. Two scenarios when converting color from the device RGB color space to a standardized color space such as CIELab are studied in this paper, blind and semi-blind color transformation, depending on the availability of the black channel information. We will show that both approaches offer satisfactory results in quantifying macroscopic color variation across pages while the semi-blind color transformation further provides fairly accurate color prediction capability.
Rough set classification based on quantum logic
Hassan, Yasser F.
2017-11-01
By combining the advantages of quantum computing and soft computing, the paper shows that rough sets can be used with quantum logic for classification and recognition systems. We suggest the new definition of rough set theory as quantum logic theory. Rough approximations are essential elements in rough set theory, the quantum rough set model for set-valued data directly construct set approximation based on a kind of quantum similarity relation which is presented here. Theoretical analyses demonstrate that the new model for quantum rough sets has new type of decision rule with less redundancy which can be used to give accurate classification using principles of quantum superposition and non-linear quantum relations. To our knowledge, this is the first attempt aiming to define rough sets in representation of a quantum rather than logic or sets. The experiments on data-sets have demonstrated that the proposed model is more accuracy than the traditional rough sets in terms of finding optimal classifications.
A convolution-superposition dose calculation engine for GPUs
Energy Technology Data Exchange (ETDEWEB)
Hissoiny, Sami; Ozell, Benoit; Despres, Philippe [Departement de genie informatique et genie logiciel, Ecole polytechnique de Montreal, 2500 Chemin de Polytechnique, Montreal, Quebec H3T 1J4 (Canada); Departement de radio-oncologie, CRCHUM-Centre hospitalier de l' Universite de Montreal, 1560 rue Sherbrooke Est, Montreal, Quebec H2L 4M1 (Canada)
2010-03-15
Purpose: Graphic processing units (GPUs) are increasingly used for scientific applications, where their parallel architecture and unprecedented computing power density can be exploited to accelerate calculations. In this paper, a new GPU implementation of a convolution/superposition (CS) algorithm is presented. Methods: This new GPU implementation has been designed from the ground-up to use the graphics card's strengths and to avoid its weaknesses. The CS GPU algorithm takes into account beam hardening, off-axis softening, kernel tilting, and relies heavily on raytracing through patient imaging data. Implementation details are reported as well as a multi-GPU solution. Results: An overall single-GPU acceleration factor of 908x was achieved when compared to a nonoptimized version of the CS algorithm implemented in PlanUNC in single threaded central processing unit (CPU) mode, resulting in approximatively 2.8 s per beam for a 3D dose computation on a 0.4 cm grid. A comparison to an established commercial system leads to an acceleration factor of approximately 29x or 0.58 versus 16.6 s per beam in single threaded mode. An acceleration factor of 46x has been obtained for the total energy released per mass (TERMA) calculation and a 943x acceleration factor for the CS calculation compared to PlanUNC. Dose distributions also have been obtained for a simple water-lung phantom to verify that the implementation gives accurate results. Conclusions: These results suggest that GPUs are an attractive solution for radiation therapy applications and that careful design, taking the GPU architecture into account, is critical in obtaining significant acceleration factors. These results potentially can have a significant impact on complex dose delivery techniques requiring intensive dose calculations such as intensity-modulated radiation therapy (IMRT) and arc therapy. They also are relevant for adaptive radiation therapy where dose results must be obtained rapidly.
International Nuclear Information System (INIS)
Omnes, R.
2000-01-01
The author presents the interpretation of quantum mechanics in a simple and direct way. This book may be considered as a complement of specialized books whose aim is to present the mathematical developments of quantum mechanics. As early as the beginning of quantum theory, Bohr, Heisenberg and Pauli proposed the basis of what is today called the interpretation of Copenhagen. This interpretation is still valid but 2 important discoveries have led to renew some aspects of the interpretation of Copenhagen. The first one was the discovery of the decoherence phenomenon which is responsible for the absence of quantum interferences in the macroscopic world. The second discovery was the achievement of the complete derivation of classical physics from quantum physics, it means that the classical determinism fits in the framework of quantum probabilism. A short summary ends each chapter. (A.C.)
Aspelmeyer, Markus; Schwab, Keith
2008-09-01
diverse backgrounds and approaches of the researchers. As diverse as the approaches are the manifold of goals and perspectives for operating mechanical systems close to or within the quantum regime. Already now, nanomechanical sensors achieve single-molecule mass detection and magnetic resonance force detection from single-electron spins although they are operated far from quantum. Quantum-limited mechanical devices promise a new technology with hitherto unachieved performance for high-resolution sensing. This is also of high relevance for macroscopic mechanical resonators used in gravitational wave detectors. Furthermore, the increasing capability to couple mechanical modes to individual quantum systems raises the interesting question of whether mechanics can serve as a quantum bus in hybrid implementations of quantum information processing. Finally, the possibility of generating quantum superposition states that involve displacements of a massive macroscopic object (such as the center of mass of a mechanical beam) provides a completely new parameter regime for testing quantum theory over the amazing range from nanomechanical objects of several picograms up to gram-scale mirrors used in gravitational wave interferometers. We are looking forward to these fascinating developments! This Focus Issue is intended to highlight the present status of the field and to provide both introduction and motivation for students and researchers who want to get familiar with this exciting area or even want to join it. It also complements the conference activities of our community during the last year, where a series of dedicated invited sessions at several international conferences (APS March Meeting 2008, CLEO/QELS 2008, OSA Frontiers in Optics 2008, PQE 2008/2009 etc) culminated in the first Gordon Conference on 'Mechanical Systems at the Quantum Limit'. Given the fast development of the field it was not surprising to see that during the collection of the following contributions new
Quantum Computing in Solid State Systems
Ruggiero, B; Granata, C
2006-01-01
The aim of Quantum Computation in Solid State Systems is to report on recent theoretical and experimental results on the macroscopic quantum coherence of mesoscopic systems, as well as on solid state realization of qubits and quantum gates. Particular attention has been given to coherence effects in Josephson devices. Other solid state systems, including quantum dots, optical, ion, and spin devices which exhibit macroscopic quantum coherence are also discussed. Quantum Computation in Solid State Systems discusses experimental implementation of quantum computing and information processing devices, and in particular observations of quantum behavior in several solid state systems. On the theoretical side, the complementary expertise of the contributors provides models of the various structures in connection with the problem of minimizing decoherence.
International Nuclear Information System (INIS)
Suzuki, Shigenari; Takeoka, Masahiro; Sasaki, Masahide; Andersen, Ulrik L.; Kannari, Fumihiko
2006-01-01
We present a simple protocol to purify a coherent-state superposition that has undergone a linear lossy channel. The scheme constitutes only a single beam splitter and a homodyne detector, and thus is experimentally feasible. In practice, a superposition of coherent states is transformed into a classical mixture of coherent states by linear loss, which is usually the dominant decoherence mechanism in optical systems. We also address the possibility of producing a larger amplitude superposition state from decohered states, and show that in most cases the decoherence of the states are amplified along with the amplitude
Weiss, Ulrich
2008-01-01
Major advances in the quantum theory of macroscopic systems, in combination with stunning experimental achievements, have brightened the field and brought it to the attention of the general community in natural sciences. Today, working knowledge of dissipative quantum mechanics is an essential tool for many physicists. This book - originally published in 1990 and republished in 1999 as an enlarged second edition - delves much deeper than ever before into the fundamental concepts, methods, and applications of quantum dissipative systems, including the most recent developments. In this third edi
Quantum nutation of the neutron spin
International Nuclear Information System (INIS)
Pleshanov, N.K.
2000-01-01
The possibility to prepare the spin particle in a state, which is a superposition of two states with different energies (in contrast to the classical particle, the energy of which is definite in any time and position) gives a purely quantum condition for the nutation behavior of its spin
Directory of Open Access Journals (Sweden)
Alessandro Sergi
2009-06-01
Full Text Available A critical assessment of the recent developmentsof molecular biology is presented.The thesis that they do not lead to a conceptualunderstanding of life and biological systems is defended.Maturana and Varela's concept of autopoiesis is briefly sketchedand its logical circularity avoided by postulatingthe existence of underlying living processes,entailing amplification from the microscopic to the macroscopic scale,with increasing complexity in the passage from one scale to the other.Following such a line of thought, the currently accepted model of condensed matter, which is based on electrostatics and short-ranged forces,is criticized. It is suggested that the correct interpretationof quantum dispersion forces (van der Waals, hydrogen bonding, and so onas quantum coherence effects hints at the necessity of includinglong-ranged forces (or mechanisms for them incondensed matter theories of biological processes.Some quantum effects in biology are reviewedand quantum mechanics is acknowledged as conceptually important to biology since withoutit most (if not all of the biological structuresand signalling processes would not even exist. Moreover, it is suggested that long-rangequantum coherent dynamics, including electron polarization,may be invoked to explain signal amplificationprocess in biological systems in general.
A cute and highly contrast-sensitive superposition eye : The diurnal owlfly Libelloides macaronius
Belušič, Gregor; Pirih, Primož; Stavenga, Doekele G.
The owlfly Libelloides macaronius (Insecta: Neuroptera) has large bipartite eyes of the superposition type. The spatial resolution and sensitivity of the photoreceptor array in the dorsofrontal eye part was studied with optical and electrophysiological methods. Using structured illumination
Czech Academy of Sciences Publication Activity Database
Červený, V.; Pšenčík, Ivan
2015-01-01
Roč. 25, - (2015), s. 109-155 ISSN 2336-3827 Institutional support: RVO:67985530 Keywords : integral superposition of paraxial Gaussian beams * inhomogeneous anisotropic media * S waves in weakly anisotropic media Subject RIV: DC - Siesmology, Volcanology, Earth Structure
On the L-characteristic of nonlinear superposition operators in lp-spaces
International Nuclear Information System (INIS)
Dedagic, F.
1995-04-01
In this paper we describe the L-characteristic of the nonlinear superposition operator F(x) f(s,x(s)) between two Banach spaces of functions x from N to R. It was shown that L-characteristic of the nonlinear superposition operator which acts between two Lebesgue spaces has so-called Σ-convexity property. In this paper we show that L-characteristic of the operator F (between two Banach spaces) has the convexity property. It means that the classical interpolation theorem of Reisz-Thorin for a linear operator holds for the nonlinear operator superposition which acts between two Banach spaces of sequences. Moreover, we consider the growth function of the operator superposition in mentioned spaces and we show that one has the logarithmically convexity property. (author). 7 refs
Pauri, Massimo
2011-11-01
, corresponding to the onset of a non-linear dynamic evolution, a `primary spatial' reduction is `continually' taking place, thereby constituting the neural precondition for the experience of distinguishable macroscopic objects in the continuous spatial extension. While preventing the theoretically possible quantum superpositions of macroscopic objects from being perceivable by living beings, the `primary reduction' has no effect on the standard processes concerning quantum level entities involved in laboratory man-made experiments. In this connection, an experimental check which might falsify the conjecture is briefly discussed. The approach suggested here, if sound, leads to a naturalization of that part of Kant's Transcendental Aesthetics than can survive the Euclidean catastrophe. According to such naturalized transcendentalism, "space can well be transcendental without the axioms being so", in agreement with a well-known statement by Boltzman. Finally, as far as QT is concerned, the conjecture entails that a scheme for quantum measurement of the von Neumann type cannot even `leave the ground', vindicating Bohr's viewpoint. A quantum theory of measurement, in a proper sense, turns out to be unnecessary and in fact impossible.
Compressor Has No Moving Macroscopic Parts
Gasser, Max
1995-01-01
Compressor containing no moving macroscopic parts functions by alternating piston and valve actions of successive beds of magnetic particles. Fabricated easily because no need for precisely fitting parts rotating or sliding on each other. Also no need for lubricant fluid contaminating fluid to be compressed. Compressor operates continuously, eliminating troublesome on/off cycling of other compressors, and decreasing consumption of energy. Phased cells push fluid from bottom to top, adding increments of pressure. Each cell contains magnetic powder particles loose when electromagnet coil deenergized, but tightly packed when coil energized.
Quantum Properties of the Superposition of Two Nearly Identical Coherent States
Othman, Anas; Yevick, David
2018-04-01
In this paper, we examine the properties of the state obtained when two nearly identical coherent states are superimposed. We found that this state exhibits many nonclassical properties such as sub-Poissonian statistics, squeezing and a partially negative Wigner function. These and other properties indicate that such states, here termed near coherent states, are significantly closer to coherent states more than the generalized Schrördinger cat states. We finally provide an experimental procedure for generating the near coherent states.
Experimental Demonstration of Capacity-Achieving Phase-Shifted Superposition Modulation
DEFF Research Database (Denmark)
Estaran Tolosa, Jose Manuel; Zibar, Darko; Caballero Jambrina, Antonio
2013-01-01
We report on the first experimental demonstration of phase-shifted superposition modulation (PSM) for optical links. Successful demodulation and decoding is obtained after 240 km transmission for 16-, 32- and 64-PSM.......We report on the first experimental demonstration of phase-shifted superposition modulation (PSM) for optical links. Successful demodulation and decoding is obtained after 240 km transmission for 16-, 32- and 64-PSM....
Efstratiadis, Stella; Baumrind, Sheldon; Shofer, Frances; Jacobsson-Hunt, Ulla; Laster, Larry; Ghafari, Joseph
2005-11-01
The aims of this study were (1) to evaluate cephalometric changes in subjects with Class II Division 1 malocclusion who were treated with headgear (HG) or Fränkel function regulator (FR) and (2) to compare findings from regional superpositions of cephalometric structures with those from conventional cephalometric measurements. Cephalographs were taken at baseline, after 1 year, and after 2 years of 65 children enrolled in a prospective randomized clinical trial. The spatial location of the landmarks derived from regional superpositions was evaluated in a coordinate system oriented on natural head position. The superpositions included the best anatomic fit of the anterior cranial base, maxillary base, and mandibular structures. Both the HG and the FR were effective in correcting the distoclusion, and they generated enhanced differential growth between the jaws. Differences between cranial and maxillary superpositions regarding mandibular displacement (Point B, pogonion, gnathion, menton) were noted: the HG had a more horizontal vector on maxillary superposition that was also greater (.0001 < P < .05) than the horizontal displacement observed with the FR. This discrepancy appeared to be related to (1) the clockwise (backward) rotation of the palatal and mandibular planes observed with the HG; the palatal plane's rotation, which was transferred through the occlusion to the mandibular plane, was factored out on maxillary superposition; and (2) the interaction between the inclination of the maxillary incisors and the forward movement of the mandible during growth. Findings from superpositions agreed with conventional angular and linear measurements regarding the basic conclusions for the primary effects of HG and FR. However, the results suggest that inferences of mandibular displacement are more reliable from maxillary than cranial superposition when evaluating occlusal changes during treatment.
Stochastic mechanics and quantum theory
International Nuclear Information System (INIS)
Goldstein, S.
1987-01-01
Stochastic mechanics may be regarded as both generalizing classical mechanics to processes with intrinsic randomness, as well as providing the sort of detailed description of microscopic events declared impossible under the traditional interpretation of quantum mechanics. It avoids the many conceptual difficulties which arise from the assumption that quantum mechanics, i.e., the wave function, provides a complete description of (microscopic) physical reality. Stochastic mechanics presents a unified treatment of the microscopic and macroscopic domains, in which the process of measurement plays no special physical role and which reduces to Newtonian mechanics in the macroscopic limit
Quantum cosmology - science of Genesis
International Nuclear Information System (INIS)
Padmanabhan, Thanu
1987-01-01
Quantum cosmology, the marriage between the theories of the microscopic and macroscopic Universe, is examined in an attempt to explain the birth of the Universe in the 'big bang'. A quantum cosmological model of the Universe does not exist, but a rough approximation, or 'poor man's' version of quantum cosmology has been developed. The idea is to combine the theory of quantum mechanics with the classical cosmological solutions to obtain a quantum mechanical version of cosmology. Such a model of quantum cosmology is described -here the quantum universe behaves like a hydrogen atom with the Planck length replacing the Bohr radius. Properties of quantum cosmologies and the significance of the Planck length are both discussed. (UK)
Optical Signatures of Coupled Quantum Dots
Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Ponomarev, I. V.; Korenev, V. L.; Ware, M. E.; Doty, M. F.; Reinecke, T. L.; Gammon, D.
2006-02-01
An asymmetric pair of coupled InAs quantum dots is tuned into resonance by applying an electric field so that a single hole forms a coherent molecular wave function. The optical spectrum shows a rich pattern of level anticrossings and crossings that can be understood as a superposition of charge and spin configurations of the two dots. Coulomb interactions shift the molecular resonance of the optically excited state (charged exciton) with respect to the ground state (single charge), enabling light-induced coupling of the quantum dots. This result demonstrates the possibility of optically coupling quantum dots for application in quantum information processing.
An introduction to: the quantum world
International Nuclear Information System (INIS)
Le Bellac, M.
2010-01-01
Quantum physics has entered our daily life since it has allowed the invention of transistors and lasers. Now quantum engineering produces atomic clocks, semi-conductors, laser diodes and Led. This book is a popularization work on the quantum world, it introduces not only the basic principles but also explains its applications. 10 chapters compose this book each one illustrating a particular feature or an application as follows: chapter 1) the superposition principle, chapter 2) application to cryptography, chapter 3) Einstein's interpretation versus Bohr's, chapter 4) Heisenberg's inequalities and energy levels, chapters 5) and 6) the collective effects of quantum particles: applications to atom cooling and semi-conductors, chapter 7) relativity and quantum physics, chapter 8) quantum computers, chapter 9) quantum decoherence phenomenon and chapter 10) new interpretations of quantum physics. (A.C.)
Babin, Anatoli
2016-01-01
In this monograph, the authors present their recently developed theory of electromagnetic interactions. This neoclassical approach extends the classical electromagnetic theory down to atomic scales and allows the explanation of various non-classical phenomena in the same framework. While the classical Maxwell–Lorentz electromagnetism theory succeeds in describing the physical reality at macroscopic scales, it struggles at atomic scales. Here, quantum mechanics traditionally takes over to describe non-classical phenomena such as the hydrogen spectrum and de Broglie waves. By means of modifying the classical theory, the approach presented here is able to consistently explain quantum-mechanical effects, and while similar to quantum mechanics in some respects, this neoclassical theory also differs markedly from it. In particular, the newly developed framework omits probabilistic interpretations of the wave function and features a new fundamental spatial scale which, at the size of the free electron, is much lar...
Foundations of Quantum Mechanics and Quantum Computation
Aspect, Alain; Leggett, Anthony; Preskill, John; Durt, Thomas; Pironio, Stefano
2013-03-01
I ask the question: What can we infer about the nature and structure of the physical world (a) from experiments already done to test the predictions of quantum mechanics (b) from the assumption that all future experiments will agree with those predictions? I discuss existing and projected experiments related to the two classic paradoxes of quantum mechanics, named respectively for EPR and Schrödinger's Cat, and show in particular that one natural conclusion from both types of experiment implies the abandonment of the concept of macroscopic counterfactual definiteness.
Quantum Image Encryption Algorithm Based on Image Correlation Decomposition
Hua, Tianxiang; Chen, Jiamin; Pei, Dongju; Zhang, Wenquan; Zhou, Nanrun
2015-02-01
A novel quantum gray-level image encryption and decryption algorithm based on image correlation decomposition is proposed. The correlation among image pixels is established by utilizing the superposition and measurement principle of quantum states. And a whole quantum image is divided into a series of sub-images. These sub-images are stored into a complete binary tree array constructed previously and then randomly performed by one of the operations of quantum random-phase gate, quantum revolving gate and Hadamard transform. The encrypted image can be obtained by superimposing the resulting sub-images with the superposition principle of quantum states. For the encryption algorithm, the keys are the parameters of random phase gate, rotation angle, binary sequence and orthonormal basis states. The security and the computational complexity of the proposed algorithm are analyzed. The proposed encryption algorithm can resist brute force attack due to its very large key space and has lower computational complexity than its classical counterparts.
Macroscopic description of isoscalar giant multipole resonances
International Nuclear Information System (INIS)
Nix, J.R.; Sierk, A.J.
1980-01-01
On the basis of a simple macroscopic model, we calculate the isoscalar giant-resonance energy as a function of mass number and multipole degree. The restoring force is determined from the distortion of the Fermi surface, and the inertia is determined for the incompressible, irrotational flow of nucleons with unit effective mass. With no adjustable parameters, the resulting closed expression reproduces correctly the available experimental data, namely the magnitude and dependence upon mass number of the giant quadrupole energy and the magnitude of the giant octupole energy for 208 Pb. We also calculate the isoscalar giant-resonance width as a function of mass number and multipole degree for various macroscopic damping mechanisms, including two-body viscosity, one-body dissipation, and modified one-body dissipation. None of these damping mechanisms reproduces correctly all features of the available experimental data, namely the magnitude and dependence upon mass number of the giant quadrupole width and the magnitude of the giant octupole width for 208 Pb
Zero time tunneling: macroscopic experiments with virtual particles
Directory of Open Access Journals (Sweden)
Nimtz Günter
2015-01-01
Full Text Available Feynman introduced virtual particles in his diagrams as intermediate states of an interaction process. They represent necessary intermediate states between observable real states. Such virtual particles were introduced to describe the interaction process between an electron and a positron and for much more complicated interaction processes. Other candidates for virtual particles are evanescent modes in optics and in elastic fields. Evanescent modes have a purely imaginary wave number, they represent the mathematical analogy of the tunneling solutions of the Schrödinger equation. Evanescent modes exist in the forbidden frequency bands of a photonic lattice and in undersized wave guides, for instance. The most prominent example for the occurrence of evanescent modes is the frustrated total internal reflection (FTIR at double prisms. Evanescent modes and tunneling lie outside the bounds of the special theory of relativity. They can cause faster than light (FTL signal velocities. We present examples of the quantum mechanical behavior of evanescent photons and phonons at a macroscopic scale. The evanescent modes of photons are described by virtual particles as predicted by former QED calculations.
A Simple Encryption Algorithm for Quantum Color Image
Li, Panchi; Zhao, Ya
2017-06-01
In this paper, a simple encryption scheme for quantum color image is proposed. Firstly, a color image is transformed into a quantum superposition state by employing NEQR (novel enhanced quantum representation), where the R,G,B values of every pixel in a 24-bit RGB true color image are represented by 24 single-qubit basic states, and each value has 8 qubits. Then, these 24 qubits are respectively transformed from a basic state into a balanced superposition state by employed the controlled rotation gates. At this time, the gray-scale values of R, G, B of every pixel are in a balanced superposition of 224 multi-qubits basic states. After measuring, the whole image is an uniform white noise, which does not provide any information. Decryption is the reverse process of encryption. The experimental results on the classical computer show that the proposed encryption scheme has better security.
Lodahl, Peter; Mahmoodian, Sahand; Stobbe, Søren; Rauschenbeutel, Arno; Schneeweiss, Philipp; Volz, Jürgen; Pichler, Hannes; Zoller, Peter
2017-01-25
Advanced photonic nanostructures are currently revolutionizing the optics and photonics that underpin applications ranging from light technology to quantum-information processing. The strong light confinement in these structures can lock the local polarization of the light to its propagation direction, leading to propagation-direction-dependent emission, scattering and absorption of photons by quantum emitters. The possibility of such a propagation-direction-dependent, or chiral, light-matter interaction is not accounted for in standard quantum optics and its recent discovery brought about the research field of chiral quantum optics. The latter offers fundamentally new functionalities and applications: it enables the assembly of non-reciprocal single-photon devices that can be operated in a quantum superposition of two or more of their operational states and the realization of deterministic spin-photon interfaces. Moreover, engineered directional photonic reservoirs could lead to the development of complex quantum networks that, for example, could simulate novel classes of quantum many-body systems.
Quantum probabilistic logic programming
Balu, Radhakrishnan
2015-05-01
We describe a quantum mechanics based logic programming language that supports Horn clauses, random variables, and covariance matrices to express and solve problems in probabilistic logic. The Horn clauses of the language wrap random variables, including infinite valued, to express probability distributions and statistical correlations, a powerful feature to capture relationship between distributions that are not independent. The expressive power of the language is based on a mechanism to implement statistical ensembles and to solve the underlying SAT instances using quantum mechanical machinery. We exploit the fact that classical random variables have quantum decompositions to build the Horn clauses. We establish the semantics of the language in a rigorous fashion by considering an existing probabilistic logic language called PRISM with classical probability measures defined on the Herbrand base and extending it to the quantum context. In the classical case H-interpretations form the sample space and probability measures defined on them lead to consistent definition of probabilities for well formed formulae. In the quantum counterpart, we define probability amplitudes on Hinterpretations facilitating the model generations and verifications via quantum mechanical superpositions and entanglements. We cast the well formed formulae of the language as quantum mechanical observables thus providing an elegant interpretation for their probabilities. We discuss several examples to combine statistical ensembles and predicates of first order logic to reason with situations involving uncertainty.
Emergent mechanics, quantum and un-quantum
Ralston, John P.
2013-10-01
There is great interest in quantum mechanics as an "emergent" phenomenon. The program holds that nonobvious patterns and laws can emerge from complicated physical systems operating by more fundamental rules. We find a new approach where quantum mechanics itself should be viewed as an information management tool not derived from physics nor depending on physics. The main accomplishment of quantum-style theory comes in expanding the notion of probability. We construct a map from macroscopic information as data" to quantum probability. The map allows a hidden variable description for quantum states, and efficient use of the helpful tools of quantum mechanics in unlimited circumstances. Quantum dynamics via the time-dependent Shroedinger equation or operator methods actually represents a restricted class of classical Hamiltonian or Lagrangian dynamics, albeit with different numbers of degrees of freedom. We show that under wide circumstances such dynamics emerges from structureless dynamical systems. The uses of the quantum information management tools are illustrated by numerical experiments and practical applications
Quantum mechanical suppression of chaos
International Nuclear Information System (INIS)
Bluemel, R.; Smilansky, U.
1990-01-01
The relation between determinism and predictability is the central issue in the study of 'deterministic chaos'. Much knowledge has been accumulated in the past 10 years about the chaotic dynamics of macroscopic (classical) systems. The implications of chaos in the microscopic quantum world is examined, in other words, how to reconcile the correspondence principle with the inherent uncertainties which reflect the wave nature of quantum dynamics. Recent atomic physics experiments demonstrate clearly that chaos is relevant to the microscopic world. In particular, such experiments emphasise the urgent need to clarify the genuine quantum mechanism which imposes severe limitations on quantum dynamics, and renders it so very different from its classical counterpart. (author)
CERN. Geneva
2006-01-01
In my lecture series, I will present the recent spectacular advances in the field of quantum gases and macroscopic quantum physics. A variety of subjects will be covered including Bose condensates and degenerate Fermi gases, ultracold molecules and chemistry near absolute zero, Rydberg gases, single-atom manipulation, quantum information processing, as well as applications of cold atoms as precision targets. The topics of the lectures are: I. Physics near absolute zero II. Bose condensation and Fermi degeneracy III. Molecules, Rydberg gases and other exotic species IV. Single-atom manipulation, quantum information processing and ultracold atoms as targets in storage rings
On Quantum Contributions to Black Hole Growth
Spaans, M.
2013-01-01
The effects of Wheeler’s quantum foam on black hole growth are explored from an astrophysical per- spective. Quantum fluctuations in the form of mini (10−5 g) black holes can couple to macroscopic black holes and allow the latter to grow exponentially in mass on a time scale of 109 years.
Experimental realization of the quantum box problem
International Nuclear Information System (INIS)
Resch, K.J.; Lundeen, J.S.; Steinberg, A.M.
2004-01-01
The three-box problem is a gedankenexperiment designed to elucidate some interesting features of quantum measurement and locality. A particle is prepared in a particular superposition of three boxes, and later found in a different (but nonorthogonal) superposition. It was predicted that appropriate 'weak' measurements of particle position in the interval between preparation and post-selection would find the particle in two different places, each with certainty. We verify these predictions in an optical experiment and address the issues of locality and of negative probability
Partitioning a macroscopic system into independent subsystems
Delle Site, Luigi; Ciccotti, Giovanni; Hartmann, Carsten
2017-08-01
We discuss the problem of partitioning a macroscopic system into a collection of independent subsystems. The partitioning of a system into replica-like subsystems is nowadays a subject of major interest in several fields of theoretical and applied physics. The thermodynamic approach currently favoured by practitioners is based on a phenomenological definition of an interface energy associated with the partition, due to a lack of easily computable expressions for a microscopic (i.e. particle-based) interface energy. In this article, we outline a general approach to derive sharp and computable bounds for the interface free energy in terms of microscopic statistical quantities. We discuss potential applications in nanothermodynamics and outline possible future directions.
Macroscopic balance model for wave rotors
Welch, Gerard E.
1996-01-01
A mathematical model for multi-port wave rotors is described. The wave processes that effect energy exchange within the rotor passage are modeled using one-dimensional gas dynamics. Macroscopic mass and energy balances relate volume-averaged thermodynamic properties in the rotor passage control volume to the mass, momentum, and energy fluxes at the ports. Loss models account for entropy production in boundary layers and in separating flows caused by blade-blockage, incidence, and gradual opening and closing of rotor passages. The mathematical model provides a basis for predicting design-point wave rotor performance, port timing, and machine size. Model predictions are evaluated through comparisons with CFD calculations and three-port wave rotor experimental data. A four-port wave rotor design example is provided to demonstrate model applicability. The modeling approach is amenable to wave rotor optimization studies and rapid assessment of the trade-offs associated with integrating wave rotors into gas turbine engine systems.
Quantum Spin Lenses in Atomic Arrays
Directory of Open Access Journals (Sweden)
A. W. Glaetzle
2017-09-01
Full Text Available We propose and discuss quantum spin lenses, where quantum states of delocalized spin excitations in an atomic medium are focused in space in a coherent quantum process down to (essentially single atoms. These can be employed to create controlled interactions in a quantum light-matter interface, where photonic qubits stored in an atomic ensemble are mapped to a quantum register represented by single atoms. We propose Hamiltonians for quantum spin lenses as inhomogeneous spin models on lattices, which can be realized with Rydberg atoms in 1D, 2D, and 3D, and with strings of trapped ions. We discuss both linear and nonlinear quantum spin lenses: in a nonlinear lens, repulsive spin-spin interactions lead to focusing dynamics conditional to the number of spin excitations. This allows the mapping of quantum superpositions of delocalized spin excitations to superpositions of spatial spin patterns, which can be addressed by light fields and manipulated. Finally, we propose multifocal quantum spin lenses as a way to generate and distribute entanglement between distant atoms in an atomic lattice array.
International Nuclear Information System (INIS)
Dubrovsky, V. G.; Topovsky, A. V.
2013-01-01
New exact solutions, nonstationary and stationary, of Veselov-Novikov (VN) equation in the forms of simple nonlinear and linear superpositions of arbitrary number N of exact special solutions u (n) , n= 1, …, N are constructed via Zakharov and Manakov ∂-dressing method. Simple nonlinear superpositions are represented up to a constant by the sums of solutions u (n) and calculated by ∂-dressing on nonzero energy level of the first auxiliary linear problem, i.e., 2D stationary Schrödinger equation. It is remarkable that in the zero energy limit simple nonlinear superpositions convert to linear ones in the form of the sums of special solutions u (n) . It is shown that the sums u=u (k 1 ) +...+u (k m ) , 1 ⩽k 1 2 m ⩽N of arbitrary subsets of these solutions are also exact solutions of VN equation. The presented exact solutions include as superpositions of special line solitons and also superpositions of plane wave type singular periodic solutions. By construction these exact solutions represent also new exact transparent potentials of 2D stationary Schrödinger equation and can serve as model potentials for electrons in planar structures of modern electronics.
Energy Technology Data Exchange (ETDEWEB)
Dubrovsky, V. G.; Topovsky, A. V. [Novosibirsk State Technical University, Karl Marx prosp. 20, Novosibirsk 630092 (Russian Federation)
2013-03-15
New exact solutions, nonstationary and stationary, of Veselov-Novikov (VN) equation in the forms of simple nonlinear and linear superpositions of arbitrary number N of exact special solutions u{sup (n)}, n= 1, Horizontal-Ellipsis , N are constructed via Zakharov and Manakov {partial_derivative}-dressing method. Simple nonlinear superpositions are represented up to a constant by the sums of solutions u{sup (n)} and calculated by {partial_derivative}-dressing on nonzero energy level of the first auxiliary linear problem, i.e., 2D stationary Schroedinger equation. It is remarkable that in the zero energy limit simple nonlinear superpositions convert to linear ones in the form of the sums of special solutions u{sup (n)}. It is shown that the sums u=u{sup (k{sub 1})}+...+u{sup (k{sub m})}, 1 Less-Than-Or-Slanted-Equal-To k{sub 1} < k{sub 2} < Horizontal-Ellipsis < k{sub m} Less-Than-Or-Slanted-Equal-To N of arbitrary subsets of these solutions are also exact solutions of VN equation. The presented exact solutions include as superpositions of special line solitons and also superpositions of plane wave type singular periodic solutions. By construction these exact solutions represent also new exact transparent potentials of 2D stationary Schroedinger equation and can serve as model potentials for electrons in planar structures of modern electronics.
Quantum Effects in Biological Systems
2016-01-01
Since the last decade the study of quantum mechanical phenomena in biological systems has become a vibrant field of research. Initially sparked by evidence of quantum effects in energy transport that is instrumental for photosynthesis, quantum biology asks the question of how methods and models from quantum theory can help us to understand fundamental mechanisms in living organisms. This approach entails a paradigm change challenging the related disciplines: The successful framework of quantum theory is taken out of its low-temperature, microscopic regimes and applied to hot and dense macroscopic environments, thereby extending the toolbox of biology and biochemistry at the same time. The Quantum Effects in Biological Systems conference is a platform for researchers from biology, chemistry and physics to present and discuss the latest developments in the field of quantum biology. After meetings in Lisbon (2009), Harvard (2010), Ulm (2011), Berkeley (2012), Vienna (2013), Singapore (2014) and Florence (2015),...
A quantum computer only needs one universe
Steane, A. M.
The nature of quantum computation is discussed. It is argued that, in terms of the amount of information manipulated in a given time, quantum and classical computation are equally efficient. Quantum superposition does not permit quantum computers to "perform many computations simultaneously" except in a highly qualified and to some extent misleading sense. Quantum computation is therefore not well described by interpretations of quantum mechanics which invoke the concept of vast numbers of parallel universes. Rather, entanglement makes available types of computation processes which, while not exponentially larger than classical ones, are unavailable to classical systems. The essence of quantum computation is that it uses entanglement to generate and manipulate a physical representation of the correlations between logical entities, without the need to completely represent the logical entities themselves.
Quantum coherence: Reciprocity and distribution
Energy Technology Data Exchange (ETDEWEB)
Kumar, Asutosh, E-mail: asukumar@hri.res.in [Harish-Chandra Research Institute, Allahabad-211019 (India); Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094 (India)
2017-03-18
Quantum coherence is the outcome of the superposition principle. Recently, it has been theorized as a quantum resource, and is the premise of quantum correlations in multipartite systems. It is therefore interesting to study the coherence content and its distribution in a multipartite quantum system. In this work, we show analytically as well as numerically the reciprocity between coherence and mixedness of a quantum state. We find that this trade-off is a general feature in the sense that it is true for large spectra of measures of coherence and of mixedness. We also study the distribution of coherence in multipartite systems by looking at monogamy-type relation–which we refer to as additivity relation–between coherences of different parts of the system. We show that for the Dicke states, while the normalized measures of coherence violate the additivity relation, the unnormalized ones satisfy the same. - Highlights: • Quantum coherence. • Reciprocity between quantum coherence and mixedness. • Distribution of quantum coherence in multipartite quantum systems. • Additivity relation for distribution of quantum coherence in Dicke and “X” states.
Hidden Statistics Approach to Quantum Simulations
Zak, Michail
2010-01-01
Recent advances in quantum information theory have inspired an explosion of interest in new quantum algorithms for solving hard computational (quantum and non-quantum) problems. The basic principle of quantum computation is that the quantum properties can be used to represent structure data, and that quantum mechanisms can be devised and built to perform operations with this data. Three basic non-classical properties of quantum mechanics superposition, entanglement, and direct-product decomposability were main reasons for optimism about capabilities of quantum computers that promised simultaneous processing of large massifs of highly correlated data. Unfortunately, these advantages of quantum mechanics came with a high price. One major problem is keeping the components of the computer in a coherent state, as the slightest interaction with the external world would cause the system to decohere. That is why the hardware implementation of a quantum computer is still unsolved. The basic idea of this work is to create a new kind of dynamical system that would preserve the main three properties of quantum physics superposition, entanglement, and direct-product decomposability while allowing one to measure its state variables using classical methods. In other words, such a system would reinforce the advantages and minimize limitations of both quantum and classical aspects. Based upon a concept of hidden statistics, a new kind of dynamical system for simulation of Schroedinger equation is proposed. The system represents a modified Madelung version of Schroedinger equation. It preserves superposition, entanglement, and direct-product decomposability while allowing one to measure its state variables using classical methods. Such an optimal combination of characteristics is a perfect match for simulating quantum systems. The model includes a transitional component of quantum potential (that has been overlooked in previous treatment of the Madelung equation). The role of the
International Nuclear Information System (INIS)
Lloyd, S.
1992-01-01
Digital computers are machines that can be programmed to perform logical and arithmetical operations. Contemporary digital computers are ''universal,'' in the sense that a program that runs on one computer can, if properly compiled, run on any other computer that has access to enough memory space and time. Any one universal computer can simulate the operation of any other; and the set of tasks that any such machine can perform is common to all universal machines. Since Bennett's discovery that computation can be carried out in a non-dissipative fashion, a number of Hamiltonian quantum-mechanical systems have been proposed whose time-evolutions over discrete intervals are equivalent to those of specific universal computers. The first quantum-mechanical treatment of computers was given by Benioff, who exhibited a Hamiltonian system with a basis whose members corresponded to the logical states of a Turing machine. In order to make the Hamiltonian local, in the sense that its structure depended only on the part of the computation being performed at that time, Benioff found it necessary to make the Hamiltonian time-dependent. Feynman discovered a way to make the computational Hamiltonian both local and time-independent by incorporating the direction of computation in the initial condition. In Feynman's quantum computer, the program is a carefully prepared wave packet that propagates through different computational states. Deutsch presented a quantum computer that exploits the possibility of existing in a superposition of computational states to perform tasks that a classical computer cannot, such as generating purely random numbers, and carrying out superpositions of computations as a method of parallel processing. In this paper, we show that such computers, by virtue of their common function, possess a common form for their quantum dynamics
Ellerman, David
2014-03-01
In models of QM over finite fields (e.g., Schumacher's ``modal quantum theory'' MQT), one finite field stands out, Z2, since Z2 vectors represent sets. QM (finite-dimensional) mathematics can be transported to sets resulting in quantum mechanics over sets or QM/sets. This gives a full probability calculus (unlike MQT with only zero-one modalities) that leads to a fulsome theory of QM/sets including ``logical'' models of the double-slit experiment, Bell's Theorem, QIT, and QC. In QC over Z2 (where gates are non-singular matrices as in MQT), a simple quantum algorithm (one gate plus one function evaluation) solves the Parity SAT problem (finding the parity of the sum of all values of an n-ary Boolean function). Classically, the Parity SAT problem requires 2n function evaluations in contrast to the one function evaluation required in the quantum algorithm. This is quantum speedup but with all the calculations over Z2 just like classical computing. This shows definitively that the source of quantum speedup is not in the greater power of computing over the complex numbers, and confirms the idea that the source is in superposition.
Two new proofs of the test particle superposition principle of plasma kinetic theory
International Nuclear Information System (INIS)
Krommes, J.A.
1975-12-01
The test particle superposition principle of plasma kinetic theory is discussed in relation to the recent theory of two-time fluctuations in plasma given by Williams and Oberman. Both a new deductive and a new inductive proof of the principle are presented. The fundamental observation is that two-time expectations of one-body operators are determined completely in terms of the (x,v) phase space density autocorrelation, which to lowest order in the discreteness parameter obeys the linearized Vlasov equation with singular initial condition. For the deductive proof, this equation is solved formally using time-ordered operators, and the solution then rearranged into the superposition principle. The inductive proof is simpler than Rostoker's, although similar in some ways; it differs in that first order equations for pair correlation functions need not be invoked. It is pointed out that the superposition principle is also applicable to the short-time theory of neutral fluids
Use of the modal superposition technique for piping system blowdown analyses
International Nuclear Information System (INIS)
Ware, A.G.; Macek, R.W.
1983-01-01
A standard method of solving for the seismic response of piping systems is the modal superposition technique. Only a limited number of structural modes are considered (typically those up to 33 Hz in the U.S.), since the effect on the calculated response due to higher modes is generally small, and the method can result in considerable computer cost savings over the direct integration method. The modal superposition technique has also been applied to piping response problems in which the forcing functions are due to fluid excitation. Application of the technique to this case is somewhat more difficult, because a well defined cutoff frequency for determining structural modes to be included has not been established. This paper outlines a method for higher mode corrections, and suggests methods to determine suitable cutoff frequencies for piping system blowdown analyses. A numerical example illustrates how uncorrected modal superposition results can produce erroneous stress results
Quantum mechanics in coherent algebras on phase space
International Nuclear Information System (INIS)
Lesche, B.; Seligman, T.H.
1986-01-01
Quantum mechanics is formulated on a quantum mechanical phase space. The algebra of observables and states is represented by an algebra of functions on phase space that fulfills a certain coherence condition, expressing the quantum mechanical superposition principle. The trace operation is an integration over phase space. In the case where the canonical variables independently run from -infinity to +infinity the formalism reduces to the representation of quantum mechanics by Wigner distributions. However, the notion of coherent algebras allows to apply the formalism to spaces for which the Wigner mapping is not known. Quantum mechanics of a particle in a plane in polar coordinates is discussed as an example. (author)
Controlled quantum-state transfer in a spin chain
International Nuclear Information System (INIS)
Gong, Jiangbin; Brumer, Paul
2007-01-01
Control of the transfer of quantum information encoded in quantum wave packets moving along a spin chain is demonstrated. Specifically, based on a relationship with control in a paradigm of quantum chaos, it is shown that wave packets with slow dispersion can automatically emerge from a class of initial superposition states involving only a few spins, and that arbitrary unspecified traveling wave packets can be nondestructively stopped and later relaunched with perfection. The results establish an interesting application of quantum chaos studies in quantum information science
International Nuclear Information System (INIS)
Sugahara, M.; Ando, N.; Kaneda, H.; Nagai, M.; Ogawa, Y.; Yoshikawa, N.
1985-01-01
Theoretical and Experimental study on granular superconductors shows that they are classified into two groups; fixed-phase superconductor (theta-superconductor) and fixed-pair-number superconductor (N-superconductor) and that a new macroscopic quantum device with conjugate property to Josephson effect can be made by use of N-superconductors
Quantum theory needs no 'Interpretation'
International Nuclear Information System (INIS)
Fuchs, Christopher A.; Peres, Asher
2000-01-01
Purpose of this article is to stress the fact that Quantum Theory does not need an interpretation other than being an algorithm for computing probabilities associated with macroscopic phenomena and measurements. It does not ''describ'' reality, and the wave function is not objective entity, it only gives the evolution of our probabilities for the outcomes potential experiments. (AIP) (c)
Ijpma, G; Al-Jumaily, A M; Cairns, S P; Sieck, G C
2010-12-01
We present a systematic quantitative analysis of power-law force relaxation and investigate logarithmic superposition of force response in relaxed porcine airway smooth muscle (ASM) strips in vitro. The term logarithmic superposition describes linear superposition on a logarithmic scale, which is equivalent to multiplication on a linear scale. Additionally, we examine whether the dynamic response of contracted and relaxed muscles is dominated by cross-bridge cycling or passive dynamics. The study shows the following main findings. For relaxed ASM, the force response to length steps of varying amplitude (0.25-4% of reference length, both lengthening and shortening) are well-fitted with power-law functions over several decades of time (10⁻² to 10³ s), and the force response after consecutive length changes is more accurately fitted assuming logarithmic superposition rather than linear superposition. Furthermore, for sinusoidal length oscillations in contracted and relaxed muscles, increasing the oscillation amplitude induces greater hysteresivity and asymmetry of force-length relationships, whereas increasing the frequency dampens hysteresivity but increases asymmetry. We conclude that logarithmic superposition is an important feature of relaxed ASM, which may facilitate a more accurate prediction of force responses in the continuous dynamic environment of the respiratory system. In addition, the single power-function response to length changes shows that the dynamics of cross-bridge cycling can be ignored in relaxed muscle. The similarity in response between relaxed and contracted states implies that the investigated passive dynamics play an important role in both states and should be taken into account.
Leghtas, Z; Touzard, S; Pop, I M; Kou, A; Vlastakis, B; Petrenko, A; Sliwa, K M; Narla, A; Shankar, S; Hatridge, M J; Reagor, M; Frunzio, L; Schoelkopf, R J; Mirrahimi, M; Devoret, M H
2015-02-20
Physical systems usually exhibit quantum behavior, such as superpositions and entanglement, only when they are sufficiently decoupled from a lossy environment. Paradoxically, a specially engineered interaction with the environment can become a resource for the generation and protection of quantum states. This notion can be generalized to the confinement of a system into a manifold of quantum states, consisting of all coherent superpositions of multiple stable steady states. We have confined the state of a superconducting resonator to the quantum manifold spanned by two coherent states of opposite phases and have observed a Schrödinger cat state spontaneously squeeze out of vacuum before decaying into a classical mixture. This experiment points toward robustly encoding quantum information in multidimensional steady-state manifolds. Copyright © 2015, American Association for the Advancement of Science.
The general use of the time-temperature-pressure superposition principle
DEFF Research Database (Denmark)
Rasmussen, Henrik Koblitz
This note is a supplement to Dynamic of Polymeric Liquids (DPL) section 3.6(a). DPL do only concern material functions and only the effect of the temperature on these. This is a short introduction to the general use of the time-temperature-pressure superposition principle.......This note is a supplement to Dynamic of Polymeric Liquids (DPL) section 3.6(a). DPL do only concern material functions and only the effect of the temperature on these. This is a short introduction to the general use of the time-temperature-pressure superposition principle....
Two quantum Simpson’s paradoxes
International Nuclear Information System (INIS)
Paris, Matteo G A
2012-01-01
The so-called Simpson’s ‘paradox’, or Yule–Simpson (YS) effect, occurs in classical statistics when the correlations that are present among different sets of samples are reversed if the sets are combined together, thus ignoring one or more lurking variables. Here we illustrate the occurrence of two analog effects in quantum measurements. The first, which we term the quantum–classical YS effect, may occur with quantum limited measurements and with lurking variables coming from the mixing of states, whereas the second, here referred to as the quantum–quantum YS effect, may take place when coherent superpositions of quantum states are allowed. By analyzing quantum measurements on low-dimensional systems (qubits and qutrits), we show that the two effects may occur independently and that the quantum–quantum YS effect is more likely to occur than the corresponding quantum–classical one. We also found that there exist classes of superposition states for which the quantum–classical YS effect cannot occur for any measurement and, at the same time, the quantum–quantum YS effect takes place in a consistent fraction of the possible measurement settings. The occurrence of the effect in the presence of partial coherence is discussed as well as its possible implications for quantum hypothesis testing. (fast track communication)
Local quantum thermal susceptibility
de Pasquale, Antonella; Rossini, Davide; Fazio, Rosario; Giovannetti, Vittorio
2016-09-01
Thermodynamics relies on the possibility to describe systems composed of a large number of constituents in terms of few macroscopic variables. Its foundations are rooted into the paradigm of statistical mechanics, where thermal properties originate from averaging procedures which smoothen out local details. While undoubtedly successful, elegant and formally correct, this approach carries over an operational problem, namely determining the precision at which such variables are inferred, when technical/practical limitations restrict our capabilities to local probing. Here we introduce the local quantum thermal susceptibility, a quantifier for the best achievable accuracy for temperature estimation via local measurements. Our method relies on basic concepts of quantum estimation theory, providing an operative strategy to address the local thermal response of arbitrary quantum systems at equilibrium. At low temperatures, it highlights the local distinguishability of the ground state from the excited sub-manifolds, thus providing a method to locate quantum phase transitions.
Local quantum thermal susceptibility
De Pasquale, Antonella; Rossini, Davide; Fazio, Rosario; Giovannetti, Vittorio
2016-01-01
Thermodynamics relies on the possibility to describe systems composed of a large number of constituents in terms of few macroscopic variables. Its foundations are rooted into the paradigm of statistical mechanics, where thermal properties originate from averaging procedures which smoothen out local details. While undoubtedly successful, elegant and formally correct, this approach carries over an operational problem, namely determining the precision at which such variables are inferred, when technical/practical limitations restrict our capabilities to local probing. Here we introduce the local quantum thermal susceptibility, a quantifier for the best achievable accuracy for temperature estimation via local measurements. Our method relies on basic concepts of quantum estimation theory, providing an operative strategy to address the local thermal response of arbitrary quantum systems at equilibrium. At low temperatures, it highlights the local distinguishability of the ground state from the excited sub-manifolds, thus providing a method to locate quantum phase transitions. PMID:27681458
Cloud Macroscopic Organization: Order Emerging from Randomness
Yuan, Tianle
2011-01-01
Clouds play a central role in many aspects of the climate system and their forms and shapes are remarkably diverse. Appropriate representation of clouds in climate models is a major challenge because cloud processes span at least eight orders of magnitude in spatial scales. Here we show that there exists order in cloud size distribution of low-level clouds, and that it follows a power-law distribution with exponent gamma close to 2. gamma is insensitive to yearly variations in environmental conditions, but has regional variations and land-ocean contrasts. More importantly, we demonstrate this self-organizing behavior of clouds emerges naturally from a complex network model with simple, physical organizing principles: random clumping and merging. We also demonstrate symmetry between clear and cloudy skies in terms of macroscopic organization because of similar fundamental underlying organizing principles. The order in the apparently complex cloud-clear field thus has its root in random local interactions. Studying cloud organization with complex network models is an attractive new approach that has wide applications in climate science. We also propose a concept of cloud statistic mechanics approach. This approach is fully complementary to deterministic models, and the two approaches provide a powerful framework to meet the challenge of representing clouds in our climate models when working in tandem.
Adiabatic process reversibility: microscopic and macroscopic views
International Nuclear Information System (INIS)
Anacleto, Joaquim; Pereira, Mario G
2009-01-01
The reversibility of adiabatic processes was recently addressed by two publications. In the first (Miranda 2008 Eur. J. Phys. 29 937-43), an equation was derived relating the initial and final volumes and temperatures for adiabatic expansions of an ideal gas, using a microscopic approach. In that relation the parameter r accounts for the process reversibility, ranging between 0 and 1, which corresponds to the free and reversible expansion, respectively. In the second (Anacleto and Pereira 2009 Eur. J. Phys. 30 177-83), the authors have shown that thermodynamics can effectively and efficiently be used to obtain the general law for adiabatic processes carried out by an ideal gas, including compressions, for which r≥1. The present work integrates and extends the aforementioned studies, providing thus further insights into the analysis of the adiabatic process. It is shown that Miranda's work is wholly valid for compressions. In addition, it is demonstrated that the adiabatic reversibility coefficient given in terms of the piston velocity and the root mean square velocity of the gas particles is equivalent to the macroscopic description, given just by the quotient between surroundings and system pressure values. (letters and comments)
The Proell Effect: A Macroscopic Maxwell's Demon
Rauen, Kenneth M.
2011-12-01
Maxwell's Demon is a legitimate challenge to the Second Law of Thermodynamics when the "demon" is executed via the Proell effect. Thermal energy transfer according to the Kinetic Theory of Heat and Statistical Mechanics that takes place over distances greater than the mean free path of a gas circumvents the microscopic randomness that leads to macroscopic irreversibility. No information is required to sort the particles as no sorting occurs; the entire volume of gas undergoes the same transition. The Proell effect achieves quasi-spontaneous thermal separation without sorting by the perturbation of a heterogeneous constant volume system with displacement and regeneration. The classical analysis of the constant volume process, such as found in the Stirling Cycle, is incomplete and therefore incorrect. There are extra energy flows that classical thermo does not recognize. When a working fluid is displaced across a regenerator with a temperature gradient in a constant volume system, complimentary compression and expansion work takes place that transfers energy between the regenerator and the bulk gas volumes of the hot and cold sides of the constant volume system. Heat capacity at constant pressure applies instead of heat capacity at constant volume. The resultant increase in calculated, recyclable energy allows the Carnot Limit to be exceeded in certain cycles. Super-Carnot heat engines and heat pumps have been designed and a US patent has been awarded.
Karlovets, Dmitry V; Serbo, Valeriy G
2017-10-27
Within a plane-wave approximation in scattering, an incoming wave packet's Wigner function stays positive everywhere, which obscures such purely quantum phenomena as nonlocality and entanglement. With the advent of the electron microscopes with subnanometer-sized beams, one can enter a genuinely quantum regime where the latter effects become only moderately attenuated. Here we show how to probe negative values of the Wigner function in scattering of a coherent superposition of two Gaussian packets with a nonvanishing impact parameter between them (a Schrödinger's cat state) by atomic targets. For hydrogen in the ground 1s state, a small parameter of the problem, a ratio a/σ_{⊥} of the Bohr radius a to the beam width σ_{⊥}, is no longer vanishing. We predict an azimuthal asymmetry of the scattered electrons, which is found to be up to 10%, and argue that it can be reliably detected. The production of beams with the not-everywhere-positive Wigner functions and the probing of such quantum effects can open new perspectives for noninvasive electron microscopy, quantum tomography, particle physics, and so forth.
Architectures for a quantum random access memory
Giovannetti, Vittorio; Lloyd, Seth; Maccone, Lorenzo
2008-01-01
A random access memory, or RAM, is a device that, when interrogated, returns the content of a memory location in a memory array. A quantum RAM, or qRAM, allows one to access superpositions of memory sites, which may contain either quantum or classical information. RAMs and qRAMs with n-bit addresses can access 2^n memory sites. Any design for a RAM or qRAM then requires O(2^n) two-bit logic gates. At first sight this requirement might seem to make large scale quantum versions of such devices ...
Information and Self-Organization A Macroscopic Approach to Complex Systems
Haken, Hermann
2006-01-01
This book presents the concepts needed to deal with self-organizing complex systems from a unifying point of view that uses macroscopic data. The various meanings of the concept "information" are discussed and a general formulation of the maximum information (entropy) principle is used. With the aid of results from synergetics, adequate objective constraints for a large class of self-organizing systems are formulated and examples are given from physics, life and computer science. The relationship to chaos theory is examined and it is further shown that, based on possibly scarce and noisy data, unbiased guesses about processes of complex systems can be made and the underlying deterministic and random forces determined. This allows for probabilistic predictions of processes, with applications to numerous fields in science, technology, medicine and economics. The extensions of the third edition are essentially devoted to an introduction to the meaning of information in the quantum context. Indeed, quantum inform...
Quantum behaviour of measuring apparatus
International Nuclear Information System (INIS)
Amri, T.
2011-05-01
This thesis explores the quantum behavior of measurement apparatus with illustrations in quantum optics. This is the first study of quantum properties of measurements performed by any kind of devices. We show that the quantum properties of a measurement, such as its projective or non-classical character, are revealed only by the quantum states of an unusual approach of quantum physics: the retrodictive approach. This approach involves retro-predictions about state preparations leading to a given measurement result, contrary to the predictive approach with which we usually make predictions about the results of an experiment. By clarifying the mathematical foundations of the retrodictive approach, we propose a general procedure for reconstructing the quantum states of this approach: the retrodicted states. We have realized these reconstructions for single-photon detectors, widely used in quantum cryptography for instance. This is the first tomography of quantum states totally based on the retrodictive approach and preparation choices, contrary to usual reconstructions based on measurement results. These tomographies enabled us to study experimentally the noise influence on the quantum properties of measurements performed by these detectors, in particular their transition from a strongly quantum behavior into a more classical behavior. Finally, we propose a detector of Schroedinger's Cat states of light, which are superpositions of incompatible quasi-classical states of light. In a modern version of a thought experiment proposed by Eugene Wigner in 1961, such a device could allow the Wigner's Friend to detect a Schroedinger's Cat, contrary to human eyes for which we specify some quantum properties. We generalize the use of such a non-classical detector to an estimation protocol, totally based on the retrodictive approach and preparation choices. Such a procedure could enable optimal estimations, by reaching the quantum Cramer-Rao bound, which is a very topical issue
The Double-Well Potential in Quantum Mechanics: A Simple, Numerically Exact Formulation
Jelic, V.; Marsiglio, F.
2012-01-01
The double-well potential is arguably one of the most important potentials in quantum mechanics, because the solution contains the notion of a state as a linear superposition of "classical" states, a concept which has become very important in quantum information theory. It is therefore desirable to have solutions to simple double-well potentials…
Postulates of quantum mechanics
International Nuclear Information System (INIS)
Cohen-Tannoudji, Claude; Diu, Bernard; Laloe, Franck.
1977-01-01
Postulates of quantum mechanics and physical interpretation on observables and their measurement are presented. The physical content of Schroedinger equation, the superposition principle and the physical forecastings are also exposed. In complement are also presented: physical study of a particle in a infinite potential well; study of probability current; mean deviations of two conjugate observables; measurements on a part only of a physical system; density operator; evolution operator; Heisenberg and Schoredinger pictures; gauge invariance; propagator of the Schroedinger equation; unsteady levels lifetime; bound states of a particle in a potential well of any shape; non-bound states of a particle in a well or a potential barrier of some shape; quantum properties of a particle in a one-dimensional periodic structure [fr
Towards a theory of macroscopic gravity
International Nuclear Information System (INIS)
Zalaletdinov, R.M.
1993-01-01
By averaging out Cartan's structure equations for a four-dimensional Riemannian space over space regions, the structure equations for the averaged space have been derived with the procedure being valid on an arbitrary Riemannian space. The averaged space is characterized by a metric, Riemannian and non-Riemannian curvature 2-forms, and correlation 2-, 3- and 4-forms, an affine deformation 1-form being due to the non-metricity of one of two connection 1-forms. Using the procedure for the space-time averaging of the Einstein equations produces the averaged ones with the terms of geometric correction by the correlation tensors. The equations of motion for averaged energy momentum, obtained by averaging out the coritracted Bianchi identifies, also include such terms. Considering the gravitational induction tensor to be the Riemannian curvature tensor (the non-Riemannian one is then the field tensor), a theorem is proved which relates the algebraic structure of the averaged microscopic metric to that of the induction tensor. It is shown that the averaged Einstein equations can be put in the form of the Einstein equations with the conserved macroscopic energy-momentum tensor of a definite structure including the correlation functions. By using the high-frequency approximation of Isaacson with second-order correction to the microscopic metric, the self-consistency and compatibility of the equations and relations obtained are shown. Macrovacuum turns out to be Ricci non-flat, the macrovacuum source being defined in terms of the correlation functions. In the high-frequency limit the equations are shown to become Isaacson's ones with the macrovacuum source becoming Isaacson's stress tensor for gravitational waves. 17 refs
Quantum Models of Classical World
Directory of Open Access Journals (Sweden)
Petr Hájíček
2013-02-01
Full Text Available This paper is a review of our recent work on three notorious problems of non-relativistic quantum mechanics: realist interpretation, quantum theory of classical properties, and the problem of quantum measurement. A considerable progress has been achieved, based on four distinct new ideas. First, objective properties are associated with states rather than with values of observables. Second, all classical properties are selected properties of certain high entropy quantum states of macroscopic systems. Third, registration of a quantum system is strongly disturbed by systems of the same type in the environment. Fourth, detectors must be distinguished from ancillas and the states of registered systems are partially dissipated and lost in the detectors. The paper has two aims: a clear explanation of all new results and a coherent and contradiction-free account of the whole quantum mechanics including all necessary changes of its current textbook version.
A review on quantum search algorithms
Giri, Pulak Ranjan; Korepin, Vladimir E.
2017-12-01
The use of superposition of states in quantum computation, known as quantum parallelism, has significant advantage in terms of speed over the classical computation. It is evident from the early invented quantum algorithms such as Deutsch's algorithm, Deutsch-Jozsa algorithm and its variation as Bernstein-Vazirani algorithm, Simon algorithm, Shor's algorithms, etc. Quantum parallelism also significantly speeds up the database search algorithm, which is important in computer science because it comes as a subroutine in many important algorithms. Quantum database search of Grover achieves the task of finding the target element in an unsorted database in a time quadratically faster than the classical computer. We review Grover's quantum search algorithms for a singe and multiple target elements in a database. The partial search algorithm of Grover and Radhakrishnan and its optimization by Korepin called GRK algorithm are also discussed.
GPU-Based Point Cloud Superpositioning for Structural Comparisons of Protein Binding Sites.
Leinweber, Matthias; Fober, Thomas; Freisleben, Bernd
2018-01-01
In this paper, we present a novel approach to solve the labeled point cloud superpositioning problem for performing structural comparisons of protein binding sites. The solution is based on a parallel evolution strategy that operates on large populations and runs on GPU hardware. The proposed evolution strategy reduces the likelihood of getting stuck in a local optimum of the multimodal real-valued optimization problem represented by labeled point cloud superpositioning. The performance of the GPU-based parallel evolution strategy is compared to a previously proposed CPU-based sequential approach for labeled point cloud superpositioning, indicating that the GPU-based parallel evolution strategy leads to qualitatively better results and significantly shorter runtimes, with speed improvements of up to a factor of 1,500 for large populations. Binary classification tests based on the ATP, NADH, and FAD protein subsets of CavBase, a database containing putative binding sites, show average classification rate improvements from about 92 percent (CPU) to 96 percent (GPU). Further experiments indicate that the proposed GPU-based labeled point cloud superpositioning approach can be superior to traditional protein comparison approaches based on sequence alignments.
Superpositions of higher-order bessel beams and nondiffracting speckle fields
CSIR Research Space (South Africa)
Dudley, Angela L
2009-08-01
Full Text Available speckle fields. The paper reports on illuminating a ring slit aperture with light which has an azimuthal phase dependence, such that the field produced is a superposition of two higher-order Bessel beams. In the case that the phase dependence of the light...
Chaos and Complexities Theories. Superposition and Standardized Testing: Are We Coming or Going?
Erwin, Susan
2005-01-01
The purpose of this paper is to explore the possibility of using the principle of "superposition of states" (commonly illustrated by Schrodinger's Cat experiment) to understand the process of using standardized testing to measure a student's learning. Comparisons from literature, neuroscience, and Schema Theory will be used to expound upon the…
Superposition of Planckian spectra and the distortions of the cosmic microwave background radiation
International Nuclear Information System (INIS)
Alexanian, M.
1982-01-01
A fit of the spectrum of the cosmic microwave background radiation (CMB) by means of a positive linear superposition of Planckian spectra implies an upper bound to the photon spectrum. The observed spectrum of the CMB gives a weighting function with a normalization greater than unity
Teleportation of a Superposition of Three Orthogonal States of an Atom via Photon Interference
Institute of Scientific and Technical Information of China (English)
ZHENG Shi-Biao
2006-01-01
We propose a scheme to teleport a superposition of three states of an atom trapped in a cavity to a second atom trapped in a remote cavity. The scheme is based on the detection of photons leaking from the cavities after the atom-cavity interaction.
On a computational method for modelling complex ecosystems by superposition procedure
International Nuclear Information System (INIS)
He Shanyu.
1986-12-01
In this paper, the Superposition Procedure is concisely described, and a computational method for modelling a complex ecosystem is proposed. With this method, the information contained in acceptable submodels and observed data can be utilized to maximal degree. (author). 1 ref
Using Musical Intervals to Demonstrate Superposition of Waves and Fourier Analysis
LoPresto, Michael C.
2013-01-01
What follows is a description of a demonstration of superposition of waves and Fourier analysis using a set of four tuning forks mounted on resonance boxes and oscilloscope software to create, capture and analyze the waveforms and Fourier spectra of musical intervals.
Superpositions of higher-order bessel beams and nondiffracting speckle fields - (SAIP 2009)
CSIR Research Space (South Africa)
Dudley, Angela L
2009-07-01
Full Text Available speckle fields. The paper reports on illuminating a ring slit aperture with light which has an azimuthal phase dependence, such that the field produced is a superposition of two higher-order Bessel beams. In the case that the phase dependence of the light...
Quantum theory and human perception of the macro-world.
Aerts, Diederik
2014-01-01
We investigate the question of 'why customary macroscopic entities appear to us humans as they do, i.e., as bounded entities occupying space and persisting through time', starting from our knowledge of quantum theory, how it affects the behavior of such customary macroscopic entities, and how it influences our perception of them. For this purpose, we approach the question from three perspectives. Firstly, we look at the situation from the standard quantum angle, more specifically the de Broglie wavelength analysis of the behavior of macroscopic entities, indicate how a problem with spin and identity arises, and illustrate how both play a fundamental role in well-established experimental quantum-macroscopical phenomena, such as Bose-Einstein condensates. Secondly, we analyze how the question is influenced by our result in axiomatic quantum theory, which proves that standard quantum theory is structurally incapable of describing separated entities. Thirdly, we put forward our new 'conceptual quantum interpretation', including a highly detailed reformulation of the question to confront the new insights and views that arise with the foregoing analysis. At the end of the final section, a nuanced answer is given that can be summarized as follows. The specific and very classical perception of human seeing-light as a geometric theory-and human touching-only ruled by Pauli's exclusion principle-plays a role in our perception of macroscopic entities as ontologically stable entities in space. To ascertain quantum behavior in such macroscopic entities, we will need measuring apparatuses capable of its detection. Future experimental research will have to show if sharp quantum effects-as they occur in smaller entities-appear to be ontological aspects of customary macroscopic entities. It remains a possibility that standard quantum theory is an incomplete theory, and hence incapable of coping ultimately with separated entities, meaning that a more general theory will be needed.
Quantum Theory and Human Perception of the Macro-World
Directory of Open Access Journals (Sweden)
Diederik eAerts
2014-06-01
Full Text Available We investigate the question of 'why customary macroscopic entities appear to us humans as they do, i.e. as bounded entities occupying space and persisting through time', starting from our knowledge of quantum theory, how it affects the behavior of such customary macroscopic entities, and how it influences our perception of them. For this purpose, we approach the question from three perspectives. Firstly, we look at the situation from the standard quantum angle, more specifically the de Broglie wavelength analysis of the behavior of macroscopic entities, indicate how a problem with spin and identity arises, and illustrate how both play a fundamental role in well-established experimental quantum-macroscopical phenomena, such as Bose-Einstein condensates. Secondly, we analyze how the question is influenced by our result in axiomatic quantum theory, which proves that standard quantum theory is structurally incapable of describing separated entities. Thirdly, we put forward our new `conceptual quantum interpretation', including a highly detailed reformulation of the question to confront the new insights and views that arise with the foregoing analysis. At the end of the final section, a nuanced answer is given that can be summarized as follows. The specific and very classical perception of human seeing -- light as a geometric theory -- and human touching -- only ruled by Pauli's exclusion principle -- plays a role in our perception of macroscopic entities as ontologically stable objects in space. To ascertain quantum behavior in such macroscopic entities, we will need measuring apparatuses capable of its detection. Future experimental research will have to show if sharp quantum effects -- as they occur in smaller entities -- appear to be ontological aspects of customary macroscopic entities. It remains a possibility that standard quantum theory is an incomplete theory, and hence incapable of coping with separated entities, meaning that a more general
National Research Council Canada - National Science Library
Agarwal, G. S
2013-01-01
.... Focusing on applications of quantum optics, the textbook covers recent developments such as engineering of quantum states, quantum optics on a chip, nano-mechanical mirrors, quantum entanglement...
Quantum entanglement and special relativity
International Nuclear Information System (INIS)
Nishikawa, Yoshihisa
2008-01-01
Quantum entanglement was suggested by Einstein to indicate that quantum mechanics was incomplete. However, against Einstein's expectation, the phenomenon due to quantum entanglement has been verified by experiments. Recently, in quantum information theory, it has been also treated as a resource for quantum teleportation and so on. In around 2000, it is recognized that quantum correlations between two particles of one pair state in an entangled spin-state are affected by the non-trivial effect due to the successive Lorentz transformation. This relativistic effect is called the Wigner rotation. The Wigner rotation has to been taken into account when we observe spin-correlation of moving particles in a different coordinate frame. In this paper, first, we explain quantum entanglement and its modification due to the Wigner rotation. After that, we introduce an extended model instead of one pair state model. In the extended model, quantum entanglement state is prepared as a superposition state of various pair states. We have computed the von Neumann entropy and the Shannon entropy to see the global behavior of variation for the spin correlation due to the relativistic effect. We also discuss distinguishability between the two particles of the pair. (author)
Spectral dimension of quantum geometries
International Nuclear Information System (INIS)
Calcagni, Gianluca; Oriti, Daniele; Thürigen, Johannes
2014-01-01
The spectral dimension is an indicator of geometry and topology of spacetime and a tool to compare the description of quantum geometry in various approaches to quantum gravity. This is possible because it can be defined not only on smooth geometries but also on discrete (e.g., simplicial) ones. In this paper, we consider the spectral dimension of quantum states of spatial geometry defined on combinatorial complexes endowed with additional algebraic data: the kinematical quantum states of loop quantum gravity (LQG). Preliminarily, the effects of topology and discreteness of classical discrete geometries are studied in a systematic manner. We look for states reproducing the spectral dimension of a classical space in the appropriate regime. We also test the hypothesis that in LQG, as in other approaches, there is a scale dependence of the spectral dimension, which runs from the topological dimension at large scales to a smaller one at short distances. While our results do not give any strong support to this hypothesis, we can however pinpoint when the topological dimension is reproduced by LQG quantum states. Overall, by exploring the interplay of combinatorial, topological and geometrical effects, and by considering various kinds of quantum states such as coherent states and their superpositions, we find that the spectral dimension of discrete quantum geometries is more sensitive to the underlying combinatorial structures than to the details of the additional data associated with them. (paper)
Optimized Binomial Quantum States of Complex Oscillators with Real Spectrum
International Nuclear Information System (INIS)
Zelaya, K D; Rosas-Ortiz, O
2016-01-01
Classical and nonclassical states of quantum complex oscillators with real spectrum are presented. Such states are bi-orthonormal superpositions of n +1 energy eigenvectors of the system with binomial-like coefficients. For large values of n these optimized binomial states behave as photon added coherent states when the imaginary part of the potential is cancelled. (paper)
Decoherence in open quantum systems
International Nuclear Information System (INIS)
Isar, A.
2005-01-01
advantage of the superposition principle. The study of classicality using QD leads to a deeper understanding of the quantum origins of the classical world. Much work has still to be done even to settle the interpretational questions, not to speak about answering them. Nevertheless, as a result of the progress made in the last two decades, the quantum to classical transition has become a subject of experimental investigations, while previously it was mostly a domain of philosophy. The issue of quantum to classical transition points to the necessity of a better understanding of open quantum systems. The Lindblad theory provides a selfconsistent treatment of damping as a general extension of quantum mechanics
Beyond quantum microcanonical statistics
International Nuclear Information System (INIS)
Fresch, Barbara; Moro, Giorgio J.
2011-01-01
Descriptions of molecular systems usually refer to two distinct theoretical frameworks. On the one hand the quantum pure state, i.e., the wavefunction, of an isolated system is determined to calculate molecular properties and their time evolution according to the unitary Schroedinger equation. On the other hand a mixed state, i.e., a statistical density matrix, is the standard formalism to account for thermal equilibrium, as postulated in the microcanonical quantum statistics. In the present paper an alternative treatment relying on a statistical analysis of the possible wavefunctions of an isolated system is presented. In analogy with the classical ergodic theory, the time evolution of the wavefunction determines the probability distribution in the phase space pertaining to an isolated system. However, this alone cannot account for a well defined thermodynamical description of the system in the macroscopic limit, unless a suitable probability distribution for the quantum constants of motion is introduced. We present a workable formalism assuring the emergence of typical values of thermodynamic functions, such as the internal energy and the entropy, in the large size limit of the system. This allows the identification of macroscopic properties independently of the specific realization of the quantum state. A description of material systems in agreement with equilibrium thermodynamics is then derived without constraints on the physical constituents and interactions of the system. Furthermore, the canonical statistics is recovered in all generality for the reduced density matrix of a subsystem.
Quantum physics; Physique quantique
Energy Technology Data Exchange (ETDEWEB)
Basdevant, J.L.; Dalibart, J. [Ecole Polytechnique, 75 - Paris (France)
1997-12-31
This pedagogical book gives an initiation to the principles and practice of quantum mechanics. A large part is devoted to experimental facts and to their analysis: concrete facts, phenomena and applications related to fundamental physics, elementary particles, astrophysics, high-technology, semi-conductors, micro-electronics and lasers. The book is divided in 22 chapters dealing with: quantum phenomena, wave function and Schroedinger equation, physical units and measurements, energy quantification of some simple systems, Hilbert space, Dirac formalism and quantum mechanics postulates, two-state systems and ammonia Maser principle, bands theory and crystals conductibility, commutation of observables, Stern and Gerlach experiment, approximation methods, kinetic momentum in quantum mechanics, first description of atoms, 1/2 spin formalism and magnetic resonance, Lagrangian, Hamiltonian and Lorentz force in quantum mechanics, addition of kinetic momenta and fine and hyper-fine structure of atomic lines, identical particle systems and Pauli principle, qualitative physics and scale of size of some microscopic and macroscopic phenomena, systems evolution, collisions and cross sections, invariance and conservation laws, quantum mechanics and astrophysics, and historical aspects of quantum mechanics. (J.S.) refs.
An operator description of entanglement matching in quantum teleportation
International Nuclear Information System (INIS)
Kurucz, Z; Koniorczyk, M; Adam, P; Janszky, J
2003-01-01
The antilinear operator representation of bipartite pure states of the relative state formulation of quantum mechanics is applied to describe quantum teleportation schemes utilizing an arbitrary pure state as the entangled resource. Bennett type teleportation schemes with nonmaximally entangled pure states are characterized and the notion of 'entanglement matching' is introduced in general. Examples, including a scheme based on coherent-state superposition states of the electromagnetic field, are provided
Quantum Phase Spase Representation for Double Well Potential
Babyuk, Dmytro
2002-01-01
A behavior of quantum states (superposition of two lowest eigenstates, Gaussian wave packet) in phase space is studied for one and two dimensional double well potential. Two dimensional potential is constructed from double well potential coupled linearly and quadratically to harmonic potential. Quantum trajectories are compared with classical ones. Preferable tunneling path in phase space is found. An influence of energy of initial Gaussian wave packet and trajectory initial condition on tunn...
A quantum liquid model for the QCD vacuum
International Nuclear Information System (INIS)
Nielsen, H.B.; Olesen, P.
1979-06-01
It is shown that domains are formed in a homogeneous SU(2) color magnetic field. Due to quantum fluctuations the domains have fluid properties. It is then argued that quantum mechanically superpositions of such domains must be considered. The resulting state is gauge and rotational invariant, in spite of the fact that the original color magnetic field breaks these invariances. It is pointed out that in the model for the QCD vacuum color magnetic monopoles are not confined. (Auth.)
Theory of Spin States of Quantum Dot Molecules
Ponomarev, I. V.; Reinecke, T. L.; Scheibner, M.; Stinaff, E. A.; Bracker, A. S.; Doty, M. F.; Gammon, D.; Korenev, V. L.
2007-04-01
The photoluminescence spectrum of an asymmetric pair of coupled InAs quantum dots in an applied electric field shows a rich pattern of level anticrossings, crossings and fine structure that can be understood as a superposition of charge and spin configurations. We present a theoretical model that provides a description of the energy positions and intensities of the optical transitions in exciton, biexciton and charged exciton states of coupled quantum dots molecules.
Thermodynamical properties and thermoelastic coupling of complex macroscopic structure
International Nuclear Information System (INIS)
Fabbri, M.; Sacripanti, A.
1996-11-01
Gross qualitative/quantitative analysis about thermodynamical properties and thermoelastic coupling (or elastocaloric effect) of complex macroscopic structure (running shoes) is performed by infrared camera. The experimental results showed the achievability of a n industrial research project
Single-Phase Bundle Flows Including Macroscopic Turbulence Model
Energy Technology Data Exchange (ETDEWEB)
Lee, Seung Jun; Yoon, Han Young [KAERI, Daejeon (Korea, Republic of); Yoon, Seok Jong; Cho, Hyoung Kyu [Seoul National University, Seoul (Korea, Republic of)
2016-05-15
To deal with various thermal hydraulic phenomena due to rapid change of fluid properties when an accident happens, securing mechanistic approaches as much as possible may reduce the uncertainty arising from improper applications of the experimental models. In this study, the turbulence mixing model, which is well defined in the subchannel analysis code such as VIPRE, COBRA, and MATRA by experiments, is replaced by a macroscopic k-e turbulence model, which represents the aspect of mathematical derivation. The performance of CUPID with macroscopic turbulence model is validated against several bundle experiments: CNEN 4x4 and PNL 7x7 rod bundle tests. In this study, the macroscopic k-e model has been validated for the application to subchannel analysis. It has been implemented in the CUPID code and validated against CNEN 4x4 and PNL 7x7 rod bundle tests. The results showed that the macroscopic k-e turbulence model can estimate the experiments properly.
Dynamical fusion thresholds in macroscopic and microscopic theories
International Nuclear Information System (INIS)
Davies, K.T.R.; Sierk, A.J.; Nix, J.R.
1983-01-01
Macroscopic and microscopic results demonstrating the existence of dynamical fusion thresholds are presented. For macroscopic theories, it is shown that the extra-push dynamics is sensitive to some details of the models used, e.g. the shape parametrization and the type of viscosity. The dependence of the effect upon the charge and angular momentum of the system is also studied. Calculated macroscopic results for mass-symmetric systems are compared to experimental mass-asymmetric results by use of a tentative scaling procedure, which takes into account both the entrance-channel and the saddle-point regions of configuration space. Two types of dynamical fusion thresholds occur in TDHF studies: (1) the microscopic analogue of the macroscopic extra push threshold, and (2) the relatively high energy at which the TDHF angular momentum window opens. Both of these microscopic thresholds are found to be very sensitive to the choice of the effective two-body interaction
A quantum speedup in machine learning: finding an N-bit Boolean function for a classification
International Nuclear Information System (INIS)
Yoo, Seokwon; Lee, Jinhyoung; Bang, Jeongho; Lee, Changhyoup
2014-01-01
We compare quantum and classical machines designed for learning an N-bit Boolean function in order to address how a quantum system improves the machine learning behavior. The machines of the two types consist of the same number of operations and control parameters, but only the quantum machines utilize the quantum coherence naturally induced by unitary operators. We show that quantum superposition enables quantum learning that is faster than classical learning by expanding the approximate solution regions, i.e., the acceptable regions. This is also demonstrated by means of numerical simulations with a standard feedback model, namely random search, and a practical model, namely differential evolution. (paper)
Energy Technology Data Exchange (ETDEWEB)
Stapp, Henry
2011-11-10
Robert Griffiths has recently addressed, within the framework of a ‘consistent quantum theory’ (CQT) that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues, on the basis of his examination of certain arguments that claim to demonstrate the existence of such nonlocal influences, that such influences do not exist. However, his examination was restricted mainly to hidden-variable-based arguments that include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. One cannot logically prove properties of a system by attributing to the system properties alien to that system. Hence Griffiths’ rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence for nonlocal influences. But he did not examine the particular proof that he cites. An examination of that particular proof by the method specified by his ‘consistent quantum theory’ shows that the cited proof is valid within that restrictive framework. This necessary existence, within the ‘consistent’ framework, of long range essentially instantaneous influences refutes the claim made by Griffiths that his ‘consistent’ framework is superior to the orthodox quantum theory of von Neumann because it does not entail instantaneous influences. An added section responds to Griffiths’ reply, which cites a litany of ambiguities that seem to restrict, devastatingly, the scope of his CQT formalism, apparently to buttress his claim that my use of that formalism to validate the nonlocality theorem is flawed. But the
From quantum foundations to applications and back.
Gisin, Nicolas; Fröwis, Florian
2018-07-13
Quantum non-locality has been an extremely fruitful subject of research, leading the scientific revolution towards quantum information science, in particular, to device-independent quantum information processing. We argue that the time is ripe to work on another basic problem in the foundations of quantum physics, the quantum measurement problem, which should produce good physics in theoretical, mathematical, experimental and applied physics. We briefly review how quantum non-locality contributed to physics (including some outstanding open problems) and suggest ways in which questions around macroscopic quantumness could equally contribute to all aspects of physics.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'. © 2018 The Author(s).
Shor's quantum factoring algorithm on a photonic chip.
Politi, Alberto; Matthews, Jonathan C F; O'Brien, Jeremy L
2009-09-04
Shor's quantum factoring algorithm finds the prime factors of a large number exponentially faster than any other known method, a task that lies at the heart of modern information security, particularly on the Internet. This algorithm requires a quantum computer, a device that harnesses the massive parallelism afforded by quantum superposition and entanglement of quantum bits (or qubits). We report the demonstration of a compiled version of Shor's algorithm on an integrated waveguide silica-on-silicon chip that guides four single-photon qubits through the computation to factor 15.
Micro- and macroscopic photonic control of matter
Ryabtsev, Anton
parameters. In order for measurements not to be skewed, these interactions need to be taken into account and mitigated at the time of the experiment or handled later in data analysis and simulations. Experimental results are presented in four chapters. Chapter 2 describes two topics: (1) single-shot real-time monitoring and correction of spectral phase drifts, which commonly originate from temperature and pointing fluctuations inside the laser cavity when the pulses are generated; (2) an all-optical method for controlling the dispersion of femtosecond pulses using other pulses. Chapter 3 focuses on the effects of the propagation media--how intense laser pulses modify media and how, in turn, the media modifies them back--and how these effects can be counteracted. Self-action effects in fused silica are discussed, along with some interesting and unexpected results. A method is then proposed for mitigating self-action processes using binary modulation of the spectral phases of laser pulses. Chapter 4 outlines the design of two laser systems, which are specifically tailored for particular spectroscopic applications and incorporate the comprehensive pulse control described in previous chapters. Chapter 5 shows how control of spatial beam characteristics can be applied to measurements of the mechanical motion of microscale particles and how it can potentially be applied to molecular motion. It also describes an experiment on laser-induced flow in air in which attempts were made to control the macroscopic molecular rotation of gases. My research, with a pulse shaper as the enabling tool, provides important insights into ultrafast scientific studies by making femtosecond laser research more predictable, reliable and practical for measurement and control. In the long term, some of the research methods in this thesis may help the transition of femtosecond lasers from the laboratory environment into clinics, factories, airports, and other everyday settings.
Macroscopic Refrigeration Using Superconducting Tunnel Junctions
Lowell, Peter; O'Neil, Galen; Underwood, Jason; Zhang, Xiaohang; Ullom, Joel
2014-03-01
Sub-kelvin temperatures are often a prerequisite for modern scientific experiments, such as quantum information processing, astrophysical missions looking for dark energy signatures and tabletop time resolved x-ray spectroscopy. Existing methods of reaching these temperatures, such as dilution refrigerators, are bulky and costly. In order to increase the accessibility of sub-Kelvin temperatures, we have developed a new method of refrigeration using normal-metal/insulator/superconductor (NIS) tunnel junctions. NIS junctions cool the electrons in the normal metal since the hottest electrons selectively tunnel from the normal metal into the superconductor. By extending the normal metal onto a thermally isolated membrane, the cold electrons can cool the phonons through the electron-phonon coupling. When these junctions are combined with a pumped 3He system, they provide a potentially inexpensive method of reaching these temperatures. Using only three devices, each with a junction area of approximately 3,500 μm2, we have cooled a 2 cm3 Cu plate from 290 mK to 256 mK. We will present these experimental results along with recent modeling predictions that strongly suggest that further refinements will allow cooling from 300 mK to 120 mK. This work is supported by the NASA APRA program.
Fractional Josephson vortices: oscillating macroscopic spins
Energy Technology Data Exchange (ETDEWEB)
Gaber, T.; Buckenmaier, K.; Koelle, D.; Kleiner, R.; Goldobin, E. [Universitaet Tuebingen, Physikalisches Institut - Experimentalphysik II, Tuebingen (Germany)
2007-11-15
Fractional Josephson vortices carry a magnetic flux {phi}, which is a fraction of the magnetic flux quantum {phi}{sub 0}{approx}2.07 x 10{sup -15} Wb. We consider a fractional vortex which spontaneously appears at a phase discontinuity. Its properties are very different from the properties of the usual integer fluxon. In particular, a fractional vortex is pinned and may have one of two possible polarities - just like a usual spin 1/2 particle. The fractional vortex may also oscillate around its equilibrium position with an eigenfrequency which is expected to be within the Josephson plasma gap. Using microwave spectroscopy, we investigate the dependence of the eigenfrequency of a fractional Josephson vortex on its magnetic flux {phi} and on the bias current. The experimental results are in good agreement with theoretical predictions. Positive result of this experiment is a cornerstone for further investigation of more complex fractional vortex systems such as fractional vortex molecules and tunable bandgap materials. (orig.)
Quantum control and representation theory
International Nuclear Information System (INIS)
Ibort, A; Perez-Pardo, J M
2009-01-01
A new notion of controllability for quantum systems that takes advantage of the linear superposition of quantum states is introduced. We call such a notion von Neumann controllability, and it is shown that it is strictly weaker than the usual notion of pure state and operator controllability. We provide a simple and effective characterization of it by using tools from the theory of unitary representations of Lie groups. In this sense, we are able to approach the problem of control of quantum states from a new perspective, that of the theory of unitary representations of Lie groups. A few examples of physical interest and the particular instances of compact and nilpotent dynamical Lie groups are discussed
Quantum perceptron over a field and neural network architecture selection in a quantum computer.
da Silva, Adenilton José; Ludermir, Teresa Bernarda; de Oliveira, Wilson Rosa
2016-04-01
In this work, we propose a quantum neural network named quantum perceptron over a field (QPF). Quantum computers are not yet a reality and the models and algorithms proposed in this work cannot be simulated in actual (or classical) computers. QPF is a direct generalization of a classical perceptron and solves some drawbacks found in previous models of quantum perceptrons. We also present a learning algorithm named Superposition based Architecture Learning algorithm (SAL) that optimizes the neural network weights and architectures. SAL searches for the best architecture in a finite set of neural network architectures with linear time over the number of patterns in the training set. SAL is the first learning algorithm to determine neural network architectures in polynomial time. This speedup is obtained by the use of quantum parallelism and a non-linear quantum operator. Copyright © 2016 Elsevier Ltd. All rights reserved.
Processing Information in Quantum Decision Theory
Yukalov, V. I.; Sornette, D.
2008-01-01
A survey is given summarizing the state of the art of describing information processing in Quantum Decision Theory, which has been recently advanced as a novel variant of decision making, based on the mathematical theory of separable Hilbert spaces. This mathematical structure captures the effect of superposition of composite prospects, including many incorporated intended actions. The theory characterizes entangled decision making, non-commutativity of subsequent decisions, and intention int...
New progress of fundamental aspects in quantum mechanics
International Nuclear Information System (INIS)
Sun Changpu
2001-01-01
The review recalls the conceptual origins of various interpretations of quantum mechanics. With the focus on quantum measurement problems, new developments of fundamental quantum theory are described in association with recent experiments such as the decoherence process in cavity quantum electrodynamics 'which-way' detection using the Bragg scattering of cold atoms, and quantum interference using the small quantum system of molecular C 60 . The fundamental problems include the quantum coherence of a macroscopic object, the von Neumann chain in quantum measurement, the Schroedinger cat paradox, et al. Many land math experiments have been accomplished with possible important applications in quantum information. The most recent research on the new quantum theory by G.'t Hooft is reviewed, as well as future prospects of quantum mechanics
Nonclassical thermal-state superpositions: Analytical evolution law and decoherence behavior
Meng, Xiang-guo; Goan, Hsi-Sheng; Wang, Ji-suo; Zhang, Ran
2018-03-01
Employing the integration technique within normal products of bosonic operators, we present normal product representations of thermal-state superpositions and investigate their nonclassical features, such as quadrature squeezing, sub-Poissonian distribution, and partial negativity of the Wigner function. We also analytically and numerically investigate their evolution law and decoherence characteristics in an amplitude-decay model via the variations of the probability distributions and the negative volumes of Wigner functions in phase space. The results indicate that the evolution formulas of two thermal component states for amplitude decay can be viewed as the same integral form as a displaced thermal state ρ(V , d) , but governed by the combined action of photon loss and thermal noise. In addition, the larger values of the displacement d and noise V lead to faster decoherence for thermal-state superpositions.
A numerical dressing method for the nonlinear superposition of solutions of the KdV equation
International Nuclear Information System (INIS)
Trogdon, Thomas; Deconinck, Bernard
2014-01-01
In this paper we present the unification of two existing numerical methods for the construction of solutions of the Korteweg–de Vries (KdV) equation. The first method is used to solve the Cauchy initial-value problem on the line for rapidly decaying initial data. The second method is used to compute finite-genus solutions of the KdV equation. The combination of these numerical methods allows for the computation of exact solutions that are asymptotically (quasi-)periodic finite-gap solutions and are a nonlinear superposition of dispersive, soliton and (quasi-)periodic solutions in the finite (x, t)-plane. Such solutions are referred to as superposition solutions. We compute these solutions accurately for all values of x and t. (paper)
Optical threshold secret sharing scheme based on basic vector operations and coherence superposition
Deng, Xiaopeng; Wen, Wei; Mi, Xianwu; Long, Xuewen
2015-04-01
We propose, to our knowledge for the first time, a simple optical algorithm for secret image sharing with the (2,n) threshold scheme based on basic vector operations and coherence superposition. The secret image to be shared is firstly divided into n shadow images by use of basic vector operations. In the reconstruction stage, the secret image can be retrieved by recording the intensity of the coherence superposition of any two shadow images. Compared with the published encryption techniques which focus narrowly on information encryption, the proposed method can realize information encryption as well as secret sharing, which further ensures the safety and integrality of the secret information and prevents power from being kept centralized and abused. The feasibility and effectiveness of the proposed method are demonstrated by numerical results.
Analysis of magnetic damping problem by the coupled mode superposition method
International Nuclear Information System (INIS)
Horie, Tomoyoshi; Niho, Tomoya
1997-01-01
In this paper we describe the coupled mode superposition method for the magnetic damping problem, which is produced by the coupled effect between the deformation and the induced eddy current of the structures for future fusion reactors and magnetically levitated vehicles. The formulation of the coupled mode superposition method is based on the matrix equation for the eddy current and the structure using the coupled mode vectors. Symmetric form of the coupled matrix equation is obtained. Coupled problems of a thin plate are solved to verify the formulation and the computer code. These problems are solved efficiently by this method using only a few coupled modes. Consideration of the coupled mode vectors shows that the coupled effects are included completely in each coupled mode. (author)
Optical information encryption based on incoherent superposition with the help of the QR code
Qin, Yi; Gong, Qiong
2014-01-01
In this paper, a novel optical information encryption approach is proposed with the help of QR code. This method is based on the concept of incoherent superposition which we introduce for the first time. The information to be encrypted is first transformed into the corresponding QR code, and thereafter the QR code is further encrypted into two phase only masks analytically by use of the intensity superposition of two diffraction wave fields. The proposed method has several advantages over the previous interference-based method, such as a higher security level, a better robustness against noise attack, a more relaxed work condition, and so on. Numerical simulation results and actual smartphone collected results are shown to validate our proposal.
On Multiple Users Scheduling Using Superposition Coding over Rayleigh Fading Channels
Zafar, Ammar
2013-02-20
In this letter, numerical results are provided to analyze the gains of multiple users scheduling via superposition coding with successive interference cancellation in comparison with the conventional single user scheduling in Rayleigh blockfading broadcast channels. The information-theoretic optimal power, rate and decoding order allocation for the superposition coding scheme are considered and the corresponding histogram for the optimal number of scheduled users is evaluated. Results show that at optimality there is a high probability that only two or three users are scheduled per channel transmission block. Numerical results for the gains of multiple users scheduling in terms of the long term throughput under hard and proportional fairness as well as for fixed merit weights for the users are also provided. These results show that the performance gain of multiple users scheduling over single user scheduling increases when the total number of users in the network increases, and it can exceed 10% for high number of users
International Nuclear Information System (INIS)
Vedral, V.
2011-01-01
Quantum effects were long thought to be observed only in atomic or molecular systems. Recent experiments made in various domains have showed that quantum phenomena are also present at a macroscopic scale. Entanglement is an essential quantum phenomenon that links together systems without references to time and space. In 2003 an experiment showed that the 10 20 atoms of a piece of salt were entangled. In 2010 an experiment showed that a 40 μm long micro-plank could vibrate at 2 frequencies simultaneously. A bird is thought to orient itself during its migratory flight through a quantum process occurring in its eyes: photons from the sun could destroy the collective state of spin of one of the electron pairs of a molecule present in the bird retina. This quantum process repeated many times could generate a signal strong enough to enable the bird to get sensitive to the tilt of the earth magnetic field. (A.C.)
Fundamental aspects of quantum theory
International Nuclear Information System (INIS)
Gorini, V.; Frigerio, A.
1986-01-01
This book presents information on the following topics: general problems and crucial experiments; the classical behavior of measuring instruments; quantum interference effect for two atoms radiating a single photon; quantization and stochastic processes; quantum Markov processes driven by Bose noise; chaotic behavior in quantum mechanics; quantum ergodicity and chaos; microscopic and macroscopic levels of description; fundamental properties of the ground state of atoms and molecules; n-level systems interacting with Bosons - semiclassical limits; general aspects of gauge theories; adiabatic phase shifts for neutrons and photons; the spins of cyons and dyons; round-table discussion the the Aharonov-Bohm effect; gravity in quantum mechanics; the gravitational phase transition; anomalies and their cancellation; a new gauge without any ghost for Yang-Mills Theory; and energy density and roughening in the 3-D Ising ferromagnet
Arfi, Badredine
2007-02-01
Most game-theoretic studies of strategic interaction assume independent individual strategies as the basic unit of analysis. This paper explores the effects of non-independence on strategic interaction. Two types of non-independence effects are considered. First, the paper considers subjective non-independence at the level of the individual actor by looking at how choice ambivalence shapes the decision-making process. Specifically, how do alternative individual choices superpose with one another to “constructively/destructively” shape each other's role within an actor's decision-making process? This process is termed as quantum superposition of alternative choices. Second, the paper considers how inter-subjective non-independence across actors engenders collective strategies among two or more interacting actors. This is termed as quantum entanglement of strategies. Taking into account both types of non-independence effect makes possible the emergence of a new collective equilibrium, without assuming signaling, prior “contract” agreement or third-party moderation, or even “cheap talk”. I apply these ideas to analyze the equilibrium possibilities of a situation wherein N actors play a quantum social game of cooperation. I consider different configurations of large- N quantum entanglement using the approach of density operator. I specifically consider the following configurations: star-shaped, nearest-neighbors, and full entanglement.
Unitary Quantum Relativity. (Work in Progress)
Finkelstein, David Ritz
2017-01-01
A quantum universe is expressed as a finite unitary relativistic quantum computer network. Its addresses are subject to quantum superposition as well as its memory. It has no exact mathematical model. It Its Hilbert space of input processes is also a Clifford algebra with a modular architecture of many ranks. A fundamental fermion is a quantum computer element whose quantum address belongs to the rank below. The least significant figures of its address define its spin and flavor. The most significant figures of it adress define its orbital variables. Gauging arises from the same quantification as space-time. This blurs star images only slightly, but perhaps measurably. General relativity is an approximation that splits nature into an emptiness with a high symmetry that is broken by a filling of lower symmetry. Action principles result from self-organization pf the vacuum.
A survey of quantum Lyapunov control methods.
Cong, Shuang; Meng, Fangfang
2013-01-01
The condition of a quantum Lyapunov-based control which can be well used in a closed quantum system is that the method can make the system convergent but not just stable. In the convergence study of the quantum Lyapunov control, two situations are classified: nondegenerate cases and degenerate cases. For these two situations, respectively, in this paper the target state is divided into four categories: the eigenstate, the mixed state which commutes with the internal Hamiltonian, the superposition state, and the mixed state which does not commute with the internal Hamiltonian. For these four categories, the quantum Lyapunov control methods for the closed quantum systems are summarized and analyzed. Particularly, the convergence of the control system to the different target states is reviewed, and how to make the convergence conditions be satisfied is summarized and analyzed.
An efficient quantum algorithm for spectral estimation
Steffens, Adrian; Rebentrost, Patrick; Marvian, Iman; Eisert, Jens; Lloyd, Seth
2017-03-01
We develop an efficient quantum implementation of an important signal processing algorithm for line spectral estimation: the matrix pencil method, which determines the frequencies and damping factors of signals consisting of finite sums of exponentially damped sinusoids. Our algorithm provides a quantum speedup in a natural regime where the sampling rate is much higher than the number of sinusoid components. Along the way, we develop techniques that are expected to be useful for other quantum algorithms as well—consecutive phase estimations to efficiently make products of asymmetric low rank matrices classically accessible and an alternative method to efficiently exponentiate non-Hermitian matrices. Our algorithm features an efficient quantum-classical division of labor: the time-critical steps are implemented in quantum superposition, while an interjacent step, requiring much fewer parameters, can operate classically. We show that frequencies and damping factors can be obtained in time logarithmic in the number of sampling points, exponentially faster than known classical algorithms.
Spectroscopy of Charged Quantum Dot Molecules
Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Ponomarev, I. V.; Ware, M. E.; Doty, M. F.; Reinecke, T. L.; Gammon, D.; Korenev, V. L.
2006-03-01
Spins of single charges in quantum dots are attractive for many quantum information and spintronic proposals. Scalable quantum information applications require the ability to entangle and operate on multiple spins in coupled quantum dots (CQDs). To further the understanding of these systems, we present detailed spectroscopic studies of InAs CQDs with control of the discrete electron or hole charging of the system. The optical spectrum reveals a pattern of energy anticrossings and crossings in the photoluminescence as a function of applied electric field. These features can be understood as a superposition of charge and spin configurations of the two dots and represent clear signatures of quantum mechanical coupling. The molecular resonance leading to these anticrossings is achieved at different electric fields for the optically excited (trion) states and the ground (hole) states allowing for the possibility of using the excited states for optically induced coupling of the qubits.
Sanchez-Garcia, Manuel; Gardin, Isabelle; Lebtahi, Rachida; Dieudonné, Arnaud
2015-10-21
Two collapsed cone (CC) superposition algorithms have been implemented for radiopharmaceutical dosimetry of photon emitters. The straight CC (SCC) superposition method uses a water energy deposition kernel (EDKw) for each electron, positron and photon components, while the primary and scatter CC (PSCC) superposition method uses different EDKw for primary and once-scattered photons. PSCC was implemented only for photons originating from the nucleus, precluding its application to positron emitters. EDKw are linearly scaled by radiological distance, taking into account tissue density heterogeneities. The implementation was tested on 100, 300 and 600 keV mono-energetic photons and (18)F, (99m)Tc, (131)I and (177)Lu. The kernels were generated using the Monte Carlo codes MCNP and EGSnrc. The validation was performed on 6 phantoms representing interfaces between soft-tissues, lung and bone. The figures of merit were γ (3%, 3 mm) and γ (5%, 5 mm) criterions corresponding to the computation comparison on 80 absorbed doses (AD) points per phantom between Monte Carlo simulations and CC algorithms. PSCC gave better results than SCC for the lowest photon energy (100 keV). For the 3 isotopes computed with PSCC, the percentage of AD points satisfying the γ (5%, 5 mm) criterion was always over 99%. A still good but worse result was found with SCC, since at least 97% of AD-values verified the γ (5%, 5 mm) criterion, except a value of 57% for the (99m)Tc with the lung/bone interface. The CC superposition method for radiopharmaceutical dosimetry is a good alternative to Monte Carlo simulations while reducing computation complexity.
International Nuclear Information System (INIS)
Gajnutdinov, R.Kh.
1983-01-01
Possibility is studied to build the nonrelativistic scattering theory on the base of the general physical principles: causality, superposition, and unitarity, making no use of the Schroedinger formalism. The suggested approach is shown to be more general than the nonrelativistic scattering theory based on the Schroedinger equation. The approach is applied to build a model ofthe scattering theory for a system which consists of heavy nonrelativistic particles and a light relativistic particle
Sanchez-Garcia, Manuel; Gardin, Isabelle; Lebtahi, Rachida; Dieudonné, Arnaud
2015-10-01
Two collapsed cone (CC) superposition algorithms have been implemented for radiopharmaceutical dosimetry of photon emitters. The straight CC (SCC) superposition method uses a water energy deposition kernel (EDKw) for each electron, positron and photon components, while the primary and scatter CC (PSCC) superposition method uses different EDKw for primary and once-scattered photons. PSCC was implemented only for photons originating from the nucleus, precluding its application to positron emitters. EDKw are linearly scaled by radiological distance, taking into account tissue density heterogeneities. The implementation was tested on 100, 300 and 600 keV mono-energetic photons and 18F, 99mTc, 131I and 177Lu. The kernels were generated using the Monte Carlo codes MCNP and EGSnrc. The validation was performed on 6 phantoms representing interfaces between soft-tissues, lung and bone. The figures of merit were γ (3%, 3 mm) and γ (5%, 5 mm) criterions corresponding to the computation comparison on 80 absorbed doses (AD) points per phantom between Monte Carlo simulations and CC algorithms. PSCC gave better results than SCC for the lowest photon energy (100 keV). For the 3 isotopes computed with PSCC, the percentage of AD points satisfying the γ (5%, 5 mm) criterion was always over 99%. A still good but worse result was found with SCC, since at least 97% of AD-values verified the γ (5%, 5 mm) criterion, except a value of 57% for the 99mTc with the lung/bone interface. The CC superposition method for radiopharmaceutical dosimetry is a good alternative to Monte Carlo simulations while reducing computation complexity.
Seismic analysis of structures of nuclear power plants by Lanczos mode superposition method
International Nuclear Information System (INIS)
Coutinho, A.L.G.A.; Alves, J.L.D.; Landau, L.; Lima, E.C.P. de; Ebecken, N.F.F.
1986-01-01
The Lanczos Mode Superposition Method is applied in the seismic analysis of nuclear power plants. The coordinate transformation matrix is generated by the Lanczos algorithm. It is shown that, through a convenient choice of the starting vector of the algorithm, modes with participation factors are automatically selected. It is performed the Response Spectra analysis of a typical reactor building. The obtained results are compared with those determined by the classical aproach stressing the remarkable computer effectiveness of the proposed methodology. (Author) [pt
Energy Technology Data Exchange (ETDEWEB)
Surovtsev, A P; Golovanenko, S A; Sukhanov, V E; Kazantsev, V F
1983-12-01
Investigation results of kinetics and quality of carbon steel joints with the steel 12Kh18N10T, obtained by pressure welding with superposition of ultrasonic oscillations with the frequency 16.5-18.0 kHz are given. The effect of ultrasonic oscillations on the process of physical contact development of the surfaces welded, formation of microstructure and impact viscosity of the compound, is shown.
Spaans, M.
General Relativity is extended into the quantum domain. A thought experiment is explored to derive a specific topological build-up for Planckian spacetime. The presented arguments are inspired by Feynman's path integral for superposition and Wheeler's quantum foam of Planck mass mini black holes
Topology change and quantum physics
International Nuclear Information System (INIS)
Balachandran, A.P.; Marmo, G.; Simoni, A.
1995-01-01
The role of topology in elementary quantum physics is discussed in detail. It is argued that attributes of classical spatial topology emerge from properties of state vectors with suitably smooth time evolution. Equivalently, they emerge from considerations on the domain of the quantum Hamiltonian, this domain being often specified by boundary conditions in elementary quantum physics. Examples are presented where classical topology is changed by smoothly altering the boundary conditions. When the parameters labelling the latter are treated as quantum variables, quantum states need not give a well-defined classical topology, instead they can give a quantum superposition of such topologies. An existing argument of Sorkin based on the spin-statistics connection and indicating the necessity of topology change in quantum gravity is recalled. It is suggested therefrom and our results here that Einstein gravity and its minor variants are effective theories of a deeper description with additional novel degrees of freedom. Other reasons for suspecting such a microstructure are also summarized. (orig.)
Topology change and quantum physics
International Nuclear Information System (INIS)
Balachandran, A.P.; Marmo, G.; Simoni, A.
1995-03-01
The role of topology in elementary quantum physics is discussed in detail. It is argued that attributes of classical spatial topology emerge from properties of state vectors with suitably smooth time evolution. Equivalently, they emerge from considerations on the domain of the quantum Hamiltonian, this domain being often specified by boundary conditions in elementary quantum physics. Several examples are presented where classical topology is changed by smoothly altering the boundary conditions. When the parameters labelling the latter are treated as quantum variables, quantum states need not give a well-defined classical topology, instead they can give a quantum superposition of such topologies. An existing argument of Sorkin based on the spin-statistics connection and indicating the necessity of topology change in quantum gravity is recalled. It is suggested therefrom and our results here that Einstein gravity and its minor variants are effective theories of a deeper description with additional novel degrees of freedom. Other reasons for suspecting such a microstructure are also summarized. (author). 22 refs, 3 figs
Quantum formalism for classical statistics
Wetterich, C.
2018-06-01
In static classical statistical systems the problem of information transport from a boundary to the bulk finds a simple description in terms of wave functions or density matrices. While the transfer matrix formalism is a type of Heisenberg picture for this problem, we develop here the associated Schrödinger picture that keeps track of the local probabilistic information. The transport of the probabilistic information between neighboring hypersurfaces obeys a linear evolution equation, and therefore the superposition principle for the possible solutions. Operators are associated to local observables, with rules for the computation of expectation values similar to quantum mechanics. We discuss how non-commutativity naturally arises in this setting. Also other features characteristic of quantum mechanics, such as complex structure, change of basis or symmetry transformations, can be found in classical statistics once formulated in terms of wave functions or density matrices. We construct for every quantum system an equivalent classical statistical system, such that time in quantum mechanics corresponds to the location of hypersurfaces in the classical probabilistic ensemble. For suitable choices of local observables in the classical statistical system one can, in principle, compute all expectation values and correlations of observables in the quantum system from the local probabilistic information of the associated classical statistical system. Realizing a static memory material as a quantum simulator for a given quantum system is not a matter of principle, but rather of practical simplicity.
Two new proofs of the test particle superposition principle of plasma kinetic theory
International Nuclear Information System (INIS)
Krommes, J.A.
1976-01-01
The test particle superposition principle of plasma kinetic theory is discussed in relation to the recent theory of two-time fluctuations in plasma given by Williams and Oberman. Both a new deductive and a new inductive proof of the principle are presented; the deductive approach appears here for the first time in the literature. The fundamental observation is that two-time expectations of one-body operators are determined completely in terms of the (x,v) phase space density autocorrelation, which to lowest order in the discreteness parameter obeys the linearized Vlasov equation with singular initial condition. For the deductive proof, this equation is solved formally using time-ordered operators, and the solution is then re-arranged into the superposition principle. The inductive proof is simpler than Rostoker's although similar in some ways; it differs in that first-order equations for pair correlation functions need not be invoked. It is pointed out that the superposition principle is also applicable to the short-time theory of neutral fluids
Sagnac interferometry with coherent vortex superposition states in exciton-polariton condensates
Moxley, Frederick Ira; Dowling, Jonathan P.; Dai, Weizhong; Byrnes, Tim
2016-05-01
We investigate prospects of using counter-rotating vortex superposition states in nonequilibrium exciton-polariton Bose-Einstein condensates for the purposes of Sagnac interferometry. We first investigate the stability of vortex-antivortex superposition states, and show that they survive at steady state in a variety of configurations. Counter-rotating vortex superpositions are of potential interest to gyroscope and seismometer applications for detecting rotations. Methods of improving the sensitivity are investigated by targeting high momentum states via metastable condensation, and the application of periodic lattices. The sensitivity of the polariton gyroscope is compared to its optical and atomic counterparts. Due to the large interferometer areas in optical systems and small de Broglie wavelengths for atomic BECs, the sensitivity per detected photon is found to be considerably less for the polariton gyroscope than with competing methods. However, polariton gyroscopes have an advantage over atomic BECs in a high signal-to-noise ratio, and have other practical advantages such as room-temperature operation, area independence, and robust design. We estimate that the final sensitivities including signal-to-noise aspects are competitive with existing methods.
International Nuclear Information System (INIS)
Lu Yanyun; Gu Shenjie; Lou Tianyang
2014-01-01
Background: As nuclear grade cable must endure harsh environment within design life, it is critical to predict cable thermal life accurately owing to thermal aging, which is one of dominant factors of aging mechanism. Purpose: Using time temperature superposition (TTS) method, the aim is to construct nuclear grade cable thermal life model, predict cable residual life and develop life model interactive interface under Matlab GUI. Methods: According to TTS, nuclear grade cable thermal life model can be constructed by shifting data groups at various temperatures to preset reference temperature with translation factor which is determined by non linear programming optimization. Interactive interface of cable thermal life model developed under Matlab GUI consists of superposition mode and standard mode which include features such as optimization of translation factor, calculation of activation energy, construction of thermal aging curve and analysis of aging mechanism., Results: With calculation result comparison between superposition and standard method, the result with TTS has better accuracy than that with standard method. Furthermore, confidence level of nuclear grade cable thermal life with TTS is higher than that with standard method. Conclusion: The results show that TTS methodology is applicable to thermal life prediction of nuclear grade cable. Interactive Interface under Matlab GUI achieves anticipated functionalities. (authors)
Superposition of configurations in semiempirical calculation of iron group ion spectra
International Nuclear Information System (INIS)
Kantseryavichyus, A.Yu.; Ramonas, A.A.
1976-01-01
The energy spectra of ions from the iron group in the dsup(N), dsup(N)s, dsup(N)p configurations are studied. A semiempirical method is used in which the effective hamiltonian contains configuration superposition. The sdsup(N+1), psup(4)dsup(N+2) quasidegenerated configurations, as well as configurations which differ by one electron are taken as correction configurations. It follows from the calculations that the most important role among the quasidegenerate configurations is played by the sdsup(N+1) correctional configuration. When it is taken into account, the introduction of the psup(4)dsup(N+2) correctional configuration practically does not affect the results. Account of the dsup(N-1)s configuration in the second order of the perturbation theory is equivalent to that of sdsup(N+1) in the sense that it results in the identical mean square deviation. As follows from the comparison of the results of the approximate and complete account of the configuration superposition, in many cases one can be satisfied with its approximate and complete account of the configuration superposition, in many cases one can be satisfied with its approximate version. The results are presented in the form of tables including the values of empirical parameters, radial integrals, mean square errors, etc
Consistent Quantum Histories: Towards a Universal Language of Physics
International Nuclear Information System (INIS)
Grygiel, W.P.
2007-01-01
The consistent histories interpretation of quantum mechanics is a reformulation of the standard Copenhagen interpretation that aims at incorporating quantum probabilities as part of the axiomatic foundations of the theory. It is not only supposed to equip quantum mechanics with clear criteria of its own experimental verification but, first and foremost, to alleviate one of the stumbling blocks of the theory - the measurement problem. Since the consistent histories interpretation operates with a series of quantum events integrated into one quantum history, the measurement problem is naturally absorbed as one of the events that build up a history. The interpretation rests upon the two following assumptions, proposed already by J. von Neumann: (1) both the microscopic and macroscopic regimes are subject to the same set of quantum laws and (2) a projector operator that is assigned to each event within a history permits to transcribe the history into a set of propositions that relate the entire course of quantum events. Based on this, a universal language of physics is expected to emerge that will bring the quantum apparatus back to common sense propositional logic. The basic philosophical issue raised this study is whether one should justify quantum mechanics by means of what emerges from it, that is, the properties of the macroscopic world, or use the axioms of quantum mechanics to demonstrate the mechanisms how the macroscopic world comes about from the quantum regime. (author)
Quantum Information: Opportunities and Challenges
Energy Technology Data Exchange (ETDEWEB)
Bennink, Ryan S [ORNL
2008-01-01
Modern society is shaped by the ability to transmit, manipulate, and store large amounts of information. Although we tend to think of information as abstract, information is physical, and computing is a physical process. How then should we understand information in a quantum world, in which physical systems may exist in multiple states at once and are altered by the very act of observation? This question has evolved into an exciting new field of research called Quantum Information (QI). QI challenges many accepted rules and practices in computer science. For example, a quantum computer would turn certain hard problems into soft problems, and would render common computationally-secure encryption methods (such as RSA) insecure. At the same time, quantum communication would provide an unprecedented kind of intrinsic information security at the level of the smallest physical objects used to store or transmit the information. This talk provides a general introduction to the subject of quantum information and its relevance to cyber security. In the first part, two of the stranger aspects of quantum physics namely, superposition and uncertainty are explained, along with their relation to the concept of information. These ideas are illustrated with a few examples: quantum ID cards, quantum key distribution, and Grover s quantum search algorithm. The state-of-the-art in quantum computing and communication hardware is then discussed, along with the daunting technological challenges that must be overcome. Relevant experimental and theoretical efforts at ORNL are highlighted. The talk concludes with speculations on the short- and long-term impact of quantum information on cyber security.
The quantum phase-transitions of water
Fillaux, François
2017-08-01
It is shown that hexagonal ices and steam are macroscopically quantum condensates, with continuous spacetime-translation symmetry, whereas liquid water is a quantum fluid with broken time-translation symmetry. Fusion and vaporization are quantum phase-transitions. The heat capacities, the latent heats, the phase-transition temperatures, the critical temperature, the molar volume expansion of ice relative to water, as well as neutron scattering data and dielectric measurements are explained. The phase-transition mechanisms along with the key role of quantum interferences and that of Hartley-Shannon's entropy are enlightened. The notions of chemical bond and force-field are questioned.
International Nuclear Information System (INIS)
Friedberg, R; Hohenberg, P C
2014-01-01
completion of the theory requires a macroscopic mechanism for selecting a physical framework, which is part of the macroscopic theory (MAQM). The selection of a physical framework involves the breaking of the microscopic ‘framework symmetry’, which can proceed either phenomenologically as in the standard quantum measurement theory, or more fundamentally by considering the quantum system under study to be a subsystem of a macroscopic quantum system. The decoherent histories formulation of Gell-Mann and Hartle, as well as that of Omnès, are theories of this fundamental type, where the physical framework is selected by a coarse-graining procedure in which the physical phenomenon of decoherence plays an essential role. Various well-known interpretations of QM are described from the perspective of CQT. Detailed definitions and proofs are presented in the appendices. (key issues reviews)
Quantum Hall Effect: proposed multi-electron tunneling experiment
International Nuclear Information System (INIS)
Kostadinov, I.Z.
1985-11-01
Here we propose a tunneling experiment for the fractional and Integral Quantum Hall Effect. It may demonstrate multi-electron tunneling and may provide information about the nature of the macroscopic quantum states of 2D electronic liquid or solid. (author)
Quantum coherence in photo-ionisation with tailored XUV pulses
Carlström, Stefanos; Mauritsson, Johan; Schafer, Kenneth J.; L'Huillier, Anne; Gisselbrecht, Mathieu
2018-01-01
Ionisation with ultrashort pulses in the extreme ultraviolet (XUV) regime can be used to prepare an ion in a superposition of spin-orbit substates. In this work, we study the coherence properties of such a superposition, created by ionising xenon atoms using two phase-locked XUV pulses at different frequencies. In general, if the duration of the driving pulse exceeds the quantum beat period, dephasing will occur. If however, the frequency difference of the two pulses matches the spin-orbit splitting, the coherence can be efficiently increased and dephasing does not occur.
Quantum Erasure: Quantum Interference Revisited
Walborn, Stephen P.; Cunha, Marcelo O. Terra; Pádua, Sebastião; Monken, Carlos H.
2005-01-01
Recent experiments in quantum optics have shed light on the foundations of quantum physics. Quantum erasers - modified quantum interference experiments - show that quantum entanglement is responsible for the complementarity principle.
On monogamy of non-locality and macroscopic averages: examples and preliminary results
Directory of Open Access Journals (Sweden)
Rui Soares Barbosa
2014-12-01
Full Text Available We explore a connection between monogamy of non-locality and a weak macroscopic locality condition: the locality of the average behaviour. These are revealed by our analysis as being two sides of the same coin. Moreover, we exhibit a structural reason for both in the case of Bell-type multipartite scenarios, shedding light on but also generalising the results in the literature [Ramanathan et al., Phys. Rev. Lett. 107, 060405 (2001; Pawlowski & Brukner, Phys. Rev. Lett. 102, 030403 (2009]. More specifically, we show that, provided the number of particles in each site is large enough compared to the number of allowed measurement settings, and whatever the microscopic state of the system, the macroscopic average behaviour is local realistic, or equivalently, general multipartite monogamy relations hold. This result relies on a classical mathematical theorem by Vorob'ev [Theory Probab. Appl. 7(2, 147-163 (1962] about extending compatible families of probability distributions defined on the faces of a simplicial complex – in the language of the sheaf-theoretic framework of Abramsky & Brandenburger [New J. Phys. 13, 113036 (2011], such families correspond to no-signalling empirical models, and the existence of an extension corresponds to locality or non-contextuality. Since Vorob'ev's theorem depends solely on the structure of the simplicial complex, which encodes the compatibility of the measurements, and not on the specific probability distributions (i.e. the empirical models, our result about monogamy relations and locality of macroscopic averages holds not just for quantum theory, but for any empirical model satisfying the no-signalling condition. In this extended abstract, we illustrate our approach by working out a couple of examples, which convey the intuition behind our analysis while keeping the discussion at an elementary level.
Towards the experimental realization of hybrid quantum systems
International Nuclear Information System (INIS)
Koller, C.
2012-01-01
One of the main interests of quantum physics in this new millennium is the exploitation of quantum mechanical principles in technical applications. One approach here is to use entanglement and superpositions of states to realize powerful algorithms capable of solving challenging computational tasks on a much faster time scale than a classical computer ever could. To find the quantum analogue of a classical bit one needs a quantum mechanical two level system that can be used to store and process quantum information. Most of the current approaches to find such a 'qubit' have the intention to find a single system that is able to fulfill all desirable tasks. But actually most quantum systems are only favorable for very specific tasks (e.g storage, processing, data exchange,..), similar as it is in classical computing. For some qubits the main disadvantages is that their quantum state is very fragile. Those systems loose their 'quantum information' (that is the possibility to store superpositions of their states coherently) easily. They 'decohere' on a timescale that is much shorter then any more involving algorithm. Other systems can keep those superposition states for quite a while, but are so difficult to address that the number of operations that can be made is very limited. The task of a so called hybrid quantum system is now to combine the strengths of these different systems, using e.g. one for manipulation and an other system for storage. Similar to a processor/memory architecture in conventional computers these systems could use a kind of bus system to couple between them. The main task of this thesis was to make steps towards the realization of such a system using two different combinations of quantum systems. Both are planned to use superconducting qubits (transmons) as processor qubit and either atoms (ultra cold rubidium 87 ensembles) or solid state spin systems (Nitrogen Vacancies in diamonds - NV centers) as memory. (author)
Bastin, Ted
2009-07-01
List of participants; Preface; Part I. Introduction: 1. The function of the colloquium - editorial; 2. The conceptual problem of quantum theory from the experimentalist's point of view O. R. Frisch; Part II. Niels Bohr and Complementarity: The Place of the Classical Language: 3. The Copenhagen interpretation C. F. von Weizsäcker; 4. On Bohr's views concerning the quantum theory D. Bohm; Part III. The Measurement Problem: 5. Quantal observation in statistical interpretation H. J. Groenewold; 6. Macroscopic physics, quantum mechanics and quantum theory of measurement G. M. Prosperi; 7. Comment on the Daneri-Loinger-Prosperi quantum theory of measurement Jeffrey Bub; 8. The phenomenology of observation and explanation in quantum theory J. H. M. Whiteman; 9. Measurement theory and complex systems M. A. Garstens; Part IV. New Directions within Quantum Theory: What does the Quantum Theoretical Formalism Really Tell Us?: 10. On the role of hidden variables in the fundamental structure of physics D. Bohm; 11. Beyond what? Discussion: space-time order within existing quantum theory C. W. Kilmister; 12. Definability and measurability in quantum theory Yakir Aharonov and Aage Petersen; 13. The bootstrap idea and the foundations of quantum theory Geoffrey F. Chew; Part V. A Fresh Start?: 14. Angular momentum: an approach to combinatorial space-time Roger Penrose; 15. A note on discreteness, phase space and cohomology theory B. J. Hiley; 16. Cohomology of observations R. H. Atkin; 17. The origin of half-integral spin in a discrete physical space Ted Bastin; Part VI. Philosophical Papers: 18. The unity of physics C. F. von Weizsäcker; 19. A philosophical obstacle to the rise of new theories in microphysics Mario Bunge; 20. The incompleteness of quantum mechanics or the emperor's missing clothes H. R. Post; 21. How does a particle get from A to B?; Ted Bastin; 22. Informational generalization of entropy in physics Jerome Rothstein; 23. Can life explain quantum mechanics? H. H
Microscopic to macroscopic depletion model development for FORMOSA-P
International Nuclear Information System (INIS)
Noh, J.M.; Turinsky, P.J.; Sarsour, H.N.
1996-01-01
Microscopic depletion has been gaining popularity with regard to employment in reactor core nodal calculations, mainly attributed to the superiority of microscopic depletion in treating spectral history effects during depletion. Another trend is the employment of loading pattern optimization computer codes in support of reload core design. Use of such optimization codes has significantly reduced design efforts to optimize reload core loading patterns associated with increasingly complicated lattice designs. A microscopic depletion model has been developed for the FORMOSA-P pressurized water reactor (PWR) loading pattern optimization code. This was done for both fidelity improvements and to make FORMOSA-P compatible with microscopic-based nuclear design methods. Needless to say, microscopic depletion requires more computational effort compared with macroscopic depletion. This implies that microscopic depletion may be computationally restrictive if employed during the loading pattern optimization calculation because many loading patterns are examined during the course of an optimization search. Therefore, the microscopic depletion model developed here uses combined models of microscopic and macroscopic depletion. This is done by first performing microscopic depletions for a subset of possible loading patterns from which 'collapsed' macroscopic cross sections are obtained. The collapsed macroscopic cross sections inherently incorporate spectral history effects. Subsequently, the optimization calculations are done using the collapsed macroscopic cross sections. Using this approach allows maintenance of microscopic depletion level accuracy without substantial additional computing resources
Metasurface-Enabled Remote Quantum Interference.
Jha, Pankaj K; Ni, Xingjie; Wu, Chihhui; Wang, Yuan; Zhang, Xiang
2015-07-10
An anisotropic quantum vacuum (AQV) opens novel pathways for controlling light-matter interaction in quantum optics, condensed matter physics, etc. Here, we theoretically demonstrate a strong AQV over macroscopic distances enabled by a judiciously designed array of subwavelength-scale nanoantennas-a metasurface. We harness the phase-control ability and the polarization-dependent response of the metasurface to achieve strong anisotropy in the decay rate of a quantum emitter located over distances of hundreds of wavelengths. Such an AQV induces quantum interference among radiative decay channels in an atom with orthogonal transitions. Quantum vacuum engineering with metasurfaces holds promise for exploring new paradigms of long-range light-matter interaction for atom optics, solid-state quantum optics, quantum information processing, etc.
Quantum physics an introduction based on photons
Lvovsky, A I
2018-01-01
This textbook is intended to accompany a two-semester course on quantum mechanics for physics students. Along with the traditional material covered in such a course (states, operators, Schrödinger equation, hydrogen atom), it offers in-depth discussion of the Hilbert space, the nature of measurement, entanglement, and decoherence – concepts that are crucial for the understanding of quantum physics and its relation to the macroscopic world, but rarely covered in entry-level textbooks. The book uses a mathematically simple physical system – photon polarization – as the visualization tool, permitting the student to see the entangled beauty of the quantum world from the very first pages. The formal concepts of quantum physics are illustrated by examples from the forefront of modern quantum research, such as quantum communication, teleportation and nonlocality. The author adopts a Socratic pedagogy: The student is guided to develop the machinery of quantum physics independently by solving sets of carefully ...
Quantum logic as superbraids of entangled qubit world lines
International Nuclear Information System (INIS)
Yepez, Jeffrey
2010-01-01
Presented is a topological representation of quantum logic that views entangled qubit spacetime histories (or qubit world lines) as a generalized braid, referred to as a superbraid. The crossing of world lines can be quantum-mechanical in nature, most conveniently expressed analytically with ladder-operator-based quantum gates. At a crossing, independent world lines can become entangled. Complicated superbraids are systematically reduced by recursively applying quantum skein relations. If the superbraid is closed (e.g., representing quantum circuits with closed-loop feedback, quantum lattice gas algorithms, loop or vacuum diagrams in quantum field theory), then one can decompose the resulting superlink into an entangled superposition of classical links. Thus, one can compute a superlink invariant, for example, the Jones polynomial for the square root of a classical knot.
Landahl, Andrew
2012-10-01
Quantum computers promise to exploit counterintuitive quantum physics principles like superposition, entanglement, and uncertainty to solve problems using fundamentally fewer steps than any conventional computer ever could. The mere possibility of such a device has sharpened our understanding of quantum coherent information, just as lasers did for our understanding of coherent light. The chief obstacle to developing quantum computer technology is decoherence--one of the fastest phenomena in all of physics. In principle, decoherence can be overcome by using clever entangled redundancies in a process called fault-tolerant quantum error correction. However, the quality and scale of technology required to realize this solution appears distant. An exciting alternative is a proposal called ``adiabatic'' quantum computing (AQC), in which adiabatic quantum physics keeps the computer in its lowest-energy configuration throughout its operation, rendering it immune to many decoherence sources. The Adiabatic Quantum Architectures In Ultracold Systems (AQUARIUS) Grand Challenge Project at Sandia seeks to demonstrate this robustness in the laboratory and point a path forward for future hardware development. We are building devices in AQUARIUS that realize the AQC architecture on up to three quantum bits (``qubits'') in two platforms: Cs atoms laser-cooled to below 5 microkelvin and Si quantum dots cryo-cooled to below 100 millikelvin. We are also expanding theoretical frontiers by developing methods for scalable universal AQC in these platforms. We have successfully demonstrated operational qubits in both platforms and have even run modest one-qubit calculations using our Cs device. In the course of reaching our primary proof-of-principle demonstrations, we have developed multiple spinoff technologies including nanofabricated diffractive optical elements that define optical-tweezer trap arrays and atomic-scale Si lithography commensurate with placing individual donor atoms with
There is No Quantum Regression Theorem
International Nuclear Information System (INIS)
Ford, G.W.; OConnell, R.F.
1996-01-01
The Onsager regression hypothesis states that the regression of fluctuations is governed by macroscopic equations describing the approach to equilibrium. It is here asserted that this hypothesis fails in the quantum case. This is shown first by explicit calculation for the example of quantum Brownian motion of an oscillator and then in general from the fluctuation-dissipation theorem. It is asserted that the correct generalization of the Onsager hypothesis is the fluctuation-dissipation theorem. copyright 1996 The American Physical Society
Observation of quantum Zeno effect in a superconducting flux qubit
International Nuclear Information System (INIS)
Kakuyanagi, K; Baba, T; Matsuzaki, Y; Nakano, H; Saito, S; Semba, K
2015-01-01
When a quantum state is subjected to frequent measurements, the time evolution of the quantum state is frozen. This is called the quantum Zeno effect. Here, we observe such an effect by performing frequent discrete measurements in a macroscopic quantum system, a superconducting quantum bit. The quantum Zeno effect induced by discrete measurements is similar to the original idea of the quantum Zeno effect. By using a Josephson bifurcation amplifier pulse readout, we have experimentally suppressed the time evolution of Rabi oscillation using projective measurements, and also observed the enhancement of the quantum state holding time by shortening the measurement period time. This is a crucial step to realize quantum information processing using the quantum Zeno effect. (papers)
Zaima, Kazunori; Sasaki, Koichi
2016-01-01
We investigated the transient phenomena in a premixed burner flame with the superposition of a pulsed dielectric barrier discharge (DBD). The length of the flame was shortened by the superposition of DBD, indicating the activation of combustion chemical reactions with the help of the plasma. In addition, we observed the modulation of the top position of the unburned gas region and the formations of local minimums in the axial distribution of the optical emission intensity of OH. These experim...
Directory of Open Access Journals (Sweden)
Ahmad Arabi Shamsabadi
2016-04-01
Full Text Available This paper presents an experimental study of the self-initiation reaction of n-butyl acrylate (n-BA in free-radical polymerization. For the first time, the frequency factor and activation energy of the monomer self-initiation reaction are estimated from measurements of n-BA conversion in free-radical homo-polymerization initiated only by the monomer. The estimation was carried out using a macroscopic mechanistic mathematical model of the reactor. In addition to already-known reactions that contribute to the polymerization, the model considers a n-BA self-initiation reaction mechanism that is based on our previous electronic-level first-principles theoretical study of the self-initiation reaction. Reaction rate equations are derived using the method of moments. The reaction-rate parameter estimates obtained from conversion measurements agree well with estimates obtained via our purely-theoretical quantum chemical calculations.
Extended Macroscopic Study of Dilute Gas Flow within a Microcavity
Directory of Open Access Journals (Sweden)
Mohamed Hssikou
2016-01-01
Full Text Available The behaviour of monatomic and dilute gas is studied in the slip and early transition regimes using the extended macroscopic theory. The gas is confined within a two-dimensional microcavity where the longitudinal sides are in the opposite motion with constant velocity ±Uw. The microcavity walls are kept at the uniform and reference temperature T0. Thus, the gas flow is transported only by the shear stress induced by the motion of upper and lower walls. From the macroscopic point of view, the regularized 13-moment equations of Grad, R13, are solved numerically. The macroscopic gas proprieties are studied for different values of the so-called Knudsen number (Kn, which gives the gas-rarefaction degree. The results are compared with those obtained using the classical continuum theory of Navier-Stokes and Fourier (NSF.
International Nuclear Information System (INIS)
Schmidt, Alexandre G M; Paiva, Milena M
2012-01-01
We revisit the quantum two-person duel. In this problem, both Alice and Bob each possess a spin-1/2 particle which models dead and alive states for each player. We review the Abbott and Flitney result—now considering non-zero α 1 and α 2 in order to decide if it is better for Alice to shoot or not the second time—and we also consider a duel where players do not necessarily start alive. This simple assumption allows us to explore several interesting special cases, namely how a dead player can win the duel shooting just once, or how can Bob revive Alice after one shot, and the better strategy for Alice—being either alive or in a superposition of alive and dead states—fighting a dead opponent. (paper)
International Nuclear Information System (INIS)
Bednorz, Adam
2015-01-01
The question of whether quantum measurements reflect some underlying objective reality has no generally accepted answer. We show that a description of such reality is possible under natural conditions such as linearity and causality, although in terms of moments and cumulants of finite order and without relativistic invariance. The proposed construction of observations’ probability distribution originates from weak, noninvasive measurements, with detection error replaced by some external finite noise. The noise allows us to construct microscopic objective reality, but remains dynamically decoupled and hence unobservable at the macroscopic level. (paper)
Confining the state of light to a quantum manifold by engineered two-photon loss
Leghtas, Z.; Touzard, S.; Pop, I. M.; Kou, A.; Vlastakis, B.; Petrenko, A.; Sliwa, K. M.; Narla, A.; Shankar, S.; Hatridge, M. J.; Reagor, M.; Frunzio, L.; Schoelkopf, R. J.; Mirrahimi, M.; Devoret, M. H.
2015-02-01
Physical systems usually exhibit quantum behavior, such as superpositions and entanglement, only when they are sufficiently decoupled from a lossy environment. Paradoxically, a specially engineered interaction with the environment can become a resource for the generation and protection of quantum states. This notion can be generalized to the confinement of a system into a manifold of quantum states, consisting of all coherent superpositions of multiple stable steady states. We have confined the state of a superconducting resonator to the quantum manifold spanned by two coherent states of opposite phases and have observed a Schrödinger cat state spontaneously squeeze out of vacuum before decaying into a classical mixture. This experiment points toward robustly encoding quantum information in multidimensional steady-state manifolds.
Quantum to classical transition in the Hořava-Lifshitz quantum cosmology
Bernardini, A. E.; Leal, P.; Bertolami, O.
2018-02-01
A quasi-Gaussian quantum superposition of Hořava-Lifshitz (HL) stationary states is built in order to describe the transition of the quantum cosmological problem to the related classical dynamics. The obtained HL phase-space superposed Wigner function and its associated Wigner currents describe the conditions for the matching between classical and quantum phase-space trajectories. The matching quantum superposition parameter is associated to the total energy of the classical trajectory which, at the same time, drives the engendered Wigner function to the classical stationary regime. Through the analysis of the Wigner flows, the quantum fluctuations that distort the classical regime can be quantified as a measure of (non)classicality. Finally, the modifications to the Wigner currents due to the inclusion of perturbative potentials are computed in the HL quantum cosmological context. In particular, the inclusion of a cosmological constant provides complementary information that allows for connecting the age of the Universe with the overall stiff matter density profile.
Plasmonic direct writing lithography with a macroscopical contact probe
Huang, Yuerong; Liu, Ling; Wang, Changtao; Chen, Weidong; Liu, Yunyue; Li, Ling
2018-05-01
In this work, we design a plasmonic direct writing lithography system with a macroscopical contact probe to achieve nanometer scale spots. The probe with bowtie-shaped aperture array adopts spring hinge and beam deflection method (BDM) to realize near-field lithography. Lithography results show that a macroscopical plasmonic contact probe can achieve a patterning resolution of around 75 nm at 365 nm wavelength, and demonstrate that the lithography system is promising for practical applications due to beyond the diffraction limit, low cost, and simplification of system configuration. CST calculations provide a guide for the design of recording structure and the arrangement of placing polarizer.
Fluctuations in macroscopically agitated plasma:quasiparticles and effective temperature
International Nuclear Information System (INIS)
Sosenko, P.P.; Gresillon, D.
1994-01-01
Fluctuations in the plasma, in which macroscopic fluid-like motion is agitated due to large-scale and low-frequency electro-magnetic fields, are studied. Such fields can be produced by external factors or internally, for example due to turbulence. Fluctuation spectral distributions are calculated with regard to the renormalization of the transition probability for a test-particle and of the test-particle shielding. If the correlation length for the random fluid-like motion is large as compared to the fluctuation scale lengths, then the fluctuation spectral distributions can be explained in terms of quasiparticles originating from macroscopic plasma agitation and of an effective temperature