Nanofriction in Cavity Quantum Electrodynamics.
Fogarty, T; Cormick, C; Landa, H; Stojanović, Vladimir M; Demler, E; Morigi, Giovanna
2015-12-01
The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics.
Mesoscopic Cavity Quantum Electrodynamics with Quantum Dots
Childress, L I; Lukin, M D
2003-01-01
We describe an electrodynamic mechanism for coherent, quantum mechanical coupling between spacially separated quantum dots on a microchip. The technique is based on capacitive interactions between the electron charge and a superconducting transmission line resonator, and is closely related to atomic cavity quantum electrodynamics. We investigate several potential applications of this technique which have varying degrees of complexity. In particular, we demonstrate that this mechanism allows design and investigation of an on-chip double-dot microscopic maser. Moreover, the interaction may be extended to couple spatially separated electron spin states while only virtually populating fast-decaying superpositions of charge states. This represents an effective, controllable long-range interaction, which may facilitate implementation of quantum information processing with electron spin qubits and potentially allow coupling to other quantum systems such as atomic or superconducting qubits.
Cavity quantum electrodynamics: coherence in context.
Mabuchi, H; Doherty, A C
2002-11-15
Modern cavity quantum electrodynamics (cavity QED) illuminates the most fundamental aspects of coherence and decoherence in quantum mechanics. Experiments on atoms in cavities can be described by elementary models but reveal intriguing subtleties of the interplay of coherent dynamics with external couplings. Recent activity in this area has pioneered powerful new approaches to the study of quantum coherence and has fueled the growth of quantum information science. In years to come, the purview of cavity QED will continue to grow as researchers build on a rich infrastructure to attack some of the most pressing open questions in micro- and mesoscopic physics.
Cavity quantum electrodynamics: Beyond strong
Murch, Kater
2017-01-01
When light and matter are strongly coupled, they lose their distinct character and merge into a hybrid state. Three experiments explore this exotic regime using artificial atoms, with promise for quantum technologies.
Fundamental tests in Cavity Quantum Electrodynamics
CERN. Geneva
2010-01-01
At the dawn of quantum physics, Einstein and Bohr had the dream to confine a photon in a box and to use this contraption in order to illustrate the strange laws of the quantum world. Cavity Quantum Electrodynamics has now made this dream real, allowing us to actually achieve in the laboratory variants of the thought experiments of the founding fathers of quantum theory. In our work at Ecole Normale Supérieure, we use a beam of Rydberg atoms to manipulate and probe non-destructively microwave photons trapped in a very high Q superconducting cavity. We realize ideal quantum non-demolition (QND) measurements of photon numbers, observe the radiation quantum jumps due to cavity relaxation and prepare non-classical fields such as Fock and Schrödinger cat states. Combining QND photon counting with a homodyne mixing method, we reconstruct the Wigner functions of these non-classical states and, by taking snapshots of these functions at increasing times, obtain movies of the decoherence process. These experiments ope...
Quantum-to-classical transition in cavity quantum electrodynamics.
Fink, J M; Steffen, L; Studer, P; Bishop, Lev S; Baur, M; Bianchetti, R; Bozyigit, D; Lang, C; Filipp, S; Leek, P J; Wallraff, A
2010-10-15
The quantum properties of electromagnetic, mechanical or other harmonic oscillators can be revealed by investigating their strong coherent coupling to a single quantum two level system in an approach known as cavity quantum electrodynamics (QED). At temperatures much lower than the characteristic energy level spacing the observation of vacuum Rabi oscillations or mode splittings with one or a few quanta asserts the quantum nature of the oscillator. Here, we study how the classical response of a cavity QED system emerges from the quantum one when its thermal occupation-or effective temperature-is raised gradually over 5 orders of magnitude. In this way we explore in detail the continuous quantum-to-classical crossover and demonstrate how to extract effective cavity field temperatures from both spectroscopic and time-resolved vacuum Rabi measurements.
Large payload quantum steganography based on cavity quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Ye Tian-Yu; Jiang Li-Zhen
2013-01-01
A large payload quantum steganography protocol based on cavity quantum electrodynamics (QED) is presented in this paper,which effectively uses the evolutionary law of atoms in cavity QED.The protocol builds up a hidden channel to transmit secret messages using entanglement swapping between one GHZ state and one Bell state in cavity QED together with the Hadamard operation.The quantum steganography protocol is insensitive to cavity decay and the thermal field.The capacity,imperceptibility and security against eavesdropping are analyzed in detail in the protocol.It turns out that the protocol not only has good imperceptibility but also possesses good security against eavesdropping.In addition,its capacity for a hidden channel achieves five bits,larger than most of the previous quantum steganography protocols.
Hybrid circuit cavity quantum electrodynamics with a micromechanical resonator.
Pirkkalainen, J-M; Cho, S U; Li, Jian; Paraoanu, G S; Hakonen, P J; Sillanpää, M A
2013-02-14
Hybrid quantum systems with inherently distinct degrees of freedom have a key role in many physical phenomena. Well-known examples include cavity quantum electrodynamics, trapped ions, and electrons and phonons in the solid state. In those systems, strong coupling makes the constituents lose their individual character and form dressed states, which represent a collective form of dynamics. As well as having fundamental importance, hybrid systems also have practical applications, notably in the emerging field of quantum information control. A promising approach is to combine long-lived atomic states with the accessible electrical degrees of freedom in superconducting cavities and quantum bits (qubits). Here we integrate circuit cavity quantum electrodynamics with phonons. Apart from coupling to a microwave cavity, our superconducting transmon qubit, consisting of tunnel junctions and a capacitor, interacts with a phonon mode in a micromechanical resonator, and thus acts like an atom coupled to two different cavities. We measure the phonon Stark shift, as well as the splitting of the qubit spectral line into motional sidebands, which feature transitions between the dressed electromechanical states. In the time domain, we observe coherent conversion of qubit excitation to phonons as sideband Rabi oscillations. This is a model system with potential for a quantum interface, which may allow for storage of quantum information in long-lived phonon states, coupling to optical photons or for investigations of strongly coupled quantum systems near the classical limit.
Ultra-high-Q toroidal microresonators for cavity quantum electrodynamics
Spillane, S M; Vahala, K J; Goh, K W; Wilcut, E; Kimble, H J
2004-01-01
We investigate the suitability of toroidal microcavities for strong-coupling cavity quantum electrodynamics (QED). Numerical modeling of the optical modes demonstrate a significant reduction of modal volume with respect to the whispering gallery modes of dielectric spheres, while retaining the high quality factors representative of spherical cavities. The extra degree of freedom of toroid microcavities can be used to achieve improved cavity QED characteristics. Numerical results for atom-cavity coupling strength, critical atom number N_0 and critical photon number n_0 for cesium are calculated and shown to exceed values currently possible using Fabry-Perot cavities. Modeling predicts coupling rates g/(2*pi) exceeding 700 MHz and critical atom numbers approaching 10^{-7} in optimized structures. Furthermore, preliminary experimental measurements of toroidal cavities at a wavelength of 852 nm indicate that quality factors in excess of 100 million can be obtained in a 50 micron principal diameter cavity, which w...
Cavity quantum electrodynamics with Anderson-localized modes.
Sapienza, Luca; Thyrrestrup, Henri; Stobbe, Søren; Garcia, Pedro David; Smolka, Stephan; Lodahl, Peter
2010-03-12
A major challenge in quantum optics and quantum information technology is to enhance the interaction between single photons and single quantum emitters. This requires highly engineered optical cavities that are inherently sensitive to fabrication imperfections. We have demonstrated a fundamentally different approach in which disorder is used as a resource rather than a nuisance. We generated strongly confined Anderson-localized cavity modes by deliberately adding disorder to photonic crystal waveguides. The emission rate of a semiconductor quantum dot embedded in the waveguide was enhanced by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices.
Interference control of perfect photon absorption in cavity quantum electrodynamics
Wang, Liyong; Zhu, Yifu; Agarwal, G S
2016-01-01
We propose and analyze a scheme for controlling coherent photon transmission and reflection in a cavity-quantum-electrodynamics (CQED) system consisting of an optical resonator coupled with three-level atoms coherently prepared by a control laser from free space. When the control laser is off and the cavity is excited by two identical light fields from two ends of the cavity, the two input light fields can be completely absorbed by the CQED system and the light energy is converted into the excitation of the polariton states, but no light can escape from the cavity. Two distinct cases of controlling the perfect photon absorption are analyzed: (a) when the control laser is tuned to the atomic resonance and creates electromagnetically induced transparency, the prefect photon absorption is suppressed and the input light fields are nearly completely transmitted through the cavity; (b) when the control laser is tuned to the polariton state resonance and inhibits the polariton state excitation, the perfect photon ab...
Measuring the effective phonon density of states of a quantum dot in cavity quantum electrodynamics
DEFF Research Database (Denmark)
Madsen, Kristian Høeg; Nielsen, Per Kær; Kreiner-Møller, Asger;
2013-01-01
We employ detuning-dependent decay-rate measurements of a quantum dot in a photonic-crystal cavity to study the influence of phonon dephasing in a solid-state quantum-electrodynamics experiment. The experimental data agree with a microscopic non-Markovian model accounting for dephasing from longi...
Teleportation of Atomic States via Cavity Quantum Electrodynamics
Guerra, E S
2004-01-01
In this article we discuss a scheme of teleportation of atomic states. The experimental realization proposed makes use of cavity Quatum Electrodynamics involving the interaction of Rydberg atoms with a micromaser cavity prepared in a coherent state. We start presenting a scheme to prepare atomic Bell states via the interaction of atoms with a cavity. In our scheme the cavity and some atoms play the role of auxiliary systems used to achieve the teleportation.
Single photon delayed feedback: a way to stabilize intrinsic quantum cavity electrodynamics.
Carmele, Alexander; Kabuss, Julia; Schulze, Franz; Reitzenstein, Stephan; Knorr, Andreas
2013-01-01
We propose a scheme to control cavity quantum electrodynamics in the single photon limit by delayed feedback. In our approach a single emitter-cavity system, operating in the weak coupling limit, can be driven into the strong coupling-type regime by an external mirror: The external loop produces Rabi oscillations directly connected to the electron-photon coupling strength. As an expansion of typical cavity quantum electrodynamics, we treat the quantum correlation of external and internal light modes dynamically and demonstrate a possible way to implement a fully quantum mechanical time-delayed feedback. Our theoretical approach proposes a way to experimentally feedback control quantum correlations in the single photon limit.
Cavity quantum electrodynamics with Anderson-localized modes
DEFF Research Database (Denmark)
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren;
2010-01-01
by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices....
Modelling and fabrication of GaAs photonic-crystal cavities for cavity quantum electrodynamics.
Khankhoje, U K; Kim, S-H; Richards, B C; Hendrickson, J; Sweet, J; Olitzky, J D; Khitrova, G; Gibbs, H M; Scherer, A
2010-02-10
In this paper, we present recent progress in the growth, modelling, fabrication and characterization of gallium arsenide (GaAs) two-dimensional (2D) photonic-crystal slab cavities with embedded indium arsenide (InAs) quantum dots (QDs) that are designed for cavity quantum electrodynamics (cQED) experiments. Photonic-crystal modelling and device fabrication are discussed, followed by a detailed discussion of different failure modes that lead to photon loss. It is found that, along with errors introduced during fabrication, other significant factors such as the presence of a bottom substrate and cavity axis orientation with respect to the crystal axis, can influence the cavity quality factor (Q). A useful diagnostic tool in the form of contour finite-difference time domain (FDTD) is employed to analyse device performance.
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
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
Institute of Scientific and Technical Information of China (English)
Tang Jing-Wu; Zhao Guan-Xiang; He Xiong-Hui
2011-01-01
Recently, Peng et al. [2010 Eur. Phys. J. D 58 403] proposed to teleport an arbitrary two-qubit state with a family of four-qubit entangled states, which simultaneously include the tensor product of two Bell states, linear cluster state and Dicke-class state. This paper proposes to implement their scheme in cavity quantum electrodynamics and then presents a new family of four-qubit entangled state |Ω4)1234. It simultaneously includes all the well-known four-qubit entangled states which can be used to teleport an arbitrary two-qubit state. The distinct advantage of the scheme is that it only needs a single setup to prepare the whole family of four-qubit entangled states, which will be very convenient for experimental realization. After discussing the experimental condition in detail, we show the scheme may be feasible based on present technology in cavity quantum electrodynamics.
Preparation of Genuinely Entangled Six-Atom State via Cavity Quantum Electrodynamics
Institute of Scientific and Technical Information of China (English)
ZHANG Wen; LIU Yi-Min; YIN Xiao-Feng; ZHANG Zhan-Jun
2011-01-01
A cavity quantum electrodynamics scheme for preparing a genuinely entangled state [A. Borras, et al., J. Phys. A 40 (2007) 13407] on six two-level atoms is proposed. In the scheme, the atom-cavity detuning is much bigger than the atom-cavity coupling strength and the necessary preparation time is much shorter than the Rydberg-atom lifespan. Hence the scheme has two distinct features, i.e., insensitive to the cavity decay and the atom radiation.
Efficient scheme for preparation of the multi-atom W state via cavity quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Zhang Jin; Ye Liu
2004-01-01
We present an efficient scheme for preparation of the multi-atom W state via cavity quantum electrodynamics.Involved in this scheme are n identical two-level atoms and a single-mode cavity field. Discussion indicates that this scheme can be realized easily by current technologies.
Multiparty Quantum Secret Sharing of Classical Message using Cavity Quantum Electrodynamic System
Institute of Scientific and Technical Information of China (English)
HAN Lian-Fang; LIU Yi-Min; ZHANG Zhan-Jun
2006-01-01
@@ An experimental feasible scheme of multiparty secret sharing of classical messages is proposed, based on a cavity quantum electrodynamic system. The secret messages are imposed on atomic Bell states initially in the sender's possession by local unitary operations. By swapping quantum entanglement of atomic Bell states, the secret messages are split into several parts and each part is distributed to a separate party. In this case, any subset of the entire party group can not read out the secret message but the entirety via mutual cooperations. In this scheme, to discriminate atomic Bell states, additional classical fields are employed besides the same highly-detuned single-mode cavities used to prepare atomic Bell states. This scheme is insensitive to the cavity decay and the thermal field, and usual joint Bell-state measurements are unnecessary.
Cavity Quantum Electrodynamics: The Strange Theory of Light in a Box
Dutra, Sergio M.
2004-12-01
What happens to light when it is trapped in a box? Cavity Quantum Electrodynamics addresses a fascinating question in physics: what happens to light, and in particular to its interaction with matter, when it is trapped inside a box? With the aid of a model-building approach, readers discover the answer to this question and come to appreciate its important applications in computing, cryptography, quantum teleportation, and opto-electronics. Instead of taking a traditional approach that requires readers to first master a series of seemingly unconnected mathematical techniques, this book engages the readers' interest and imagination by going straight to the point, introducing the mathematics along the way as needed. Appendices are provided for the additional mathematical theory. Researchers, scientists, and students of modern physics can refer to Cavity Quantum Electrodynamics and examine the field thoroughly. Several key topics covered that readers cannot find in any other quantum optics book include: * Introduction to the problem of the "vacuum catastrophe" and the cosmological constant * Detailed up-to-date account of cavity QED lasers and thresholdless lasing * Examination of cavities with movable walls * First-principles discussion about cavity QED in open cavities * Pedagogical account of microscopic quantization in dielectrics Complementing the coverage of the most advanced theory and techniques, the author provides context by discussing the historical evolution of the field and its discoveries. In that spirit, "recommended reading," provided in each chapter, leads readers to both contemporary literature as well as key historical papers. Despite being one of many specialties within physics, cavity quantum electrodynamics serves as a window to many of the fundamental issues of physics. Cavity Quantum Electrodynamics will serve as an excellent resource for advanced undergraduate quantum mechanics courses as well as for graduate students, researchers, and
A scheme for transferring an unknown atomic entangled state via cavity quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Wu Tao; Ye Liu; Ni Zhi-Xiang
2006-01-01
In this paper, we propose a scheme for transferring an unknown atomic entangled state via cavity quantum electrodynamics (QED). This scheme, which has a successful probability of 100 percent, does not require Bell-state measurement and performing any operations to reconstruct an initial state. Meanwhile, the scheme only involves atomfield interaction with a large detuning and does not require the transfer of quantum information between the atoms and cavity. Thus the scheme is insensitive to the cavity field states and cavity decay. This scheme can also be extended to transfer ring an entangled state of n-atom.
Interference control of nonlinear excitation in a multi-atom cavity quantum electrodynamics system.
Yang, Guoqing; Tan, Zheng; Zou, Bichen; Zhu, Yifu
2014-12-01
We show that by manipulating quantum interference in a multi-atom cavity quantum electrodynamics (CQED) system, the nonlinear excitation of the cavity-atom polariton can be resonantly enhanced while the linear excitation is suppressed. Under the appropriate conditions, it is possible to selectively enhance or suppress the polariton excitation with two free-pace laser fields. We report on an experiment with cold Rb atoms in an optical cavity and present experimental results that demonstrate such interference control of the CQED excitation and its direct application to studies of all-optical switching and cross-phase modulation of the cavity-transmitted light.
DEFF Research Database (Denmark)
Reitzenstein, S.; Schneider, C.; Albert, F.;
2011-01-01
Semiconductor quantum dots (QDs) are fascinating nanoscopic structures for photonics and future quantum information technology. However, the random position of self-organized QDs inhibits a deterministic coupling in devices relying on cavity quantum electrodynamics (cQED) effects which complicates...
Sound-based analogue of cavity quantum electrodynamics in silicon.
Soykal, Ö O; Ruskov, Rusko; Tahan, Charles
2011-12-01
A quantum mechanical superposition of a long-lived, localized phonon and a matter excitation is described. We identify a realization in strained silicon: a low-lying donor transition (P or Li) driven solely by acoustic phonons at wavelengths where high-Q phonon cavities can be built. This phonon-matter resonance is shown to enter the strongly coupled regime where the "vacuum" Rabi frequency exceeds the spontaneous phonon emission into noncavity modes, phonon leakage from the cavity, and phonon anharmonicity and scattering. We introduce a micropillar distributed Bragg reflector Si/Ge cavity, where Q≃10(5)-10(6) and mode volumes V≲25λ(3) are reachable. These results indicate that single or many-body devices based on these systems are experimentally realizable.
Analysis of adiabatic transfer in cavity quantum electrodynamics
Indian Academy of Sciences (India)
Joyee Ghosh; R Ghosh; Deepak Kumar
2011-10-01
A three-level atom in a conﬁguration trapped in an optical cavity forms a basic unit in a number of proposed protocols for quantum information processing. This system allows for efﬁcient storage of cavity photons into long-lived atomic excitations, and their retrieval with high ﬁdelity, in an adiabatic transfer process through the ‘dark state’ by a slow variation of the control laser intensity. We study the full quantum mechanics of this transfer process with a view to examine the non-adiabatic effects arising from inevitable excitations of the system to states involving the upper level of , which is radiative. We ﬁnd that the ﬁdelity of storage is better, the stronger the control ﬁeld and the slower the rate of its switching off. On the contrary, unlike the adiabatic notion, retrieval is better with faster rates of switching on of an optimal control ﬁeld. Also, for retrieval, the behaviour with dissipation is non-monotonic. These results lend themselves to experimental tests. Our exact computations, when applied to slow variations of the control intensity for strong atom–photon couplings, are in very good agreement with Berry’s superadiabatic transfer results without dissipation.
DEFF Research Database (Denmark)
Madsen, Kristian Høeg; Ates, Serkan; Reitzenstein, S.;
2010-01-01
The coupling between a quantum dot (QD) and a micropillar cavity is experimentally investigated by performing time-resolved, correlation, and two-photon interference measurements. The Jaynes-Cummings model including dissipative Lindblad terms and dephasing is analyzed, and all the parameters...... for the model are experimentally determined allowing for a complete comparison between experiment and theory....
Institute of Scientific and Technical Information of China (English)
郑仕标
2001-01-01
A scheme is proposed for generating the superpositions of several coherent states in a cavity field with dispersive cavity quantum electrodynamics (QED). In the scheme, a sequence of atoms interacts dispersively with the cavity field, connected with a microwave source, and is manipulated by classical fields, followed by state-selective measurements. In this way, the cavity field is collapsed onto a superposition of several coherent states along a straight line with controllable coefficients. This scheme provides the possibility for quantum state engineering via coherent-state superpositions along a straight line in cavity QED for the first time.
Self-formed cavity quantum electrodynamics in coupled dipole cylindrical-waveguide systems.
Afshar V, S; Henderson, M R; Greentree, A D; Gibson, B C; Monro, T M
2014-05-01
An ideal optical cavity operates by confining light in all three dimensions. We show that a cylindrical waveguide can provide the longitudinal confinement required to form a two dimensional cavity, described here as a self-formed cavity, by locating a dipole, directed along the waveguide, on the interface of the waveguide. The cavity resonance modes lead to peaks in the radiation of the dipole-waveguide system that have no contribution due to the skew rays that exist in longitudinally invariant waveguides and reduce their Q-factor. Using a theoretical model, we evaluate the Q-factor and modal volume of the cavity formed by a dipole-cylindrical-waveguide system and show that such a cavity allows access to both the strong and weak coupling regimes of cavity quantum electrodynamics.
Vacuum-Induced Abelian and Non-Abelian Gauge Potentials in Cavity Quantum Electrodynamics
Institute of Scientific and Technical Information of China (English)
张海龙; 梁奇锋; 俞立先; 陈刚
2011-01-01
Gauge potential plays an important role in exploring exotic phenomena in the single- and many-body quantum systems. In this paper, we propose a scheme to create both new Abelian and non-Abelian gauge potentials by adiabatically controlling the degenerate Dicke model in cavity quantum electrodynamics. It is shown that a non-Abelian gauge potential is achieved only for a single atom, whereas an Abelianizen diagonal gauge potential is realized for the atomic ensemble. More importantly, two interesting quantum phenomena such as the geometric phase and the magnetic monopole induced by our created gauge potentials are also predicted. The possible physical realization is presented in the macroscopic circuit quantum electrodynamics with the Cooper pair boxes, which act as the artificial two-level atoms controlled by the gate voltage and the external magnetic flux.
Three-qubit Fredkin gate based on cavity quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Shao Xiao-Qiang; Chen Li; Zhang Shou
2009-01-01
This paper presents a scheme for implementing a Fredkin gate on three modes of a cavity.The scheme is based on the dispersive atom-cavity interaction.By modulating the cavity frequency and the atomic transition frequency appropriately,it obtains the effective form of nonlinear interaction between photons in the three-mode cavity.This availability is testified via numerical analysis.It also considers both the situations with and without dissipation.
Cavity quantum electrodynamics on a nanofiber using a composite photonic crystal cavity.
Yalla, Ramachandrarao; Sadgrove, Mark; Nayak, Kali P; Hakuta, Kohzo
2014-10-01
We demonstrate cavity QED conditions in the Purcell regime for single quantum emitters on the surface of an optical nanofiber. The cavity is formed by combining an optical nanofiber and a nanofabricated grating to create a composite photonic crystal cavity. By using this technique, significant enhancement of the spontaneous emission rate into the nanofiber guided modes is observed for single quantum dots. Our results pave the way for enhanced on-fiber light-matter interfaces with clear applications to quantum networks.
Preparation of W state in resonant bimodal cavity quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
2007-01-01
A scheme is proposed for generating entangled W states with four cavity modes. In this scheme, we send a Ⅴ-type three-level atom through two identical two-mode cavities in succession. After the atom exits from the second cavity,the four cavity modes are prepared in the W state. On the other hand we can obtain three-atom W states by sending three Ⅴ-type three-level atoms through a two-mode cavity in turn. The present scheme does not require conditional measurement, and it is easily generalized to preparing 2n-mode W states and n-atom W states.
Epitaxial lift-off for solid-state cavity quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Greuter, Lukas; Najer, Daniel; Kuhlmann, Andreas V.; Starosielec, Sebastian; Warburton, Richard J. [Department of Physics, University of Basel, Klingelbergstrasse 82, Basel 4056 (Switzerland); Valentin, Sascha R.; Ludwig, Arne; Wieck, Andreas D. [Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)
2015-08-21
We demonstrate an approach to incorporate self-assembled quantum dots into a Fabry-Pérot-like microcavity. Thereby, a 3λ/4 GaAs layer containing quantum dots is epitaxially removed and attached by van der Waals bonding to one of the microcavity mirrors. We reach a finesse as high as 4100 with this configuration limited by the reflectivity of the dielectric mirrors and not by scattering at the semiconductor-mirror interface, demonstrating that the epitaxial lift-off procedure is a promising procedure for cavity quantum electrodynamics in the solid state. As a first step in this direction, we demonstrate a clear cavity-quantum dot interaction in the weak coupling regime with a Purcell factor in the order of 3. Estimations of the coupling strength via the Purcell factor suggest that we are close to the strong coupling regime.
Epitaxial lift-off for solid-state cavity quantum electrodynamics
Greuter, Lukas; Kuhlmann, Andreas V; Valentin, Sascha; Ludwig, Arne; Wieck, Andreas D; Starosielec, Sebastian; Warburton, Richard J
2015-01-01
We present a new approach to incorporate self-assembled quantum dots into a Fabry-P\\'{e}rot-like microcavity. Thereby a 3$\\lambda$/4 GaAs layer containing quantum dots is epitaxially removed and attached by van der Waals bonding to one of the microcavity mirrors. We reach a finesse as high as 4,100 with this configuration limited by the reflectivity of the dielectric mirrors and not by scattering at the semiconductor - mirror interface, demonstrating that the epitaxial lift-off procedure is a promising procedure for cavity quantum electrodynamics in the solid state. As a first step in this direction, we demonstrate a clear cavity-quantum dot interaction in the weak coupling regime with a Purcell factor in the order of 3. Estimations of the coupling strength via the Purcell factor suggests that we are close to the strong coupling regime.
Cavity quantum electrodynamics with separate photon storage and qubit readout modes.
Leek, P J; Baur, M; Fink, J M; Bianchetti, R; Steffen, L; Filipp, S; Wallraff, A
2010-03-12
We present the realization of a cavity quantum electrodynamics setup in which photons of strongly different lifetimes are engineered in different harmonic modes of the same cavity. We achieve this in a superconducting transmission line resonator with superconducting qubits coupled to the different modes. One cavity mode is strongly coupled to a detection line for qubit state readout, while a second long lifetime mode is used for photon storage and coherent quantum operations. We demonstrate sideband-based measurement of photon coherence, generation of n photon Fock states and the scaling of the sideband Rabi frequency with square root of n using a scheme that may be extended to realize sideband-based two-qubit logic gates.
Cavity quantum electrodynamics with a Rydberg-blocked atomic ensemble
DEFF Research Database (Denmark)
Guerlin, Christine; Brion, Etienne; Esslinger, Tilman
2010-01-01
The realization of a Jaynes-Cummings model in the optical domain is proposed for an atomic ensemble. The scheme exploits the collective coupling of the atoms to a quantized cavity mode and the nonlinearity introduced by coupling to high-lying Rydberg states. A two-photon transition resonantly...... effective Jaynes-Cummings model. We use numerical simulations to show that the cavity transmission can be used to reveal detailed properties of the Jaynes-Cummings ladder of excited states and that the atomic nonlinearity gives rise to highly nontrivial photon emission from the cavity. Finally, we suggest...... couples the single-atom ground state |g> to a Rydberg state |e>via a nonresonant intermediate state |i>, but due to the interaction between Rydberg atoms only a single atom can be resonantly excited in the ensemble. This restricts the state space of the ensemble to the collective ground state |G...
Teleportation of two-atom entangled state in resonant cavity quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Yang Zhen-Biao
2007-01-01
An alternative scheme is presented for teleportation of a two-atom entangled state in cavity quantum electrodynamics (QED). It is based on the resonant atom-cavity field interaction. In the scheme, only one cavity is involved, and the number of the atoms needed to be detected is decreased compared with the previous scheme. Since the resonant atom-cavity field interaction greatly reduces the interaction time, the decoherence effect can be effectively suppressed during the teleportation process. The experimental feasibility of the scheme is discussed. The scheme can easily be generalized to the teleportation of N-atom Greeninger-Horne-Zeilinger (GHZ) entangled states. The number of atoms needed to be detected does not increase as the number of the atoms in the GHZ state increases.
Cavity quantum electrodynamics in the Anderson-localized regime
DEFF Research Database (Denmark)
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren;
2010-01-01
We experimentally measure, by means of time-resolved photoluminescence spectroscopy, a 15-fold enhancement of the spontaneous emission decay rate of single semiconductor quantum dots coupled to disorder-induced Anderson-localized modes with efficiencies reaching 94%....
DEFF Research Database (Denmark)
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren;
2011-01-01
of the spontaneous emission decay rate by up to a factor 15 and an efficiency of channeling single photons into Anderson-localized modes reaching values as high as 94%. These results prove that disordered photonic media provide an efficient platform for quantum electrodynamics, offering a novel route to quantum...
A nanophotonic probe for quantum electrodynamics in random cavities
DEFF Research Database (Denmark)
Huisman, S. R.; Frater, E. H.; Korterik, J. P.;
2011-01-01
Disorder in photonic-crystal slab waveguides can cause localization of light [1, 2]. Sapienza et al. observed that the interaction of localized light with embedded quantum dots is so strong that it yields a considerable Purcell enhancement of the emission rate [3]. This coupling between emitters...
1990-01-01
Quantum electrodynamics is an essential building block and an integral part of the gauge theory of unified electromagnetic, weak, and strong interactions, the so-called standard model. Its failure or breakdown at some level would have a most profound impact on the theoretical foundations of elementary particle physics as a whole. Thus the validity of QED has been the subject of intense experimental tests over more than 40 years of its history. This volume presents an up-to-date review of high precision experimental tests of QED together with comprehensive discussion of required theoretical wor
Cavity quantum electrodynamics with three-dimensional photonic bandgap crystals
Vos, W L
2015-01-01
This paper gives an overview of recent work on three-dimensional (3D) photonic crystals with a "full and complete" 3D photonic band gap. We review five main aspects: 1) spontaneous emission inhibition, 2) spatial localization of light within a tiny nanoscale volume (aka "a nanobox for light"), 3) the introduction of a gain medium leading to thresholdless lasers, 4) breaking of the weak-coupling approximation of cavity QED, both in the frequency and in the time-domain, 5) decoherence, in particular the shielding of vacuum fluctuations by a 3D photonic bandgap. In addition, we list and evaluate all known photonic crystal structures with a demonstrated 3D band gap.
Flick, Johannes; Ruggenthaler, Michael; Appel, Heiko; Rubio, Angel
2017-03-21
In this work, we provide an overview of how well-established concepts in the fields of quantum chemistry and material sciences have to be adapted when the quantum nature of light becomes important in correlated matter-photon problems. We analyze model systems in optical cavities, where the matter-photon interaction is considered from the weak- to the strong-coupling limit and for individual photon modes as well as for the multimode case. We identify fundamental changes in Born-Oppenheimer surfaces, spectroscopic quantities, conical intersections, and efficiency for quantum control. We conclude by applying our recently developed quantum-electrodynamical density-functional theory to spontaneous emission and show how a straightforward approximation accurately describes the correlated electron-photon dynamics. This work paves the way to describe matter-photon interactions from first principles and addresses the emergence of new states of matter in chemistry and material science.
Nanofiber Fabry-Perot microresonator for nonlinear optics and cavity quantum electrodynamics.
Wuttke, C; Becker, M; Brückner, S; Rothhardt, M; Rauschenbeutel, A
2012-06-01
We experimentally realize a Fabry-Perot-type optical microresonator near the cesium D2 line wavelength based on a tapered optical fiber, equipped with two fiber Bragg gratings that enclose a subwavelength diameter waist. Owing to the very low taper losses, the finesse of the resonator reaches F=86 while the on-resonance transmission is T=11%. The characteristics of our resonator fulfill the requirements of nonlinear optics and cavity quantum electrodynamics in the strong coupling regime. These characteristics, combined with the demonstrated ease of use and advantageous mode geometry, open a realm of applications.
Nanofiber Fabry-Perot microresonator for non-linear optics and cavity quantum electrodynamics
Wuttke, C; Brückner, S; Rothhardt, M; Rauschenbeutel, A
2012-01-01
We experimentally realize a Fabry-Perot-type optical microresonator near the cesium D2 line wavelength based on a tapered optical fiber, equipped with two fiber Bragg gratings which enclose a sub-wavelength diameter waist. Owing to the very low taper losses, the finesse of the resonator reaches F = 86 while the on-resonance transmission is T = 11 %. The characteristics of our resonator fulfill the requirements of non-linear optics and cavity quantum electrodynamics in the strong coupling regime. In combination with its demonstrated ease of use and its advantageous mode geometry, it thus opens a realm of applications.
Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics
DEFF Research Database (Denmark)
Madsen, Kristian Høeg; Lodahl, Peter
2013-01-01
–Cummings model, whereas systematic deviations are observed for the emission spectra. The discrepancy for the spectra is attributed to the coupling of other exciton lines to the cavity and interference of different propagation paths toward the detector of the fields emitted by the quantum dot. In contrast......We present detuning-dependent spectral and decay-rate measurements to study the difference between the spectral and dynamical properties of single quantum dots embedded in micropillar and photonic crystal cavities. For the micropillar cavity, the dynamics is well described by the dissipative Jaynes......, quantitative information about the system can readily be extracted from the dynamical measurements. In the case of photonic crystal cavities, we observe an anti-crossing in the spectra when detuning a single quantum dot through resonance, which is the spectral signature of a strong coupling. However, time...
Eremeev, Vitalie; Ciobanu, Nellu; Orszag, Miguel
2014-05-01
We investigate thermal effects on sudden changes and freezing of the quantum and classical correlations of remote qubits in a cavity quantum electrodynamics (CQED) network with losses. We find that the detrimental effect of thermal reservoirs on the freezing of correlations can be compensated via an efficient coupling of the fiber connecting the two cavities of the system. Furthermore, for certain initial conditions, we find a double sudden transition in the dynamics of Bures geometrical quantum discord. The second transition tends to disappear at a critical temperature, hence freezing the discord. Finally, we discuss the feasibility of the experimental realization of the present proposal.
Schuster, D I; Fragner, A; Dykman, M I; Lyon, S A; Schoelkopf, R J
2010-07-23
We propose a hybrid architecture in which an on-chip high finesse superconducting cavity is coupled to the lateral motion and spin state of a single electron trapped on the surface of superfluid helium. We estimate the motional coherence times to exceed 15 μs, while energy will be coherently exchanged with the cavity photons in less than 10 ns for charge states and faster than 1 μs for spin states, making the system attractive for quantum information processing and strong coupling cavity quantum electrodynamics experiments. The cavity is used for nondestructive readout and as a quantum bus mediating interactions between distant electrons or an electron and a superconducting qubit.
Bloch-wave engineering of quantum dot-micropillars for cavity quantum electrodynamics experiments
Lermer, Matthias; Dunzer, Florian; Reitzenstein, Stephan; Höfling, Sven; Mørk, Jesper; Worschech, Lukas; Kamp, Martin; Forchel, Alfred
2011-01-01
We have employed Bloch-wave engineering to realize submicron diameter ultra-high quality factor GaAs/AlAs micropillars (MPs). The design features a tapered cavity in which the fundamental Bloch mode is subject to an adiabatic transition to match the Bragg mirror Bloch mode. The resulting reduced scattering loss leads to record-high visibility of the strong coupling in MPs with modest oscillator strength quantum dots. A quality factor of 13,600 and a Rabi splitting of 85 \\mueV with an estimated visibility v of 0.38 are observed for a small mode volume MP with a diameter dc of 850 nm.
Environment-Assisted Speed-up of the Field Evolution in Cavity Quantum Electrodynamics.
Cimmarusti, A D; Yan, Z; Patterson, B D; Corcos, L P; Orozco, L A; Deffner, S
2015-06-12
We measure the quantum speed of the state evolution of the field in a weakly driven optical cavity QED system. To this end, the mode of the electromagnetic field is considered as a quantum system of interest with a preferential coupling to a tunable environment: the atoms. By controlling the environment, i.e., changing the number of atoms coupled to the optical cavity mode, an environment-assisted speed-up is realized: the quantum speed of the state repopulation in the optical cavity increases with the coupling strength between the optical cavity mode and this non-Markovian environment (the number of atoms).
Bloch-wave engineering of quantum dot micropillars for cavity quantum electrodynamics experiments.
Lermer, M; Gregersen, N; Dunzer, F; Reitzenstein, S; Höfling, S; Mørk, J; Worschech, L; Kamp, M; Forchel, A
2012-02-01
We have employed Bloch-wave engineering to realize submicron diameter high quality factor GaAs/AlAs micropillars (MPs). The design features a tapered cavity in which the fundamental Bloch mode is subject to an adiabatic transition to match the Bragg mirror Bloch mode. The resulting reduced scattering loss leads to record-high vacuum Rabi splitting of the strong coupling in MPs with modest oscillator strength quantum dots. A quality factor of 13, 600 and a splitting of 85 μeV with an estimated visibility v of 0.41 are observed for a small mode volume MP with a diameter d{c} of 850 nm.
Bloch-wave engineering of quantum dot-micropillars for cavity quantum electrodynamics experiments
DEFF Research Database (Denmark)
Lermer, Matthias; Gregersen, Niels; Dunzer, Florian;
2012-01-01
We have employed Bloch-wave engineering to realize submicron diameter ultra-high quality factor GaAs/AlAs micropillars (MPs). The design features a tapered cavity in which the fundamental Bloch mode is subject to an adiabatic transition to match the Bragg mirror Bloch mode. The resulting reduced ...
Two-photon gateway in one-atom cavity quantum electrodynamics.
Kubanek, A; Ourjoumtsev, A; Schuster, I; Koch, M; Pinkse, P W H; Murr, K; Rempe, G
2008-11-14
Single atoms absorb and emit light from a resonant laser beam photon by photon. We show that a single atom strongly coupled to an optical cavity can absorb and emit resonant photons in pairs. The effect is observed in a photon correlation experiment on the light transmitted through the cavity. We find that the atom-cavity system transforms a random stream of input photons into a correlated stream of output photons, thereby acting as a two-photon gateway. The phenomenon has its origin in the quantum anharmonicity of the energy structure of the atom-cavity system. Future applications could include the controlled interaction of two photons by means of one atom.
Molecular quantum electrodynamics
Craig, D P
1998-01-01
This systematic introduction to quantum electrodynamics focuses on the interaction of radiation with outer electrons and nuclei of atoms and molecules, answering the long-standing need of chemists and physicists for a comprehensive text on this highly specialized subject.Geared toward postgraduate students in the chemical sciences who require an understanding of quantum electrodynamics as applied to the interpretation of optical experiments on atoms and molecules, the text offers a detailed explanation of the quantum theory of electromagnetic radiation and its interaction with matter. It feat
Nonlinear optical effects and Hong-Ou-Mandel interference in cavity quantum electrodynamics
Mirza, Imran M.; van Enk, Steven J.
Pure quantum interference among single photons is one of the key ingredients to perform linear optics quantum computation (LOQC). The Hong-Ou-Mandel interference (HOMI) [C. K. Hong, Z. Y. Ou and L. Mandel, Phys. Rev. Lett. 59, (18), 2044-2046 (1987)] i.e. complete destructive interference between two identical and indistinguishable photons simultaneously entering input ports of a 50/50 beam splitter, is a well-known example in this context. In this talk, I'll present our theoretical study of HOMI in a coupled Jaynes-Cummings array. In particular and by applying quantum jump/trajectory formalism, I'll focus on how partial quantum interference between two photons survive both non-linearities produced by two-level emitter and spectral filtering due to optical cavities in our coupled cavity array setup [Imran M. Mirza and Steven J. van Enk, Opt. Comm. 343, 172-177 (2015)]. Along with LOQC, this work is crucial from the perspective of exploiting coupled cavity arrays to store single photons reliably (without altering their temporal and spectral traits) [Imran M. Mirza, Steven J. van Enk and Jeff Kimble, JOSA B, 10, 2640-2649, (2013)].
Cavity quantum electrodynamics with many-body states of a two-dimensional electron gas.
Smolka, Stephan; Wuester, Wolf; Haupt, Florian; Faelt, Stefan; Wegscheider, Werner; Imamoglu, Ataç
2014-10-17
Light-matter interaction has played a central role in understanding as well as engineering new states of matter. Reversible coupling of excitons and photons enabled groundbreaking results in condensation and superfluidity of nonequilibrium quasiparticles with a photonic component. We investigated such cavity-polaritons in the presence of a high-mobility two-dimensional electron gas, exhibiting strongly correlated phases. When the cavity was on resonance with the Fermi level, we observed previously unknown many-body physics associated with a dynamical hole-scattering potential. In finite magnetic fields, polaritons show distinct signatures of integer and fractional quantum Hall ground states. Our results lay the groundwork for probing nonequilibrium dynamics of quantum Hall states and exploiting the electron density dependence of polariton splitting so as to obtain ultrastrong optical nonlinearities.
No drama quantum electrodynamics?
Energy Technology Data Exchange (ETDEWEB)
Akhmeteli, Andrey [LTASolid Inc, Houston, TX (United States)
2013-04-15
This article builds on recent work (Akhmeteli in Int. J. Quantum Inf. 9(Supp01):17, 2011; J. Math. Phys. 52:082303, 2011), providing a theory that is based on spinor electrodynamics, is described by a system of partial differential equations in 3+1 dimensions, but reproduces unitary evolution of a quantum field theory in the Fock space. To this end, after introduction of a complex four-potential of electromagnetic field, which generates the same electromagnetic fields as the initial real four-potential, the spinor field is algebraically eliminated from the equations of spinor electrodynamics. It is proven that the resulting equations for electromagnetic field describe independent evolution of the latter and can be embedded into a quantum field theory using a generalized Carleman linearization procedure. The theory provides a simple and at least reasonably realistic model, valuable for interpretation of quantum theory. The issues related to the Bell theorem are discussed. (orig.)
Quantum entanglement purification in cavities
Romero, J L; Saavedra, C; Retamal, J C
2002-01-01
A physical implementation of an entanglement purification protocol is studied using a cavity quantum electrodynamic based proposal, where, the quantum information is stored in quantum field sates inside cavities. Also a procedure is given for quantifying the degree of entanglement between quantum fields. (Author)
Energy Technology Data Exchange (ETDEWEB)
Sarabi, B.; Ramanayaka, A. N. [Laboratory for Physical Sciences, College Park, Maryland 20740 (United States); Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Burin, A. L. [Department of Chemistry, Tulane University, New Orleans, Louisiana 70118 (United States); Wellstood, F. C. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Joint Quantum Institute, University of Maryland, College Park, Maryland 20742 (United States); Osborn, K. D. [Laboratory for Physical Sciences, College Park, Maryland 20740 (United States); Joint Quantum Institute, University of Maryland, College Park, Maryland 20742 (United States)
2015-04-27
Random tunneling two-level systems (TLSs) in dielectrics have been of interest recently because they adversely affect the performance of superconducting qubits. The coupling of TLSs to qubits has allowed individual TLS characterization, which has previously been limited to TLSs within (thin) Josephson tunneling barriers made from aluminum oxide. Here, we report on the measurement of an individual TLS within the capacitor of a lumped-element LC microwave resonator, which forms a cavity quantum electrodynamics (CQED) system and allows for individual TLS characterization in a different structure and material than demonstrated with qubits. Due to the reduced volume of the dielectric (80 μm{sup 3}), even with a moderate dielectric thickness (250 nm), we achieve the strong coupling regime as evidenced by the vacuum Rabi splitting observed in the cavity spectrum. A TLS with a coherence time of 3.2 μs was observed in a film of silicon nitride as analyzed with a Jaynes-Cummings spectral model, which is larger than seen from superconducting qubits. As the drive power is increased, we observe an unusual but explicable set of continuous and discrete crossovers from the vacuum Rabi split transitions to the Glauber (coherent) state.
Sarabi, B.; Ramanayaka, A. N.; Burin, A. L.; Wellstood, F. C.; Osborn, K. D.
2015-04-01
Random tunneling two-level systems (TLSs) in dielectrics have been of interest recently because they adversely affect the performance of superconducting qubits. The coupling of TLSs to qubits has allowed individual TLS characterization, which has previously been limited to TLSs within (thin) Josephson tunneling barriers made from aluminum oxide. Here, we report on the measurement of an individual TLS within the capacitor of a lumped-element LC microwave resonator, which forms a cavity quantum electrodynamics (CQED) system and allows for individual TLS characterization in a different structure and material than demonstrated with qubits. Due to the reduced volume of the dielectric (80 μm3), even with a moderate dielectric thickness (250 nm), we achieve the strong coupling regime as evidenced by the vacuum Rabi splitting observed in the cavity spectrum. A TLS with a coherence time of 3.2 μs was observed in a film of silicon nitride as analyzed with a Jaynes-Cummings spectral model, which is larger than seen from superconducting qubits. As the drive power is increased, we observe an unusual but explicable set of continuous and discrete crossovers from the vacuum Rabi split transitions to the Glauber (coherent) state.
Two-photon gateway in one-atom cavity quantum electrodynamics
2008-01-01
Single atoms absorb and emit light from a resonant laser beam photon by photon. We show that a single atom strongly coupled to an optical cavity can absorb and emit resonant photons in pairs. The effect is observed in a photon correlation experiment on the light transmitted through the cavity. We find that the atom-cavity system transforms a random stream of input photons into a correlated stream of output photons, thereby acting as a two-photon gateway. The phenomenon has its origin in the q...
Institute of Scientific and Technical Information of China (English)
Shao Xiao-Qiang; Chen Li; Zhang Shou
2009-01-01
This paper proposes two schemes for implementing three-qubit Toffoli gate with an atom (as target qubit) sent through a two-mode cavity (as control qubits). The first scheme is based on the large-detuning atom-cavity field interaction and the second scheme is based on the resonant atom-field interaction. Both the situations with and without cavity decay and atomic spontaneous emission are considered. The advantages and the experimental feasibility of these two schemes are discussed.
One-step generation of qutrit entanglement via adiabatic passage in cavity quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Ma Song-She; Chen Mei-Feng; Jiang Xia-Ping
2011-01-01
A scheme is proposed for generating a three-dimensional entangled state for two atoms trapped in a cavity by one step via adiabatic passage.In the scheme,the two atoms are always in ground states and the field mode of the cavity excited is negligible under a certain condition.Therefore,the scheme is very robust against decoherence.Furthermore,it needs neither the exact control of all parameters nor the accurate control of the interaction time.It is shown that qutrit entanglement can be generated with a high fidelity.
Ancillary qubit spectroscopy of vacua in cavity and circuit quantum electrodynamics.
Lolli, Jared; Baksic, Alexandre; Nagy, David; Manucharyan, Vladimir E; Ciuti, Cristiano
2015-05-01
We investigate theoretically how the spectroscopy of an ancillary qubit can probe cavity (circuit) QED ground states containing photons. We consider three classes of systems (Dicke, Tavis-Cummings, and Hopfield-like models), where nontrivial vacua are the result of ultrastrong coupling between N two-level systems and a single-mode bosonic field. An ancillary qubit detuned with respect to the boson frequency is shown to reveal distinct spectral signatures depending on the type of vacua. In particular, the Lamb shift of the ancilla is sensitive to both ground state photon population and correlations. Backaction of the ancilla on the cavity ground state is investigated, taking into account the dissipation via a consistent master equation for the ultrastrong coupling regime. The conditions for high-fidelity measurements are determined.
Existence of Majorana fermion mode and Dirac equation in cavity quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Sarkar, Sujit, E-mail: sujit.tifr@gmail.com
2015-10-15
We present the results of low lying collective mode of coupled optical cavity arrays. We derive the Dirac equation for this system and explain the existence of Majorana fermion mode in the system. We present quite a few analytical relations between the Rabi frequency oscillation and the atom–photon coupling strength to explain the different physical situation of our study and also the condition for massless collective mode in the system. We present several analytical relations between the Dirac spinor field, order and disorder operators for our systems. We also show that the Luttinger liquid physics is one of the intrinsic concepts in our system.
Nahri, Davoud G.; Mathkoor, Faisal H. A.; Ooi, C. H. Raymond
2017-02-01
A dissipative quantum dot (QD)-cavity system, where the QD is initially prepared in the excited state with no photon in the cavity, coupled to a longitudinal acoustic (LA) phonon reservoir is studied using a numerically exact real-time path-integral approach. Three distinct dynamical regimes of weak (WC), strong (SC), and coherent coupling (CC) are discussed and more accurate conditions identifying them are presented. Our results show that to have the CC regime, which is characterized by clear vacuum Rabi oscillation (VRO), vacuum Rabi splitting (VRS) should be larger than the sum of the widths of the corresponding peaks. In order to distinguish between contributions of population decay and impure dephasing, induced by LA phonon bath and the dissipations, we propose a two-part phenomenological expression, corresponding to the population decay and impure dephasing, which fits the QD-cavity decay curves perfectly and is used to calculate the corresponding spectra. We demonstrate that the effective population decay rate (the emission rate) increases from the carrier recombination rate to a maximum value, which is the mean of the QD and cavity dissipation rates, with QD-cavity coupling strength. To study the role of the effective impure dephasing rate on the width of the central peak of the spectra we introduce a quantity that can also be applied in determining the distinct coupling regimes. This quantity enables us to identify the onset of the SC regime as the point where the impure dephasing term begins to contribute to the central band of the spectrum significantly, as a result of the existence of VRO with a very small frequency (unclear VRO) at the corresponding decay curve. Its contribution to the width of the central peak increases with the coupling strength up to the onset of the CC regime, then reduces as a result of the appearance of sidebands in the spectra, which originates from clear VRO. The effective population decay and impure dephasing rate contribute
Schneeweiss, Philipp; Hoinkes, Thomas; Rauschenbeutel, Arno; Volz, Jürgen
2016-01-01
We experimentally realize an optical fiber ring resonator that includes a tapered section with subwavelength-diameter waist. In this section, the guided light exhibits a significant evanescent field which allows for efficient interfacing with optical emitters. A commercial tunable fiber beam splitter provides simple and robust coupling to the resonator. Key parameters of the resonator such as its out-coupling rate, free spectral range, and birefringence can be adjusted. Thanks to the low taper- and coupling-losses, the resonator exhibits an unloaded finesse of F=75+/-1, sufficient for reaching the regime of strong coupling for emitters placed in the evanescent field. The system is ideally suited for trapping ensembles of laser-cooled atoms along the nanofiber section. Based on measured parameters, we estimate that the system can serve as a platform for optical multimode strong coupling experiments. Finally, we discuss the possibilities of using the resonator for applications based on chiral quantum optics.
Timelike Momenta In Quantum Electrodynamics
Brodsky, S. J.; Ting, S. C. C.
1965-12-01
In this note we discuss the possibility of studying the quantum electrodynamics of timelike photon propagators in muon or electron pair production by incident high energy muon or electron beams from presently available proton or electron accelerators.
Circuit quantum electrodynamics with a spin qubit.
Petersson, K D; McFaul, L W; Schroer, M D; Jung, M; Taylor, J M; Houck, A A; Petta, J R
2012-10-18
Electron spins trapped in quantum dots have been proposed as basic building blocks of a future quantum processor. Although fast, 180-picosecond, two-quantum-bit (two-qubit) operations can be realized using nearest-neighbour exchange coupling, a scalable, spin-based quantum computing architecture will almost certainly require long-range qubit interactions. Circuit quantum electrodynamics (cQED) allows spatially separated superconducting qubits to interact via a superconducting microwave cavity that acts as a 'quantum bus', making possible two-qubit entanglement and the implementation of simple quantum algorithms. Here we combine the cQED architecture with spin qubits by coupling an indium arsenide nanowire double quantum dot to a superconducting cavity. The architecture allows us to achieve a charge-cavity coupling rate of about 30 megahertz, consistent with coupling rates obtained in gallium arsenide quantum dots. Furthermore, the strong spin-orbit interaction of indium arsenide allows us to drive spin rotations electrically with a local gate electrode, and the charge-cavity interaction provides a measurement of the resulting spin dynamics. Our results demonstrate how the cQED architecture can be used as a sensitive probe of single-spin physics and that a spin-cavity coupling rate of about one megahertz is feasible, presenting the possibility of long-range spin coupling via superconducting microwave cavities.
Quantum electrodynamics near a photonic bandgap
Liu, Yanbing; Houck, Andrew A.
2017-01-01
Photonic crystals are a powerful tool for the manipulation of optical dispersion and density of states, and have thus been used in applications from photon generation to quantum sensing with nitrogen vacancy centres and atoms. The unique control provided by these media makes them a beautiful, if unexplored, playground for strong-coupling quantum electrodynamics, where a single, highly nonlinear emitter hybridizes with the band structure of the crystal. Here we demonstrate that such a hybridization can create localized cavity modes that live within the photonic bandgap, whose localization and spectral properties we explore in detail. We then demonstrate that the coloured vacuum of the photonic crystal can be employed for efficient dissipative state preparation. This work opens exciting prospects for engineering long-range spin models in the circuit quantum electrodynamics architecture, as well as new opportunities for dissipative quantum state engineering.
Institute of Scientific and Technical Information of China (English)
YANG Wen-Xing; ZHAN Zhi-Ming; LI Jia-Hua
2004-01-01
@@ We propose a simple method to generate a practical SU(2)-Schrodinger-cat state of a single trapped-ion vibration mode and the light field state, using the method based on a quantum system, which is composed of the onedimensional trapped-ion motion and a single cavity field mode. Moreover, the method proposed can be used for the generation two-mode maximal quantum entangled state. The detection of such a state is also briefly discussed.
Cavity QED: applications to quantum computation
Xiong, Han; Zubairy, M. Suhail
2004-10-01
Possible schemes to implement the basic quantum gates for quantum computation have been presented based on cavity quantum electrodynamics (QED) systems. We then discuss schemes to implement several important quantum algorithms such as the discrete quantum fourier transform (QFT) algorithm and Grover's quantum search algorithm based on these quantum gates. Some other applications of cavity QED based systems including the implementations of a quantum disentanglement eraser and an entanglement amplifier are also discussed.
Quantum Electrodynamics in Photonic Crystal Waveguides
DEFF Research Database (Denmark)
Nielsen, Henri Thyrrestrup
In this thesis we have performed quantum electrodynamics (QED) experiments in photonic crystal (PhC) waveguides and cavity QED in the Anderson localized regime in disordered PhC waveguides. Decay rate measurements of quantum dots embedded in PhC waveguides has been used to map out the variations...... probability. The Q-factor distributions of Anderson localized modes have been measured in PhC waveguides with articial induced disorder with embedded emitters. The largest Q-factors are found in the sample with the smallest amount of disorder. From a comparison with the waveguide model the localization length...
The Relation between Classical and Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Mario Bacelar Valente
2011-01-01
Full Text Available Quantum electrodynamics presents intrinsic limitations in the description of physical processes that make it impossible to recover from it the type of description we have in classical electrodynamics. Hence one cannot consider classical electrodynamics as reducing to quantum electrodynamics and being recovered from it by some sort of limiting procedure. Quantum electrodynamics has to be seen not as an more fundamental theory, but as an upgrade of classical electrodynamics, which permits an extension of classical theory to the description of phenomena that, while being related to the conceptual framework of the classical theory, cannot be addressed from the classical theory.
QUANTUM ELECTRODYNAMICS - AN INDIVIDUAL VIEW
1982-01-01
The aim of this report is to describe the development of the quantum electrodynamics in the years from the 1930's to the 1950's. It is based on the way the author saw and participate to this development. Four phases are discussed : preparation (1934 - 1946) ; non-covariant relativistic theory (1947) ; first covariant relativistic theory (1947 - 1948) ; second covariant relativistic theory (1949 - 1950). A detailed technical description is presented. The author shows the influence of quantum e...
Quantum gravitational contributions to quantum electrodynamics.
Toms, David J
2010-11-01
Quantum electrodynamics describes the interactions of electrons and photons. Electric charge (the gauge coupling constant) is energy dependent, and there is a previous claim that charge is affected by gravity (described by general relativity) with the implication that the charge is reduced at high energies. However, that claim has been very controversial and the matter has not been settled. Here I report an analysis (free from the earlier controversies) demonstrating that quantum gravity corrections to quantum electrodynamics have a quadratic energy dependence that result in the electric charge vanishing at high energies, a result known as asymptotic freedom.
Roy, C; Hughes, S
2011-06-17
We study the resonance fluorescence spectra of a driven quantum dot placed inside a high-Q semiconductor cavity and interacting with an acoustic phonon bath. The dynamics is calculated using a time-convolutionless master equation in the polaron frame. We predict pronounced spectral broadening of the Mollow sidebands through off-resonant cavity emission which, for small cavity-coupling rates, increases quadratically with the Rabi frequency in direct agreement with recent experiments using semiconductor micropillars [S. M. Ulrich et al., preceding Letter, Phys. Rev. Lett. 106, 247402 (2011)]. We also demonstrate that, surprisingly, phonon coupling actually helps resolve signatures of the elusive second rungs of the Jaynes-Cummings ladder states via off-resonant cavity feeding. Both multiphonon and multiphoton effects are shown to play a qualitatively important role on the fluorescence spectra.
Subcycle Quantum Electrodynamics
Riek, Claudius; Seeger, Maximilian; Moskalenko, Andrey S; Burkard, Guido; Seletskiy, Denis V; Leitenstorfer, Alfred
2016-01-01
Besides their stunning physical properties which are unmatched in a classical world, squeezed states of electromagnetic radiation bear advanced application potentials in quantum information systems and precision metrology, including gravitational wave detectors with unprecedented sensitivity. Since the first experiments on such nonclassical light, quantum analysis has been based on homodyning techniques and photon correlation measurements. These methods require a well-defined carrier frequency and photons contained in a quantum state need to be absorbed or amplified. They currently function in the visible to near-infrared and microwave spectral ranges. Quantum nondemolition experiments may be performed at the expense of excess fluctuations in another quadrature. Here we generate mid-infrared time-locked patterns of squeezed vacuum noise. After propagation through free space, the quantum fluctuations of the electric field are studied in the time domain by electro-optic sampling with few-femtosecond laser pulse...
von Klitzing, W; Long, R; Ilchenko, V S; Hare, J; Lefèvre-Seguin, V
2001-02-01
We have tuned the whispering-gallery modes of a fused-silica microresonator over nearly 1 nm at 800 nm, i.e., over half a free spectral range, or 10(6) linewidths of the resonator. This result has been achieved by use of a new method based on the stretching of a two-stem microsphere. We describe devices that will permit new cavity QED experiments with this high- Q optical resonator when it is desirable to optimize its coupling to emitters with given transition frequencies. The demonstrated tuning capability is compatible with both UHV and low-temperature operation, which should be useful for future experiments with laser-cooled atoms or single quantum dots.
Subcycle quantum electrodynamics.
Riek, C; Sulzer, P; Seeger, M; Moskalenko, A S; Burkard, G; Seletskiy, D V; Leitenstorfer, A
2017-01-18
Squeezed states of electromagnetic radiation have quantum fluctuations below those of the vacuum field. They offer a unique resource for quantum information systems and precision metrology, including gravitational wave detectors, which require unprecedented sensitivity. Since the first experiments on this non-classical form of light, quantum analysis has been based on homodyning techniques and photon correlation measurements. These methods currently function in the visible to near-infrared and microwave spectral ranges. They require a well-defined carrier frequency, and photons contained in a quantum state need to be absorbed or amplified. Quantum non-demolition experiments may be performed to avoid the influence of a measurement in one quadrature, but this procedure comes at the expense of increased uncertainty in another quadrature. Here we generate mid-infrared time-locked patterns of squeezed vacuum noise. After propagation through free space, the quantum fluctuations of the electric field are studied in the time domain using electro-optic sampling with few-femtosecond laser pulses. We directly compare the local noise amplitude to that of bare (that is, unperturbed) vacuum. Our nonlinear approach operates off resonance and, unlike homodyning or photon correlation techniques, without absorption or amplification of the field that is investigated. We find subcycle intervals with noise levels that are substantially less than the amplitude of the vacuum field. As a consequence, there are enhanced fluctuations in adjacent time intervals, owing to Heisenberg's uncertainty principle, which indicate generation of highly correlated quantum radiation. Together with efforts in the far infrared, this work enables the study of elementary quantum dynamics of light and matter in an energy range at the boundary between vacuum and thermal background conditions.
Quantum Electrodynamics of Nanosystems
Masood, Samina S
2012-01-01
Quantum description of mulitiparticle nano-systems is studied in a hot and dense electromagnetic medium. We use renormalization techniques of quantum field theory to show that the electromagnetic properties like electric permittivity and magnetic permeability depend on the temperature and density of the media. Casimir force also depends upon the physical properties of the medium and becomes a function of these parameters within the nano-systems. We discuss the effect of the Casimir force on the nanosystems in terms of temperature and density of the system. We present carbon nanotubes and biomolecules as examples.
Scheme for Implementation of Quantum Game in Cavity QED
Institute of Scientific and Technical Information of China (English)
ZHANG Li-Chun; CAO Shu-Ai; WU Yue-Qin; FANG Mao-Fa; LI Huai-Fan; ZHENG Xiao-Juan; ZHAO Ren; WANG Xin-Wen; LI Ze-Hua
2008-01-01
We propose an experimentally feasible scheme to implement two-player quantum game in cavity quantum electrodynamics (QED). During the process, the cavity is only virtually excited, thus our scheme is insensitive to the cavity field states and cavity decay. The scheme can be realized in the range of current cavity QED techniques.
A scheme for implementing quantum game in cavity QED
Institute of Scientific and Technical Information of China (English)
CaoShuai; Fang Mao-Fa; Liu Jian-Bin; Wang Xin-Wen; Zheng Xiao-juan
2009-01-01
In this paper, we propose a scheme fot implementing quantum game (QG) in cavity quantum electrodynam-ics(QED). In the scheme, the cavity is only virtually excited and thus the proposal is insensitive to the cavity fields states and cavity decay. So our proposal can be experimentally realized in the range of current cavity QED techniques.
Institute of Scientific and Technical Information of China (English)
SHAO Xiao-Qiang; ZHANG Shou
2008-01-01
We propose a scheme for one-step generation of cluster states with atoms sent through a thermal cavity with strong classical driving field, based on the resonant atom-cavity interaction so that the operating time is sharply short, which is important in the view of decoherence.
Scheme for implementing quantum secret sharing via cavity QED
Institute of Scientific and Technical Information of China (English)
Chen Zhi-Hua; Lin Xiu-Min
2005-01-01
An experimentally feasible scheme for implementing quantum secret sharing via cavity quantum electrodynamics (QED) is proposed. The scheme requires the large detuning of the cavity field from the atomic transition, the cavity is only virtually excited, thus the requirement on the quality factor of the cavity is greatly loosened.
Potentialities of Revised Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Lehnert B.
2013-10-01
Full Text Available The potentialities of a revised quantum electrodynamic theory (RQED earlier established by the author are reconsidered, also in respect to other fundamental theories such as those by Dirac and Higgs. The RQED theory is characterized by intrinsic linear symmetry breaking due to a nonzero divergence of the electric field strength in the vacuum state, as supported by the Zero Point Energy and the experimentally confirmed Casimir force. It includes the results of electron spin and antimatter by Dirac, as well as the rest mass of elementary particles predicted by Higgs in terms of spontaneous nonlinear symmetry breaking. It will here be put into doubt whether the approach by Higgs is the only theory which becomes necessary for explaining the particle rest masses. In addition, RQED theory leads to new results beyond those being available from the theories by Dirac, Higgs and the Standard Model, such as in applications to leptons and the photon.
Directory of Open Access Journals (Sweden)
Sergey N. Andrianov
2011-03-01
Full Text Available Creation of quantum computer is outstanding fundamental and practical problem. The quantum computer could be used for execution of very complicated tasks which are not solvable with the classical computers. The first prototype of solid state quantum computer was created in 2009 with superconducting qubits. However, it suffers from the decoherent processes and it is desirable to find more practical encoding of qubits with long-lived coherence. It could be single impurity or vacancy centers in solids, but their interaction with electromagnetic radiation is rather weak. So, here, ensembles of atoms were proposed for the qubit encoding by using the dipole blockade mechanism in order to turn multilevel systems in two level ones. But dipole-dipole based blockade introduces an additional decoherence that limits its practical significance. Recently, the collective blockade mechanism has been proposed for the system of three-level atoms by using the different frequency shifts for the Raman transitions between the collective atomic states characterized by a different number of the excited atoms. Here, we propose two qubit gate by using another collective blockade mechanism in the system of two level atoms based on exchange interaction via the virtual photons between the multi-atomic ensembles in the resonator. Also we demonstrate the possibility of three qubit gate (Controlled SWAP gate using a suppression of the swap-process between two multi-atomic ensembles due to dynamical shift of the atomic levels controlled by the states of photon encoded qubit.
Quantum electrodynamics on background external fields
2003-01-01
The quantum electrodynamics in presence of background external fields is developed. Modern methods of local quantum physics allow to formulate the theory on arbitrarily strong possibly time-dependent external fields. Non-linear observables which depend only locally on the external field are constructed. The tools necessary for this formulation, the parametrices of the Dirac operator, are investigated.
Quantum mechanics as electrodynamics of curvilinear waves
2002-01-01
The suggested theory is the new quantum mechanics (QM) interpretation.The research proves that QM represents the electrodynamics of the curvilinear closed (non-linear) waves. It is entirely according to the modern interpretation and explains the particularities and the results of the quantum field theory.
Quantum Electrodynamics on background external fields
Marecki, P
2003-01-01
The quantum electrodynamics in presence of background external fields is developed. Modern methods of local quantum physics allow to formulate the theory on arbitrarily strong possibly time-dependent external fields. Non-linear observables which depend only locally on the external field are constructed. The tools necessary for this formulation, the parametrices of the Dirac operator, are investigated.
Quantum Electrodynamics in a Uniform Magnetic Field
Suzuki, J
2005-01-01
A systematic formalism for quantum electrodynamics in a classical uniform magnetic field is discussed. The first order radiative correction to the ground state energy of an electron is calculated. This then leads to the anomalous magnetic moment of an electron without divergent integrals. Thorough analyses of this problem are given for the weak magnetic field limit. A new expression for the radiative correction to the ground state energy is obtained. This contains only one integral with an additional summation with respect to each Landau level. The importance of this formalism is also addressed in order to deal with quantum electrodynamics in an intense external field.
Lamb Shift in Nonrelativistic Quantum Electrodynamics.
Grotch, Howard
1981-01-01
The bound electron self-energy or Lamb shift is calculated in nonrelativistic quantum electrodynamics. Retardation is retained and also an interaction previously dropped in other nonrelativistic approaches is kept. Results are finite without introducing a cutoff and lead to a Lamb shift in hydrogen of 1030.9 MHz. (Author/JN)
Quantum electrodynamics and the fundamental constants
Directory of Open Access Journals (Sweden)
Peter J. Mohr
2000-07-01
Full Text Available the results of critical experiments and the theoretical expressions for these results written in terms of the constants. Many of the theoretical expressions are based on quantum electrodynamics (QED, so the consistency of the comparison provides a critical test of the validity of the theory.
Minimal resonator loss for circuit quantum electrodynamics
Barends, R.; Vercruyssen, N.; Endo, A.; De Visser, P.J.; Zijlstra, T.; Klapwijk, T.M.; Diener, P.; Yates, S.J.C.; Baselmans, J.J.A.
2010-01-01
We report quality factors of up to 500x10³ in superconducting resonators at the single photon levels needed for circuit quantum electrodynamics. This result is achieved by using NbTiN and removing the dielectric from regions with high electric fields. As demonstrated by a comparison with Ta, the cru
Comparison of coherently coupled multi-cavity and quantum dot embedded single cavity systems.
Kocaman, Serdar; Sayan, Gönül Turhan
2016-12-12
Temporal group delays originating from the optical analogue to electromagnetically induced transparency (EIT) are compared in two systems. Similar transmission characteristics are observed between a coherently coupled high-Q multi-cavity array and a single quantum dot (QD) embedded cavity in the weak coupling regime. However, theoretically generated group delay values for the multi-cavity case are around two times higher. Both configurations allow direct scalability for chip-scale optical pulse trapping and coupled-cavity quantum electrodynamics (QED).
Finite quantum electrodynamics the causal approach
Scharf, Günter
2014-01-01
In this classic text for advanced undergraduates and graduate students of physics, author Günter Scharf carefully analyzes the role of causality in quantum electrodynamics. His approach offers full proofs and detailed calculations of scattering processes in a mathematically rigorous manner. This third edition contains Scharf's revisions and corrections plus a brief new Epilogue on gauge invariance of quantum electrodynamics to all orders. The book begins with Dirac's theory, followed by the quantum theory of free fields and causal perturbation theory, a powerful method that avoids ultraviolet divergences and solves the infrared problem by means of the adiabatic limit. Successive chapters explore properties of the S-matrix — such as renormalizability, gauge invariance, and unitarity — the renormalization group, and interactive fields. Additional topics include electromagnetic couplings and the extension of the methods to non-abelian gauge theories. Each chapter is supplemented with problems, and four appe...
Quantum-classical crossover in electrodynamics
Polonyi, J
2006-01-01
A classical field theory is proposed for the electric current and the electromagnetic field interpolating between microscopic and macroscopic domains. It represents a generalization of the density functional for the dynamics of the current and the electromagnetic field in the quantum side of the crossover and reproduces standard classical electrodynamics on the other side. The effective action derived in the closed time path formalism and the equations of motion follow from the variational principle. The polarization of the Dirac-see can be taken into account in the quadratic approximation of the action by the introduction of the deplacement field strengths as in conventional classical electrodynamics. Decoherence appears naturally as a simple one-loop effect in this formalism. It is argued that the radiation time arrow is generated from the quantum boundary conditions in time by decoherence at the quantum-classical crossover and the Abraham-Lorentz force arises from the accelerating charge or from other char...
Third emission mechanism in solid-state nanocavity quantum electrodynamics.
Yamaguchi, Makoto; Asano, Takashi; Noda, Susumu
2012-09-01
Photonic crystal (PC) nanocavities have been receiving a great deal of attention recently because of their ability to strongly confine photons in a tiny space with a high quality factor. According to cavity quantum electrodynamics (cavity QED), such confined photons can achieve efficient interactions with excitons in semiconductors, leading to the Purcell effect in the weak coupling regime and vacuum Rabi splitting (VRS) in the strong coupling regime. These features are promising for applications such as quantum information processing, highly efficient single photon sources and ultra-low threshold lasers. In this context, the coupled system of a semiconductor quantum dot (QD) and a PC nanocavity has been intensively investigated in recent years.Although experimental reports have demonstrated such fundamental features, two anomalous phenomena have also been observed. First, photon emission from the cavity occurs even when it is significantly detuned from the QD. Second, spectral triplets are formed by additional bare-cavity lines between the VRS lines. These features cannot be explained by standard cavity QED theories and have prompted controversy regarding their physical mechanisms. In this review we describe the recent experimental and theoretical progress made in the investigation of these phenomena. Similar mechanisms will also occur in many other coupled quantum systems, and thus the findings are applicable to a wide range of fields.
Soliton-like solution in quantum electrodynamics
Skoromnik, O D; Keitel, C H
2016-01-01
A novel soliton-like solution in quantum electrodynamics is obtained via a self-consistent field method. By writing the Hamiltonian of quantum electrodynamics in the Coulomb gauge, we separate out a classical component in the density operator of the electron-positron field. Then, by modeling the state vector in analogy with the theory of superconductivity, we minimize the functional for the energy of the system. This results in the equations of the self-consistent field, where the solutions are associated with the collective excitation of the electron-positron field---the soliton-like solution. In addition, the canonical transformation of the variables allowed us to separate out the total momentum of the system and, consequently, to find the relativistic energy dispersion relation for the moving soliton.
Foundations of classical and quantum electrodynamics
Toptygin, Igor N
2014-01-01
This advanced textbook covers many fundamental, traditional and new branches of electrodynamics, as well as the related fields of special relativity, quantum mechanics and quantum electrodynamics. The book introduces the material at different levels, oriented towards 3rd–4th year bachelor, master, and PhD students. This is so as to describe the whole complexity of physical phenomena. The required mathematical background is collated in Chapter 1, while the necessary physical background is included in the main text of the corresponding chapters and also given in appendices. It contains approximately 800 examples and problems, many of which are described in detail. Some of these problems are designed for students to work on their own with only the answers and descriptions of results, and may be solved selectively. Equally suitable as a reference for researchers specialized in science and engineering.
Discrepancies in quantum electro-dynamics
Chantler, C. T.
2004-10-01
Experimental tests of quantum electro-dynamics (QED) have developed dramatically for simple atomic systems such as hydrogen. However, a range of anomalies has been discovered recently. There has also been significant progress for medium- Z hydrogenic and helium-like atoms. In this area tests are often based on X-ray spectroscopic measurements. Future prospects for critical insight into the nature and convergence of QED in multi-electron systems will be discussed.
Discrepancies in quantum electro-dynamics
Energy Technology Data Exchange (ETDEWEB)
Chantler, C.T. E-mail: chantler@ph.unimelb.edu.au
2004-11-01
Experimental tests of quantum electro-dynamics (QED) have developed dramatically for simple atomic systems such as hydrogen. However, a range of anomalies has been discovered recently. There has also been significant progress for medium-Z hydrogenic and helium-like atoms. In this area tests are often based on X-ray spectroscopic measurements. Future prospects for critical insight into the nature and convergence of QED in multi-electron systems will be discussed.
Time-symmetric electrodynamics and quantum measurement
Pegg, D. T.
The application of the Wheeler-Feynman theory of time-symmetric electrodynamics to obtain definite answers to questions concerning the objective existence of quantum states in an optical EPR type of experiment is discussed. This theory allows the influence of the detector on the system being studied to be taken into account. The result is an entirely fresh understanding of experiments of the Kocher-Commins type.
Clothed Particles in Quantum Electrodynamics and Quantum Chromodynamics
Directory of Open Access Journals (Sweden)
Shebeko Alexander
2016-01-01
Full Text Available The notion of clothing in quantum field theory (QFT, put forward by Greenberg and Schweber and developed by M. Shirokov, is applied in quantum electrodynamics (QED and quantum chromodynamics (QCD. Along the guideline we have derived a novel analytic expression for the QED Hamiltonian in the clothed particle representation (CPR. In addition, we are trying to realize this notion in QCD (to be definite for the gauge group SU(3 when drawing parallels between QCD and QED.
Investigation on regulators in quantum electrodynamics
Stora, Raymond Félix
We present in this work three models which are able to suppress the divergences of approximate versions of Quantum Electrodynamics.It is indeed argued that, in view of the smallness of the fine structure constant, not only the first terms of a perturbation expansion, or of an expansion according to the number of particles involved in intermediate states, gives a fair approximattonbut furthermore, that it is in these terms that a breakdown of electrodynamics should be sought. Our goal is to connect the high energy behaviour of relevant physical processes with the suppression of the divergences. Our goal is to connect the high energy behaviour of relevant physical processes with the suppression of the divergences. The first model assumes the existence of a photon cut off, whose observable consequences are clearly stated, and of a fermion out off which, although unable to give a satisfactory ...
Quantum measurements of atoms using cavity QED
Dada, Adetunmise C; Jones, Martin L; Kendon, Vivien M; Everitt, Mark S
2010-01-01
Generalized quantum measurements are an important extension of projective or von Neumann measurements, in that they can be used to describe any measurement that can be implemented on a quantum system. We describe how to realize two non-standard quantum measurements using cavity quantum electrodynamics (QED). The first measurement optimally and unabmiguously distinguishes between two non-orthogonal quantum states. The second example is a measurement that demonstrates superadditive quantum coding gain. The experimental tools used are single-atom unitary operations effected by Ramsey pulses and two-atom Tavis-Cummings interactions. We show how the superadditive quantum coding gain is affected by errors in the field-ionisation detection of atoms, and that even with rather high levels of experimental imperfections, a reasonable amount of superadditivity can still be seen. To date, these types of measurement have only been realized on photons. It would be of great interest to have realizations using other physical ...
New Approach to Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Sze Kui Ng
2008-04-01
Full Text Available It is shown that a photon with a specific frequency can be identified with the Dirac magnetic monopole. When a Dirac-Wilson line forms a Dirac-Wilson loop, it is a photon. This loop model of photon is exactly solvable. From the winding numbers of this loop-form of photon, we derive the quantization properties of energy and electric charge. A new QED theory is presented that is free of ultravioletdivergences. The Dirac-Wilson line is as the quantum photon propagator of the new QED theory from which we can derive known QED effects such as the anomalous magnetic moment and the Lamb shift. The one-loop computation of these effects is simpler and is more accurate than that in the conventional QED theory. Furthermore, from the new QED theory, we have derived a new QED effect. A new formulation of the Bethe-Salpeter (BS equation solves the difficulties of the BS equation and gives a modified ground state of the positronium. By the mentioned new QED effect and by the new formulation of the BS equation, a term in the orthopositronium decay rate that is missing in the conventional QED is found, resolving the orthopositronium lifetime puzzle completely. It is also shown that the graviton can be constructed from the photon, yielding a theory of quantum gravity that unifies gravitation and electromagnetism.
New Approach to Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Sze Kui Ng
2008-04-01
Full Text Available It is shown that a photon with a specific frequency can be identified with the Dirac mag- netic monopole. When a Dirac-Wilson line forms a Dirac-Wilson loop, it is a photon. This loop model of photon is exactly solvable. From the winding numbers of this loop- form of photon, we derive the quantization properties of energy and electric charge. A new QED theory is presented that is free of ultraviolet divergences. The Dirac-Wilson line is as the quantum photon propagator of the new QED theory from which we can derive known QED e ects such as the anomalous magnetic moment and the Lamb shift. The one-loop computation of these e ects is simpler and is more accurate than that in the conventional QED theory. Furthermore, from the new QED theory, we have derived a new QED e ect. A new formulation of the Bethe-Salpeter (BS equation solves the di culties of the BS equation and gives a modified ground state of the positronium. By the mentioned new QED e ect and by the new formulation of the BS equation, a term in the orthopositronium decay rate that is missing in the conventional QED is found, resolving the orthopositronium lifetime puzzle completely. It is also shown that the graviton can be constructed from the photon, yielding a theory of quantum gravity that unifies gravitation and electromagnetism.
Thermal quantum electrodynamics of nonrelativistic charged fluids
Buenzli, Pascal R.; Martin, Philippe A.; Ryser, Marc D.
2007-04-01
The theory relevant to the study of matter in equilibrium with the radiation field is thermal quantum electrodynamics (TQED). We present a formulation of the theory, suitable for nonrelativistic fluids, based on a joint functional integral representation of matter and field variables. In this formalism cluster expansion techniques of classical statistical mechanics become operative. They provide an alternative to the usual Feynman diagrammatics in many-body problems, which is not perturbative with respect to the coupling constant. As an application we show that the effective Coulomb interaction between quantum charges is partially screened by thermalized photons at large distances. More precisely one observes an exact cancellation of the dipolar electric part of the interaction, so that the asymptotic particle density correlation is now determined by relativistic effects. It still has the r-6 decay typical for quantum charges, but with an amplitude strongly reduced by a relativistic factor.
Thermal quantum electrodynamics of nonrelativistic charged fluids.
Buenzli, Pascal R; Martin, Philippe A; Ryser, Marc D
2007-04-01
The theory relevant to the study of matter in equilibrium with the radiation field is thermal quantum electrodynamics (TQED). We present a formulation of the theory, suitable for nonrelativistic fluids, based on a joint functional integral representation of matter and field variables. In this formalism cluster expansion techniques of classical statistical mechanics become operative. They provide an alternative to the usual Feynman diagrammatics in many-body problems, which is not perturbative with respect to the coupling constant. As an application we show that the effective Coulomb interaction between quantum charges is partially screened by thermalized photons at large distances. More precisely one observes an exact cancellation of the dipolar electric part of the interaction, so that the asymptotic particle density correlation is now determined by relativistic effects. It still has the r(-6) decay typical for quantum charges, but with an amplitude strongly reduced by a relativistic factor.
Quantum electrodynamics with arbitrary charge on a noncommutative space
Institute of Scientific and Technical Information of China (English)
ZHOU Wan-Ping; CAI Shao-Hong; LONG Zheng-Wen
2009-01-01
Using the Seiberg-Witten map,we obtain a quantum electrodynamics on a noncommutative space,which has arbitrary charge and keep the gauge invariance to at the leading order in theta.The one-loop divergence and Compton scattering are reinvestigated.The uoncommutative effects are larger than those in ordinary noncommutative quantum electrodynamics.
Quantum Electrodynamics vacuum polarization solver
Carneiro, Pedro; Fonseca, Ricardo; Silva, Luís
2016-01-01
The self-consistent modeling of vacuum polarization due to virtual electron-positron fluctuations is of relevance for many near term experiments associated with high intensity radiation sources and represents a milestone in describing scenarios of extreme energy density. We present a generalized finite-difference time-domain solver that can incorporate the modifications to Maxwells equations due to virtual vacuum polarization. Our multidimensional solver reproduced in one dimensional configurations the results for which an analytic treatment is possible, yielding vacuum harmonic generation and birefringence. The solver has also been tested for two-dimensional scenarios where finite laser beam spot sizes must be taken into account. We employ this solver to explore different types of counter-propagating configurations that can be relevant for future planned experiments aiming to detect quantum vacuum dynamics at ultra-high electromagnetic field intensities.
Quantum Electrodynamical Shifts in Multivalent Heavy Ions
Tupitsyn, I. I.; Kozlov, M. G.; Safronova, M. S.; Shabaev, V. M.; Dzuba, V. A.
2016-12-01
The quantum electrodynamics (QED) corrections are directly incorporated into the most accurate treatment of the correlation corrections for ions with complex electronic structure of interest to metrology and tests of fundamental physics. We compared the performance of four different QED potentials for various systems to access the accuracy of QED calculations and to make a prediction of highly charged ion properties urgently needed for planning future experiments. We find that all four potentials give consistent and reliable results for ions of interest. For the strongly bound electrons, the nonlocal potentials are more accurate than the local potential.
Quantum Electrodynamics Theory of Laser Assisted Recombination
Institute of Scientific and Technical Information of China (English)
敖淑艳; 程太旺; 李晓峰; 潘守甫; 傅盘铭
2003-01-01
Using a formal scattering theoretical approach, we develop a nonperturbative quantum electrodynamics theory to describe laser assisted recombination (LAR), in which an electron initially in the quantized Volkov state recombines with an ion and emits a high-energy photon with frequency defined by energy conservation laws.The transition probability is expressed as an analytic closed form and the spectrum of LAR reflects mainly the properties of general Bessel functions. For the case of a fast electron the LAR spectrum is confined in a well-defined range, while for a slow electron, the LAR spectrum exhibits a double-plateau structure.
Implementing phase-covariant cloning in circuit quantum electrodynamics
Zhu, Meng-Zheng; Ye, Liu
2016-10-01
An efficient scheme is proposed to implement phase-covariant quantum cloning by using a superconducting transmon qubit coupled to a microwave cavity resonator in the strong dispersive limit of circuit quantum electrodynamics (QED). By solving the master equation numerically, we plot the Wigner function and Poisson distribution of the cavity mode after each operation in the cloning transformation sequence according to two logic circuits proposed. The visualizations of the quasi-probability distribution in phase-space for the cavity mode and the occupation probability distribution in the Fock basis enable us to penetrate the evolution process of cavity mode during the phase-covariant cloning (PCC) transformation. With the help of numerical simulation method, we find out that the present cloning machine is not the isotropic model because its output fidelity depends on the polar angle and the azimuthal angle of the initial input state on the Bloch sphere. The fidelity for the actual output clone of the present scheme is slightly smaller than one in the theoretical case. The simulation results are consistent with the theoretical ones. This further corroborates our scheme based on circuit QED can implement efficiently PCC transformation.
PT-symmetric quantum electrodynamics and unitarity.
Milton, Kimball A; Abalo, E K; Parashar, Prachi; Pourtolami, Nima; Wagner, J
2013-04-28
More than 15 years ago, a new approach to quantum mechanics was suggested, in which Hermiticity of the Hamiltonian was to be replaced by invariance under a discrete symmetry, the product of parity and time-reversal symmetry, PT. It was shown that, if PT is unbroken, energies were, in fact, positive, and unitarity was satisfied. Since quantum mechanics is quantum field theory in one dimension--time--it was natural to extend this idea to higher-dimensional field theory, and in fact an apparently viable version of PT-invariant quantum electrodynamics (QED) was proposed. However, it has proved difficult to establish that the unitarity of the scattering matrix, for example, the Källén spectral representation for the photon propagator, can be maintained in this theory. This has led to questions of whether, in fact, even quantum mechanical systems are consistent with probability conservation when Green's functions are examined, since the latter have to possess physical requirements of analyticity. The status of PT QED will be reviewed in this paper, as well as the general issue of unitarity.
Coherent Dynamics of Quantum Dots in Photonic-Crystal Cavities
DEFF Research Database (Denmark)
Madsen, Kristian Høeg
deviations. Similar measurements on a quantum dot in a photonic-crystal cavity sow a Rabi splitting on resonance, while time-resolved measurements prove that the system is in the weak coupling regime. Whle tuning the quantum dot through resonance of the high-Q mode we observe a strong and surprisingly...... Successfully model the decay rates with a microscopic model that allows us to for the first time extract the effective phonon density of states, which we can model with bulk phonons. Studies on a quantum dot detuned from a low-Q mode of a photonic-crystal cavity show a high collection efficiency at the first......In this thesis we have performed quantum-electrodynamics experiments on quantum dots embedded in photonic-crystal cavities. We perform a quantitative comparison of the decay dynamics and emission spectra of quantum dots embedded in a micropillar cavity and a photonic-crystal cavity. The light...
Does quantum electrodynamics have an arrow of time?
Atkinson, David
2006-01-01
Quantum electrodynamics is a time-symmetric theory that is part of the electroweak interaction, which is invariant under a generalized form of this symmetry, the PCT transformation. The thesis is defended that the arrow of time in electrodynamics is a consequence of the assumption of an initial stat
Thompson's Method applied to Quantum Electrodynamics (QED)
Nassif, C; Nassif, Claudio
2000-01-01
In this work we apply Thompson's method (of the dimensions) to study the quantum electrodynamics (QED). This method can be considered as a simple and alternative way to the renormalisation group (R.G) approach and when applied to QED lagrangian is able to obtain the running coupling constant behavior $\\alpha (\\mu)$, namely the dependence of $\\alpha$ on the energy scale. We also obtain the dependence of the mass on the energy scale. The calculations are evaluated just at $d_c=4$, where $d_c$ is the upper critical dimension of the problem, so that we obtain logarithmic behavior both for the coupling $\\alpha$ and the mass $m$ on the energy scale $\\mu$.
Mechanical momentum in nonequilibrium quantum electrodynamics
de Haan, M
2006-01-01
The reformulation of field theory in which self-energy processes are no longer present [Annals of Physics, {\\bf311} (2004), 314.], [ Progr. Theor. Phys., {\\bf 109} (2003), 881.], [Trends in Statistical Physics {\\bf 3} (2000), 115.] provides an adequate tool to transform Swinger-Dyson equations into a kinetic description outside any approximation scheme. Usual approaches in quantum electrodynamics (QED) are unable to cope with the mechanical momentum of the electron and replace it by the canonical momentum. The use of that unphysical momentum is responsible for the divergences that are removed by the renormalization procedure in the $S$-matrix theory. The connection between distribution functions in terms of the canonical and those in terms of the mechanical momentum is now provided by a dressing operator [Annals of Physics, {\\bf314} (2004), 10] that allows the elimination of the above divergences, as the first steps are illustrated here.
Chun, Sehun
2013-01-01
To provide a unified theoretical framework ranging from a cellular-level excitation mechanism to organic-level geometric propagation, a new theory inspired by quantum electrodynamic theory for light propagation is proposed by describing the cardiac excitation propagation as the continuation of absorption and emission of charged ions by myocardial cells. By the choice of gauge and the membrane current density, a set of Maxwell's equations with a charge density and a current density is constructed in macroscopic bidomain and is shown to be equivalent to the diffusion-reaction system with the B. van der Pol oscillator. The derived Maxwell's equations for the excitation propagation obeys the conservational laws of the number of the cations, energy and momentum, but the total charge is not conserved. The Lagrangian is derived to reveal that the trajectory and wavefront of the excitation propagation are the same as the electrodynamic wave if ion channels work uniformly. From the second quantization, the Hamiltonian...
Orgiazzi, J.-L.; Deng, C.; Layden, D.; Marchildon, R.; Kitapli, F.; Shen, F.; Bal, M.; Ong, F. R.; Lupascu, A.
2016-03-01
We report experiments on superconducting flux qubits in a circuit quantum electrodynamics (cQED) setup. Two qubits, independently biased and controlled, are coupled to a coplanar waveguide resonator. Dispersive qubit state readout reaches a maximum contrast of 72%. We measure energy relaxation times at the symmetry point of 5 and 10 μ s , corresponding to 7 and 20 μ s when relaxation through the resonator due to Purcell effect is subtracted out, and levels of flux noise of 2.6 and 2.7 μ Φ0/√{Hz} at 1 Hz for the two qubits. We discuss the origin of decoherence in the measured devices. The strong coupling between the qubits and the cavity leads to a large, cavity-mediated, qubit-qubit coupling. This coupling, which is characterized spectroscopically, reaches 38 MHz. These results demonstrate the potential of cQED as a platform for fundamental investigations of decoherence and quantum dynamics of flux qubits.
A scheme for implementing quantum clock synchronization algorithm in cavity QED
Institute of Scientific and Technical Information of China (English)
Wu Qin-Qin; Kuang Le-Man
2006-01-01
In this paper, we propose a scheme for implementing the quantum clock synchronization (QCS) algorithm in cavity quantum electrodynamic (QED) formalism. Our method is based on three-level ladder-type atoms interacting with classical and quantized cavity fields. Atom-qubit realizations of three-qubit and four-qubit QCS algorithms are explicitly presented.
Quantum Logic Network for Cloning a State Near a Given One Based on Cavity QED
Institute of Scientific and Technical Information of China (English)
ZHANG Da-Wei; SHAO Xiao-Qiang; ZHU Ai-Dong
2008-01-01
A quantum logic network is constructed to simulate a cloning machine which copies states near a given one. Meanwhile, a scheme for implementing this cloning network based on the technique of cavity quantum electrody-namics (QED) is presented. It is easy to implement this network of cloning machine in the framework of cavity QED and feasible in the experiment.
Implementing quantum electrodynamics with ultracold atomic systems
Kasper, V.; Hebenstreit, F.; Jendrzejewski, F.; Oberthaler, M. K.; Berges, J.
2017-02-01
We discuss the experimental engineering of model systems for the description of quantum electrodynamics (QED) in one spatial dimension via a mixture of bosonic 23Na and fermionic 6Li atoms. The local gauge symmetry is realized in an optical superlattice, using heteronuclear boson–fermion spin-changing interactions which preserve the total spin in every local collision. We consider a large number of bosons residing in the coherent state of a Bose–Einstein condensate on each link between the fermion lattice sites, such that the behavior of lattice QED in the continuum limit can be recovered. The discussion about the range of possible experimental parameters builds, in particular, upon experiences with related setups of fermions interacting with coherent samples of bosonic atoms. We determine the atomic system’s parameters required for the description of fundamental QED processes, such as Schwinger pair production and string breaking. This is achieved by benchmark calculations of the atomic system and of QED itself using functional integral techniques. Our results demonstrate that the dynamics of one-dimensional QED may be realized with ultracold atoms using state-of-the-art experimental resources. The experimental setup proposed may provide a unique access to longstanding open questions for which classical computational methods are no longer applicable.
A Way to Revised Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Lehnert B.
2012-04-01
Full Text Available In conventional theoretical physics and its Standard Model the guiding principle is that the equations are symmetrical. This limitation leads to a number of difficulties, because it does not permit masses for leptons and quarks, the electron tends to “explode” un- der the action of its self-charge, a corresponding photon model has no spin, and such a model cannot account for the “needle radiation” proposed by Einstein and observed in the photoelectric e ff ect and in two-slit experiments. This paper summarizes a revised Lorentz and gauge invariant quantum electrodynamic theory based on a nonzero electric field divergence in the vacuum and characterized by linear intrinsic broken symmetry. It thus provides an alternative to the Higgs concept of nonlinear spontaneous broken sym- metry, for solving the difficulties of the Standard Model. New results are obtained, such as nonzero and finite lepton rest masses, a point-charge-like behavior of the electron due to a revised renormalization procedure, a magnetic volume force which counteracts the electrostatic eigen-force of the electron, a nonzero spin of the photon and of light beams, needle radiation, and an improved understanding of the photoelectric effect, two-slit ex- periments, electron-positron pair formation, and cork-screw-shaped light beams.
Quantum electrodynamics of inhomogeneous anisotropic media
Energy Technology Data Exchange (ETDEWEB)
Lopez, Adrian E.R.; Lombardo, Fernando C. [Ciudad Universitaria, Departamento de Fisica Juan Jose Giambiagi, Buenos Aires (Argentina); IFIBA CONICET-UBA, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)
2015-02-01
In this work we calculate the closed time path generating functional for the electromagnetic (EM) field interacting with inhomogeneous anisotropic matter. For this purpose, we first find a general expression for the electromagnetic field's influence action from the interaction of the field with a composite environment consisting in the quantum polarization degrees of freedom in each point of space, at arbitrary temperatures, connected to thermal baths. Then we evaluate the generating functional for the gauge field, in the temporal gauge, by implementing the Faddeev-Popov procedure. Finally, through the point-splitting technique, we calculate closed expressions for the energy, the Poynting vector, and the Maxwell tensor in terms of the Hadamard propagator. We show that all the quantities have contributions from the field's initial conditions and also from the matter degrees of freedom. Throughout the whole work we discuss how the gauge invariance must be treated in the formalism when the EM-field is interacting with inhomogeneous anisotropic matter. We study the electrodynamics in the temporal gauge, obtaining the EM-field's equation and a residual condition. Finally we analyze the case of the EM-field in bulk material and also discuss several general implications of our results in relation with the Casimir physics in a non-equilibrium scenario. (orig.)
On the quantum (in)stability in cavity QED
Prants, S V
2005-01-01
The stability and instability of quantum motion is studied in the context of cavity quantum electrodynamics (QED). It is shown that the Jaynes-Cummings dynamics can be unstable in the regime of chaotic walking of an atom in the quantized field of a standing wave in the absence of any other interaction with environment. This quantum instability manifests itself in strong variations of quantum purity and entropy and in exponential sensitivity of fidelity of quantum states to small variations in the atom-field detuning. It is quantified in terms of the respective classical maximal Lyapunov exponent that can be estimated in appropriate in-out experiments.
An Experiment on the Limits of Quantum Electro-dynamics
Barber, W. C.; Richter, B.; Panofsky, W. K. H.; O'Neill, G. K.; Gittelman, B.
1959-06-01
The limitations of previously performed or suggested electrodynamic cutoff experiments are reviewed, and an electron-electron scattering experiment to be performed with storage rings to investigate further the limits of the validity of quantum electrodynamics is described. The foreseen experimental problems are discussed, and the results of the associated calculations are given. The parameters and status of the equipment are summarized. (D.C.W.)
A Toy Model of Quantum Electrodynamics in (1 + 1) Dimensions
Boozer, A. D.
2008-01-01
We present a toy model of quantum electrodynamics (QED) in (1 + 1) dimensions. The QED model is much simpler than QED in (3 + 1) dimensions but exhibits many of the same physical phenomena, and serves as a pedagogical introduction to both QED and quantum field theory in general. We show how the QED model can be derived by quantizing a toy model of…
Photon physics: from wave mechanics to quantum electrodynamics
Keller, Ole
2009-05-01
When rewritten in an appropriate manner, the microscopic Maxwell-Lorentz equations appear as a wave-mechanical theory for photons, and their quantum physical interaction with matter. A natural extension leads from photon wave mechanics to quantum electrodynamics (QED). In its modern formulation photon wave mechanics has given us valuable new insight in subjects such as spatial photon localization, near-field photon dynamics, transverse photon mass, photon eikonal theory, photon tunneling, and rim-zone electrodynamics. The present review is based on my plenary lecture at the SPIE-Europe 2009 Optics and Optoelectronics International Symposium in Prague.
Autonomous quantum thermal machines in atom-cavity systems
Mitchison, Mark T; Prior, Javier; Woods, Mischa P; Plenio, Martin B
2016-01-01
An autonomous quantum thermal machine comprising a trapped atom or ion placed inside an optical cavity is proposed and analysed. Such a machine can operate as a heat engine whose working medium is the quantised atomic motion, or as an absorption refrigerator which cools without any work input. Focusing on the refrigerator mode, we predict that it is possible with state-of-the-art technology to cool a trapped ion almost to its motional ground state using a thermal light source such as sunlight. We nonetheless find that a laser or similar reference system is necessary to stabilise the cavity frequencies. Furthermore, we establish a direct and heretofore unacknowledged connection between the abstract theory of quantum absorption refrigerators and practical sideband cooling techniques. We also highlight and clarify some assumptions underlying several recent theoretical studies on self-contained quantum engines and refrigerators. Our work indicates that cavity quantum electrodynamics is a promising and versatile e...
DEFF Research Database (Denmark)
Nielsen, Per Kær; Lodahl, Peter; Jauho, Antti-Pekka;
2013-01-01
We study the fundamental limit on single-photon indistinguishability imposed by decoherence due to phonon interactions in semiconductor quantum dot-cavity quantum electrodynamics systems. Employing an exact diagonalization approach we find large differences compared to standard methods...
An Extension of Type I Gaugeon Formalism for Quantum Electrodynamics
Endo, R
1993-01-01
By introducing two kinds of gaugeon fields, we extend Yokoyama's Type I gaugeon formalism for quantum electrodynamics. The theory admits a q-number gauge transformation by which we can shift the gauge parameter into arbitrary numerical value; whereas in the original theory we cannot change the sign of the parameter. The relation to the Type II theory is also discussed.
Infrared phenomena in quantum electrodynamics : II. Bremsstrahlung and compton scattering
Haeringen, W. van
1960-01-01
The infrared aspects of quantum electrodynamics are discussed by treating two examples of scattering processes, bremsstrahlung and Compton scattering. As in the previous paper one uses a non-covariant diagram technique which gives very clear insight in the cancelling of infrared divergences between
Probing Features of the Lee-Wick Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
R. Turcati
2014-01-01
Full Text Available We discuss some aspects concerning the electromagnetic sector of the abelian Lee-Wick (LW quantum electrodynamics (QED. Using the Dirac’s theory of constrained systems, the higher-order canonical quantization of the LW electromagnetism is performed. A quantum bound on the LW heavy mass is also estimated using the best known measurement of the anomalous magnetic moment of the electron. Finally, it is shown that magnetic monopoles can coexist peacefully in the LW scenario.
Quantum electrodynamics in finite volume and nonrelativistic effective field theories
Directory of Open Access Journals (Sweden)
Z. Fodor
2016-04-01
Full Text Available Electromagnetic effects are increasingly being accounted for in lattice quantum chromodynamics computations. Because of their long-range nature, they lead to large finite-size effects over which it is important to gain analytical control. Nonrelativistic effective field theories provide an efficient tool to describe these effects. Here we argue that some care has to be taken when applying these methods to quantum electrodynamics in a finite volume.
Quantum electrodynamics in finite volume and nonrelativistic effective field theories
Energy Technology Data Exchange (ETDEWEB)
Fodor, Z. [Department of Physics, University of Wuppertal, D-42119 Wuppertal (Germany); Jülich Supercomputing Centre, Forschungszentrum Jülich, D-52428 Jülich (Germany); Institute for Theoretical Physics, Eötvös University, H-1117 Budapest (Hungary); Hoelbling, C. [Department of Physics, University of Wuppertal, D-42119 Wuppertal (Germany); Katz, S.D. [Institute for Theoretical Physics, Eötvös University, H-1117 Budapest (Hungary); MTA-ELTE Lendület Lattice Gauge Theory Research Group, H-1117 Budapest (Hungary); Lellouch, L., E-mail: lellouch@cpt.univ-mrs.fr [CNRS, Aix-Marseille U., U. de Toulon, CPT, UMR 7332, F-13288, Marseille (France); Portelli, A. [School of Physics & Astronomy, University of Southampton, SO17 1BJ (United Kingdom); Szabo, K.K. [Department of Physics, University of Wuppertal, D-42119 Wuppertal (Germany); Jülich Supercomputing Centre, Forschungszentrum Jülich, D-52428 Jülich (Germany); Toth, B.C. [Department of Physics, University of Wuppertal, D-42119 Wuppertal (Germany)
2016-04-10
Electromagnetic effects are increasingly being accounted for in lattice quantum chromodynamics computations. Because of their long-range nature, they lead to large finite-size effects over which it is important to gain analytical control. Nonrelativistic effective field theories provide an efficient tool to describe these effects. Here we argue that some care has to be taken when applying these methods to quantum electrodynamics in a finite volume.
Quantum Zeno Effect in the Strong Measurement Regime of Circuit Quantum Electrodynamics
2016-05-17
New J. Phys. 18 (2016) 053031 doi:10.1088/1367-2630/18/5/053031 PAPER Quantum Zeno effect in the strongmeasurement regime of circuit quantum ...Keywords: quantumZeno effect, quantum jumps, superconducting qubit, circuit QED, random telegraph signals Abstract Weobserve the quantumZeno effect...where the act ofmeasurement slows the rate of quantum state transitions—in a superconducting qubit using linear circuit quantum electrodynamics readout
K\\"all\\'en-Lehmann representation of noncommutative quantum electrodynamics
Bufalo, R; Pimentel, B M
2014-01-01
Noncommutative (NC) quantum field theory is the subject of many analyses on formal and general aspects looking for deviations and, therefore, potential noncommutative spacetime effects. Within of this large class, we may now pay some attention to the quantization of NC field theory on lower dimensions and look closely at the issue of dynamical mass generation to the gauge field. This work encompasses the quantization of the two-dimensional massive quantum electrodynamics and three-dimensional topologically massive quantum electrodynamics. We begin by addressing the problem on a general dimensionality making use of the perturbative Seiberg-Witten map to, thus, construct a general action, to only then specify the problem to two and three dimensions. The quantization takes place through the K\\"all\\'en-Lehmann spectral representation and Yang-Feldman-K\\"all\\'en formulation, where we calculate the respective spectral density function to the gauge field. Furthermore, regarding the photon two-point function, we disc...
Path Integral Quantization of Generalized Quantum Electrodynamics
Bufalo, Rodrigo; Zambrano, German Enrique Ramos
2010-01-01
It is shown in this paper a complete covariant quantization of Generalized Electrodynamics by path integral approach. To this goal we first studied the hamiltonian structure of system following Dirac's methodology, and then we follow the Faddeev-Senjanovic procedure to attain the amplitude transition. The complete propagators (Schwinger-Dyson-Fradkin equations) on correct gauge fixation and the generalized Ward-Fradkin-Takahashi identities are also obtained. Afterwards, an explicit calculation on one-loop approximation of all Green's functions and a discussion about the obtained results are presented.
Experiments on two-resonator circuit quantum electrodynamics. A superconducting quantum switch
Energy Technology Data Exchange (ETDEWEB)
Hoffmann, Elisabeth Christiane Maria
2013-05-29
The field of cavity quantum electrodynamics (QED) studies the interaction between light and matter on a fundamental level. In typical experiments individual natural atoms are interacting with individual photons trapped in three-dimensional cavities. Within the last decade the prospering new field of circuit QED has been developed. Here, the natural atoms are replaced by artificial solid state quantum circuits offering large dipole moments which are coupled to quasi-onedimensional cavities providing a small mode volume and hence a large vacuum field strength. In our experiments Josephson junction based superconducting quantum bits are coupled to superconducting microwave resonators. In circuit QED the number of parameters that can be varied is increased and regimes that are not accessible using natural atoms can be entered and investigated. Apart from design flexibility and tunability of system parameters a particular advantage of circuit QED is the scalability to larger system size enabled by well developed micro- and nanofabrication tools. When scaling up the resonator-qubit systems beyond a few coupled circuits, the rapidly increasing number of interacting subsystems requires an active control and directed transmission of quantum signals. This can, for example, be achieved by implementing switchable coupling between two microwave resonators. To this end, a superconducting flux qubit is used to realize a suitable coupling between two microwave resonators, all working in the Gigahertz regime. The resulting device is called quantum switch. The flux qubit mediates a second order tunable and switchable coupling between the resonators. Depending on the qubit state, this coupling can compensate for the direct geometric coupling of the two resonators. As the qubit may also be in a quantum superposition state, the switch itself can be ''quantum'': it can be a superposition of ''on'' and ''off''. This work
Quantum electrodynamics near a photonic band-gap
Liu, Yanbing; Houck, Andrew
Quantum electrodynamics predicts the localization of light around an atom in photonic band-gap (PBG) medium or photonic crystal. Here we report the first experimental realization of the strong coupling between a single artificial atom and an one dimensional PBG medium using superconducting circuits. In the photonic transport measurement, we observe an anomalous Lamb shift and a large band-edge avoided crossing when the artificial atom frequency is tuned across the band-edge. The persistent peak within the band-gap indicates the single photon bound state. Furthermore, we study the resonance fluorescence of this bound state, again demonstrating the breakdown of the Born-Markov approximation near the band-edge. This novel architecture can be directly generalized to study many-body quantum electrodynamics and to construct more complicated spin chain models.
Landau-Khalatnikov-Fradkin transformations in Reduced Quantum Electrodynamics
Ahmad, A; Concha-Sánchez, Y; Raya, A
2016-01-01
We derive the Landau-Khalatnikov-Frandkin transformation (LKFT) for the fermion propagator in quantum electrodynamics (QED) described within a brane-world inspired framework where photons are allowed to move in $d_\\gamma$ space-time (bulk) dimensions while electrons remain confined to a $d_e$-dimensional brane, with $d_e < d_\\gamma$, referred to in the literature as Reduced Quantum Electrodynamics, RQED$_{d_\\gamma,d_e}$. Specializing to the case of graphene, namely RQED$_{4,3}$ with massless fermions, we derive the non-perturbative form of the fermion propagator starting from its bare counterpart and then compare its weak coupling expansion to known one- and two-loop perturbative results. The agreement of the gauge dependent terms at order $\\alpha$ and $\\alpha^{2}$ is reminiscent from the structure of LKFT in ordinary QED in arbitrary space-time dimensions and provides strong constraints for the multiplicative renormalizability of RQED$_{d_\\gamma,d_e}$.
A Coherence Preservation Control Strategy in Cavity QED Based on Classical Quantum Feedback
Directory of Open Access Journals (Sweden)
Ming Li
2013-01-01
Full Text Available For eliminating the unexpected decoherence effect in cavity quantum electrodynamics (cavity QED, the transfer function of Rabi oscillation is derived theoretically using optical Bloch equations. In particular, the decoherence in cavity QED from the atomic spontaneous emission is especially considered. A feedback control strategy is proposed to preserve the coherence through Rabi oscillation stabilization. In the scheme, a classical quantum feedback channel for the quantum information acquisition is constructed via the quantum tomography technology, and a compensation system based on the root locus theory is put forward to suppress the atomic spontaneous emission and the associated decoherence. The simulation results have proved its effectiveness and superiority for the coherence preservation.
Progress in quantum electrodynamics theory of highly charged ions
Volotka, A. V.; Glazov, D. A.; Plunien, G.; Shabaev, V. M.
2013-01-01
Recent progress in quantum electrodynamics (QED) calculations of highly charged ions is reviewed. The theoretical predictions for the binding energies, the hyperfine splittings, and the g factors are presented and compared with available experimental data. Special attention is paid to tests of bound-state QED at strong field regime. Future prospects for tests of QED at the strongest electric and magnetic fields as well as for determination of the fine structure constant and the nuclear magnet...
Quantum electrodynamics of one-photon wave packets
Stobińska, M; Leuchs, G
2010-01-01
In this contribution we investigate quantum electrodynamical many-mode aspects by exploring the simplest possible situation in this context, namely the interaction of a single atom, modeled by a simple two-level system, with many-mode one-photon quantum states of the electromagnetic field. In particular, we concentrate on the question how the engineering of electromagnetic field modes influences the atom-field interaction. An interesting problem in this context is the engineering of ideal one-photon multi-mode quantum states which may excite a single atom perfectly [M. Stobi\\'nska, G. Alber, and G. Leuchs, EPL {\\bf 86}, 14007 (2009)]. For purposes of quantum information processing such one-photon multi-mode states are particularly well suited for transmitting quantum information and for storing it in a material memory again.
High-energy limit of quantum electrodynamics beyond Sudakov approximation
Directory of Open Access Journals (Sweden)
Alexander A. Penin
2015-05-01
Full Text Available We study the high-energy behavior of the scattering amplitudes in quantum electrodynamics beyond the leading order of the small electron mass expansion in the leading logarithmic approximation. In contrast to the Sudakov logarithms, the mass-suppressed double-logarithmic radiative corrections are induced by a soft electron pair exchange and result in enhancement of the power-suppressed contribution, which dominates the amplitudes at extremely high energies. Possible applications of our result to the analysis of the high-energy processes in quantum chromodynamics is also discussed.
High-energy limit of quantum electrodynamics beyond Sudakov approximation
Energy Technology Data Exchange (ETDEWEB)
Penin, Alexander A., E-mail: penin@ualberta.ca [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2J1 (Canada); Institut für Theoretische Teilchenphysik, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany)
2015-05-18
We study the high-energy behavior of the scattering amplitudes in quantum electrodynamics beyond the leading order of the small electron mass expansion in the leading logarithmic approximation. In contrast to the Sudakov logarithms, the mass-suppressed double-logarithmic radiative corrections are induced by a soft electron pair exchange and result in enhancement of the power-suppressed contribution, which dominates the amplitudes at extremely high energies. Possible applications of our result to the analysis of the high-energy processes in quantum chromodynamics is also discussed.
Nanoscale electrodynamics of strongly correlated quantum materials
Liu, Mengkun; Sternbach, Aaron J.; Basov, D. N.
2017-01-01
Electronic, magnetic, and structural phase inhomogeneities are ubiquitous in strongly correlated quantum materials. The characteristic length scales of the phase inhomogeneities can range from atomic to mesoscopic, depending on their microscopic origins as well as various sample dependent factors. Therefore, progress with the understanding of correlated phenomena critically depends on the experimental techniques suitable to provide appropriate spatial resolution. This requirement is difficult to meet for some of the most informative methods in condensed matter physics, including infrared and optical spectroscopy. Yet, recent developments in near-field optics and imaging enabled a detailed characterization of the electromagnetic response with a spatial resolution down to 10 nm. Thus it is now feasible to exploit at the nanoscale well-established capabilities of optical methods for characterization of electronic processes and lattice dynamics in diverse classes of correlated quantum systems. This review offers a concise description of the state-of-the-art near-field techniques applied to prototypical correlated quantum materials. We also discuss complementary microscopic and spectroscopic methods which reveal important mesoscopic dynamics of quantum materials at different energy scales.
Quantum Electrodynamics with the Pauli Term
Sastry, R R
1999-01-01
The quantum field theory of extended objects is employed to address the hitherto nonrenormalizable Pauli interaction. This is achieved by quantizing the Dirac field using the infinite dimensional generalization of the extended object formulation. The order $\\alpha$ contribution to the anomalous magnetic moment of the electron (and of the muon) arising from the Pauli term is calculated.
Multi-qubit circuit quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Viehmann, Oliver
2013-09-03
Circuit QED systems are macroscopic, man-made quantum systems in which superconducting artificial atoms, also called Josephson qubits, interact with a quantized electromagnetic field. These systems have been devised to mimic the physics of elementary quantum optical systems with real atoms in a scalable and more flexible framework. This opens up a variety of possible applications of circuit QED systems. For instance, they provide a promising platform for processing quantum information. Recent years have seen rapid experimental progress on these systems, and experiments with multi-component circuit QED architectures are currently starting to come within reach. In this thesis, circuit QED systems with multiple Josephson qubits are studied theoretically. We focus on simple and experimentally realistic extensions of the currently operated circuit QED setups and pursue investigations in two main directions. First, we consider the equilibrium behavior of circuit QED systems containing a large number of mutually noninteracting Josephson charge qubits. The currently accepted standard description of circuit QED predicts the possibility of superradiant phase transitions in such systems. However, a full microscopic treatment shows that a no-go theorem for superradiant phase transitions known from atomic physics applies to circuit QED systems as well. This reveals previously unknown limitations of the applicability of the standard theory of circuit QED to multi-qubit systems. Second, we explore the potential of circuit QED for quantum simulations of interacting quantum many-body systems. We propose and analyze a circuit QED architecture that implements the quantum Ising chain in a time-dependent transverse magnetic field. Our setup can be used to study quench dynamics, the propagation of localized excitations, and other non-equilibrium features in this paradigmatic model in the theory of non-equilibrium thermodynamics and quantumcritical phenomena. The setup is based on a
Quantum electrodynamics with 1D arti cial atoms
DEFF Research Database (Denmark)
Javadi, Alisa
atom. One of the signatures and functions of a 1D atom is the nonlinear optical response at the single-photon level. A PCW chip is designed to experimentally study the transmission spectrum of an embedded QD. The transmission spectrum is shown to be modi_ed by 30% around the resonance of the QD......A 1D atom, a single quantum emitter coupled to a single optical mode, exhibits rich quantum electrodynamic (QED) e_ects and is thought to be the key ingredient for many applications in quantuminformation processing. Single quantum dots (QD) in photonic-crystal waveguides (PCW) constitute a robust...... platform for realizing a 1D atom, and are the subject of theoretical and experimental investigations in this thesis. We use _nite element method in 3D to calculate the local density of states (LDOS) in photonic-crystal membranes. The detailed spatial maps show strong inhibition of LDOS in the bandgap...
Entangling distant resonant exchange qubits via circuit quantum electrodynamics
Srinivasa, V.; Taylor, J. M.; Tahan, Charles
2016-11-01
We investigate a hybrid quantum system consisting of spatially separated resonant exchange qubits, defined in three-electron semiconductor triple quantum dots, that are coupled via a superconducting transmission line resonator. Drawing on methods from circuit quantum electrodynamics and Hartmann-Hahn double resonance techniques, we analyze three specific approaches for implementing resonator-mediated two-qubit entangling gates in both dispersive and resonant regimes of interaction. We calculate entangling gate fidelities as well as the rate of relaxation via phonons for resonant exchange qubits in silicon triple dots and show that such an implementation is particularly well suited to achieving the strong coupling regime. Our approach combines the favorable coherence properties of encoded spin qubits in silicon with the rapid and robust long-range entanglement provided by circuit QED systems.
Applications of the Fokker-Planck equation in circuit quantum electrodynamics
Elliott, Matthew; Ginossar, Eran
2016-10-01
We study exact solutions of the steady-state behavior of several nonlinear open quantum systems which can be applied to the field of circuit quantum electrodynamics. Using Fokker-Planck equations in the generalized P representation, we investigate the analytical solutions of two fundamental models. First, we solve for the steady-state response of a linear cavity that is coupled to an approximate transmon qubit and use this solution to study both the weak and strong driving regimes, using analytical expressions for the moments of both cavity and transmon fields, along with the Husimi Q function for the transmon. Second, we revist exact solutions of a quantum Duffing oscillator, which is driven both coherently and parametrically while also experiencing decoherence by the loss of single photons and pairs of photons. We use this solution to discuss both stabilization of Schrödinger cat states and the generation of squeezed states in parametric amplifiers, in addition to studying the Q functions of the different phases of the quantum system. The field of superconducting circuits, with its strong nonlinearities and couplings, has provided access to parameter regimes in which returning to these exact quantum optics methods can provide valuable insights.
Casimir effect from macroscopic quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Philbin, T G, E-mail: tgp3@st-andrews.ac.uk [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS (United Kingdom)
2011-06-15
The canonical quantization of macroscopic electromagnetism was recently presented in (Philbin 2010 New J. Phys. 12 123008). This theory is used here to derive the Casimir effect, by considering the special case of thermal and zero-point fields. The stress-energy-momentum tensor of the canonical theory follows from Noether's theorem, and its electromagnetic part in thermal equilibrium gives the Casimir energy density and stress tensor. The results hold for arbitrary inhomogeneous magnetodielectrics and are obtained from a rigorous quantization of electromagnetism in dispersive, dissipative media. Continuing doubts about the status of the standard Lifshitz theory as a proper quantum treatment of Casimir forces do not apply to the derivation given here. Moreover, the correct expressions for the Casimir energy density and stress tensor inside media follow automatically from the simple restriction to thermal equilibrium, without the need for complicated thermodynamical or mechanical arguments.
Infrared multiphoton resummation in quantum electrodynamics
Mati, P
2015-01-01
Infrared singularities in massless gauge theories are known since the foundation of quantum field theories. The root of this problem can be tracked back to the very definition of these long-range interacting theories such as QED. It can be shown that singularities are caused by the massless degrees of freedom (i.e. the photons in the case of QED). In the Bloch-Nordsieck model the absence of the infrared catastrophe can be shown exactly by the complete summation of the radiative corrections. In this paper we will give the idea of the derivation of the Bloch-Nordsieck propagator, that describes the infrared structure of the electron propagation, at zero and finite temperatures. Some ideas of the possible applications are also mentioned.
Quantum electrodynamics of inhomogeneous anisotropic media
Lopez, Adrian E Rubio
2014-01-01
In this work we calculate the closed time path (CTP) generating functional for the electromagnetic (EM) field interacting with inhomogeneous anisotropic matter. For this purpose, we first find a general expression for the electromagnetic field's influence action from the interaction of the field with a composite environment consisting in the quantum polarization degrees of freedom in each point of space, at arbitrary temperatures, connected to thermal baths. Then, we evaluate the generating functional for the gauge field, in the temporal gauge, by implementing the Faddeev-Popov procedure. Finally, through the point-splitting technique, we calculate closed expressions for the energy, the Poynting vector and the Maxwell tensor in terms of the Hadamard propagator. We show that all the quantities have contributions from the field's initial conditions and also from the matter degrees of freedom. Throughout the whole work we discuss and give insights about how the gauge invariance must be treated in the formalism w...
Strong-Field Quantum Electrodynamics and Muonic Hydrogen
Jentschura, U D
2014-01-01
We explore the possibility of a breakdown of perturbative quantum electrodynamics in light muonic bound systems, notably, muonic hydrogen. The average electric field seen by a muon orbiting a proton is shown to be comparable to hydrogenlike Uranium and, notably, larger than the electric field achievable using even the most advanced strong-laser facilities. Following Maltman and Isgur who have shown that fundamental forces such as the meson exchange force may undergo a qualitative change in the strong-coupling regime, we investigate a concomitant possible existence of muon-proton and electron-proton contact interactions, of nonperturbative origin, and their influence on transition frequencies in light one-muon ions.
Single-photon transistor in circuit quantum electrodynamics.
Neumeier, Lukas; Leib, Martin; Hartmann, Michael J
2013-08-01
We introduce a circuit quantum electrodynamical setup for a "single-photon" transistor. In our approach photons propagate in two open transmission lines that are coupled via two interacting transmon qubits. The interaction is such that no photons are exchanged between the two transmission lines but a single photon in one line can completely block or enable the propagation of photons in the other line. High on-off ratios can be achieved for feasible experimental parameters. Our approach is inherently scalable as all photon pulses can have the same pulse shape and carrier frequency such that output signals of one transistor can be input signals for a consecutive transistor.
Relativistic and quantum electrodynamics effects in the helium pair potential.
Przybytek, M; Cencek, W; Komasa, J; Łach, G; Jeziorski, B; Szalewicz, K
2010-05-01
The helium pair potential was computed including relativistic and quantum electrodynamics contributions as well as improved accuracy adiabatic ones. Accurate asymptotic expansions were used for large distances R. Error estimates show that the present potential is more accurate than any published to date. The computed dissociation energy and the average R for the (4)He(2) bound state are 1.62+/-0.03 mK and 47.1+/-0.5 A. These values can be compared with the measured ones: 1.1(-0.2)(+0.3) mK and 52+/-4 A [R. E. Grisenti, Phys. Rev. Lett. 85, 2284 (2000)].
Solvable Models Of Infrared Gupta-Bleuler Quantum Electrodynamics
Zerella, Simone
2010-01-01
Solvable hamiltonian models are employed to investigate the extent and limitations of the procedures adopted in the perturbative treatment of the infrared divergences, occurring in the Feynman-Dyson expansion of Quantum Electrodynamics. Isometric M\\"oller operators are obtained in the presence of an infrared regularization, after the removal of an adiabatic switching, with the aid of a suitable mass renormalization. We gain an hamiltonian control of the Yennie-Frautschi-Suura infrared factors and discuss the implications on the perturbative prescriptions for inclusive cross-sections.
Landau-Zener-Stückelberg-Majorana lasing in circuit quantum electrodynamics
Neilinger, P.; Shevchenko, S. N.; Bogár, J.; Rehák, M.; Oelsner, G.; Karpov, D. S.; Hübner, U.; Astafiev, O.; Grajcar, M.; Il'ichev, E.
2016-09-01
We demonstrate amplification (and attenuation) of a probe signal by a driven two-level quantum system in the Landau-Zener-Stückelberg-Majorana regime by means of an experiment, in which a superconducting qubit was strongly coupled to a microwave cavity, in a conventional arrangement of circuit quantum electrodynamics. Two different types of flux qubit, specifically a conventional Josephson junctions qubit and a phase-slip qubit, show similar results, namely, lasing at the working points where amplification takes place. The experimental data are explained by the interaction of the probe signal with Rabi-like oscillations. The latter are created by constructive interference of Landau-Zener-Stückelberg-Majorana (LZSM) transitions during the driving period of the qubit. A detailed description of the occurrence of these oscillations and a comparison of obtained data with both analytic and numerical calculations are given.
Relativistic quantum transport theory for electrodynamics
Zhuang, P; Zhuang, P; Heinz, U
1995-01-01
We investigate the relationship between the covariant and the three-dimensional (equal-time) formulations of quantum kinetic theory. We show that the three-dimensional approach can be obtained as the energy average of the covariant formulation. We illustrate this statement in scalar and spinor QED. For scalar QED we derive Lorentz covariant transport and constraint equations directly from the Klein-Gordon equation rather than through the previously used Feshbach-Villars representation. We then consider pair production in a spatially homogeneous but time-dependent electric field and show that the pair density is derived much more easily via the energy averaging method than in the equal-time representation. Proceeding to spinor QED, we derive the covariant version of the equal-time equation derived by Bialynicki-Birula et al. We show that it must be supplemented by another self-adjoint equation to obtain a complete description of the covariant spinor Wigner operator. After spinor decomposition and energy averag...
Dispersion relations in quantum electrodynamics on the noncommutative Minkowski space
Energy Technology Data Exchange (ETDEWEB)
Zahn, J.W.
2006-12-15
We study field theories on the noncommutative Minkowski space with noncommuting time. The focus lies on dispersion relations in quantized interacting models in the Yang-Feldman formalism. In particular, we compute the two-point correlation function of the field strength in noncommutative quantum electrodynamics to second order. At this, we take into account the covariant coordinates that allow the construction of local gauge invariant quantities (observables). It turns out that this does not remove the well-known severe infrared problem, as one might have hoped. Instead, things become worse, since nonlocal divergences appear. We also show that these cancel in a supersymmetric version of the theory if the covariant coordinates are adjusted accordingly. Furthermore, we study the {phi}{sup 3} and the Wess-Zumino model and show that the distortion of the dispersion relations is moderate for parameters typical for the Higgs field. We also discuss the formulation of gauge theories on noncommutative spaces and study classical electrodynamics on the noncommutative Minkowski space using covariant coordinates. In particular, we compute the change of the speed of light due to nonlinear effects in the presence of a background field. Finally, we examine the so-called twist approach to quantum field theory on the noncommutative Minkowski space and point out some conceptual problems of this approach. (orig.)
Scheme for implementing quantum dense coding with W-class state in cavity QED
Institute of Scientific and Technical Information of China (English)
He Juan; Ye Liu; Ni Zhi-Xiang
2008-01-01
An experimentally feasible protocol for realizing dense coding by using a class of W-state in cavity quantum electrodynamics (QED) is proposed in this paper.The prominent advantage of our scheme is that the succeasful probability of the dense coding with a W-class state can reach 1.In addition,the scheme can be implemented by the present cavity QED techniques.
Hu, Can-Ming
2015-01-01
Merging the progress of spintronics with the advancement in cavity quantum electrodynamics and cavity polaritons, a new field of Cavity Spintronics is forming, which connects some of the most exciting modern physics, such as quantum information and quantum optics, with one of the oldest science on the earth, the magnetism.
Cavity tests of parity-odd Lorentz violations in electrodynamics
Mewes, Matthew; Petroff, Alexander
2007-03-01
Electromagnetic resonant cavities form the basis for a number modern tests of Lorentz invariance. The geometry of most of these experiments implies unsuppressed sensitivities to parity-even Lorentz violations only. Parity-odd violations typically enter through suppressed boost effects, causing a reduction in sensitivity by roughly 4 orders of magnitude. Here we discuss possible techniques for achieving unsuppressed sensitivities to parity-odd violations using asymmetric resonators.
Quantum corrections to the Larmor radiation formula in scalar electrodynamics
Higuchi, A
2009-01-01
We use the semi-classical approximation in perturbative scalar quantum electrodynamics to calculate the quantum correction to the Larmor radiation formula to first order in Planck's constant in the non-relativistic approximation, choosing the initial state of the charged particle to be a momentum eigenstate. We calculate this correction in two cases: in the first case the charged particle is accelerated by a time-dependent but space-independent vector potential whereas in the second case it is accelerated by a time-independent vector potential which is a function of one spatial coordinate. We find that the corrections in these two cases are different even for a charged particle with the same classical motion. The correction in each case turns out to be non-local in time in contrast to the classical approximation.
Dipolar quantum electrodynamics of the two-dimensional electron gas
Todorov, Yanko
2015-03-01
Similarly to a previous work on the homogeneous electron gas [Y. Todorov, Phys. Rev. B 89, 075115 (2014), 10.1103/PhysRevB.89.075115], we apply the Power-Zienau-Wooley (PZW) formulation of the quantum electrodynamics to the case of an electron gas quantum confined by one-dimensional potential. We provide a microscopic description of all collective plasmon modes of the gas, oscillating both along and perpendicular to the direction of quantum confinement. Furthermore, we study the interaction of the collective modes with a photonic structure, planar metallic waveguide, by using the full expansion of the electromagnetic field into normal modes. We show how the boundary conditions for the electromagnetic field influence both the transverse light-matter coupling and the longitudinal particle-particle interactions. The PZW descriptions appear thus as a convenient tool to study semiconductor quantum optics in geometries where quantum-confined particles interact with strongly confined electromagnetic fields in microresonators, such as the ones used to achieve the ultrastrong light-matter coupling regime.
Institute of Scientific and Technical Information of China (English)
ZHENG An-Shou; LIU Ji-Bing; XIANG Dong; LIU Cui-Lan; YUAN Hong
2007-01-01
An alternative approach is proposed to realize an n-qubit Toffoli gate with superconducting quantum-interference devices (SQUIDs) in cavity quantum electrodynamics (QED). In the proposal, we represent two logical gates of a qubit with the two lowest levels of a SQUID while a higher-energy intermediate level of each SQUID is utilized for the gate manipulation. During the operating process, because the cavity field is always in vacuum state, the requirement on the cavity is greatly loosened and there is no transfer of quantum information between the cavity and SQUIDs.
Quantum networks based on cavity QED
Energy Technology Data Exchange (ETDEWEB)
Ritter, Stephan; Bochmann, Joerg; Figueroa, Eden; Hahn, Carolin; Kalb, Norbert; Muecke, Martin; Neuzner, Andreas; Noelleke, Christian; Reiserer, Andreas; Uphoff, Manuel; Rempe, Gerhard [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany)
2014-07-01
Quantum repeaters require an efficient interface between stationary quantum memories and flying photons. Single atoms in optical cavities are ideally suited as universal quantum network nodes that are capable of sending, storing, retrieving, and even processing quantum information. We demonstrate this by presenting an elementary version of a quantum network based on two identical nodes in remote, independent laboratories. The reversible exchange of quantum information and the creation of remote entanglement are achieved by exchange of a single photon. Quantum teleportation is implemented using a time-resolved photonic Bell-state measurement. Quantum control over all degrees of freedom of the single atom also allows for the nondestructive detection of flying photons and the implementation of a quantum gate between the spin state of the atom and the polarization of a photon upon its reflection from the cavity. Our approach to quantum networking offers a clear perspective for scalability and provides the essential components for the realization of a quantum repeater.
di, Tiegang; Hillery, Mark; Zubairy, M. Suhail
2004-09-01
We discuss a possible experimental scheme for the implementation of a quantum walk. The scheme is based on the passage of an atom inside a high- Q cavity. The chirality is characterized by the atomic states and the displacement is characterized by the photon number inside the cavity. The quantum steps are described by appropriate interactions with a sequence of classical and quantized cavity fields.
Quantum electrodynamics and plasmonic resonance of metallic nanostructures.
Zhang, Mingliang; Xiang, Hongping; Zhang, Xu; Lu, Gang
2016-04-20
Plasmonic resonance of a metallic nanostructure results from coherent motion of its conduction electrons driven by incident light. At the resonance, the induced dipole in the nanostructure is proportional to the number of the conduction electrons, hence 10(7) times larger than that in an atom. The interaction energy between the induced dipole and fluctuating virtual field of the incident light can reach a few tenths of an eV. Therefore, the classical electromagnetism dominating the field may become inadequate. We propose that quantum electrodynamics (QED) may be used as a fundamental theory to describe the interaction between the virtual field and the oscillating electrons. Based on QED, we derive analytic expressions for the plasmon resonant frequency, which depends on three easily accessible material parameters. The analytic theory reproduces very well the experimental data, and can be used in rational design of materials for plasmonic applications.
Quantum Electrodynamics Effects in Rovibrational Spectra of Molecular Hydrogen.
Komasa, Jacek; Piszczatowski, Konrad; Łach, Grzegorz; Przybytek, Michał; Jeziorski, Bogumił; Pachucki, Krzysztof
2011-10-11
The dissociation energies from all rovibrational levels of H2 and D2 in the ground electronic state are calculated with high accuracy by including relativistic and quantum electrodynamics (QED) effects in the nonadiabatic treatment of the nuclear motion. For D2, the obtained energies have theoretical uncertainties of 0.001 cm(-1). For H2, similar uncertainties are for the lowest levels, while for the higher ones the uncertainty increases to 0.005 cm(-1). Very good agreement with recent high-resolution measurements of the rotational v = 0 levels of H2, including states with large angular momentum J, is achieved. This agreement would not have been possible without accurate evaluation of the relativistic and QED contributions and may be viewed as the first observation of the QED effects, mainly the electron self-energy, in a molecular spectrum. For several electric quadrupole transitions, we still observe certain disagreement with experimental results, which remains to be explained.
Higgs-Like Particle due to Revised Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Lehnert B.
2013-07-01
Full Text Available A Higgs-like particle having zero net electric charge, zero spin, and a nonzero rest mass can be deduced from an earlier elaborated revised quantum electrodynamical theory which is based on linear symmetry breaking through a nonzero electric ﬁeld divergence in the vacuum state. This special particle is obtained from a composite longitudinal solution based on a zero magnetic ﬁeld strength and on a nonzero divergence but a vanishing curl of the electric ﬁeld strength. The present theory further diﬀers from that of the nonlinear spontaneously broken symmetry by Higgs, in which elementary particles obtain their masses through an interaction with the Higgs ﬁeld. An experimental proof of the basic features of a Higgs-like particle thus supports the present theory, but does not for certain conﬁrm the process which would generate massive particles through a Higgs ﬁeld
Quantum electrodynamical corrections to a magnetic dipole in general relativity
Pétri, J
2015-01-01
Magnetized neutron stars are privileged places where strong electromagnetic fields as high as $\\BQ=4.4\\times10^9$~T exist, giving rise to non-linear corrections to Maxwell equations described by quantum electrodynamics (QED). These corrections need to be included to the general relativistic (GR) description of a magnetic dipole supposed to be anchored in the neutron star. In this paper, these QED and GR perturbations to the standard flat space-time dipole are calculated to the lowest order in the fine structure constant~$\\alpha_{\\rm sf}$ and to any order in the ratio $\\Rs/R$ where $R$ is the neutron star radius and $\\Rs$ its Schwarzschild radius. Following our new 3+1~formalism developed in a previous work, we compute the multipolar non-linear corrections to this dipole and demonstrate the presence of a small dipolar~$\\ell=1$ and hexapolar~$\\ell=3$ component.
Quantum electrodynamics and plasmonic resonance of metallic nanostructures
Zhang, Mingliang; Xiang, Hongping; Zhang, Xu; Lu, Gang
2016-04-01
Plasmonic resonance of a metallic nanostructure results from coherent motion of its conduction electrons driven by incident light. At the resonance, the induced dipole in the nanostructure is proportional to the number of the conduction electrons, hence 107 times larger than that in an atom. The interaction energy between the induced dipole and fluctuating virtual field of the incident light can reach a few tenths of an eV. Therefore, the classical electromagnetism dominating the field may become inadequate. We propose that quantum electrodynamics (QED) may be used as a fundamental theory to describe the interaction between the virtual field and the oscillating electrons. Based on QED, we derive analytic expressions for the plasmon resonant frequency, which depends on three easily accessible material parameters. The analytic theory reproduces very well the experimental data, and can be used in rational design of materials for plasmonic applications.
Quantum electrodynamic corrections for valence electrons in Eka-Hg
Golovko, O. A.; Goidenko, I. A.; Tupitsyn, I. I.
2008-05-01
The quantum electrodynamic (QED) corrections to the coupling energy of valence electrons in heavy and superheavy nuclei are calculated in the effective local-potential approximation, as well as by the Hartree-Fock-Dirac self-consistent method. It is clearly shown that the contribution from the QED corrections is within the accuracy of modern calculations, which do not take into account QED effects. It is shown that, in certain cases, to exactly calculate the coupling energy of electrons in heavy and superheavy atoms, it is necessary to take into account the self-consistency, which shows that the inaccuracy of the use of the method of the effective local potential in calculations of QED effects can exceed 10%, which is also within the limits of calculations of the coupling energy without taking into account QED effects.
Renormalization group approach to scalar quantum electrodynamics on de Sitter
González, Francisco Fabián
2016-01-01
We consider the quantum loop effects in scalar electrodynamics on de Sitter space by making use of the functional renormalization group approach. We first integrate out the photon field, which can be done exactly to leading (zeroth) order in the gradients of the scalar field, thereby making this method suitable for investigating the dynamics of the infrared sector of the theory. Assuming that the scalar remains light we then apply the functional renormalization group methods to the resulting effective scalar theory and focus on investigating the effective potential, which is the leading order contribution in the gradient expansion of the effective action. We find symmetry restoration at a critical renormalization scale $\\kappa=\\kappa_{\\rm cr}$ much below the Hubble scale $H$. When compared with the results of Serreau and Guilleux [arXiv:1306.3846 [hep-th], arXiv:1506.06183 [hep-th
Quantum Dynamics of Nonlinear Cavity Systems
Nation, Paul D.
2010-01-01
We investigate the quantum dynamics of three different configurations of nonlinear cavity systems. To begin, we carry out a quantum analysis of a dc superconducting quantum interference device (SQUID) mechanical displacement detector comprised of a SQUID with a mechanically compliant loop segment. The SQUID is approximated by a nonlinear current-dependent inductor, inducing a flux tunable nonlinear Duffing term in the cavity equation of motion. Expressions are derived for the detector signal ...
On The Origin Of The Classical And Quantum Electrodynamic Arrows Of Time
Leiter, Darryl
2009-01-01
In order to describe the microscopic classical electrodynamic measurement process in an operational, relativistic, observer-participant manner, an Abelian operator symmetry of microscopic observer-participation called Measurement Color (MC) is incorporated into the field theoretic structure of the Classical Electrodynamics (CED) of interacting point charges. The new formalism, called Measurement Color Classical Electrodynamics (MC-CED), is shown to be a nonlocal, time reversal violating, classical field theory of interacting point charges in which a microscopic classical electrodynamic arrow of time emerges dynamically, independent of any external thermodynamic or cosmological assumptions. We then show how the standard canonical quantum field quantization program can be applied to the classical observer-participant MC-CED theory. This leads to the development of a relativistic, observer-participant Measurement Color Quantum Electrodynamic (MC-QED) formalism in the Heisenberg Picture, which contains an intrins...
Role of the lightmatter coupling strength on nonMarkovian phonon effects in semiconductor cavity QED
DEFF Research Database (Denmark)
Nielsen, Per Kær; Nielsen, Torben Roland; Lodahl, Peter;
2011-01-01
Semiconductor cavity quantum electrodynamical (CQED) devices are believed to be important components for future quantum information technologies. Being composed of a single quantum dot (QD) embedded in a cavity, semiconductor CQED systems resemble atomic CQED systems. However, recent experiments ...
Quantum Electrodynamics of Quantum Dot-Metal Nanoparticles Molecules
Ridolfo, A; Fina, N; Saija, R; Savasta, S
2010-01-01
We study theoretically the quantum optical properties of hybrid molecules composed of an individual quantum dot and a metallic nanoparticle. We calculate the resonance fluorescence of this hybrid system. Its incoherent part, the one arising from nonlinear quantum processes, results to be enhanced by more than two orders of magnitude as compared to that in the absence of the metallic nanoparticle. Scattering spectra at different excitation powers and nonperturbative calculations of intensity-field correlation functions show that this system can act as a nonlinear ultra-compact two-photon switch for incident photons, where the presence (or absence) of a single incident photon field is sufficient to allow (or prevent) the scattering of subsequent photons. We also find that a small frequency shift of the incident light field may cause changes in the intensity field correlation function of orders of magnitude.
Enhancing Quantum Discord in Cavity QED by Applying Classical Driving Field
Institute of Scientific and Technical Information of China (English)
QIAN Yi; XU Jing-Bo
2012-01-01
We investigate the quantum discord dynamics in a cavity quantum electrodynamics system, which consists of two noninteracting two-level atoms driven by independent optical Gelds and classical fields, and find that the quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution in the absence of classical fields. It is shown that the amount of quantum discord can be increased by adjusting the classical driving fields because the increasing degree of the amount of quantum mutual information is greater than classical correlation by applying the classical driving fields. Finally, the influence of the classical driving field on the fidelity of the system is also examined.%We investigate the quantum discord dynamics in a cavity quantum electrodynamics system,which consists of two noninteracting two-level atoms driven by independent optical fields and classical fields,and find that the quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution in the absence of classical fields.It is shown that the amount of quantum discord can be increased by adjusting the classical driving fields because the increasing degree of the amount of quantum mutual information is greater than classical correlation by applying the classical driving fields.Finally,the influence of the classical driving field on the fidelity of the system is also examined.
Student friendly quantum field theory basic principles & quantum electrodynamics
Klauber, Robert D
2013-01-01
By incorporating extensive student input and innovative teaching methodologies, this book aims to make the process of learning quantum field theory easier, and thus more rapid, profound, and efficient, for both students and instructors. Comprehensive explanations are favored over conciseness, every step in derivations is included, and ‘big picture’ overviews are provided throughout. Typical student responses indicate how well the text achieves its aim.
Nanobeam photonic crystal cavity quantum dot laser
Gong, Yiyang; Shambat, Gary; Sarmiento, Tomas; Harris, James S; Vuckovic, Jelena
2010-01-01
The lasing behavior of one dimensional GaAs nanobeam cavities with embedded InAs quantum dots is studied at room temperature. Lasing is observed throughout the quantum dot PL spectrum, and the wavelength dependence of the threshold is calculated. We study the cavity lasers under both 780 nm and 980 nm pump, finding thresholds as low as 0.3 uW and 19 uW for the two pump wavelengths, respectively. Finally, the nanobeam cavity laser wavelengths are tuned by up to 7 nm by employing a fiber taper in near proximity to the cavities. The fiber taper is used both to efficiently pump the cavity and collect the cavity emission.
Many-body quantum electrodynamics networks: Non-equilibrium condensed matter physics with light
Le Hur, Karyn; Henriet, Loïc; Petrescu, Alexandru; Plekhanov, Kirill; Roux, Guillaume; Schiró, Marco
2016-10-01
We review recent developments regarding the quantum dynamics and many-body physics with light, in superconducting circuits and Josephson analogues, by analogy with atomic physics. We start with quantum impurity models addressing dissipative and driven systems. Both theorists and experimentalists are making efforts towards the characterization of these non-equilibrium quantum systems. We show how Josephson junction systems can implement the equivalent of the Kondo effect with microwave photons. The Kondo effect can be characterized by a renormalized light frequency and a peak in the Rayleigh elastic transmission of a photon. We also address the physics of hybrid systems comprising mesoscopic quantum dot devices coupled with an electromagnetic resonator. Then, we discuss extensions to Quantum Electrodynamics (QED) Networks allowing one to engineer the Jaynes-Cummings lattice and Rabi lattice models through the presence of superconducting qubits in the cavities. This opens the door to novel many-body physics with light out of equilibrium, in relation with the Mott-superfluid transition observed with ultra-cold atoms in optical lattices. Then, we summarize recent theoretical predictions for realizing topological phases with light. Synthetic gauge fields and spin-orbit couplings have been successfully implemented in quantum materials and with ultra-cold atoms in optical lattices - using time-dependent Floquet perturbations periodic in time, for example - as well as in photonic lattice systems. Finally, we discuss the Josephson effect related to Bose-Hubbard models in ladder and two-dimensional geometries, producing phase coherence and Meissner currents. The Bose-Hubbard model is related to the Jaynes-Cummings lattice model in the large detuning limit between light and matter (the superconducting qubits). In the presence of synthetic gauge fields, we show that Meissner currents subsist in an insulating Mott phase. xml:lang="fr"
The quantum Hall's effect:A quantum electrodynamic phenomenon
Institute of Scientific and Technical Information of China (English)
A.I. Arbab
2012-01-01
We have applied Maxwell's equations to study the physics of quantum Hall's effect.The electromagnetic properties of this system are obtained.The Hall's voltage,VH =2πh2ns/e rn,where ns is the electron number density,for a 2-dimensional system,and h =2πh is the Planck's constant,is found to coincide with the voltage drop across the quantum capacitor.Consideration of the cyclotronic motion of electrons is found to give rise to Hall's resistance.Ohmic resistances in the horizontal and vertical directions have been found to exist before equilibrium state is reached.At a fundamental level,the Hall's effect is found to be equivalent to a resonant LCR circuit with LH =2π m/e2ns and CH =me2/2πh2ns satisfying the resonance condition with resonant frequency equal to the inverse of the scattering (relaxation) time,Ts.The Hall's resistance is found to be RH =√LH/CH.The Hall's resistance may be connected with the impedance that the electron wave experiences when it propagates in the 2-dimeasional gas.
Nonlinear quantum electrodynamic and electroweak processes in strong laser fields
Energy Technology Data Exchange (ETDEWEB)
Meuren, Sebastian
2015-06-24
Various nonlinear electrodynamic and electroweak processes in strong plane-wave laser fields are considered with an emphasis on short-pulse effects. In particular, the momentum distribution of photoproduced electron-positron pairs is calculated numerically and a semiclassical interpretation of its characteristic features is established. By proving the optical theorem, compact double-integral expressions for the total pair-creation probability are obtained and numerically evaluated. The exponential decay of the photon wave function in a plane wave is included by solving the Schwinger-Dyson equations to leading-order in the quasistatic approximation. In this respect, the polarization operator in a plane wave is investigated and its Ward-Takahashi identity verified. A classical analysis indicates that a photoproduced electron-positron pair recollides for certain initial conditions. The contributions of such recollision processes to the polarization operator are identified and calculated both analytically and numerically. Furthermore, the existence of nontrivial electron-spin dynamics induced by quantum fluctuations is verified for ultra-short laser pulses. Finally, the exchange of weak gauge bosons is considered, which is essential for neutrino-photon interactions. In particular, the axial-vector-vector coupling tensor is calculated and the so-called Adler-Bell-Jackiw (ABJ) anomaly investigated.
Quantum electrodynamic approach to the conductivity of gapped graphene
Klimchitskaya, G. L.; Mostepanenko, V. M.
2016-11-01
The electrical conductivity of graphene with a nonzero mass-gap parameter is investigated starting from the first principles of quantum electrodynamics in (2+1)-dimensional space time at any temperature. The formalism of the polarization tensor defined over the entire plane of complex frequency is used. At zero temperature we reproduce the results for both real and imaginary parts of the conductivity, obtained previously in the local approximation, and generalize them taking into account the effects of nonlocality. At nonzero temperature the exact analytic expressions for real and imaginary parts of the longitudinal and transverse conductivities of gapped graphene are derived, as well as their local limits and approximate expressions in several asymptotic regimes. Specifically, a simple local result for the real part of conductivity of gapped graphene valid at any temperature is obtained. According to our results, the real part of the conductivity is not equal to zero for frequencies exceeding the width of the gap and goes to the universal conductivity with increasing frequency. The imaginary part of conductivity of gapped graphene varies from infinity at zero frequency to minus infinity at the frequency defined by the gap parameter and then goes to zero with further increase of frequency. The analytic expressions are accompanied by the results of numerical computations. Possible future generalization of the used formalism is discussed.
Quantum Electrodynamics in d=3 from the ε Expansion.
Di Pietro, Lorenzo; Komargodski, Zohar; Shamir, Itamar; Stamou, Emmanuel
2016-04-01
We study quantum electrodynamics in d=3 coupled to N_{f} flavors of fermions. The theory flows to an IR fixed point for N_{f} larger than some critical number N_{f}^{c}. For N_{f}≤N_{f}^{c}, chiral-symmetry breaking is believed to take place. In analogy with the Wilson-Fisher description of the critical O(N) models in d=3, we make use of the existence of a fixed point in d=4-2ε to study the three-dimensional conformal theory. We compute, in perturbation theory, the IR dimensions of fermion bilinear and quadrilinear operators. For small N_{f}, a quadrilinear operator can become relevant in the IR and destabilize the fixed point. Therefore, the epsilon expansion can be used to estimate N_{f}^{c}. An interesting novelty compared to the O(N) models is that the theory in d=3 has an enhanced symmetry due to the structure of 3D spinors. We identify the operators in d=4-2ε that correspond to the additional conserved currents at d=3 and compute their infrared dimensions.
A toy model of quantum electrodynamics in (1 + 1) dimensionsB
Boozer, A. D.
2008-01-01
We present a toy model of quantum electrodynamics (QED) in (1 + 1) dimensions. The QED model is much simpler than QED in (3 + 1) dimensions but exhibits many of the same physical phenomena, and serves as a pedagogical introduction to both QED and quantum field theory in general. We show how the QED model can be derived by quantizing a toy model of classical electrodynamics, and we discuss the connections between the classical and quantum models. In addition, we use the QED model to discuss th...
Quantum Electrodynamics Basis of Classical-Field High-Harmonic Generation Theory
Institute of Scientific and Technical Information of China (English)
王兵兵; 高靓辉; 傅盘铭; 郭东升; R. R. Freeman
2001-01-01
From the nonperturbative quantum electrodynamics theory, we derive the Landau-Dykhne formula which represents the quantum-mechanical formulation of the three-step model. These studies provide a basis for the classical-field approaches to high-order harmonic generation and justify some assumptions used in classical-field modelling.
Vacuum Photon Splitting in Lorentz-Violating Quantum Electrodynamics
Kostelecky, V A; Kostelecky, Alan; Pickering, Austin
2003-01-01
Radiative corrections arising from Lorentz violation in the fermion sector induce a nonzero amplitude for vacuum photon splitting. At one loop, the on-shell amplitude acquires both CPT-even and CPT-odd contributions forbidden in conventional electrodynamics.
Quantum search via superconducting quantum interference devices in a cavity
Institute of Scientific and Technical Information of China (English)
Lu Yan; Dong Ping; Xue Zheng-Yuan; Cao Zhuo-Liang
2007-01-01
We propose a scheme for implementing the Grover search algorithm with two superconducing quantum interference devices (SQUIDs) in a cavity. Our scheme only requires single resonant interaction of the SQUID-cavity system and the required interaction time is very short. The simplicity of the process and the reduction of the interaction time are important for restraining decoherence.
Impedance-matched cavity quantum memory
Afzelius, Mikael
2010-01-01
We consider an atomic frequency comb based quantum memory inside an asymmetric optical cavity. In this configuration it is possible to absorb the input light completely in a system with an effective optical depth of one, provided that the absorption per cavity round trip exactly matches the transmission of the coupling mirror ("impedance matching"). We show that the impedance matching results in a readout efficiency only limited by irreversible atomic dephasing, whose effect can be made very small in systems with large inhomogeneous broadening. Our proposal opens up an attractive route towards quantum memories with close to unit efficiency.
Phenomenology of the vacuum in quantum electrodynamics and beyond
Energy Technology Data Exchange (ETDEWEB)
Doebrich, Babette
2011-09-30
Determining forces that arise by the restriction of the fluctuation modes of the vacuum by the insertion of boundaries or the observation of altered light propagation in external fields is a versatile means to investigate the vacuum structure of quantum electrodynamics. For these quantum vacuum probes, the vacuum can be understood and effectively modeled as a medium. Investigating the properties of this medium cannot only test and broaden our understanding of known interactions but can also be a valuable tool in the search for particles at low energy scales which arise in extensions of the standard model. In this thesis, we first study the geometry dependence of fluctuation modes in the Dirichlet-scalar analog of Casimir-Polder forces between an atom and a surface with arbitrary uniaxial corrugations. To this end we employ a technique which is fully nonperturbative in the height profile. We parameterize the differences to the distance dependencies in the planar limit in terms of an anomalous dimension quantifying the power-law deviation from the planar case. In numerical studies of experimentally relevant corrugations, we identify a universal regime of the anomalous dimension at larger distances. We argue that this universality arises as the relevant fluctuations average over corrugation structures smaller than the atom-wall distance. Turning to modified light propagation as a probe of the quantum vacuum, we show that a combination of strong, pulsed magnets and gravitational-wave interferometers can not only facilitate the detection of strong-field QED phenomena, but also significantly enlarges the accessible parameter space of hypothetical hidden-sector particles. We identify pulsed magnets as a suitable strong-field source to induce quantum nonlinearities, since their pulse frequency can be perfectly matched with the domain of highest sensitivity of modern gravitational-wave interferometers. Pushing current laboratory field-strengths to their limits, we suggest a
Popa, Alexandru
2013-01-01
Applications of Quantum and Classical Connections in Modeling Atomic, Molecular and Electrodynamical Systems is a reference on the new field of relativistic optics, examining topics related to relativistic interactions between very intense laser beams and particles. Based on 30 years of research, this unique book connects the properties of quantum equations to corresponding classical equations used to calculate the energetic values and the symmetry properties of atomic, molecular and electrodynamical systems. In addition, it examines applications for these methods, and for the calculation of
Excess of positrons in cosmic rays: A Lindbladian model of quantum electrodynamics
Campos, Andre G; Bondar, Denys I; Rabitz, Herschel
2015-01-01
The fraction of positrons and electrons in cosmic rays recently observed on the International Space Station unveiled an unexpected excess of the positrons, undermining the current foundations of cosmic rays sources. We provide a quantum electrodynamics phenomenological model explaining the observed data. This model incorporates electroproduction, in which cosmic ray electrons decelerating in the interstellar medium emit photons that turn into electron-positron pairs. These findings not only advance our knowledge of cosmic ray physics, but also pave the way for computationally efficient formulations of quantum electrodynamics, critically needed in physics and chemistry.
Nonlocal quantum cloning via quantum dots trapped in distant cavities
Institute of Scientific and Technical Information of China (English)
Yu Tao; Zhu Ai-Dong; Zhang Shou
2012-01-01
A scheme for implementing nonlocal quantum cloning via quantum dots trapped in cavities is proposed.By modulating the parameters of the system,the optimal 1 → 2 universal quantum cloning machine,1 → 2 phase-covariant cloning machine,and 1 → 3 economical phase-covariant cloning machine are constructed.The present scheme,which is attainable with current technology,saves two qubits compared with previous cloning machines.
Photon antibunching and nonlinear effects for a quantum dot coupled to a semiconductor cavity
Bello, F.; Whittaker, D. M.
2010-09-01
The models presented simulate pumping techniques that can be used on modern semiconductor devices which are capable of coupling a quantum dot and cavity mode in order to determine a more efficient method of producing a single-photon emitter while taking into consideration typical parameters which are achievable given today’s standards of coupling strength. Cavity quantum electrodynamics are incorporated in the calculations as we compare various pumping schemes for the system that either use on-resonant laser excitation or nonresonant excitation due to a wetting layer. In particular, we look to study how antibunching effects change for each method as the cavity finesse is increased toward the strong coupling regime. Experimentally these studies are equivalent to nonlinear pump-probe measurements, where a strong pump, either resonant or nonresonant, is used to excite the coupled system, and the resulting state is characterized using a weak, resonant probe beam.
Mode expansions in the quantum electrodynamics of photonic media with disorder
DEFF Research Database (Denmark)
Wubs, Martijn; Mortensen, N. Asger
2012-01-01
We address two issues in the quantum electrodynamical description of photonic media with some disorder, neglecting material dispersion. When choosing a gauge in which the static potential vanishes, the normal modes of the medium with disorder satisfy another transversality condition than the modes...
Fukuda, Masahiro; Ichikawa, Kazuhide; Tachibana, Akitomo
2016-01-01
We discuss the method to compute the integrals which appear in the retarded potential term for a real-time simulation based on QED (Quantum Electrodynamics). We show that the oscillatory integrals over the infinite interval involved in them can be efficiently performed by the method developed by Ooura and Mori based on the double exponential (DE) formula.
Circuit quantum electrodynamics architecture for gate-defined quantum dots in silicon
Mi, X.; Cady, J. V.; Zajac, D. M.; Stehlik, J.; Edge, L. F.; Petta, J. R.
2017-01-01
We demonstrate a hybrid device architecture where the charge states in a double quantum dot (DQD) formed in a Si/SiGe heterostructure are read out using an on-chip superconducting microwave cavity. A quality factor Q = 5400 is achieved by selectively etching away regions of the quantum well and by reducing photon losses through low-pass filtering of the gate bias lines. Homodyne measurements of the cavity transmission reveal DQD charge stability diagrams and a charge-cavity coupling rate gc/2 π= 23 MHz. These measurements indicate that electrons trapped in a Si DQD can be effectively coupled to microwave photons, potentially enabling coherent electron-photon interactions in silicon.
Photon antibunching and bunching in a ring-resonator waveguide quantum electrodynamics system.
Chen, Zihao; Zhou, Yao; Shen, Jung-Tsung
2016-07-15
We numerically investigate the photonic state generation and its nonclassical correlations in a ring-resonator waveguide quantum electrodynamics system. Specifically, we discuss photon antibunching and bunching in various scenarios, including the imperfect resonator with backscattering and dissipations. Our numerical results indicate that an imperfect ring resonator with backscattering can enhance the quality of antibunching. In addition, we also identify the quantum photonic halo phenomenon in the photon scattering dynamics and the shoulder effect in the second-order correlation function.
Bernard, M
2016-01-01
Recent technological advancements have allowed to implement in solid-state cavity-based devices phenomena of quantum nature such as vacuum Rabi splitting, controllable single photon emission and quantum entanglement. For a sufficiently strong coupling between a quantum emitter and a cavity, large quality factors ($Q$) along with small modal volume ($V_{eff}$) are essential. Here we show that by applying a 5nm Al coating to the sidewalls of a submicrometer-sized Fabry-P\\'{e}rot microcavity, the cavity $Q$ can be temperature-tuned from few hundreds at room temperatures to 2$\\times$10$^5$ below 30~K. This is achieved by, first, a complete shielding of the sidewall loss with ideally reflecting lateral metallic mirrors and, secondly, a dramatic decrease of the cavity's axial loss for small-sized devices due to the largely off-axis wavevector within the multilayered structure. Our findings offer a novel temperature-tunable platform to study quantum electrodynamical phenomena of emitter-cavity coupling. We demonstra...
Inflationary universe from higher derivative quantum gravity coupled with scalar electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Myrzakulov, R. [Department of General & Theoretical Physics and Eurasian Center for Theoretical Physics, Eurasian National University, Astana 010008 (Kazakhstan); Odintsov, S.D. [Consejo Superior de Investigaciones Científicas, ICE/CSIC-IEEC, Campus UAB, Facultat de Ciències, Torre C5-Parell-2a pl, E-08193 Bellaterra, Barcelona (Spain); Institut de Ciencies de l' Espai (IEEC-CSIC), Campus UAB, Carrer de Can Magrans, s/n 08193 Cerdanyola del Valles, Barcelona (Spain); Tomsk State Pedagogical University, 634050 Tomsk (Russian Federation); Tomsk State University of Control Systems and Radioelectronics (TUSUR) 634050 Tomsk (Russian Federation); Sebastiani, L., E-mail: lorenzo.sebastiani@unitn.it [Department of General & Theoretical Physics and Eurasian Center for Theoretical Physics, Eurasian National University, Astana 010008 (Kazakhstan)
2016-06-15
We study inflation for a quantum scalar electrodynamics model in curved space–time and for higher-derivative quantum gravity (QG) coupled with scalar electrodynamics. The corresponding renormalization-group (RG) improved potential is evaluated for both theories in Jordan frame where non-minimal scalar-gravitational coupling sector is explicitly kept. The role of one-loop quantum corrections is investigated by showing how these corrections enter in the expressions for the slow-roll parameters, the spectral index and the tensor-to-scalar ratio and how they influence the bound of the Hubble parameter at the beginning of the primordial acceleration. We demonstrate that the viable inflation maybe successfully realized, so that it turns out to be consistent with last Planck and BICEP2/Keck Array data.
Classical and quantum electrodynamics and the B(3) field
Evans, Myron W
2001-01-01
It is well known that classical electrodynamics is riddled with internal inconsistencies springing from the fact that it is a linear, Abelian theory in which the potentials are unphysical. This volume offers a self-consistent hypothesis which removes some of these problems, as well as builds a framework on which linear and nonlinear optics are treated as a non-Abelian gauge field theory based on the emergence of the fundamental magnetizing field of radiation, the B(3) field. Contents: Interaction of Electromagnetic Radiation with One Fermion; The Field Equations of Classical O (3) b Electrodyn
Popa, Alexandru
2013-01-01
Quantum and Classical Connections in Modeling Atomic, Molecular and Electrodynamic Systems is intended for scientists and graduate students interested in the foundations of quantum mechanics and applied scientists interested in accurate atomic and molecular models. This is a reference to those working in the new field of relativistic optics, in topics related to relativistic interactions between very intense laser beams and particles, and is based on 30 years of research. The novelty of this work consists of accurate connections between the properties of quantum equations and correspon
Quantum state engineering and reconstruction in cavity QED. An analytical approach
Energy Technology Data Exchange (ETDEWEB)
Lougovski, P.
2004-09-25
The models of a strongly-driven micromaser and a one-atom laser are developed. Their analytical solutions are obtained by means of phase space techniques. It is shown how to exploit the model of a one-atom laser for simultaneous generation and monitoring of the decoherence of the atom-field ''Schroedinger cat'' states. The similar machinery applied to the problem of the generation of the maximally-entangled states of two atoms placed inside an optical cavity permits its analytical solution. The steady-state solution of the problem exhibits a structure in which the two-atom maximally-entangled state correlates with the vacuum state of the cavity. As a consequence, it is demonstrated that the atomic maximally-entangled state, depending on a coupling regime, can be produced via a single or a sequence of no-photon measurements. The question of the implementation of a quantum memory device using a dispersive interaction between the collective internal ground state of an atomic ensemble and two orthogonal modes of a cavity is addressed. The problem of quantum state reconstruction in the context of cavity quantum electrodynamics is considered. The optimal operational definition of the Wigner function of a cavity field is worked out. It is based on the Fresnel transform of the atomic inversion of a probe atom. The general integral transformation for the Wigner function reconstruction of a particle in an arbitrary symmetric potential is derived.
Three qubit quantum phase gate based on cavity QED
Chang, Juntao; Zubairy, M. Suhail
2004-10-01
We describe a three qubit quantum phase gate in which the three qubits are represented by the photons in a three-modes optical cavity. This gate is implemented by passing a four-level atom in a cascade configuration through the cavity. We shall discuss the application of such a quantum phase gate to quantum searching.
Phase-selective reversible quantum decoherence in cavity QED experiment
Filip, R
2001-01-01
New feasible cavity QED experiment is proposed to analyse reversible quantum decoherence in consequence of quantum complementarity and entanglement. Utilizing the phase selective manipulations with enviroment, it is demonstrated how the complementarity particularly induces a preservation of visibility, whereas quantum decoherence is more progressive due to pronounced entanglement between system and enviroment. This effect can be directly observed using the proposed cavity QED measurements.
Schatz, George
2008-03-01
This talk will describe the use of electrodynamics and quantum mechanics methods to describe the optical properties of silver and gold nanoparticles and other nanostructures. This work has been done in collaboration with several experimental colleagues, including Chad Mirkin, Rick Van Duyne and Teri Odom. Our recent work has focused on the optical properties of metal nanoparticles that are coated with molecules that are detected either through their influence plasmon resonance excitation, or via surface enhanced Raman spectroscopy (SERS). Electrodynamics calculations using either the DDA or FDTD methods provide a quantitative tool for characterizing far field properties, and at a more primitive level estimates of SERS intensities. Quantum mechanics, as developed using time dependent density functional theory, is restricted to small metal clusters, but the same methods of far field spectroscopy and SERS can still be studied.
Chen, Xing; Moore, Justin E; Zekarias, Meserret; Jensen, Lasse
2015-11-10
The optical properties of metallic nanoparticles with nanometre dimensions exhibit features that cannot be described by classical electrodynamics. In this quantum size regime, the near-field properties are significantly modified and depend strongly on the geometric arrangements. However, simulating realistically sized systems while retaining the atomistic description remains computationally intractable for fully quantum mechanical approaches. Here we introduce an atomistic electrodynamics model where the traditional description of nanoparticles in terms of a macroscopic homogenous dielectric constant is replaced by an atomic representation with dielectric properties that depend on the local chemical environment. This model provides a unified description of bare and ligand-coated nanoparticles, as well as strongly interacting nanoparticle dimer systems. The non-local screening owing to an inhomogeneous ligand layer is shown to drastically modify the near-field properties. This will be important to consider in optimization of plasmonic nanostructures for near-field spectroscopy and sensing applications.
Baumann, Gerd
2005-01-01
Mathematica for Theoretical Physics: Electrodynamics, Quantum Mechanics, General Relativity, and Fractals This second edition of Baumann's Mathematica® in Theoretical Physics shows readers how to solve physical problems and deal with their underlying theoretical concepts while using Mathematica® to derive numeric and symbolic solutions. Each example and calculation can be evaluated by the reader, and the reader can change the example calculations and adopt the given code to related or similar problems. The second edition has been completely revised and expanded into two volumes: The first volume covers classical mechanics and nonlinear dynamics. Both topics are the basis of a regular mechanics course. The second volume covers electrodynamics, quantum mechanics, relativity, and fractals and fractional calculus. New examples have been added and the representation has been reworked to provide a more interactive problem-solving presentation. This book can be used as a textbook or as a reference work, by student...
Multimode circuit quantum electrodynamics with hybrid metamaterial transmission lines.
Egger, D J; Wilhelm, F K
2013-10-18
Quantum transmission lines are central to superconducting and hybrid quantum computing. In this work we show how coupling them to a left-handed transmission line allows circuit QED to reach a new regime: multimode ultrastrong coupling. Out of the many potential applications of this novel device, we discuss the preparation of multipartite entangled states and the simulation of the spin-boson model where a quantum phase transition is reached up to finite size effects.
Directory of Open Access Journals (Sweden)
Gustavo A. Aucar
2002-08-01
Full Text Available Abstract: A theory for the calculation of self-energy corrections to the nuclear magnetic parameters is given in this paper. It is based on the S-matrix formulation of bound-state quantum electrodynamics (QED. Explicit expressions for the various terms of the S-matrix are given. The interpretation of the self-energy, one- and two-vertex terms and some perspective for possible future developments are discussed.
Dynamical Mass Generation and Confinement in Maxwell-Chern-Simons Planar Quantum Electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Sanchez Madrigal, S; Raya, A [Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio C-3, Ciudad Universitaria, Morelia, Michoacan 58040 (Mexico); Hofmann, C P, E-mail: saul@ifm.umicri.mx, E-mail: christoph@ucol.mx, E-mail: raya@ifm.umich.mx [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima, Colima 28045 (Mexico)
2011-04-01
We study the non-perturbative phenomena of Dynamical Mass Generation and Confinement by truncating at the non-perturbative level the Schwinger-Dyson equations in Maxwell-Chern-Simons planar quantum electrodynamics. We obtain numerical solutions for the fermion propagator in Landau gauge within the so-called rainbow approximation. A comparison with the ordinary theory without the Chern-Simons term is presented.
Ultraviolet finiteness of Chiral Perturbation Theory for two-dimensional Quantum Electrodynamics
Paston, S A; Franke, V A
2003-01-01
We consider the perturbation theory in the fermion mass (chiral perturbation theory) for the two-dimensional quantum electrodynamics. With this aim, we rewrite the theory in the equivalent bosonic form in which the interaction is exponential and the fermion mass becomes the coupling constant. We reformulate the bosonic perturbation theory in the superpropagator language and analyze its ultraviolet behavior. We show that the boson Green's functions without vacuum loops remain finite in all orders of the perturbation theory in the fermion mass.
Inducing nonclassical lasing via periodic drivings in circuit quantum electrodynamics.
Navarrete-Benlloch, Carlos; García-Ripoll, Juan José; Porras, Diego
2014-11-01
We show how a pair of superconducting qubits coupled to a microwave cavity mode can be used to engineer a single-atom laser that emits light into a nonclassical state. Our scheme relies on the dressing of the qubit-field coupling by periodic modulations of the qubit energy. In the dressed basis, the radiative decay of the first qubit becomes an effective incoherent pumping mechanism that injects energy into the system, hence turning dissipation to our advantage. A second, auxiliary qubit is used to shape the decay within the cavity, in such a way that lasing occurs in a squeezed basis of the cavity mode. We characterize the system both by mean-field theory and exact calculations. Our work may find applications in the generation of squeezing and entanglement in circuit QED, as well as in the study of dissipative few- and many-body phase transitions.
Flick, Johannes; Ruggenthaler, Michael; Appel, Heiko; Rubio, Angel
2015-12-15
The density-functional approach to quantum electrodynamics extends traditional density-functional theory and opens the possibility to describe electron-photon interactions in terms of effective Kohn-Sham potentials. In this work, we numerically construct the exact electron-photon Kohn-Sham potentials for a prototype system that consists of a trapped electron coupled to a quantized electromagnetic mode in an optical high-Q cavity. Although the effective current that acts on the photons is known explicitly, the exact effective potential that describes the forces exerted by the photons on the electrons is obtained from a fixed-point inversion scheme. This procedure allows us to uncover important beyond-mean-field features of the effective potential that mark the breakdown of classical light-matter interactions. We observe peak and step structures in the effective potentials, which can be attributed solely to the quantum nature of light; i.e., they are real-space signatures of the photons. Our findings show how the ubiquitous dipole interaction with a classical electromagnetic field has to be modified in real space to take the quantum nature of the electromagnetic field fully into account.
Payton, John L; Morton, Seth M; Moore, Justin E; Jensen, Lasse
2014-01-21
Surface-enhanced Raman scattering (SERS) is a technique that has broad implications for biological and chemical sensing applications by providing the ability to simultaneously detect and identify a single molecule. The Raman scattering of molecules adsorbed on metal nanoparticles can be enhanced by many orders of magnitude. These enhancements stem from a twofold mechanism: an electromagnetic mechanism (EM), which is due to the enhanced local field near the metal surface, and a chemical mechanism (CM), which is due to the adsorbate specific interactions between the metal surface and the molecules. The local field near the metal surface can be significantly enhanced due to the plasmon excitation, and therefore chemists generally accept that the EM provides the majority of the enhancements. While classical electrodynamics simulations can accurately simulate the local electric field around metal nanoparticles, they offer few insights into the spectral changes that occur in SERS. First-principles simulations can directly predict the Raman spectrum but are limited to small metal clusters and therefore are often used for understanding the CM. Thus, there is a need for developing new methods that bridge the electrodynamics simulations of the metal nanoparticle and the first-principles simulations of the molecule to facilitate direct simulations of SERS spectra. In this Account, we discuss our recent work on developing a hybrid atomistic electrodynamics-quantum mechanical approach to simulate SERS. This hybrid method is called the discrete interaction model/quantum mechanics (DIM/QM) method and consists of an atomistic electrodynamics model of the metal nanoparticle and a time-dependent density functional theory (TDDFT) description of the molecule. In contrast to most previous work, the DIM/QM method enables us to retain a detailed atomistic structure of the nanoparticle and provides a natural bridge between the electronic structure methods and the macroscopic
An Elementary Quantum Network of Single Atoms in Optical Cavities
Ritter, Stephan; Hahn, Carolin; Reiserer, Andreas; Neuzner, Andreas; Uphoff, Manuel; Mücke, Martin; Figueroa, Eden; Bochmann, Jörg; Rempe, Gerhard
2012-01-01
Quantum networks are distributed quantum many-body systems with tailored topology and controlled information exchange. They are the backbone of distributed quantum computing architectures and quantum communication. Here we present a prototype of such a quantum network based on single atoms embedded in optical cavities. We show that atom-cavity systems form universal nodes capable of sending, receiving, storing and releasing photonic quantum information. Quantum connectivity between nodes is achieved in the conceptually most fundamental way: by the coherent exchange of a single photon. We demonstrate the faithful transfer of an atomic quantum state and the creation of entanglement between two identical nodes in independent laboratories. The created nonlocal state is manipulated by local qubit rotation. This efficient cavity-based approach to quantum networking is particularly promising as it offers a clear perspective for scalability, thus paving the way towards large-scale quantum networks and their applicati...
Classical Electrodynamics and the Quantum Nature of Light
De Souza, M M
1996-01-01
A review of old inconsistencies of Classical Electrodynamics (CED) and of some new ideas that solve them is presented. Problems with causality violating solutions of the wave equation and of the electron equation of motion, and problems with the non-integrable singularity of its self-field energy tensor are well known. The correct interpretation of the two (advanced and retarded) Lienard-Wiechert solutions are in terms of creation and annihilation of particles in classical physics. They are both retarded solutions. Previous work on the short distance limit of CED of a spinless point electron are based on a faulty assumption which causes the well known inconsistencies of the theory: a diverging self-energy (the non-integrable singularity of its self-field energy tensor) and a causality-violating third order equation of motion (the Lorentz-Dirac equation). The correct assumption fixes these problems without any change in the Maxwell's equations and let exposed, in the zero-distance limit, the discrete nature of...
A Scheme for Preparation of W-Type Entangled Coherent State of Three-Cavity Fields
Institute of Scientific and Technical Information of China (English)
YUAN Chun-Hua; OU Yong-Cheng; ZHANG Zhi-Ming
2006-01-01
@@ We present an experimental scheme to prepare the three-cavity W-type entangled coherent state in the context of dispersive cavity quantum electrodynamics. The discussion of our scheme indicates that it can be realized by current technology.
Higuchi, Atsushi; Martin, Giles D. R.
2006-01-01
We extend our previous work [A. Higuchi and G. D. R. Martin, Found. Phys. 35, 1149 (2005)FNDPA40015-901810.1007/s10701-005-6405-0], which compared the predictions of quantum electrodynamics concerning radiation reaction with those of the Abraham-Lorentz-Dirac theory for a charged particle in linear motion. Specifically, we calculate the predictions for the change in position of a charged-scalar particle, moving in three-dimensional space, due to the effect of radiation reaction in the one-photon-emission process in quantum electrodynamics. The scalar particle is assumed to be accelerated for a finite period of time by a three-dimensional electromagnetic potential dependent only on one of the spacetime coordinates. We perform this calculation in the ℏ→0 limit and show that the change in position agrees with that obtained in classical electrodynamics with the Lorentz-Dirac force treated as a perturbation. We also show for a time-dependent but space-independent electromagnetic potential that the forward-scattering amplitude at order e2 does not contribute to the position change in the ℏ→0 limit after the mass renormalization is taken into account.
A scanning transmon qubit for strong coupling circuit quantum electrodynamics.
Shanks, W E; Underwood, D L; Houck, A A
2013-01-01
Like a quantum computer designed for a particular class of problems, a quantum simulator enables quantitative modelling of quantum systems that is computationally intractable with a classical computer. Superconducting circuits have recently been investigated as an alternative system in which microwave photons confined to a lattice of coupled resonators act as the particles under study, with qubits coupled to the resonators producing effective photon-photon interactions. Such a system promises insight into the non-equilibrium physics of interacting bosons, but new tools are needed to understand this complex behaviour. Here we demonstrate the operation of a scanning transmon qubit and propose its use as a local probe of photon number within a superconducting resonator lattice. We map the coupling strength of the qubit to a resonator on a separate chip and show that the system reaches the strong coupling regime over a wide scanning area.
The quantum vacuum at the foundations of classical electrodynamics
Leuchs, G; Sánchez-Soto, L L
2010-01-01
In the classical theory of electromagnetism, the permittivity and the permeability of free space are constants whose magnitudes do not seem to possess any deeper physical meaning. By replacing the free space of classical physics with the quantum notion of the vacuum, we speculate that the values of the aforementioned constants could arise from the polarization and magnetization of virtual pairs in vacuum. A classical dispersion model with parameters determined by quantum and particle physics is employed to estimate their values. We find the correct orders of magnitude. Additionally, our simple assumptions yield an independent estimate for the number of charged elementary particles based on the known values of the permittivity and the permeability, and for the volume of a virtual pair. Such interpretation would provide an intriguing connection between the celebrated theory of classical electromagnetism and the quantum theory in the weak field limit.
Scalable photonic quantum computation through cavity-assisted interactions.
Duan, L-M; Kimble, H J
2004-03-26
We propose a scheme for scalable photonic quantum computation based on cavity-assisted interaction between single-photon pulses. The prototypical quantum controlled phase-flip gate between the single-photon pulses is achieved by successively reflecting them from an optical cavity with a single-trapped atom. Our proposed protocol is shown to be robust to practical noise and experimental imperfections in current cavity-QED setups.
Quantum correlations in non-inertial cavity systems
Harsij, Zeynab; Mirza, Behrouz
2016-10-01
Non-inertial cavities are utilized to store and send Quantum Information between mode pairs. A two-cavity system is considered where one is inertial and the other accelerated in a finite time. Maclaurian series are applied to expand the related Bogoliubov coefficients and the problem is treated perturbatively. It is shown that Quantum Discord, which is a measure of quantumness of correlations, is degraded periodically. This is almost in agreement with previous results reached in accelerated systems where increment of acceleration decreases the degree of quantum correlations. As another finding of the study, it is explicitly shown that degradation of Quantum Discord disappears when the state is in a single cavity which is accelerated for a finite time. This feature makes accelerating cavities useful instruments in Quantum Information Theory.
The current density in quantum electrodynamics in external potentials
Energy Technology Data Exchange (ETDEWEB)
Schlemmer, Jan, E-mail: jan.schlemmer@univie.ac.at [Fakultät für Physik, Universität Wien, Boltzmanngasse 5, 1090 Wien (Austria); Zahn, Jochen, E-mail: jochen.zahn@itp.uni-leipzig.de [Institut für Theoretische Physik, Universität Leipzig, Brüderstr. 16, 04103 Leipzig (Germany)
2015-08-15
We review different definitions of the current density for quantized fermions in the presence of an external electromagnetic field. Several deficiencies in the popular prescription due to Schwinger and the mode sum formula for static external potentials are pointed out. We argue that Dirac’s method, which is the analog of the Hadamard point-splitting employed in quantum field theory in curved space–times, is conceptually the most satisfactory. As a concrete example, we discuss vacuum polarization and the stress–energy tensor for massless fermions in 1+1 dimension. Also a general formula for the vacuum polarization in static external potentials in 3+1 dimensions is derived.
Jian, Shao-Kai; Maciejko, Joseph; Yao, Hong
2016-01-01
We show that a supersymmetric gauge theory with dynamical gauge bosons and fermionic gauginos emerges naturally at the pair-density-wave (PDW) quantum phase transition on the surface of a correlated topological insulator (TI) hosting three Dirac cones, such as the candidate topological Kondo insulator SmB$_6$. At the tricritical point separating the first- and second-order quantum phase transitions between the surface Dirac semimetal and nematic PDW phases, three massless bosonic Cooper pair fields emerge as the superpartners of three massless surface Dirac fermions. The resulting low-energy effective theory is the supersymmetric XYZ model, which is dual by mirror symmetry to $\\mathcal{N}=2$ supersymmetric quantum electrodynamics (SQED) in 2+1 dimensions. Using supersymmetry, we calculate exactly certain critical exponents and the optical conductivity of the surface states at the tricritical point, which may be measured in future experiments.
Quantum Electrodynamic Modeling of Silicon-Based Active Devices
Directory of Open Access Journals (Sweden)
Shouyuan Shi
2008-01-01
Full Text Available We propose a time-domain analysis of an active medium based on a coupled quantum mechanical and electromagnetic model to accurately simulate the dynamics of silicon-based photonic devices. To fully account for the nonlinearity of an active medium, the rate equations of a four-level atomic system are introduced into the electromagnetic polarization vector. With these auxiliary differential equations, we solve the time evolution of the electromagnetic waves and atomic population densities using the FDTD method. The developed simulation approach has been used to model light amplification and amplified spontaneous emission in silicon nanocrystals, as well as the lasing dynamics in a novel photonic crystal-based silicon microcavity.
Mross, David F.; Alicea, Jason; Motrunich, Olexei I.
2016-07-01
We explicitly derive the duality between a free electronic Dirac cone and quantum electrodynamics in (2 +1 ) dimensions (QED3 ) with N =1 fermion flavors. The duality proceeds via an exact, nonlocal mapping from electrons to dual fermions with long-range interactions encoded by an emergent gauge field. This mapping allows us to construct parent Hamiltonians for exotic topological-insulator surface phases, derive the particle-hole-symmetric field theory of a half-filled Landau level, and nontrivially constrain QED3 scaling dimensions. We similarly establish duality between bosonic topological insulator surfaces and N =2 QED3 .
Green, D. G.; Harvey, C. N.
2015-07-01
We present the Fortran program SIMLA, which is designed for the study of charged particle dynamics in laser and other background fields. The dynamics can be determined classically via the Lorentz force and Landau-Lifshitz equations or, alternatively, via the simulation of photon emission events determined by strong-field quantum-electrodynamics amplitudes and implemented using Monte-Carlo routines. Multiple background fields can be included in the simulation and, where applicable, the propagation direction, field type (plane wave, focussed paraxial, constant crossed, or constant magnetic), and time envelope of each can be independently specified.
Quantum electrodynamics corrections to the 2P fine splitting in Li.
Puchalski, Mariusz; Pachucki, Krzysztof
2014-08-15
We consider quantum electrodynamics (QED) corrections to the fine splitting E(2P_{3/2})-E(2P_{1/2}) in the Li atom. We derive complete formulas for the mα^{6} and mα^{7}lnα contributions and calculate them numerically using highly optimized, explicitly correlated basis functions. The obtained results are in agreement with the most recent measurement, helping to resolve discrepancies between former ones and lay the foundation for the investigation of QED effects in light, many-electron atoms.
Mesoscopic entangled coherent states implemented with a circuit quantum electrodynamics system
Institute of Scientific and Technical Information of China (English)
Zhao Ying-Yan; Jiang Nian-Quan
2013-01-01
We show a scheme to generate entangled coherent states in a circuit quantum electrodynamics system,which consists of a nanomechanical resonator,a superconducting Cooper-pair box (CPB),and a superconducting transmission line resonator.In the system,the CPB plays the role of a nonlinear medium and can be conveniently controlled by a gate voltage including direct-current and alternating-current components.The scheme provides a powerful tool for preparing the multipartite mesoscopic entangled coherent states.
Ni, G; Ni, Guang-jiong; Wang, Haibin
1997-01-01
A simple but effective method for regularization-renormalization (R-R) is proposed for handling the Feynman diagram integral (FDI) at one loop level in quantum electrodynamics (QED). The divergence is substituted by some constants to be fixed via experiments. So no counter term, no bare parameter and no arbitrary running mass scale is involved. Then the Lamb Shift in Hydrogen atom can be calculated qualitatively and simply as $\\Delta E(2S_{1/2})- \\Delta E(2P_{1/2})=996.7 MHz$ versus the experimental value $1057.85 MHz$.
SIMLA: Simulating laser-particle interactions via classical and quantum electrodynamics
Green, D G
2014-01-01
We present the Fortran code SIMLA, which is designed for the study of charged particle dynamics in laser and other background fields. This can be done classically via the Landau-Lifshitz equation, or alternatively, via the simulation of photon emission events determined by strong-field quantum-electrodynamics amplitudes and implemented using Monte-Carlo type routines. Multiple laser fields can be included in the simulation and the propagation direction, beam shape (plane wave, focussed paraxial, constant crossed, or constant magnetic), and time envelope of each can be independently specified.
Normalizability analysis of the generalized quantum electrodynamics from the causal point of view
Bufalo, R; Soto, D E
2015-01-01
The causal perturbation theory is an axiomatic perturbative theory of the S-matrix. This formalism has as its essence the following axioms: causality, Lorentz invariance and asymptotic conditions. Any other property must be showed via the inductive method order-by-order and, of course, it depends on the particular physical model. In this work we shall study the normalizability of the generalized quantum electrodynamics in the framework of the causal approach. Furthermore, we analyse the implication of the gauge invariance onto the model and obtain the respective Ward-Takahashi-Fradkin identities.
On refractive processes in strong laser field quantum electrodynamics
Di Piazza, A
2013-01-01
Refractive processes in strong-field QED are pure quantum processes, which involve only external photons and the background electromagnetic field. We show analytically that such processes occurring in a plane-wave field are all characterized by a surprisingly modest net exchange of laser photons even at ultrarelativistic laser intensities. We obtain this result by a direct calculation of the transition matrix element of an arbitrary refractive QED process and accounting exactly for the background plane-wave field. A simple physical explanation of this modest net exchange of laser photons is provided, based on the fact that the laser field couples with the external photons only indirectly through virtual electron-positron pairs. For stronger and stronger laser fields, the pairs cover a shorter and shorter distance before they annihilate again, such that the laser can transfer to them an energy corresponding to only a few photons. These results apply to both optical and x-free electron lasers, and are relevant ...
Time Evolution in the external field problem of Quantum Electrodynamics
Lazarovici, Dustin
2013-01-01
A general problem of quantum field theories is the fact that the free vacuum and the vacuum for an interacting theory belong to different, non-equivalent representations of the canonical (anti-)commutation relations. In the external field problem of QED, we encounter this problem in the form that the Dirac time evolution for an external field with non-vanishing magnetic components will not satisfy the Shale-Stinespring condition, known to be necessary and sufficient for the existence of an implementation on the fermionic Fock space. Therefore, a second quantization of the time evolution in the usual way is impossible. In this thesis, we present several rigorous approaches to QED with time-dependent, external fields and analyze in what sense a time evolution can exist in the second quantized theory. We study different constructions of the fermionic Fock space and prove their equivalence. We study and compare the results of Deckert et. al. (2010), where the time evolution is realized as unitary transformations ...
Nonlinear Electrodynamics and QED
2003-01-01
The limits of linear electrodynamics are reviewed, and possible directions of nonlinear extension are explored. The central theme is that the qualitative character of the empirical successes of quantum electrodynamics must be used as a guide for understanding the nature of the nonlinearity of electrodynamics at the subatomic level. Some established theories of nonlinear electrodynamics, namely, those of Mie, Born, and Infeld are presented in the language of the modern geometrical and topologi...
Unconventional geometric quantum phase gates with a cavity QED system
Zheng, Shi-Biao
2004-11-01
We propose a scheme for realizing two-qubit quantum phase gates via an unconventional geometric phase shift with atoms in a cavity. In the scheme the atoms interact simultaneously with a highly detuned cavity mode and a classical field. The atoms undergo no transitions during the gate operation, while the cavity mode is displaced along a circle in the phase space, aquiring a geometric phase conditional upon the atomic state. Under certain conditions, the atoms are disentangled with the cavity mode and thus the gate is insensitive to both the atomic spontaneous emission and the cavity decay.
Scheme for Quantum Entanglement Swapping on Cavity QED System
Institute of Scientific and Technical Information of China (English)
CHEN Chang-Yong; YU Yan
2006-01-01
We propose a scheme for realizing quantum entanglement swapping between the atoms in cavity QED.With only virtual excitation of the cavity during the interaction between the atoms and cavity, the scheme is insensitive to the cavity mode states and the cavity decay. The ideas can also be utilized for realizing entanglement swapping between the atomic levels in a single atom and the atomic levels in the Bell states and between the atomic levels in the Bell states and the atomic levels in the W states.
Heo, Jino; Kang, Min-Sung; Hong, Chang-Ho; Yang, Hyeon; Choi, Seong-Gon
2017-01-01
We propose quantum information processing schemes based on cavity quantum electrodynamics (QED) for quantum communication. First, to generate entangled states (Bell and Greenberger-Horne-Zeilinger [GHZ] states) between flying photons and three-level atoms inside optical cavities, we utilize a controlled phase flip (CPF) gate that can be implemented via cavity QED). Subsequently, we present an entanglement swapping scheme that can be realized using single-qubit measurements and CPF gates via optical cavities. These schemes can be directly applied to construct an entanglement channel for a communication system between two users. Consequently, it is possible for the trust center, having quantum nodes, to accomplish the linked channel (entanglement channel) between the two separate long-distance users via the distribution of Bell states and entanglement swapping. Furthermore, in our schemes, the main physical component is the CPF gate between the photons and the three-level atoms in cavity QED, which is feasible in practice. Thus, our schemes can be experimentally realized with current technology.
Zohar, Erez; Cirac, J Ignacio; Reznik, Benni
2012-09-21
Recently, there has been much interest in simulating quantum field theory effects of matter and gauge fields. In a recent work, a method for simulating compact quantum electrodynamics (CQED) using Bose-Einstein condensates has been suggested. We suggest an alternative approach, which relies on single atoms in an optical lattice, carrying 2l + 1 internal levels, which converges rapidly to CQED as l increases. That enables the simulation of CQED in 2 + 1 dimensions in both the weak and the strong coupling regimes, hence, allowing us to probe confinement as well as other nonperturbative effects of the theory. We provide an explicit construction for the case l = 1 which is sufficient for simulating the effect of confinement between two external static charges.
Fractional charges and fractional spins for composite fermions in quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Wang Yong-Long; Lu Wei-Tao; Jiang Hua; Xu Chang-Tan; Pan Hong-Zhe
2012-01-01
By using the Faddeev-senjanovic path integral quantization method,we quantize the composite fermions in quantum electrodynamics (QED).In the sense of Dirac's conjecture,we deduce all the constraints and give Dirac's gauge transformations (DGT).According to that the effective action is invariant under the DGT,we obtain the Noether theorem at the quantum level,which shows the fractional charges for the composite fermions in QED.This result is better than the one deduced from the equations of motion for the statistical potentials,because this result contains both odd and even fractional numbers.Furthermore,we deduce the Noether theorem from the invariance of the effective action under the rotational transformations in 2-dimensional (x,y) plane.The result shows that the composite fermions have fractional spins and fractional statistics.These anomalous properties are given by the constraints for the statistical gauge potential.
Controllable cross-Kerr interaction between microwave photons in circuit quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Wu Qin-Qin; Liao Jie-Qiao; Kuang Le-Man
2011-01-01
We propose a scheme to enable a controllable cross-Kerr interaction between microwave photons in a circuit quantum electrodynamics (QED) system. In this scheme we use two transmission-line resonators (TLRs) and one superconducting quantum interference device (SQUID) type charge qubit, which acts as an artificial atom. It is shown that in the dispersive regime of the circuit-QED system, a controllable cross-Kerr interaction can be obtained by properly preparing the initial state of the qubit, and a large cross-phase shift between two microwave fields in the two TLRs can then be reached. Based on this cross-Kerr interaction, we show how to create a macroscopic entangled state between the two TLRs.
Quantum Dot-Photonic Crystal Cavity QED Based Quantum Information Processing
2012-08-14
Physical Review A, 2012] 3. Study of the off-resonant quantum dot-cavity coupling in solid-state cavity QED system, and the phonon mediated off...resonant interaction between two quantum dots [Majumdar et al., Physical Review B , 2012] 4. Coherent optical spectroscopy of a single quantum dot via an off...Resonant cavity - much simpler than in conventional approaches [Majumdar et al, Physical Review B, 2011; Papageorge et al., New. Journal of Physics
Quantum superdense coding via cavity-assisted interactions
Institute of Scientific and Technical Information of China (English)
Pan Guo-Zhu; Yang Ming; Cao Zhuo-Liang
2009-01-01
Quantum superdense coding (QSC) is an example of how entanglement can be used to minimize the number of carriers of classical information. This paper proposes two schemes for implementing QSC by means of cavity assisted interactions with single-photon pulses. The schemes are insensitive to the cavity decay and the thermal field, thus it might be realizable based on the current cavity QED techniques.
Wang, W -M; Gibbon, P; Li, Y -T
2016-01-01
We develop the particle-in-cell (PIC) code KLAPS to include the photon generation via the Compton scattering and electron-positron creation via the Breit-Wheeler process due to quantum electrodynamics (QED) effects. We compare two sets of existing formulas for the photon generation and different Monte Carlo algorithms. Then we benchmark the PIC simulation results.
Measurement of electrodynamics characteristics of higher order modes for harmonic cavity at 2400 MHz
Shashkov, Ya V.; Sobenin, N. P.; Gusarova, M. A.; Lalayan, M. V.; Bazyl, D. S.; Donetskiy, R. V.; Orlov, A. I.; Zobov, M. M.; Zavadtsev, A. A.
2016-09-01
In the frameworks of the High Luminosity Large Hadron Collider (HL-LHC) upgrade program an application of additional superconducting harmonic cavities operating at 800 MHz is currently under discussion. As a possible candidate, an assembly of two cavities with grooved beam pipes connected by a drift tube and housed in a common cryomodule, was proposed. In this article we discuss measurements of loaded Q-factors of higher order modes (HOM) performed on a scaled aluminium single cell cavity prototype with the fundamental frequency of 2400 MHz and on an array of two such cavities connected by a narrow beam pipe. The measurements were performed for the system with and without the matching load in the drift tube..
Joo, Jaewoo; Ginossar, Eran
2016-06-01
We propose a deterministic scheme for teleporting an unknown qubit state through continuous-variable entangled states in superconducting circuits. The qubit is a superconducting two-level system and the bipartite quantum channel is a microwave photonic entangled coherent state between two cavities. A Bell-type measurement performed on the hybrid state of solid and photonic states transfers a discrete-variable unknown electronic state to a continuous-variable photonic cat state in a cavity mode. In order to facilitate the implementation of such complex protocols we propose a design for reducing the self-Kerr nonlinearity in the cavity. The teleporation scheme enables quantum information processing operations with circuit-QED based on entangled coherent states. These include state verification and single-qubit operations with entangled coherent states. These are shown to be experimentally feasible with the state of the art superconducting circuits.
Joo, Jaewoo; Ginossar, Eran
2016-06-01
We propose a deterministic scheme for teleporting an unknown qubit state through continuous-variable entangled states in superconducting circuits. The qubit is a superconducting two-level system and the bipartite quantum channel is a microwave photonic entangled coherent state between two cavities. A Bell-type measurement performed on the hybrid state of solid and photonic states transfers a discrete-variable unknown electronic state to a continuous-variable photonic cat state in a cavity mode. In order to facilitate the implementation of such complex protocols we propose a design for reducing the self-Kerr nonlinearity in the cavity. The teleporation scheme enables quantum information processing operations with circuit-QED based on entangled coherent states. These include state verification and single-qubit operations with entangled coherent states. These are shown to be experimentally feasible with the state of the art superconducting circuits.
Linewidth broadening of a quantum dot coupled to an off-resonant cavity
Majumdar, Arka; Kim, Erik; Englund, Dirk; Kim, Hyochul; Petroff, Pierre; Vuckovic, Jelena
2010-01-01
We study the coupling between a photonic crystal cavity and an off-resonant quantum dot under resonant excitation of the cavity or the quantum dot. Linewidths of the quantum dot and the cavity as a function of the excitation laser power are measured. We show that the linewidth of the quantum dot, measured by observing the cavity emission, is significantly broadened compared to the theoretical estimate. This indicates additional incoherent coupling between the quantum dot and the cavity.
Shatrov, A. D.; Dubrov, M. N.; Aleksandrov, D. V.
2016-12-01
The behaviour of the electromagnetic field in a three-mirror laser cavity is described using the method of integral equations. The results of numerical calculations and experimental studies for particular examples implementing the considered configuration are presented. The conditions for optimal tuning of a laser interferometer-deformograph with a three-mirror cavity are determined. The contribution of the reflected and scattered light and arising additional seismic noises to the resulting error of laser gravitational wave detectors is studied.
Berestetskii, Vladimir B; Pitaevskii, L P
1982-01-01
Several significant additions have been made to the second edition, including the operator method of calculating the bremsstrahlung cross-section, the calcualtion of the probabilities of photon-induced pair production and photon decay in a magneticfield, the asymptotic form of the scattering amplitudes at high energies, inelastic scattering of electrons by hadrons, and the transformation of electron-positron pairs into hadrons.
Realizing quantum controlled phase flip through cavity QED
Xiao, Yun-Feng; Lin, Xiu-Min; Gao, Jie; Yang, Yong; Han, Zheng-Fu; Guo, Guang-Can
2004-10-01
We propose a scheme to realize quantum controlled phase flip (CPF) between two rare-earth ions embedded in the respective microsphere cavity via interacting with a single-photon pulse in sequence. The numerical simulations illuminate that the CPF gate between ions is robust and scalable with extremely high fidelity and low error rate. Our scheme is more applicable than other schemes presented before based on current laboratory cavity-QED technology, and it is possible to be used as an applied unit gate in future quantum computation and quantum communication.
Realizing Quantum Controlled Phase Flip through Cavity-QED
Xiao, Y F; Gao, J; Yang, Y; Han, Z F; Guo, G C; Xiao, Yun-Feng; Lin, Xiu-Min; Gao, Jie; Yang, Yong; Han, Zheng-Fu; Guo, Guang-Can
2004-01-01
We propose a scheme to realize quantum controlled phase flip (CPF) between two rare earth ions embedded in respective microsphere cavity via interacting with a single-photon pulse in sequence. The numerical simulations illuminate that the CPF gate between ions is robust and scalable with extremely high fidelity and low error rate. Our scheme is more applicable than other schemes presented before based on current laboratory cavity-QED technology, and it is possible to be used as an applied unit gate in future quantum computation and quantum communication.
Cavity QED based tuneable, delayed-choice quantum eraser
Imran, Muhammad; Abbas, Tasawar; -ul-Islam, Rameez; Ikram, Manzoor
2016-01-01
We propose an experimentally feasible idea for the delayed-choice quantum eraser, having adjustable path distinguishability/fringe visibility. The schematics are based on resonant, dispersive and Ramsey interactions of atoms under cavity QED scenario. The option for tuneability of the fringes in a delayed-choice setup stringently marks the conception of the time in the quantum theory, operational meanings of the state vector reduction and raises questions about Ψ-ontic models while helping to shed out the controversies surrounding the quantum eraser theme. The proposal can be efficiently executed experimentally within the prevailing cavity QED experimental research scenario with good overall success probability and fidelity.
Ichikawa, Kazuhide; Tachibana, Akitomo
2014-01-01
We discuss a method to follow step-by-step time evolution of atomic and molecular systems based on QED (Quantum Electrodynamics). Our strategy includes expanding the electron field operator by localized wavepackets to define creation and annihilation operators and following the time evolution using the equations of motion of the field operator in the Heisenberg picture. We first derive a time evolution equation for the excitation operator, the product of two creation or annihilation operators, which is necessary for constructing operators of physical quantities such as the electronic charge density operator. We then describe our approximation methods to obtain time differential equations of the electronic density matrix, which is defined as the expectation value of the excitation operator. By solving the equations numerically, we show "electron-positron oscillations", the fluctuations originated from virtual electron-positron pair creations and annihilations, appear in the charge density of a hydrogen atom an...
Reduced Dirac equation and Lamb shift as off-mass-shell effect in quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Ni Guang-Jiong; Xu Jian-Jun; Lou Sea-Yue
2011-01-01
Based on the accurate experimental data of energy-level differences in hydrogen-like atoms, especially the 1S-2S transitions of hydrogen and deuterium, the necessity of introducing a reduced Dirac equation with reduced mass as the substitution of original electron mass is stressed. Based on new cognition about the essence of special relativity, we provide a reasonable argument for the reduced Dirac equation to have two symmetries, the invariance under the (newly defined) space-time inversion and that under the pure space inversion, in a noninertial frame. By using the reduced Dirac equation and within the framework of quantum electrodynamics in covariant form, the Lamb shift can be evaluated (at one-loop level) as the radiative correction on a bound electron staying in an off-mass-shell state-a new approach eliminating the infrared divergence. Hence the whole calculation, though with limited accuracy, is simplified, getting rid of all divergences and free of ambiguity.
Ding, Xiaobin; Sun, Rui; Koike, Fumihiro; Kato, Daiji; Murakami, Izumi; Sakaue, Hiroyuki A.; Dong, Chenzhong
2017-03-01
The electron correlation effects and Breit interaction as well as Quantum Electro-Dynamics (QED) effects were expected to have important contribution to the energy level and transition properties of heavy highly charged ions. The ground states [Ne]3 s 23 p 63 d 2 and first excited states [Ne]3 s 23 p 53 d 3 of W54+ ion have been studied by using Multi-Configuration Dirac-Fock method with the implementation of Grasp2K package. A restricted active space method was employed to investigate the correlation contribution from different models. The Breit interaction and QED effects were taken into account in the relativistic configuration interaction calculation with the converged wavefunction. It is found that the correlation contribution from 3 s and 3 p orbital have important contribution to the energy level, transition wavelength and probability of the ground and the first excited state of W54+ ion.
On How the Scalar Propagator Transforms Covariantly in Spinless Quantum Electrodynamics
Sánchez, Yajaira Concha; Villanueva-Sandoval, Victor M; Raya, Alfredo
2013-01-01
Gauge covariance properties of the scalar propagator in spinless/scalar quantum electrodynamics (SQED) are explored in the light of the corresponding Landau-Khalatnikov-Fradkin transformation (LKFT). These transformations are non perturbative in nature and describe how each Green function of the gauge theory changes under a variation of the gauge parameter. With a simple strategy, considering the scalar propagator at the tree level in Landau gauge, we derive a non perturbative expression for this propagator in an arbitrary covariant gauge and three as well as four space-time dimensions. Some relevant kinematical limits are discussed. Particularly, we compare our findings in the weak coupling regime with the direct one-loop calculation of the said propagator and observe perfect agreement up to an expected gauge independent term. We further notice that some of the coefficients of the all-order expansion for the propagator are fixed directly from the LKFT, a fact that makes this set of transformations appealing ...
Zahn, Jochen
2015-01-01
In the framework of quantum electrodynamics (QED) in external potentials, we introduce a method to compute the time-dependence of the expectation value of the current density for time-dependent homogeneous external electric fields. We apply it to the so-called Sauter pulse. For late times, our results agree with the asymptotic value due to electron-positron pair production. For sub-critical peak field strengths, or results agree very well with the general expression derived by Serber for the linearization in the external field. In particular, the expectation value of the current density at intermediate times can be much greater than at asymptotic times. We comment on consequences of these findings for recent proposals to test the Schwinger effect with high intensity lasers using processes at intermediate times.
Dudley, J. M.; Kwan, A. M.
1996-06-01
The subject of quantum electrodynamics (QED) was the subject of QED—The Strange Theory of Light and Matter, the popular book by Richard Feynman which was published by Princeton University Press in 1985. On p. 1, Feynman makes passing reference to the fact that the book is based on a series of general lectures on QED which were, however, first delivered in New Zealand. At Auckland University, these lectures were delivered in 1979, as the Sir Douglas Robb lectures, and videotapes of the lectures are held by the Auckland University Physics Department. We have carried out a detailed examination of these videotapes, and we discuss here the major differences between the original Auckland lectures and the published version. We use selected quotations from the lectures to show that the original lectures provide additional insight into Feynman's character, and have great educational value.
Reduced Dirac Equation and Lamb Shift as an Off-mass-shell effect in Quantum Electrodynamics
Ni, G; Xu, J; Lou, Senyue; Ni, Guang-jiong; Xu, Jianjun
2005-01-01
Based on the precision experimental data of energy-level differences in hydrogenlike atoms, especially the 1S-2S transition of hydrogen and deuterium, the necessity of establishing a reduced Dirac equation (RDE) with reduced mass as the substitution of original electron mass is stressed. The theoretical basis of RDE lies on two symmetries, the invariance under the space-time inversion and that under the pure space inversion. Based on RDE and within the framework of quantum electrodynamics in covariant form, the Lamb shift can be evaluated (at one-loop level) as the radiative correction on a bound electron staying in an off-mass-shell state--a new approach eliminating the infrared divergence. Hence the whole calculation, though with limited accuracy, is simplified, getting rid of all divergences and free of ambiguity.
Ohsaku, T; Yamaki, D; Yamaguchi, K
2002-01-01
For studying the group theoretical classification of the solutions of the density functional theory in relativistic framework, we propose quantum electrodynamical density-matrix functional theory (QED-DMFT). QED-DMFT gives the energy as a functional of a local one-body $4\\times4$ matrix $Q(x)\\equiv -$, where $\\psi$ and $\\bar{\\psi}$ are 4-component Dirac field and its Dirac conjugate, respectively. We examine some characters of QED-DMFT. After these preparations, by using Q(x), we classify the solutions of QED-DMFT under O(3) rotation, time reversal and spatial inversion. The behavior of Q(x) under nonrelativistic and ultrarelativistic limits are also presented. Finally, we give plans for several extensions and applications of QED-DMFT.
Gao, Yi; Neuhauser, Daniel
2012-08-21
We develop an approach for dynamical (ω > 0) embedding of mixed quantum mechanical (QM)/classical (or more precisely QM/electrodynamics) systems with a quantum sub-region, described by time-dependent density functional theory (TDDFT), within a classical sub-region, modeled here by the recently proposed near-field (NF) method. Both sub-systems are propagated simultaneously and are coupled through a common Coulomb potential. As a first step we implement the method to study the plasmonic response of a metal film which is half jellium-like QM and half classical. The resulting response is in good agreement with both full-scale TDDFT and the purely classical NF method. The embedding method is able to describe the optical response of the whole system while capturing quantum mechanical effects, so it is a promising approach for studying electrodynamics in hybrid molecules-metals nanostructures.
Broadband filters for abatement of spontaneous emission in circuit quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Bronn, Nicholas T., E-mail: ntbronn@us.ibm.com; Hertzberg, Jared B.; Córcoles, Antonio D.; Gambetta, Jay M.; Chow, Jerry M. [IBM T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States); Liu, Yanbing; Houck, Andrew A. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States)
2015-10-26
The ability to perform fast, high-fidelity readout of quantum bits (qubits) is essential to the goal of building a quantum computer. However, coupling a fast measurement channel to a superconducting qubit typically also speeds up its relaxation via spontaneous emission. Here, we use impedance engineering to design a filter by which photons may easily leave the resonator at the cavity frequency but not at the qubit frequency. We implement this broadband filter in both an on-chip and off-chip configuration.
Wu, Wei; Xu, Jing-Bo
2016-09-01
We investigate the quantum phase transition of an atomic ensemble trapped in a single-mode optical cavity via the geometric phase and quantum Fisher information of an extra probe atom which is injected into the optical cavity and interacts with the cavity field. We also find that the geometric quantum correlation between two probe atoms exhibits a double sudden transition phenomenon and show this double sudden transition phenomenon is closely associated with the quantum phase transition of the atomic ensemble. Furthermore, we propose a theoretical scheme to prolong the frozen time during which the geometric quantum correlation remains constant by applying time-dependent electromagnetic field.
Goñi, Alejandro R; Güell, Frank; Pérez, Luis A; López-Vidrier, Julian; Ossó, J Oriol; Coronado, Eduardo A; Morante, Joan R
2012-03-01
For good performance of photonic devices whose working principle is based on the enhancement of electromagnetic fields obtained by confining light into dielectric resonators with dimensions in the nanometre length scale, a detailed knowledge of the optical mode structure becomes essential. However, this information is usually lacking and can only be indirectly obtained by conventional spectroscopic techniques. Here we unraveled the influence of wire size, incident wavelength, degree of polarization and the presence of a substrate on the optical near fields generated by cavity modes of individual hexagonal ZnO nanowires by combining scanning near-field optical microscopy (SNOM) with electrodynamics calculations within the discrete dipole approximation (DDA). The near-field patterns obtained with very high spatial resolution, better than 50 nm, exhibit striking size and spatial-dispersion effects, which are well accounted for within DDA, using a wavevector-dependent dipolar interaction and considering the dielectric anisotropy of ZnO. Our results show that both SNOM and DDA simulations are powerful tools for the design of optoelectronic devices able to manipulate light at the nanoscale.
Scheme for Implementing Quantum Cloning Restoring Machine in Cavity QED
Institute of Scientific and Technical Information of China (English)
YU Long-Bao; ZHANG Wen-Hai; YE Liu
2007-01-01
We propose an experimentally feasible scheme for implementing quantum restoring machine of the optimal universal 1 → 2 quanturn cloning machine in the context of cavity QED.In our scheme,two atoms (the clones) simultaneously interact with a cavity field,and meanwhile they are driven by a classical field.Then an arbitrary unknown input state can be restored in the ancilla by applying appropriate unitary local operation.
Conditional control of quantum beats in a cavity QED system
Norris, D G; Orozco, L A; 10.1088/1742-6596/274/1/012143
2011-01-01
We probe a ground-state superposition that produces a quantum beat in the intensity correlation of a two-mode cavity QED system. We mix drive with scattered light from an atomic beam traversing the cavity, and effectively measure the interference between the drive and the light from the atom. When a photon escapes the cavity, and upon detection, it triggers our feedback which modulates the drive at the same beat frequency but opposite phase for a given time window. This results in a partial interruption of the beat oscillation in the correlation function, that then returns to oscillate.
Weeraddana, Dilusha; Premaratne, Malin; Gunapala, Sarath D.; Andrews, David L.
2016-08-01
A fundamental theory is developed for describing laser-driven resonance energy transfer (RET) in dimensionally constrained nanostructures within the framework of quantum electrodynamics. The process of RET communicates electronic excitation between suitably disposed emitter and detector particles in close proximity, activated by the initial excitation of the emitter. Here, we demonstrate that the transfer rate can be significantly increased by propagation of an auxiliary laser beam through a pair of nanostructure particles. This is due to the higher order perturbative contribution to the Förster-type RET, in which laser field is applied to stimulate the energy transfer process. We construct a detailed picture of how excitation energy transfer is affected by an off-resonant radiation field, which includes the derivation of second and fourth order quantum amplitudes. The analysis delivers detailed results for the dependence of the transfer rates on orientational, distance, and laser intensity factor, providing a comprehensive fundamental understanding of laser-driven RET in nanostructures. The results of the derivations demonstrate that the geometry of the system exercises considerable control over the laser-assisted RET mechanism. Thus, under favorable conformational conditions and relative spacing of donor-acceptor nanostructures, the effect of the auxiliary laser beam is shown to produce up to 70% enhancement in the energy migration rate. This degree of control allows optical switching applications to be identified.
Quantum feedback in a weakly driven cavity QED system
Reiner, J. E.; Smith, W. P.; Orozco, L. A.; Wiseman, H. M.; Gambetta, Jay
2004-08-01
Quantum feedback in strongly coupled systems can probe a regime where one quantum of excitation is a large fluctuation. We present theoretical and experimental studies of quantum feedback in an optical cavity QED system. The time evolution of the conditional state, following a photodetection, can be modified by changing the drive of the cavity. For the appropriate feedback, the conditional state can be captured in a new steady state and then released. The feedback protocol requires resonance operation, and proper amplitude and delay for the change in the drive. We demonstrate the successful use of feedback in the suppression of the vacuum Rabi oscillations for the length of the feedback pulse and their subsequent return to steady state. The feedback works only because we have an entangled quantum system, rather than an analogous correlated classical system.
Quantum entanglement for two qubits in a nonstationary cavity
Berman, Oleg L; Lozovik, Yurii E
2016-01-01
The quantum entanglement and the probability of the dynamical Lamb effect for two qubits caused by non-adiabatic fast change of the boundary conditions are studied. The conditional concurrence of the qubits for each fixed number of created photons in a nonstationary cavity is obtained as a measure of the dynamical quantum entanglement due to the dynamical Lamb effect. We discuss the physical realization of the dynamical Lamb effect, based on superconducting qubits.
Quantum entanglement for two qubits in a nonstationary cavity
Berman, Oleg L.; Kezerashvili, Roman Ya.; Lozovik, Yurii E.
2016-11-01
The quantum entanglement and the probability of the dynamical Lamb effect for two qubits caused by nonadiabatic fast change of the boundary conditions are studied. The conditional concurrence of the qubits for each fixed number of created photons in a nonstationary cavity is obtained as a measure of the dynamical quantum entanglement due to the dynamical Lamb effect. We discuss the physical realization of the dynamical Lamb effect, based on superconducting qubits.
Quantum dynamic behaviour in a coupled cavities system
Institute of Scientific and Technical Information of China (English)
Peng Jun; Wu Yun-Wen; Li Xiao-Juan
2012-01-01
The dynamic behaviour of the two-site coupled cavities model which is doped with ta wo-level system is investigated.The exact dynamic solutions in the general condition are obtained via Laplace transform.The simple analytical solutions are obtained in several particular cases,which demonstrate the clear and simple physical picture for the quantum state transition of the system.In the large detuning or hoppling case,the quantum states transferring between qubits follow a slow periodic oscillation induced by the very weak excitation of the cavity mode.In the large coupling case,the system can be interpreted as two Jaynes-Cummings model subsystems which interact through photon hop between the two cavities.In the case of λ≈△(》) g,the quantum states transition of qubits is accompanied by the excitation of the cavity,and the cavity modes have the same dynamic behaviours and the amplitude of probability is equal to 0.25 which does not change with the variation of parameter.
Cavity quantum networks for quantum information processing in decoherence-free subspace
Institute of Scientific and Technical Information of China (English)
Hua WEI; Zhi-jiao DENG; Wan-li YANG; Fei ZHOU
2009-01-01
We give a brief review on the quantum infor- mation processing in decoherence-free subspace (DFS). We show how to realize the initialization of the entangled quantum states, information transfer and teleportation of quantum states, two-qubit Grover search and how to construct the quantum network in DFS, within the cav- ity QED regime based on a cavity-assisted interaction by single-photon pulses.
Efficient scheme for two-atom entanglement and quantum information processing in cavity QED
Zheng; Guo
2000-09-11
A scheme is proposed for the generation of two-atom maximally entangled states and realization of quantum logic gates and teleportation with cavity QED. The scheme does not require the transfer of quantum information between the atoms and cavity. In the scheme the cavity is only virtually excited and thus the requirement on the quality factor of the cavities is greatly loosened.
Quantum Logic with Cavity Photons From Single Atoms
Holleczek, Annemarie; Barter, Oliver; Rubenok, Allison; Dilley, Jerome; Nisbet-Jones, Peter B. R.; Langfahl-Klabes, Gunnar; Marshall, Graham D.; Sparrow, Chris; O'Brien, Jeremy L.; Poulios, Konstantinos; Kuhn, Axel; Matthews, Jonathan C. F.
2016-07-01
We demonstrate quantum logic using narrow linewidth photons that are produced with an a priori nonprobabilistic scheme from a single 87Rb atom strongly coupled to a high-finesse cavity. We use a controlled-not gate integrated into a photonic chip to entangle these photons, and we observe nonclassical correlations between photon detection events separated by periods exceeding the travel time across the chip by 3 orders of magnitude. This enables quantum technology that will use the properties of both narrow-band single photon sources and integrated quantum photonics.
Quantum repeater based on cavity QED evolutions and coherent light
Gonţa, Denis; van Loock, Peter
2016-05-01
In the framework of cavity QED, we propose a quantum repeater scheme that uses coherent light and chains of atoms coupled to optical cavities. In contrast to conventional repeater schemes, in our scheme there is no need for an explicit use of two-qubit quantum logical gates by exploiting solely the cavity QED evolution. In our previous work (Gonta and van Loock in Phys Rev A 88:052308, 2013), we already proposed a quantum repeater in which the entanglement between two neighboring repeater nodes was distributed using controlled displacements of input coherent light, while the produced low-fidelity entangled pairs were purified using ancillary (four-partite) entangled states. In the present work, the entanglement distribution is realized using a sequence of controlled phase shifts and displacements of input coherent light. Compared to previous coherent-state-based distribution schemes for two-qubit entanglement, our scheme here relies only upon a simple discrimination of two coherent states with opposite signs, which can be performed in a quantum mechanically optimal fashion via a beam splitter and two on-off detectors. For the entanglement purification, we employ a method that avoids the use of extra entangled ancilla states. Our repeater scheme exhibits reasonable fidelities and repeater rates providing an attractive platform for long-distance quantum communication.
Causal signal transmission by quantum fields. V: Quantum electrodynamics in response representation
Plimak, L I
2011-01-01
Using electromagnetic interaction as an example, response transformations [L.P. and S.S., Ann.Phys. 323, 1963, 1989 (2008), 324, 600 (2009)] are applied to the standard perturbative approach of quantum field theory. This approach is rewritten in the form where the place of field propagators is taken by the retarded Green function of the field. Unlike in conventional quantum-field-theoretical techniques, the concept of space-time propagation of quantized field is built into our techniques.
Nataf, Pierre; Ciuti, Cristiano
2010-09-07
In cavity quantum electrodynamics (QED), the interaction between an atomic transition and the cavity field is measured by the vacuum Rabi frequency Ω(0). The analogous term 'circuit QED' has been introduced for Josephson junctions, because superconducting circuits behave as artificial atoms coupled to the bosonic field of a resonator. In the regime with Ω(0) comparable with the two-level transition frequency, 'superradiant' quantum phase transitions for the cavity vacuum have been predicted, for example, within the Dicke model. In this study, we prove that if the time-independent light-matter Hamiltonian is considered, a superradiant quantum critical point is forbidden for electric dipole atomic transitions because of the oscillator strength sum rule. In circuit QED, the analogous of the electric dipole coupling is the capacitive coupling, and such no-go property can be circumvented by Cooper pair boxes capacitively coupled to a resonator, because of their peculiar Hilbert space topology and a violation of the corresponding sum rule.
Gauged Nambu-Jona Lasinio Studies of the Triviality of Quantum Electrodynamics
Kim, S; Lombardo, M P; Kogut, John B.; Lombardo, Maria-Paola
2002-01-01
By adding a small, irrelevant four fermi interaction to the action of noncompact lattice Quantum Electrodynamics (QED), the theory can be simulated with massless quarks in a vacuum free of lattice monopoles. The lattice theory possesses a second order chiral phase transition which we show is logarithmically trivial, with the same systematics as the Nambu-Jona Lasinio model. The irrelevance of the four fermi coupling is established numerically. The widths of the scaling windows are examined in both the coupling constant and bare fermion mass directions in parameter space. For vanishing fermion mass we find a broad scaling window in coupling. By adding a small bare fermion mass to the action we find that the width of the scaling window in the fermion mass direction is very narrow. Only when a subdominant scaling term is added to the leading term of the equation of state are adequate fits to the data possible. The failure of past studies of lattice QED to produce equation of state fits with adequate confidence l...
Sarabi, B; Ramanayaka, A N; Burin, A L; Wellstood, F C; Osborn, K D
2016-04-22
Material-based two-level systems (TLSs), appearing as defects in low-temperature devices including superconducting qubits and photon detectors, are difficult to characterize. In this study we apply a uniform dc electric field across a film to tune the energies of TLSs within. The film is embedded in a superconducting resonator such that it forms a circuit quantum electrodynamical system. The energy of individual TLSs is observed as a function of the known tuning field. By studying TLSs for which we can determine the tunneling energy, the actual p_{z}, dipole moments projected along the uniform field direction, are individually obtained. A distribution is created with 60 p_{z}. We describe the distribution using a model with two dipole moment magnitudes, and a fit yields the corresponding values p=p_{1}=2.8±0.2 D and p=p_{2}=8.3±0.4 D. For a strong-coupled TLS the vacuum-Rabi splitting can be obtained with p_{z} and tunneling energy. This allows a measurement of the circuit's zero-point electric-field fluctuations, in a method that does not need the electric-field volume.
Self-Localized Quasi-Particle Excitation in Quantum Electrodynamics and Its Physical Interpretation
Directory of Open Access Journals (Sweden)
Ilya D. Feranchuk
2007-12-01
Full Text Available The self-localized quasi-particle excitation of the electron-positron field (EPF is found for the first time in the framework of a standard form of the quantum electrodynamics. This state is interpreted as the ''physical'' electron (positron and it allows one to solve the following problems: i to express the ''primary'' charge $e_0$ and the mass $m_0$ of the ''bare'' electron in terms of the observed values of $e$ and $m$ of the ''physical'' electron without any infinite parameters and by essentially nonperturbative way; ii to consider $mu$-meson as another self-localized EPF state and to estimate the ratio $m_mu/m$; iii to prove that the self-localized state is Lorentz-invariant and its energy spectrum corresponds to the relativistic free particle with the observed mass $m$; iv to show that the expansion in a power of the observed charge $e ll 1$ corresponds to the strong coupling expansion in a power of the ''primary'' charge $e^{-1}_0 sim e$ when the interaction between the ''physical'' electron and the transverse electromagnetic field is considered by means of the perturbation theory and all terms of this series are free from the ultraviolet divergence.
Brilliant petawatt gamma-ray pulse generation in quantum electrodynamic laser-plasma interaction
Chang, H. X.; Qiao, B.; Huang, T. W.; Xu, Z.; Zhou, C. T.; Gu, Y. Q.; Yan, X. Q.; Zepf, M.; He, X. T.
2017-03-01
We show a new resonance acceleration scheme for generating ultradense relativistic electron bunches in helical motions and hence emitting brilliant vortical γ-ray pulses in the quantum electrodynamic (QED) regime of circularly-polarized (CP) laser-plasma interactions. Here the combined effects of the radiation reaction recoil force and the self-generated magnetic fields result in not only trapping of a great amount of electrons in laser-produced plasma channel, but also significant broadening of the resonance bandwidth between laser frequency and that of electron betatron oscillation in the channel, which eventually leads to formation of the ultradense electron bunch under resonant helical motion in CP laser fields. Three-dimensional PIC simulations show that a brilliant γ-ray pulse with unprecedented power of 6.7 PW and peak brightness of 1025 photons/s/mm2/mrad2/0.1% BW (at 15 MeV) is emitted at laser intensity of 1.9 × 1023 W/cm2.
Exciton-polariton dynamics in quantum dot-cavity system
Energy Technology Data Exchange (ETDEWEB)
Neto, Antonio F.; Lima, William J.; Villas-Boas, Jose M. [Universidade Federal de Uberlandia (UFU), MG (Brazil). Inst. de Fisica
2012-07-01
Full text: One of the basic requirement for quantum information processing systems is the ability to completely control the state of a single qubit. This imply in know all sources of decoherence and elaborate ways to avoid them. In recent work, A. Laucht et al. [1] presented detailed theoretical and experimental investigations of electrically tunable single quantum dot (QD) - photonic crystal (PhC) nanocavity systems operating in the strong coupling regime of the light matter interaction. Unlike previous studies, where the exciton-cavity spectral detuning was varied by changing the lattice temperature, or by the adsorption of inert gases at low temperatures, they employ the quantum confined Stark-effect to electro-optically control the exciton-cavity detuning. The new built device enabled them to systematically probe the emission spectrum of the strongly coupled system as a function of external control parameters, as for example the incoherent excitation power density or the lattice temperature. Those studies reveal for the first time insights in dephasing mechanisms of 0D exciton polaritons [1]. In another study [2], using a similar device, they investigate the coupling between two different QDs with a single cavity mode. In both works, incoherent pumping was used, but for quantum information, coherent and controlled excitations are necessary. Here, we theoretically investigate the dynamics a single quantum dot inside a cavity under coherent pulse excitation and explore a wide range of parameters, as for example, the exciton-cavity detunings, the excitation power, the spontaneous decay, and pure dephasing. We use density matrix formalism in the Lindblad form, and we solve it numerically. Our results show that coherent excitation can be used to probe strong coupling between exciton and cavity mode by monitoring the exciton Rabi oscillation as function of the cavity detuning. This can give new insights for future experimental measurement focusing on quantum
A Monolithic Filter Cavity for Experiments in Quantum Optics
Palittapongarnpim, Pantita; Lvovsky, A I
2012-01-01
By applying a high-reflectivity dielectric coating on both sides of a commercial plano-convex lens, we produce a stable monolithic Fabry-Perot cavity suitable for use as a narrow band filter in quantum optics experiments. The resonant frequency is selected by means of thermal expansion. Owing to the long term mechanical stability, no optical locking techniques are required. We characterize the cavity performance as an optical filter, obtaining a 45 dB suppression of unwanted modes while maintaining a transmission of 60%.
Quantum Cavity Optomechanics with Phononic Bandgap Shielded Silicon Nitride Membranes
DEFF Research Database (Denmark)
Nielsen, William Hvidtfelt Padkær
Cavity optomechanics, a field which has matured tremendously over the last decade,has conclusively reached the quantum regime. Noteworthy experimentalachievements include cooling of the vibrational motion of macroscopic objects tothe quantum ground state, the observation of shot noise of radiation...... two highly reflective mirrors, all of which are embedded in a helium flowcryostat. In order to reach truly quantum territory, severe shielding of the membranefrom the environment is required, as well as meticulous concern for auxiliarysources of noise, both from the laser and mirrors used.The purpose...... of this thesis is to document the development of the experimentfrom its initial stages to its final quantum enabled incarnation, as well as to providethe necessary theoretical machinery to interpret the experimental results. A strongemphasis is placed on the unique challenges posed by our unique monolithic...
From quantum feedback to probabilistic error correction: manipulation of quantum beats in cavity QED
Energy Technology Data Exchange (ETDEWEB)
Barberis-Blostein, P [Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, 04510, Mexico, DF (Mexico); Norris, D G; Orozco, L A; Carmichael, H J [Joint Quantum Institute, Department of Physics, University of Maryland and National Institute of Standards and Technology, College Park, MD 20742 (United States)], E-mail: lorozco@umd.edu
2010-02-15
It is shown how one can implement quantum feedback and probabilistic error correction in an open quantum system consisting of a single atom, with ground- and excited-state Zeeman structure, in a driven two-mode optical cavity. The ground-state superposition is manipulated and controlled through conditional measurements and external fields, which shield the coherence and correct quantum errors. Modeling an experimentally realistic situation demonstrates the robustness of the proposal for realization in the laboratory.
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
We propose a scheme for generating a maximally entangled state of two three-level superconducting quantum interference devices (SQUIDs) by using a quantized cavity field and classical microwave pluses in cavity. In this scheme, no quantum information will be transferred from the SQUIDs to the cavity since the cavity field is only virtually excited. Thus, the cavity decay is suppressed during the entanglement generation.
Space-time evolution of ultrarelativistic quantum dipoles in quantum electrodynamics
Blok, B.
2004-09-01
We discuss space-time evolution of ultrarelativistic quantum dipole in QED. We show that the space-time evolution can be described, in a certain approximation, by means of a regularized wave function, whose parameters are determined by the process of the dipole creation by a local current. Using these wave functions, we derive the dipole expansion law that is found to coincide parametrically in the leading order with the one suggested by G. R. Farrar et al. (G. R. Farrar, H. Liu, L. Frankfurt and M. Strikman, Phys. Rev. Lett, Vol.61, p.686, 1988).
Heusler, Stefan
2006-12-01
The main focus of the second, enlarged edition of the book Mathematica for Theoretical Physics is on computational examples using the computer program Mathematica in various areas in physics. It is a notebook rather than a textbook. Indeed, the book is just a printout of the Mathematica notebooks included on the CD. The second edition is divided into two volumes, the first covering classical mechanics and nonlinear dynamics, the second dealing with examples in electrodynamics, quantum mechanics, general relativity and fractal geometry. The second volume is not suited for newcomers because basic and simple physical ideas which lead to complex formulas are not explained in detail. Instead, the computer technology makes it possible to write down and manipulate formulas of practically any length. For researchers with experience in computing, the book contains a lot of interesting and non-trivial examples. Most of the examples discussed are standard textbook problems, but the power of Mathematica opens the path to more sophisticated solutions. For example, the exact solution for the perihelion shift of Mercury within general relativity is worked out in detail using elliptic functions. The virial equation of state for molecules' interaction with Lennard-Jones-like potentials is discussed, including both classical and quantum corrections to the second virial coefficient. Interestingly, closed solutions become available using sophisticated computing methods within Mathematica. In my opinion, the textbook should not show formulas in detail which cover three or more pages—these technical data should just be contained on the CD. Instead, the textbook should focus on more detailed explanation of the physical concepts behind the technicalities. The discussion of the virial equation would benefit much from replacing 15 pages of Mathematica output with 15 pages of further explanation and motivation. In this combination, the power of computing merged with physical intuition
Directory of Open Access Journals (Sweden)
Guilherme Tosi
2014-08-01
Full Text Available Recent advances in silicon nanofabrication have allowed the manipulation of spin qubits that are extremely isolated from noise sources, being therefore the semiconductor equivalent of single atoms in vacuum. We investigate the possibility of directly coupling an electron spin qubit to a superconducting resonator magnetic vacuum field. By using resonators modified to increase the vacuum magnetic field at the qubit location, and isotopically purified 28Si substrates, it is possible to achieve coupling rates faster than the single spin dephasing. This opens up new avenues for circuit-quantum electrodynamics with spins, and provides a pathway for dispersive read-out of spin qubits via superconducting resonators.
Mross, David F; Alicea, Jason; Motrunich, Olexei I
2016-07-01
We explicitly derive the duality between a free electronic Dirac cone and quantum electrodynamics in (2+1) dimensions (QED_{3}) with N=1 fermion flavors. The duality proceeds via an exact, nonlocal mapping from electrons to dual fermions with long-range interactions encoded by an emergent gauge field. This mapping allows us to construct parent Hamiltonians for exotic topological-insulator surface phases, derive the particle-hole-symmetric field theory of a half-filled Landau level, and nontrivially constrain QED_{3} scaling dimensions. We similarly establish duality between bosonic topological insulator surfaces and N=2 QED_{3}.
Energy Technology Data Exchange (ETDEWEB)
Radozycki, Tomasz [Cardinal Stefan Wyszynski University, Faculty of Mathematics and Natural Sciences, College of Sciences, Warsaw (Poland)
2015-09-15
The Lorentz transformation properties of the equal-time bound-state Bethe-Salpeter amplitude in the two-dimensional massless quantum electrodynamics (the so-called Schwinger model) are considered. It is shown that while boosting a bound state (a 'meson') this amplitude is subject to approximate Lorentz contraction. The effect is exact for large separations of constituent particles ('quarks'), while for small distances the deviation is more significant. For this phenomenon to appear, the full function, i.e. with the inclusion of all instanton contributions, has to be considered. The amplitude in each separate topological sector does not exhibit such properties. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Radożycki, Tomasz, E-mail: t.radozycki@uksw.edu.pl [Faculty of Mathematics and Natural Sciences, College of Sciences, Cardinal Stefan Wyszyński University, Wóycickiego 1/3, 01-938, Warsaw (Poland)
2015-09-24
The Lorentz transformation properties of the equal-time bound-state Bethe–Salpeter amplitude in the two-dimensional massless quantum electrodynamics (the so-called Schwinger model) are considered. It is shown that while boosting a bound state (a ‘meson’) this amplitude is subject to approximate Lorentz contraction. The effect is exact for large separations of constituent particles (‘quarks’), while for small distances the deviation is more significant. For this phenomenon to appear, the full function, i.e. with the inclusion of all instanton contributions, has to be considered. The amplitude in each separate topological sector does not exhibit such properties.
Voisin, G.; Bonazzola, S.; Mottez, F.
2016-12-01
Curvature radiation is a key phenomenon in pulsar and magnetar magnetospheres. It is classically conceptually very close to synchrotron radiation, however we will show that in ultra-relativistic very-high-magnetic-field environments, the same approximations that lead to its use are also leading quickly to a potential quantized regime where the classical theory may fail. We explain in some details these caveats and give an outline of a quantum-electrodynamics treatment. We show that the internal consistency of the theory of curvature radiation is improved, and some interesting effects due to spin-flip transitions may occur.
Energy Technology Data Exchange (ETDEWEB)
Tosi, Guilherme, E-mail: g.tosi@unsw.edu.au; Mohiyaddin, Fahd A.; Morello, Andrea, E-mail: a.morello@unsw.edu.au [Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia. (Australia); Huebl, Hans [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching (Germany); Nanosystems Initiative Munich (NIM), Schellingstr. 4, D-80799 Munich, Germany. (Germany)
2014-08-15
Recent advances in silicon nanofabrication have allowed the manipulation of spin qubits that are extremely isolated from noise sources, being therefore the semiconductor equivalent of single atoms in vacuum. We investigate the possibility of directly coupling an electron spin qubit to a superconducting resonator magnetic vacuum field. By using resonators modified to increase the vacuum magnetic field at the qubit location, and isotopically purified {sup 28}Si substrates, it is possible to achieve coupling rates faster than the single spin dephasing. This opens up new avenues for circuit-quantum electrodynamics with spins, and provides a pathway for dispersive read-out of spin qubits via superconducting resonators.
Preparation of the W state via cavity QED
Institute of Scientific and Technical Information of China (English)
ZHANG Jin; YE Liu
2004-01-01
A scheme for preparation of the tripartite W state via cavity quantum electrodynamics is presented in this paper. And the scheme can be generalized to prepare the n-atom W states. The second part of this paper shows how to prepare n-cavity W states. All cavities involved are initially in the vacuum states, thus the requirement on the quality factor of the cavities is greatly loosened.
Teleportation of atomic entangled states with a thermal cavity
Institute of Scientific and Technical Information of China (English)
Zheng Xiao-Juan; Fang Mao-Fa; Cai Jian-Wu; Liao Xiang-Ping
2006-01-01
We propose a most simple and experimentally feasible scheme for teleporting unknown atomic entangled states in driven cavity quantum electrodynamics (QED). In our scheme, the joint Bell-state measurement (BSM) is not required,and the successful probability can reach 1.0. Furthermore, the scheme is insensitive to the cavity decay and the thermal field.
Probing anharmonicity of a quantum oscillator in an optomechanical cavity
Latmiral, Ludovico; Armata, Federico; Genoni, Marco G.; Pikovski, Igor; Kim, M. S.
2016-05-01
We present a way of measuring with high precision the anharmonicity of a quantum oscillator coupled to an optical field via radiation pressure. Our protocol uses a sequence of pulsed interactions to perform a loop in the phase space of the mechanical oscillator, which is prepared in a thermal state. We show how the optical field acquires a phase depending on the anharmonicity. Remarkably, one only needs small initial cooling of the mechanical motion to probe even small anharmonicities. Finally, by applying tools from quantum estimation theory, we calculate the ultimate bound on the estimation precision posed by quantum mechanics and compare it with the precision obtainable with feasible measurements such as homodyne and heterodyne detection on the cavity field. In particular we demonstrate that homodyne detection is nearly optimal in the limit of a large number of photons of the field and we discuss the estimation precision of small anharmonicities in terms of its signal-to-noise ratio.
Schemes for Generating Cluster States via Cavity Systems
Institute of Scientific and Technical Information of China (English)
DU Gang; LAI Bo-Hui; YU Ya-Fei; ZHANG Zhi-Ming
2009-01-01
We propose a scheme for generating an N-atom cluster state via cavity quantum electrodynamics (CQED).In our scheme, there is no transfer of quantum information between the atoms and the cavity, i.e., the cavity is always in the vacuum state, so the cavity decay can be suppressed.Also, the generated cluster state is the entanglement of the ground states, so the atomic spontaneous emission can be avoided.Therefore, the cluster state generated in our scheme has a longer lifetime. Furthermore, the requirement on the quality factor of the cavity greatly loosened for the cavity is only virtually excited.
Cavity-assisted dynamical quantum phase transition in superconducting quantum simulators
Tian, Lin
Coupling a quantum many-body system to a cavity can create bifurcation points in the phase diagram, where the many-body system switches between different phases. Here I will discuss the dynamical quantum phase transitions at the bifurcation points of a one-dimensional transverse field Ising model coupled to a cavity. The Ising model can be emulated with various types of superconducting qubits connected in a chain. With a time-dependent Bogoliubov method, we show that an infinitesimal quench of the driving field can cause gradual evolution of the transverse field on the Ising spins to pass through the quantum critical point. Our calculation shows that the cavity-induced nonlinearity plays an important role in the dynamics of this system. Quasiparticles can be excited in the Ising chain during this process, which results in the deviation of the system from its adiabatic ground state. This work is supported by the National Science Foundation under Award Number 0956064.
Energy Technology Data Exchange (ETDEWEB)
Rueda, A.
1986-11-11
Further discussions and detailed calculations on the problem of the spontaneous acceleration of free electromagnetically interacting particles by the zero-point field in the light of a quantum version of the Einstein-Hopf model are presented. It is shown that acceleration occurs if the zero-point field is represented in a time-symmetric fashion within the viewpoint of the Wheeler-Feynman radiant-absorber theory. However, if the zero-point field is represented in the time-asymmetric form, the quantum Einstein-Hopf model yields no translational kinetic-energy growth in disagreement with the previous prediction and with the result of the classical version of the zero-point field in stochastic electrodynamics. The calculations are clear and compelling. Despite that the last no-acceleration result is germane to phenomenological thermodynamics expectations and to a more consistent perspective of quantum theory, the second quantization that leads to the time-symmetric zero-point field yields a conceptually more satisfactory view of this background field which is no longer a free virtual field but becomes a real field which is originated in and is associated with particles. The discussion is based on the different boundary conditions for the electromagnetic-field tensor that the zero-point field (asymmetric vs. symmetric) requires in quantum and in classical theory: time symmetry presupposes a universe that is opaque. If this condition does not hold, we are forced to ordinary time asymmetry and, if a correspondence with quantum electrodynamics is desired, some modification of the hypothesis of stochastic electrodynamics would be required to prevent acceleration. The possible form of that modification is suggested.
Kotikov, A V
2013-01-01
We compute the two-loop fermion self-energy in massless reduced quantum electrodynamics for an arbitrary gauge using the method of integration by parts. Focusing on the limit where the photon field is four-dimensional, our formula involves only recursively one-loop integrals and can therefore be evaluated exactly. From this formula, we deduce the anomalous scaling dimension of the fermion field as well as the renormalized fermion propagator up to two loops. The results are then applied to the ultra-relativistic limit of graphene and compared with similar results obtained for four-dimensional and three-dimensional quantum electrodynamics.
Realizing and characterizing chiral photon flow in a circuit quantum electrodynamics necklace.
Wang, Yan-Pu; Wang, Wei; Xue, Zheng-Yuan; Yang, Wan-Li; Hu, Yong; Wu, Ying
2015-02-10
Gauge theory plays the central role in modern physics. Here we propose a scheme of implementing artificial Abelian gauge fields via the parametric conversion method in a necklace of superconducting transmission line resonators (TLRs) coupled by superconducting quantum interference devices (SQUIDs). The motivation is to synthesize an extremely strong effective magnetic field for charge-neutral bosons which can hardly be achieved in conventional solid-state systems. The dynamic modulations of the SQUIDs can induce effective magnetic fields for the microwave photons in the TLR necklace through the generation of the nontrivial hopping phases of the photon hopping between neighboring TLRs. To demonstrate the synthetic magnetic field, we study the realization and detection of the chiral photon flow dynamics in this architecture under the influence of decoherence. Taking the advantages of its simplicity and flexibility, this parametric scheme is feasible with state-of-the-art technology and may pave an alternative way for investigating the gauge theories with superconducting quantum circuits. We further propose a quantitative measure for the chiral property of the photon flow. Beyond the level of qualitative description, the dependence of the chiral flow on external pumping parameters and cavity decay is characterized.
Realizing and characterizing chiral photon flow in a circuit quantum electrodynamics necklace
Wang, Yan-Pu; Wang, Wei; Xue, Zheng-Yuan; Yang, Wan-Li; Hu, Yong; Wu, Ying
2015-02-01
Gauge theory plays the central role in modern physics. Here we propose a scheme of implementing artificial Abelian gauge fields via the parametric conversion method in a necklace of superconducting transmission line resonators (TLRs) coupled by superconducting quantum interference devices (SQUIDs). The motivation is to synthesize an extremely strong effective magnetic field for charge-neutral bosons which can hardly be achieved in conventional solid-state systems. The dynamic modulations of the SQUIDs can induce effective magnetic fields for the microwave photons in the TLR necklace through the generation of the nontrivial hopping phases of the photon hopping between neighboring TLRs. To demonstrate the synthetic magnetic field, we study the realization and detection of the chiral photon flow dynamics in this architecture under the influence of decoherence. Taking the advantages of its simplicity and flexibility, this parametric scheme is feasible with state-of-the-art technology and may pave an alternative way for investigating the gauge theories with superconducting quantum circuits. We further propose a quantitative measure for the chiral property of the photon flow. Beyond the level of qualitative description, the dependence of the chiral flow on external pumping parameters and cavity decay is characterized.
Quantum frequency doubling based on tripartite entanglement with cavities
Juan, Guo; Zhi-Feng, Wei; Su-Ying, Zhang
2016-02-01
We analyze the entanglement characteristics of three harmonic modes, which are the output fields from three cavities with an input tripartite entangled state at fundamental frequency. The entanglement properties of the input beams can be maintained after their frequencies have been up-converted by the process of second harmonic generation. We have calculated the parametric dependences of the correlation spectrum on the initial squeezing factor, the pump power, the transmission coefficient, and the normalized analysis frequency of cavity. The numerical results provide references to choose proper experimental parameters for designing the experiment. The frequency conversion of the multipartite entangled state can also be applied to a quantum communication network. Project supported by the National Natural Science Foundation of China (Grant No. 91430109), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111401110004), and the Natural Science Foundation of Shanxi Province, China (Grant No. 2014011005-3).
Quantum state transfer and logic gates with two 3-level atoms in cavity QED
Yang, Chui-Ping; Chu, Shih-I.
2004-08-01
We present a new way to implement quantum controlled phase-shift gate, quantum exchange gate (SWAP gate), and quantum state transfer with two 3-level atoms in cavity QED. The method does not involve real excitation of a cavity photon during the operation, thus decoherence induced due to the cavity-photon decay is minimized. In addition, it is remarkable that for all present purposes, no auxiliary atoms or any measurement is needed. Therefore, the operation is significantly simplified.
Quantum Interference Induced Photon Blockade in a Coupled Single Quantum Dot-Cavity System
Tang, Jing; Xu, Xiulai
2015-01-01
We propose an experimental scheme to implement a strong photon blockade with a single quantum dot coupled to a nanocavity. The photon blockade effect can be tremendously enhanced by driving the cavity and the quantum dot simultaneously with two classical laser fields. This enhancement of photon blockade is ascribed to the quantum interference effect to avoid two-photon excitation of the cavity field. Comparing with Jaynes-Cummings model, the second-order correlation function at zero time delay $g^{(2)}(0)$ in our scheme can be reduced by two orders of magnitude and the system sustains a large intracavity photon number. A red (blue) cavity-light detuning asymmetry for photon quantum statistics with bunching or antibunching characteristics is also observed. The photon blockade effect has a controllable flexibility by tuning the relative phase between the two pumping laser fields and the Rabi coupling strength between the quantum dot and the pumping field. Moreover, the photon blockade scheme based on quantum in...
Quantum computation in decoherence-free subspace via cavity-decay-assisted adiabatic passage
Directory of Open Access Journals (Sweden)
FENG Xunli
2015-08-01
Full Text Available In this work,a scheme for quantum computation based on cavity QED in a decoherence-free subspaces via using the technique of stimulated Raman adiabatic passage (STIRAP is proposed.To implement universal quantum logic gates that form basic blocks of quantum computation,we suppose two atoms are trapped in a single-mode cavity with large decay rates and are driven by the laser fields.The relatively large cavity decay can be used for the continuous detection of the cavity mode as so-called ″cavity-decay-induced quantum Zeno effect″.The results show that,decoherence induced by the atomic spontaneous emission and cavity decay can be efficiently suppress with the STIRAP technique and the quantum Zeno effect.
Farzanehpour, Mehdi; Tokatly, Ilya; Nano-Bio Spectroscopy Group; ETSF Scientific Development Centre Team
2015-03-01
We present a rigorous formulation of the time-dependent density functional theory for interacting lattice electrons strongly coupled to cavity photons. We start with an example of one particle on a Hubbard dimer coupled to a single photonic mode, which is equivalent to the single mode spin-boson model or the quantum Rabi model. For this system we prove that the electron-photon wave function is a unique functional of the electronic density and the expectation value of the photonic coordinate, provided the initial state and the density satisfy a set of well defined conditions. Then we generalize the formalism to many interacting electrons on a lattice coupled to multiple photonic modes and prove the general mapping theorem. We also show that for a system evolving from the ground state of a lattice Hamiltonian any density with a continuous second time derivative is locally v-representable. Spanish Ministry of Economy and Competitiveness (Grant No. FIS2013-46159-C3-1-P), Grupos Consolidados UPV/EHU del Gobierno Vasco (Grant No. IT578-13), COST Actions CM1204 (XLIC) and MP1306 (EUSpec).
Decoherence in semiconductor cavity QED systems due to phonon couplings
DEFF Research Database (Denmark)
Nielsen, Per Kær; Mørk, Jesper
2014-01-01
We investigate the effect of electron-phonon interactions on the coherence properties of single photons emitted from a semiconductor cavity QED (quantum electrodynamics) system, i.e., a quantum dot embedded in an optical cavity. The degree of indistinguishability, governing the quantum mechanical...... interference between two single photons, is calculated as a function of important parameters describing the cavity QED system and the phonon reservoir, e.g., cavity quality factor, light-matter coupling strength, temperature, and phonon lifetime. We show that non-Markovian effects play an important role...
Near-field Electrodynamics of Atomically Doped Carbon Nanotubes
Bondarev, Igor V.; Lambin, Philippe
2005-01-01
We develop a quantum theory of near-field electrodynamical properties of carbon nanotubes and investigate spontaneous decay dynamics of excited states and van der Waals attraction of the ground state of an atomic system close to a single-wall nanotube surface. Atomic spontaneous decay exhibits vacuum-field Rabi oscillations -- a principal signature of strong atom-vacuum-field coupling. The strongly coupled atomic state is nothing but a 'quasi-1D cavity polariton'. Its stability is mainly dete...
DEFF Research Database (Denmark)
Unsleber, S.; McCutcheon, Dara; Dambach, M.;
We demonstrate the emission of highly indistinguishable photons from a quasiresonantly pumped coupled quantum dot–microcavity system operating in the regime of cavity quantum electrodynamics. Changing the sample temperature allows us to vary the quantum dot–cavity detuning, and on spectral...
Energy Technology Data Exchange (ETDEWEB)
Steinmetz, Tilo
2008-04-29
In the present dissertation experiments on resonator quantum electrodynamics on a microtrap chip are described. Thereby for the first time single atoms catched in a chip trap could be detected. For this in the framework of this thesis a novel optical microresonator was developed, which can because of its miniaturization be combined with the microtrap technique introduced in our working group for the manipulation of ultracold atoms. For this resonator glass-fiber ends are used as mirror substrates, between which a standing light wave is formed. With such a fiber Fabry-Perot resonator we obtain a finess of up to {approx}37,000. Because of the small mode volumina in spite of moderate resonator quality the coherent interaction between an atom and a photon can be made so large that the regime of the strong atom-resonator coupling is reached. For the one-atom-one-photon coupling rate and the one-atom-one-photon cooperativity thereby record values of g{sub 0}=2{pi}.300 MHz respectively C{sub 0}=210 are reached. Just so for the first time the strong coupling regime between a Bose-Einstein condensate (BEC) and the field of a high-quality resonator could be reached. The BEC was thereby by means of the magnetic microtrap potentials deterministically brought to a position within the resonator and totally transformed in a well defined antinode of an additionally optical standing-wave trap. The spectrum of the coupled atom-resonator system was measured for different atomic numbers and atom-resonator detunings, whereby a collective vacuum Rabi splitting of more than 20 GHz could be reached. [German] In der vorliegenden Dissertation werden Experimente zur Resonator-Quantenelektrodynamik auf einem Mikrofallenchip beschrieben. Dabei konnte u. a. erstmals einzelne, in einer Chipfalle gefangene Atome detektiert werden. Hier fuer wurde im Rahmen dieser Arbeit ein neuartiger optischer Mikroresonator entwickelt, der sich dank seiner Miniaturisierung mit der in unserer Arbeitsgruppe
Scheme for splitting quantum information via W states in cavity QED systems
Institute of Scientific and Technical Information of China (English)
Yu Xi-Mei; Gu Yong-Jian; Ma Li-Zhen; Zhou Bang-An
2008-01-01
Assisted by multipartite entanglement,Quantum information may be split so that the original qubit can be reconstructed if and only if the recipients cooperate.This paper proposes an experimentally feasible scheme for splitting quantum information via W-type entangled states in cavity QED systems,where three-level Rydberg atoms interact with nonresonant cavities.Since W-type states are used as the quantum channel and the cavities are only virtually excited,the scheme is easy to implement and robust against decoherence,and the dependence on the quality factor of the cavities is greatly reduced.
Institute of Scientific and Technical Information of China (English)
ZHAN Zhi-Ming; LI Wei-Bin
2007-01-01
We present a scheme to generate cluster states with many atoms in cavity QED via Raman transition. In this scheme, no transfer of quantum information between the atoms and cavities is required, the cavity fields are only virtually excited and thus the cavity decay is suppressed during the generation of cluster states. The atoms are always populated in the two ground states. Therefore, the scheme is insensitive to the atomic spontaneous emission and cavity decay. We also show how to transfer quantum information from one atom to another.
Electrodynamics and quantum capacity: The case of Bi{sub 2}Se{sub 3} topological insulator
Energy Technology Data Exchange (ETDEWEB)
Craco, L. [Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá, MT (Brazil)
2015-11-14
Layered Bi-chalcogenide topological insulators are among the most available energy conversion (thermoelectric) and storage (battery) materials. Motivated by this applied aspect of fundamental importance and the good agreement between theory and key experiments probing spectroscopy and dc transport, we undertake a detailed study of electrodynamic responses of bulk Bi{sub 2}Se{sub 3} topological insulator. In particular, we confirm that the interplay between spin-orbit and electron correlations underpins its bulk metallicity. We show the implications of our proposal for the multi-channel nature of galvanostatic, voltage-capacity profiles intrinsic to Li{sub x}Bi{sub 2}Se{sub 3} battery material. Supported by a microscopic description of quantum capacity, we predict that layered Bi-based topological insulators are promising candidates for future high-voltage solid-state batteries.
Perturbing open cavities: Anomalous resonance frequency shifts in a hybrid cavity-nanoantenna system
Ruesink, Freek; Hendrikx, Ruud; Koenderink, A Femius; Verhagen, Ewold
2015-01-01
The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a non-trivial phase relation between cavity and nanoparticle radiation, allowing back-action via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems.
Perturbing Open Cavities: Anomalous Resonance Frequency Shifts in a Hybrid Cavity-Nanoantenna System
Ruesink, Freek; Doeleman, Hugo M.; Hendrikx, Ruud; Koenderink, A. Femius; Verhagen, Ewold
2015-11-01
The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics, and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here, we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a nontrivial phase relation between cavity and nanoparticle radiation, allowing backaction via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems.
Protocol for multi-party superdense coding by using multi-atom in cavity QED
Institute of Scientific and Technical Information of China (English)
Tan Jia; Fang Mao-Fa
2006-01-01
We present a protocol for multi-party superdense coding by using multi-atom in cavity quantum electrodynamics (QED). It is shown that, with a highly detuned cavity mode and a strong driving field, the protocol is insensitive to both cavity decay and thermal field. It is even certain to identify GHZ states via detecting the atomic states. Therefore we can realize the quantum dense coding in a simple way in the multiparty system.
Srinivasan, S J; Hoffman, A J; Gambetta, J M; Houck, A A
2011-02-25
We introduce a new type of superconducting charge qubit that has a V-shaped energy spectrum and uses quantum interference to provide independently tunable qubit energy and coherent coupling to a superconducting cavity. Dynamic access to the strong coupling regime is demonstrated by tuning the coupling strength from less than 200 kHz to greater than 40 MHz. This tunable coupling can be used to protect the qubit from cavity-induced relaxation and avoid unwanted qubit-qubit interactions in a multiqubit system.
Cavity QED and quantum computation in the weak coupling regime
Fujii, Kazuyuki; Higashida, Kyoko; Kato, Ryosuke; Wada, Yukako
2004-12-01
In this paper we consider a model of quantum computation based on n atoms, laser cooled and trapped linearly in a cavity, and realize it as the n-atom Tavis-Cummings Hamiltonian interacting with n external (laser) fields. We solve the Schrödinger equation of the model in the case of n = 2 and construct the controlled NOT gate by making use of a resonance condition and the rotating wave approximation associated with it. Our method is not heuristic but completely mathematical, and the significant feature is the consistent use of Rabi oscillations. We also present an idea for the construction of three controlled NOT gates in the case of n = 3 which gives a controlled-controlled NOT gate.
Cavity QED and Quantum Computation in the Weak Coupling Regime
Fujii, K; Kato, R; Wada, Y; Fujii, Kazuyuki; Higashida, Kyoko; Kato, Ryosuke; Wada, Yukako
2004-01-01
In this paper we consider a model of quantum computation based on n atoms of laser--cooled and trapped linearly in a cavity and realize it as the n atoms Tavis--Cummings Hamiltonian interacting with n external (laser) fields. We solve the Schr{\\" o}dinger equation of the model in the case of n=2 and construct the controlled NOT gate by making use of a resonance condition and rotating wave approximation associated to it. Our method is not heuristic but completely mathematical, and the significant feature is a consistent use of Rabi oscillations. We also present a problem related to the construction of (three) controlled NOT gates in the case of n=3 which gives the controlled-controlled NOT gate.
Cavity QED and quantum computation in the weak coupling regime
Energy Technology Data Exchange (ETDEWEB)
Fujii, Kazuyuki; Higashida, Kyoko; Kato, Ryosuke; Wada, Yukako [Department of Mathematical Sciences, Yokohama City University, Yokohama 236-0027 (Japan)
2004-12-01
In this paper we consider a model of quantum computation based on n atoms, laser cooled and trapped linearly in a cavity, and realize it as the n-atom Tavis-Cummings Hamiltonian interacting with n external (laser) fields. We solve the Schroedinger equation of the model in the case of n = 2 and construct the controlled NOT gate by making use of a resonance condition and the rotating wave approximation associated with it. Our method is not heuristic but completely mathematical, and the significant feature is the consistent use of Rabi oscillations. We also present an idea for the construction of three controlled NOT gates in the case of n = 3 which gives a controlled-controlled NOT gate.
Proposal for a telecom quantum repeater with single atoms in optical cavities
Uphoff, Manuel; Brekenfeld, Manuel; Niemietz, Dominik; Ritter, Stephan; Rempe, Gerhard
2016-05-01
Quantum repeaters hold the promise to enable long-distance quantum communication via entanglement generation over arbitrary distances. Single atoms in optical cavities have been shown to be ideally suited for the experimental realization of many tasks in quantum communication. To utilize these systems for a quantum repeater, it would be desirable to operate them at telecom wavelengths. We propose to use a cascaded scheme employing transitions at telecom wavelengths between excited states of alkali atoms for entanglement generation between a single photon at telecom wavelength and a single atom at the crossing point of two cavity modes. A cavity-assisted quantum gate can be used for entanglement swapping. We estimate the performance of these systems using numerical simulations based on experimental parameters obtained for CO2 laser-machined fiber cavities in our laboratory. Finally, we show that a quantum repeater employing the aforementioned scheme and current technology could outperform corresponding schemes based on direct transmission.
Efficient generation of Bell-cat states in remote cavities
Institute of Scientific and Technical Information of China (English)
LI Xing; ZHANG Ying-Jie; XIA Yun-Jie
2008-01-01
In the context of cavity quantum electrodynamics (QED), a potential scheme is proposed to generate entangled coherentstates. The scheme includes twice interactions of two-level atoms with cavities. In the first interaction, two atoms are sentinto a microwave cavity with the large detuning respectively. And then the second interaction is that the two atoms enteranother microwave cavity and are driven by a resonant classical field meantime. When we choose the proper interactiontime and make measurement on the two atoms, the two microwave cavity mode fields are determinatively entangled. Inaddition, it is easy to generalize the scheme to multi-cavity and multi-atom.
Scheme to Implement Optimal Asymmetric Economical Phase-Covariant Quantum Cloning in Cavity QED
Institute of Scientific and Technical Information of China (English)
YANG Chun-Nuan; ZHANG Wen-Hai; HE Jin-Chun; DAI Jie-Lin; HUANG Nian-Ning; YE Liu
2008-01-01
We propose an experimentally feasible scheme to implement the optimal asymmetric economical 1 → 2 phase-covariant quantum cloning in two dimensions based on the cavity QED technique. The protocol is very simple and only two atoms are required. Our scheme is insensitive to the cavity field states and cavity decay. During the processes, the cavity is only virtually excited and it thus greatly prolongs the efficient decoherent time. Therefore, it may be realized in experiment.
Reinisch, Gilbert C.; Gazeau, Maxime
2016-07-01
In this paper we consider a basic two-level nonlinear quantum model consisting in a two-particle interacting bound-state system. It is described by means of two different approaches: i) the mean-field stationary nonlinear Schrödinger-Poisson equation with classical Coulomb interaction and harmonic potential; ii) the linear quantum electrodynamics Hamiltonian of a quantized field coupled to two fixed charges. Computing numerically the ground state and the first excited state about the maximum eigenstate overlap (which is not zero because of eigenstate non-orthogonality), we numerically demonstrate that these two descriptions coincide at first order. As a consequence, a specific definition of the fine-structure constant α is provided within 99.95% accuracy by the present first-order non-relativistic and nonlinear quantum description. This result also means that the internal Coulomb interaction commutes with external particle confinement for the calculation of the ground state. Consequently peculiar nonlinear quantum properties become observable (an experiment with GaAs quantum-dot helium is suggested).
Femtojoule-Scale All-Optical Latching and Modulation via Cavity Nonlinear Optics
Kwon, Yeong-Dae; Armen, Michael A.; Mabuchi, Hideo
2013-11-01
We experimentally characterize Hopf bifurcation phenomena at femtojoule energy scales in a multiatom cavity quantum electrodynamical (cavity QED) system and demonstrate how such behaviors can be exploited in the design of all-optical memory and modulation devices. The data are analyzed by using a semiclassical model that explicitly treats heterogeneous coupling of atoms to the cavity mode. Our results highlight the interest of cavity QED systems for ultralow power photonic signal processing as well as for fundamental studies of mesoscopic nonlinear dynamics.
Cavity-photon-switched coherent transient transport in a double quantum waveguide
Energy Technology Data Exchange (ETDEWEB)
Abdullah, Nzar Rauf, E-mail: nra1@hi.is; Gudmundsson, Vidar, E-mail: vidar@raunvis.hi.is [Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik (Iceland); Tang, Chi-Shung [Department of Mechanical Engineering, National United University, 1, Lienda, 36003 Miaoli, Taiwan (China); Manolescu, Andrei [School of Science and Engineering, Reykjavik University, Menntavegur 1, IS-101 Reykjavik (Iceland)
2014-12-21
We study a cavity-photon-switched coherent electron transport in a symmetric double quantum waveguide. The waveguide system is weakly connected to two electron reservoirs, but strongly coupled to a single quantized photon cavity mode. A coupling window is placed between the waveguides to allow electron interference or inter-waveguide transport. The transient electron transport in the system is investigated using a quantum master equation. We present a cavity-photon tunable semiconductor quantum waveguide implementation of an inverter quantum gate, in which the output of the waveguide system may be selected via the selection of an appropriate photon number or “photon frequency” of the cavity. In addition, the importance of the photon polarization in the cavity, that is, either parallel or perpendicular to the direction of electron propagation in the waveguide system is demonstrated.
Hwang, Myung-Joong; Kim, M S; Choi, Mahn-Soo
2016-04-15
We explore the photon population dynamics in two coupled circuit QED systems. For a sufficiently weak intercavity photon hopping, as the photon-cavity coupling increases, the dynamics undergoes double transitions first from a delocalized to a localized phase and then from the localized to another delocalized phase. The latter delocalized phase is distinguished from the former one; instead of oscillating between the two cavities, the photons rapidly quasiequilibrate over the two cavities. These intriguing features are attributed to an interplay between two qualitatively distinctive nonlinear behaviors of the circuit QED systems in the utrastrong coupling regime, whose distinction has been widely overlooked.
Engineering topological materials in microwave cavity arrays
Anderson, Brandon M; Owens, Clai; Schuster, David I; Simon, Jonathan
2016-01-01
We present a scalable architecture for the exploration of interacting topological phases of photons in arrays of microwave cavities, using established techniques from cavity and circuit quantum electrodynamics. A time-reversal symmetry breaking (non-reciprocal) flux is induced by coupling the microwave cavities to ferrites, allowing for the production of a variety of topological band structures including the $\\alpha=1/4$ Hofstadter model. Effective photon-photon interactions are included by coupling the cavities to superconducting qubits, and are sufficient to produce a $\
Mullin, Jonathan; Valley, Nicholas; Blaber, Martin G; Schatz, George C
2012-09-27
Multiscale models that combine quantum mechanics and classical electrodynamics are presented, which allow for the evaluation of surface-enhanced Raman (SERS) and hyper-Raman scattering spectra (SEHRS) for both chemical (CHEM) and electrodynamic (EM) enhancement mechanisms. In these models, time-dependent density functional theory (TDDFT) for a system consisting of the adsorbed molecule and a metal cluster fragment of the metal particle is coupled to Mie theory for the metal particle, with the surface of the cluster being overlaid with the surface of the metal particle. In model A, the electromagnetic enhancement from plasmon-excitation of the metal particle is combined with the chemical enhancement associated with a static treatment of the molecule-metal structure to determine overall spectra. In model B, the frequency dependence of the Raman spectrum of the isolated molecule is combined with the enhancements determined in model A to refine the enhancement estimate. An equivalent theory at the level of model A is developed for hyper-Raman spectra calculations. Application to pyridine interacting with a 20 nm diameter silver sphere is presented, including comparisons with an earlier model (denoted G), which combines plasmon enhanced fields with gas-phase Raman (or hyper-Raman) spectra. The EM enhancement factor for spherical particles at 357 nm is found to be 10(4) and 10(6) for SERS and SEHRS, respectively. Including both chemical and electromagnetic mechanisms at the level of model A leads to enhancements on the order of 10(4) and 10(9) for SERS and SEHRS.
Classical and Quantum Theory of Photothermal Cavity Cooling of a Mechanical Oscillator
Restrepo, Juan; Ciuti, Cristiano; Favero, Ivan
2010-01-01
Photothermal effects allow very efficient optomechanical coupling between mechanical degrees of freedom and photons. In the context of cavity cooling of a mechanical oscillator, the question of if the quantum ground state of the oscillator can be reached using photothermal back-action has been debated and remains an open question. Here we address this problem by complementary classical and quantum calculations. Both lead us to conclude that: first, the ground-state can indeed be reached using photothermal cavity cooling, second, it can be reached in a regime where the cavity detuning is small allowing a large amount of photons to enter the cavity.
Fundamental properties of devices for quantum information technology
DEFF Research Database (Denmark)
Nielsen, Per Kær
This thesis reports a theoretical investigation of the influence of the electronphonon interaction on semiconductor cavity quantum electrodynamical systems, specifically a quantum dot coupled to an optical microcavity. We develop a theoretical description of the decay dynamics of the quantum dot ...
Many-Body Quantum Electrodynamics Networks: Non-Equilibrium Condensed Matter Physics with Light
Hur, Karyn Le; Henriet, Loïc; Petrescu, Alexandru; Plekhanov, Kirill; Roux, Guillaume; Schiró, Marco
2015-01-01
We review recent developments concerning non-equilibrium quantum dynamics and many-body physics with light, in superconducting circuits and Josephson analogues. We start with quantum impurity models summarizing the effect of dissipation and of driving the system. We mention theoretical and experimental efforts to characterize these non-equilibrium quantum systems. We show how Josephson junction systems can implement the equivalent of the Kondo effect with microwave photons. The Kondo effect i...
Coherent quantum state storage and transfer between two phase qubits via a resonant cavity.
Sillanpää, Mika A; Park, Jae I; Simmonds, Raymond W
2007-09-27
As with classical information processing, a quantum information processor requires bits (qubits) that can be independently addressed and read out, long-term memory elements to store arbitrary quantum states, and the ability to transfer quantum information through a coherent communication bus accessible to a large number of qubits. Superconducting qubits made with scalable microfabrication techniques are a promising candidate for the realization of a large-scale quantum information processor. Although these systems have successfully passed tests of coherent coupling for up to four qubits, communication of individual quantum states between superconducting qubits via a quantum bus has not yet been realized. Here, we perform an experiment demonstrating the ability to coherently transfer quantum states between two superconducting Josephson phase qubits through a quantum bus. This quantum bus is a resonant cavity formed by an open-ended superconducting transmission line of length 7 mm. After preparing an initial quantum state with the first qubit, this quantum information is transferred and stored as a nonclassical photon state of the resonant cavity, then retrieved later by the second qubit connected to the opposite end of the cavity. Beyond simple state transfer, these results suggest that a high-quality-factor superconducting cavity could also function as a useful short-term memory element. The basic architecture presented here can be expanded, offering the possibility for the coherent interaction of a large number of superconducting qubits.
Efficient scheme of quantum SWAP gate and multi-atom cluster state via cavity QED
Institute of Scientific and Technical Information of China (English)
Jiang Chun-Lei; Fang Mao-Fa; Hu Yao-Hua
2008-01-01
In this paper,we propose a physical scheme to realize quantum SWAP gate by using a large-detuned single-mode cavity field and two identical Rydberg atoms.It is shown that the scheme can also be used to create multi-atom cluster state.During the interaction between atom and cavity,the cavity is only virtually excited and thus the scheme is insensitive to the cavity field states and cavity decay.With the help of our scheme it is very simple to prepare the N-atom cluster state with perfect fidelity and probability.The practical feasibility of this method is also discussed.
Quantum Statistical Properties of the Exciton in a Leaky Quasi-Mode Cavity
Institute of Scientific and Technical Information of China (English)
YU Zhao-Xian; JIAO Zhi-Yong
2002-01-01
We have studied quantum statistical properties of the exciton in a leaky quasi-mode cavity. It is shown that when the exciton is initially in a squeezed coherent state whereas cavity initially in a vacuum state, there is energy exchange between the exciton and cavity. Both the exciton and cavity may exhibit sub-Poissonian distribution and exist quadrature squeezing. Calculation shows that correlation between the exciton and cavity is classical, which implies that there is not the violation of the Cauchy-Schwartz inequality.
Francis, C
2006-01-01
A Relational Quantum Theory Incorporating Gravity developed the concept of quantum covariance and argued that this is the correct expression of the fundamental physical principle that the behaviour of matter is everywhere the same in the quantum domain, as well as being the required condition for the unification of general relativity with quantum mechanics for non-interacting particles. This paper considers the interactions of elementary particles. Quantum covariance describes families of finite dimensional Hilbert spaces with an inbuilt cut-off in energy-momentum and using flat space metric (quantum coordinates) between initial and final states. It is shown by direct construction that it is possible to construct a quantum field theory of operators on members of these families, obeying locality, suitable for a description of particle interactions, and leading to a general formulation of particle theoretic field theory incorporating qed. The construction is consistent and effectively identical in the continuum...
Institute of Scientific and Technical Information of China (English)
YANG Zhen; ZHANG Wen-Hai; HE Juan; YE Liu
2008-01-01
We propose a scheme to implement the optimal symmetric 1 → 2 universal quantum telecloning through cavity-assisted interaction. In our scheme, an arbitrary single atomic state can be telecloned to two single atomic states. And three atoms are trapped in three spatially separated cavities respectively. With a particular multiparticle entangled state acting as a quantum information channel and the trapped single atom acting as a quantum network node for its long-lived internal state, quantum information can be telecloned among nodes and can stored in the nodes.
Optical scatter of quantum noise filter cavity optics
Vander-Hyde, Daniel; Smith, Joshua R
2014-01-01
We report on measurements of light scattering from two two-inch super-polished fused silica substrates before and after applying (ATFilms) ion-beam sputtered highly-reflective dielectric coatings. We used an imaging scatterometer, that illuminates the sample with a linearly polarized 1064 nm wavelength laser at a fixed angle of incidence and records images of back scatter for azimuthal angles in the plane of the laser beam, to measure the Bidirectional Reflectance Distribution Function (BRDF) and estimate the total integrated scatter for both samples, before and after coating. We find application of these highly reflective coatings leads to an increase of the integrated scatter of the primary surface by more than 50 %. In addition, the BRDF function of the coated optics takes on a pattern of maxima and zeroes versus azimuthal angle that is qualitatively consistent with bulk scattering from the coating layers. These results are part of a broader study to understand optical loss in quantum noise filter cavities...
Analysis of Trace Gas Mixtures Using an External Cavity Quantum Cascade Laser Sensor
Energy Technology Data Exchange (ETDEWEB)
Phillips, Mark C.; Taubman, Matthew S.; Brumfield, Brian E.; Kriesel, Jason M.
2015-07-01
We measure and analyze mixtures of trace gases at ppb-ppm levels using an external cavity quantum cascade laser sensor with a 1-second response time. Accurate spectral fits are obtained in the presence of overlapping spectra.
Rapid Swept-Wavelength External Cavity Quantum Cascade Laser for Open Path Sensing
Energy Technology Data Exchange (ETDEWEB)
Brumfield, Brian E.; Phillips, Mark C.
2015-07-01
A rapidly tunable external cavity quantum cascade laser system is used for open path sensing. The system permits acquisition of transient absorption spectra over a 125 cm-1 tuning range in less than 0.01 s.
Quantum repeater with Rydberg-blocked atomic ensembles in fiber-coupled cavities
DEFF Research Database (Denmark)
Brion, Etienne; Carlier, F.; Akulin, M.;
2012-01-01
We propose and analyze a quantum repeater architecture in which Rydberg-blocked atomic ensembles inside optical cavities are linked by optical fibers. Entanglement generation, swapping, and purification are achieved through collective laser manipulations of the ensembles and photon transmission...
Nonradiating and radiating modes excited by quantum emitters in open epsilon-near-zero cavities
Liberal, Iñigo
2015-01-01
Controlling the emission and interaction properties of quantum emitters (QEs) embedded within an optical cavity is a key technique in engineering light-matter interactions at the nanoscale, as well as in the development of quantum information processing. State-of-the-art optical cavities are based on high Q photonics crystals and dielectric resonators. However, wealthier responses might be attainable with cavities carved in more exotic materials. Here, we theoretically investigate the emission and interaction properties of QEs embedded in open epsilon-near-zero (ENZ) cavities. Using analytical methods and numerical simulations, it is demonstrated that open ENZ cavities present the unique property of supporting nonradiating modes independently of the geometry of the external boundary of the cavity (shape, size, topology...). Moreover, the possibility of switching between radiating and nonradiating modes enables a dynamic control of both the emission by, and the interaction between, QEs. These phenomena provide...
Spatial mode effects in a cavity-EIT based quantum memory with ion Coulomb crystals
DEFF Research Database (Denmark)
Zangenberg, Kasper Rothe; Dantan, Aurelien Romain; Drewsen, Michael
2012-01-01
Quantum storage and retrieval of light in ion Coulomb crystals using cavity electromagnetically induced transparency are investigated theoretically. It is found that when both the control and the probe fields are coupled to the same spatial cavity mode, their transverse mode profile affects the q...... the quantum memory efficiency in a non-trivial way. Under such conditions, the control-field parameters and crystal dimensions that maximize the memory efficiency are calculated....
Spatial mode effects in a cavity EIT-based quantum memory with ion Coulomb crystals
Zangenberg, Kasper R; Drewsen, Michael
2012-01-01
Quantum storage and retrieval of light in ion Coulomb crystals using cavity electromagnetically induced transparency is investigated theoretically. It is found that, when both the control and probe fields are coupled to the same cavity mode, their transverse mode profile affects the quantum memory efficiency in a non-trivial way. Under such conditions the control field parameters and crystal dimensions that maximize the memory efficiency are calculated.
Quantum Photonic in Hybrid Cavity Systems with Strong Matter-Light Couplings
2015-08-24
AFRL-AFOSR-VA-TR-2015-0246 Quantum Photonic in Hybrid Cavity Systems with Strong Matter-Light Couplings Hui Deng UNIVERSITY OF MICHIGAN Final Report...TITLE AND SUBTITLE Quantum Photonic in Hybrid Cavity Systems with Strong Matter-Light Couplings 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-12-1-0256... photons was demonstrated in the designable microcavity structure for the first time, establishing a robust light-matter hybrid states with designable
Scheme for Generation of Entanglement among Bimodal Cavities
Institute of Scientific and Technical Information of China (English)
SONG Xin-Guo; FENG Xun-Li
2004-01-01
@@ We present a scheme for generation of an entangled state in many spatially separated bimodal cavity modes via cavity quantum electrodynamics. A V-type three-level atom, initially prepared in a coherent superposition of its excited states, successively passes through both the bimodal cavities. If the atom is measured in its ground state after leaving the last cavity, an entangled state of many cavity modes can be generated. The conditions to generate the maximally entangled state with unity probability are worked out.
Efficient transfer of an arbitrary qutrit state in circuit quantum electrodynamics.
Liu, Tong; Xiong, Shao-Jie; Cao, Xiao-Zhi; Su, Qi-Ping; Yang, Chui-Ping
2015-12-01
Compared with a qubit, a qutrit (i.e., three-level quantum system) has a larger Hilbert space and thus can be used to encode more information in quantum information processing and communication. Here, we propose a method to transfer an arbitrary quantum state between two flux qutrits coupled to two resonators. This scheme is simple because it only requires two basic operations. The state-transfer operation can be performed fast because only resonant interactions are used. Numerical simulations show that the high-fidelity transfer of quantum states between the two qutrits is feasible with current circuit-QED technology. This scheme is quite general and can be applied to accomplish the same task for other solid-state qutrits coupled to resonators.
A Scheme for Atomic Entangled States and Quantum Gate Operations in Cavity QED
Institute of Scientific and Technical Information of China (English)
LI Peng-Bo; GU Ying; GONG Qi-Huang; GUO Guang-Can
2009-01-01
We propose a scheme for controllably entangling the ground states of five-state W-type atoms confined in a cavity and realizing swap gate and phase gate operations.In this scheme the cavity is only virtually excited and the atomic excited states are almost not occupied,so the produced entangled states and quantum logic operations are very robust against the cavity decay and atomic spontaneous emission.
Quantum atomic lithography via cross-cavity optical Stern-Gerlach setup
Máximo, C. E.; Batalhão, T. B.; Bachelard, R.; de Moraes Neto, G. D.; de Ponte, M. A.; Moussa, M. H. Y.
2014-10-01
We present a fully quantum scheme to perform 2D atomic lithography based on a cross-cavity optical Stern-Gerlach setup: an array of two mutually orthogonal cavities crossed by an atomic beam perpendicular to their optical axes, which is made to interact with two identical modes. After deriving an analytical solution for the atomic momentum distribution, we introduce a protocol allowing us to control the atomic deflection by manipulating the amplitudes and phases of the cavity field states.
Quantum state engineering in a cavity by Stark chirped rapid adiabatic passage
Amniat-Talab, M; Guérin, S
2006-01-01
We propose a robust scheme to generate single-photon Fock states and atom-photon and atom-atom entanglement in atom-cavity systems. We also present a scheme for quantum networking between two cavity nodes using an atomic channel. The mechanism is based on Stark-chirped rapid adiabatic passage (SCRAP) and half-SCRAP processes in a microwave cavity. The engineering of these states depends on the design of the adiabatic dynamics through the static and dynamic Stark shifts.
Generation of Entangled States of Multiple Superconducting Quantum Interference Devices in Cavity
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
We propose a scheme for generating the maximally entangled states of many superconducting quantum interference devices (SQUIDs) by using a quantized cavity field and classicalmicrowave pulses in cavity. In the scheme,the maximally entangled states can be generated without requiring the measurement and individual addressing of the SQUIDs.
Proposed Coupling of an Electron Spin in a Semiconductor Quantum Dot to a Nanosize Optical Cavity
DEFF Research Database (Denmark)
Majumdar, Arka; Nielsen, Per Kær; Bajcsy, Michal
2013-01-01
We propose a scheme to efficiently couple a single quantum dot electron spin to an optical nano-cavity, which enables us to simultaneously benefit from a cavity as an efficient photonic interface, as well as to perform high fidelity (nearly 100%) spin initialization and manipulation achievable in...
Reducing dephasing in coupled quantum dot-cavity systems by engineering the carrier wavefunctions
DEFF Research Database (Denmark)
Nysteen, Anders; Nielsen, Per Kær; Mørk, Jesper
2012-01-01
We demonstrate theoretically how photon-assisted dephasing by the electron-phonon interaction in a coupled cavity-quantum dot system can be significantly reduced for specific QD-cavity detunings. Our starting point is a recently published theory,1 which considers longitudinal acoustic phonons, de...
Vacuum Rabi splitting in a plasmonic cavity at the single quantum emitter limit
Santhosh, Kotni; Chuntonov, Lev; Haran, Gilad
2015-01-01
The strong interaction of individual quantum emitters with resonant cavities is of fundamental interest for understanding light matter interactions, as well as for quantum information processing and quantum communication applications. Plasmonic cavities hold the promise of attaining the strong coupling regime even under ambient conditions and within subdiffraction volumes. Recent experiments revealed strong coupling between individual plasmonic structures and multiple organic molecules, but so far strong coupling at the limit of a single quantum emitter has not been reported. Here we demonstrate vacuum Rabi splitting, a manifestation of strong coupling, using silver bowtie plasmonic cavities loaded with semiconductor quantum dots (QDs). A transparency dip is observed in the scattering spectra of individual bowties with one to a few QDs in their gaps. Rabi splitting values as high as 180 meV are registered with a single QD. These observations are verified by polarization-dependent experiments and validated by ...
Wundt, B J; 10.1103/PhysRevA.80.022505
2009-01-01
We calculate the relativistic corrections of relative order (Z alpha)^2$ to the two-photon decay rate of higher excited S and D states in ionic atomic systems, and we also evaluate the leading radiative corrections of relative order alpha (Z alpha)^2 ln[(Z alpha)^(-2)]. We thus complete the theory of the two-photon decay rates up to relative order alpha^3 ln(alpha). An approach inspired by nonrelativistic quantum electrodynamics is used. We find that the corrections of relative order (Z alpha)^2 to the two-photon decay are given by the zitterbewegung, the spin-orbit coupling and by relativistic corrections to the electron mass, and by quadrupole interactions. We show that all corrections are separately gauge-invariant with respect to a "hybrid" transformation from velocity to length gauge, where the gauge transformation of the wave function is neglected. The corrections are evaluated for the two-photon decay from 2S, 3S, 3D, and 4S states in one-electron (hydrogenlike) systems, with 1S and 2S final states.
Liu, Qi-Chun; Li, Tie-Fu; Luo, Xiao-Qing; Zhao, Hu; Xiong, Wei; Zhang, Ying-Shan; Chen, Zhen; Liu, J. S.; Chen, Wei; Nori, Franco; Tsai, J. S.; You, J. Q.
2016-05-01
Electromagnetically induced transparency (EIT) has been realized in atomic systems, but fulfilling the EIT conditions for artificial atoms made from superconducting circuits is a more difficult task. Here we report an experimental observation of the EIT in a tunable three-dimensional transmon by probing the cavity transmission. To fulfill the EIT conditions, we tune the transmon to adjust its damping rates by utilizing the effect of the cavity on the transmon states. From the experimental observations, we clearly identify the EIT and Autler-Townes splitting (ATS) regimes as well as the transition regime in between. Also, the experimental data demonstrate that the threshold ΩAIC determined by the Akaike information criterion can describe the EIT-ATS transition better than the threshold ΩEIT given by the EIT theory.
An integrated quantum repeater at telecom wavelength with single atoms in optical fiber cavities
Uphoff, Manuel; Brekenfeld, Manuel; Rempe, Gerhard; Ritter, Stephan
2016-03-01
Quantum repeaters promise to enable quantum networks over global distances by circumventing the exponential decrease in success probability inherent in direct photon transmission. We propose a realistic, functionally integrated quantum-repeater implementation based on single atoms in optical cavities. Entanglement is directly generated between the single-atom quantum memory and a photon at telecom wavelength. The latter is collected with high efficiency and adjustable temporal and spectral properties into a spatially well-defined cavity mode. It is heralded by a near-infrared photon emitted from a second, orthogonal cavity. Entanglement between two remote quantum memories can be generated via an optical Bell-state measurement, while we propose entanglement swapping based on a highly efficient, cavity-assisted atom-atom gate. Our quantum-repeater scheme eliminates any requirement for wavelength conversion such that only a single system is needed at each node. We investigate a particular implementation with rubidium and realistic parameters for Fabry-Perot cavities based on hbox {CO}_2 laser-machined optical fibers. We show that the scheme enables the implementation of a rather simple quantum repeater that outperforms direct entanglement generation over large distances and does not require any improvements in technology beyond the state of the art.
Cross-Kerr-effect induced by coupled Josephson qubits in circuit quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Hu Yong; Ge Guoqin; Chen Shi; Yang Xiaofei; Chen Youling [School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Department of Physics, Peking University, Beijing 100871 (China)
2011-07-15
We propose a scheme for implementing cross-Kerr nonlinearity between two superconducting transmission line resonators (TLRs) via their interactions with a coupler constructed by two superconducting transmon qubits connected to each other through a superconducting quantum interference device. When suitably driven, the coupler can induce very strong cross phase modulation (XPM) between the two TLRs due to its N-type level structure and the consequent electromagnetically induced transparency in its lowest states. The flexibility of our design can lead to various inter-TLR coupling configurations. The obtained cross-Kerr coefficient is large enough to allow many important quantum operations in which only few photons are involved. We further show that this scheme is very robust against fluctuations in solid-state quantum circuits. Our numerical calculations imply that the absorption and the dispersion of the TLRs resulting from the decoherence of the coupler are very small compared with the proposed XPM strength.
On Real and Virtual Photons in the Davies Theory of Time-Symmetric Quantum Electrodynamics
Kastner, R. E.
2013-01-01
This paper explores the distinction between virtual and real photons in the context of the Davies quantum relativistic extension of the Wheeler-Feynman classical electromagnetic theory. An alternative way of understanding this distinction is proposed, based on the transactional model.
High-fidelity readout in circuit quantum electrodynamics using the Jaynes-Cummings nonlinearity.
Reed, M D; DiCarlo, L; Johnson, B R; Sun, L; Schuster, D I; Frunzio, L; Schoelkopf, R J
2010-10-22
We demonstrate a qubit readout scheme that exploits the Jaynes-Cummings nonlinearity of a superconducting cavity coupled to transmon qubits. We find that, in the strongly driven dispersive regime of this system, there is the unexpected onset of a high-transmission "bright" state at a critical power which depends sensitively on the initial qubit state. A simple and robust measurement protocol exploiting this effect achieves a single-shot fidelity of 87% using a conventional sample design and experimental setup, and at least 61% fidelity to joint correlations of three qubits.
Cavity-mediated coupling of mechanical oscillators limited by quantum backaction
Spethmann, Nicolas; Schreppler, Sydney; Buchmann, Lukas; Stamper-Kurn, Dan M
2015-01-01
A complex quantum system can be constructed by coupling simple quantum elements to one another. For example, trapped-ion or superconducting quantum bits may be coupled by Coulomb interactions, mediated by the exchange of virtual photons. Alternatively quantum objects can be coupled by the exchange of real photons, particularly when driven within resonators that amplify interactions with a single electro-magnetic mode. However, in such an open system, the capacity of a coupling channel to convey quantum information or generate entanglement may be compromised. Here, we realize phase-coherent interactions between two spatially separated, near-ground-state mechanical oscillators within a driven optical cavity. We observe also the noise imparted by the optical coupling, which results in correlated mechanical fluctuations of the two oscillators. Achieving the quantum backaction dominated regime opens the door to numerous applications of cavity optomechanics with a complex mechanical system. Our results thereby illu...
Virtual-photon-induced quantum phase gates for two distant atoms trapped in separate cavities
Zheng, Shi-Biao
2012-01-01
We propose a scheme for implementing quantum gates for two atoms trapped in distant cavities connected by an optical fiber. The effective long-distance coupling between the two distributed qubits is achieved without excitation and transportation of photons through the optical fiber. Since the cavity modes and fiber mode are never populated and the atoms undergo no transitions, the gate operation is insensitive to the decoherence effect when the thermal photons in the environment are negligible. The scheme opens promising perspectives for networking quantum information processors and implementing distributed and scalable quantum computation.
Controlled phase gates based on two nonidentical quantum dots trapped in separate cavities
Institute of Scientific and Technical Information of China (English)
Wang Xiao-Xia; Zhang Jian-Qi; Yu Ya-Fei; Zhang Zhi-Ming
2011-01-01
We propose a scheme for realizing two-qubit controlled phase gates on two nonidentical quantum dots trapped in separate cavities.In our scheme,each dot simultaneously interacts with one highly detuned cavity mode and two strong driven classical fields.During the gate operation,the quantum dots undergo no transition,while the system can acquire different phases conditional on different states of the quantum dots.With the application of the single-qubit operations,two-qubit controlled phase gates can be realized.
Distinctive signature of indium gallium nitride quantum dot lasing in microdisk cavities.
Woolf, Alexander; Puchtler, Tim; Aharonovich, Igor; Zhu, Tongtong; Niu, Nan; Wang, Danqing; Oliver, Rachel; Hu, Evelyn L
2014-09-30
Low-threshold lasers realized within compact, high-quality optical cavities enable a variety of nanophotonics applications. Gallium nitride materials containing indium gallium nitride (InGaN) quantum dots and quantum wells offer an outstanding platform to study light-matter interactions and realize practical devices such as efficient light-emitting diodes and nanolasers. Despite progress in the growth and characterization of InGaN quantum dots, their advantages as the gain medium in low-threshold lasers have not been clearly demonstrated. This work seeks to better understand the reasons for these limitations by focusing on the simpler, limited-mode microdisk cavities, and by carrying out comparisons of lasing dynamics in those cavities using varying gain media including InGaN quantum wells, fragmented quantum wells, and a combination of fragmented quantum wells with quantum dots. For each gain medium, we use the distinctive, high-quality (Q ∼ 5,500) modes of the cavities, and the change in the highest-intensity mode as a function of pump power to better understand the dominant radiative processes. The variations of threshold power and lasing wavelength as a function of gain medium help us identify the possible limitations to lower-threshold lasing with quantum dot active medium. In addition, we have identified a distinctive lasing signature for quantum dot materials, which consistently lase at wavelengths shorter than the peak of the room temperature gain emission. These findings not only provide better understanding of lasing in nitride-based quantum dot cavity systems but also shed insight into the more fundamental issues of light-matter coupling in such systems.
Hughes, Stephen; Yao, P
2009-03-02
We present a rigorous medium-dependent theory for describing the quantum field emitted and detected from a single quantum dot exciton, strongly coupled to a planar photonic crystal nanocavity, from which the exact spectrum is derived. By using simple mode decomposition techniques, this exact spectrum is subsequently reduced to two separate user-friendly forms, in terms of the leaky cavity mode emission and the radiation mode emission. On application to study exciton-cavity coupling in the strong coupling regime, besides a pronounced modification of the usual vacuum Rabi spectral doublet, we predict several new effects associated with the leaky cavity mode emission, including the appearance of an off-resonance cavity mode and a loss-induced on-resonance spectral triplet. The cavity mode emission is shown to completely dominate the emitted spectrum, even for large cavity-exciton detunings, whereby the usual cavity-QED formulas developed for radiation-mode emission drastically fail. These predictions are in qualitative agreement with several "mystery observations" reported in recent experiments, and apply to a wide range of semiconductor cavities.
On Real and Virtual Photons in the Davies Theory of Time-Symmetric Quantum Electrodynamics
Kastner, R E
2013-01-01
This paper explores the distinction between virtual and real photons in the context of the Davies quantum relativistic extension of the Wheeler-Feynman classical electromagnetic theory. An alternative way of understanding this distinction is proposed, based on the transactional picture as first proposed by Cramer. It is noted that this proposed account of the relationship between virtual and real photons might have empirically detectable consequences.
BRST Quantisation of Histories Electrodynamics
Noltingk, D.
2001-01-01
This paper is a continuation of earlier work where a classical history theory of pure electrodynamics was developed in which the the history fields have \\emph{five} components. The extra component is associated with an extra constraint, thus enlarging the gauge group of histories electrodynamics. In this paper we quantise the classical theory developed previously by two methods. Firstly we quantise the reduced classical history space, to obtain a reduced quantum history theory. Secondly we qu...
Clark, Lewis A.; Stokes, Adam; Beige, Almut
2016-08-01
In this paper, we use the nonlinear generator of dynamics of the individual quantum trajectories of an optical cavity inside an instantaneous quantum feedback loop to measure the phase shift between two pathways of light with a precision above the standard quantum limit. The feedback laser provides a reference frame and constantly increases the dependence of the state of the resonator on the unknown phase. Since our quantum metrology scheme can be implemented with current technology and does not require highly efficient single photon detectors, it should be of practical interest until highly entangled many-photon states become more readily available.
Hybrid Circuit Quantum Electrodynamics: Coupling a Single Silicon Spin Qubit to a Photon
2015-01-01
bits. The main goal of this research program was to make the first steps toward combing elements of the superconducting and semiconductor qubit...electric field amplitude of 0.2 V /m (4, 6). It is this electric field that couples to the charge trapped in the InAs nanowire quantum dot. Figure 1...dephasing times that are at least a factor of 20 larger than in III/ V semiconductors. However, the spin-orbit interaction is weaker in silicon. As a
Universal quantum gates for photon-atom hybrid systems assisted by bad cavities.
Wang, Guan-Yu; Liu, Qian; Wei, Hai-Rui; Li, Tao; Ai, Qing; Deng, Fu-Guo
2016-01-01
We present two deterministic schemes for constructing a CNOT gate and a Toffoli gate on photon-atom and photon-atom-atom hybrid quantum systems assisted by bad cavities, respectively. They are achieved by cavity-assisted photon scattering and work in the intermediate coupling region with bad cavities, which relaxes the difficulty of their implementation in experiment. Also, bad cavities are feasible for fast quantum operations and reading out information. Compared with previous works, our schemes do not need any auxiliary qubits and measurements. Moreover, the schematic setups for these gates are simple, especially that for our Toffoli gate as only a quarter wave packet is used to interact the photon with each of the atoms every time. These atom-cavity systems can be used as the quantum nodes in long-distance quantum communication as their relatively long coherence time is suitable for multi-time operations between the photon and the system. Our calculations show that the average fidelities and efficiencies of our two universal hybrid quantum gates are high with current experimental technology.
Local effects of the quantum vacuum in Lorentz-violating electrodynamics
Martín-Ruiz, A
2016-01-01
The Casimir effect is one of the most remarkable consequences of the non-zero vacuum energy predicted by quantum field theory. In this paper we use a local approach to study the Lorentz violation effects of the minimal standard model extension on the Casimir force between two parallel conducting plates in the vacuum. Using a perturbative method similar to that used for obtaining the Born series for the scattering amplitudes in quantum mechanics, we compute, at leading order in the Lorentz-violating coefficients, the relevant Green's function which satisfies given boundary conditions. The standard point-splitting technique allow us to express the vacuum expectation value of the stress-energy tensor in terms of the Green's function. We discuss its structure in the region between the plates. We compute the renormalized vacuum stress, which is obtained as the difference between the vacuum stress in the presence of the plates and that of the vacuum. The Casimir force is evaluated in an analytical fashion by two me...
Waveguide quantum electrodynamics - nonlinear physics at the few-photon level
Energy Technology Data Exchange (ETDEWEB)
Schneider, Michael; Sproll, Tobias; Martens, Christoph [Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin (Germany); Schmitteckert, Peter [Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie (KIT), 76344 Eggenstein-Leopoldshafen (Germany); Busch, Kurt [Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin (Germany); Humboldt-Universitaet zu Berlin, Institut fuer Physik, AG Theoretische Optik und Photonik, Newtonstr. 15, 12489 Berlin (Germany)
2014-07-01
The transport of few photons in 1D structures coupled to a fermionic impurity gives rise to a set of non-linear effects, induced by an effective interaction due to Pauli blocking such as photon bunching and the formation of atom-photon bound states. We analyze a specific example of such systems, namely a 1-D waveguide coupled to a 2-level system, for the case of one and two-photon transport. Therefore we have developed a general theoretical framework, which contains analytic approaches originating in methods of quantum field theory, like path integrals and Feynman diagrams as well as powerful numerical tools based on solving the time-dependent Schroedinger equation. Owing its generality, our approach is also applicable to more involved setups, including disorder and dissipation as well as more complicated impurities such as driven and undriven 3-level systems.
Energy Technology Data Exchange (ETDEWEB)
Field, J H [Departement de Physique Nucleaire et Corpusculaire, Universite de Geneve, 24, quai Ernest-Ansermet CH-1211 Geneva 4 (Switzerland)
2006-12-15
It is demonstrated how all the mechanical equations of classical electromagnetism (CEM) may be derived from only Coulomb's inverse square force law, special relativity and Hamilton's principle. The instantaneous nature of the Coulomb force in the centre-of-mass frame of two interacting charged objects, mediated by the exchange of space-like virtual photons, is predicted by quantum electrodynamics (QED). The interaction Lagrangian of QED is shown to be identical, in the appropriate limit, to the potential energy term in the Lorentz-invariant Lagrangian of CEM. A comparison is made with the Feynman-Wheeler action-at-a-distance formulation of CEM.
Electrodynamic absorber theory
Deckert, Dirk-André
2010-01-01
This work deals with questions that arise in classical and quantum electrodynamics when describing the phenomena of radiation reaction and pair creation. The two guiding ideas are the absorber idea of Wheeler and Feynman (i.e. all emitted radiation will be again be absorbed by matter) and the electron sea idea of Dirac. In the first part classical dynamics are studied which allow for a description of radiation reaction without the need of renormalization. The starting point are the couple...
Institute of Scientific and Technical Information of China (English)
S. H. Kim
2006-01-01
We calculate the scattering cross section of an electron with respect to the spontaneously produced laser radiation in the first free-electron laser (FEL) with quantum-wiggler electrodynamics (QWD). The cross section is 1016 times the Thomson cross section, confirming the result obtained by a previous analysis of the experimental data. A QWD calculation show that spontaneous emission in an FEL using only an electric wiggler can be very strong while amplification through net stimulated emission is practically negligible.
On a modified electrodynamics.
Reiss, H R
2012-09-01
A modification of electrodynamics is proposed, motivated by previously unremarked paradoxes that can occur in the standard formulation. It is shown by specific examples that gauge transformations exist that radically alter the nature of a problem, even while maintaining the values of many measurable quantities. In one example, a system with energy conservation is transformed to a system where energy is not conserved. The second example possesses a ponderomotive potential in one gauge, but this important measurable quantity does not appear in the gauge-transformed system. A resolution of the paradoxes comes from noting that the change in total action arising from the interaction term in the Lagrangian density cannot always be neglected, contrary to the usual assumption. The problem arises from the information lost by employing an adiabatic cutoff of the field. This is not necessary. Its replacement by a requirement that the total action should not change with a gauge transformation amounts to a supplementary condition for gauge invariance that can be employed to preserve the physical character of the problem. It is shown that the adiabatic cutoff procedure can also be eliminated in the construction of quantum transition amplitudes, thus retaining consistency between the way in which asymptotic conditions are applied in electrodynamics and in quantum mechanics. The 'gauge-invariant electrodynamics' of Schwinger is shown to depend on an ansatz equivalent to the condition found here for maintenance of the ponderomotive potential in a gauge transformation. Among the altered viewpoints required by the modified electrodynamics, in addition to the rejection of the adiabatic cutoff, is the recognition that the electric and magnetic fields do not completely determine a physical problem, and that the electromagnetic potentials supply additional information that is required for completeness of electrodynamics.
Manipulating nanoscale atom-atom interactions with cavity QED
Pal, Arpita; Deb, Bimalendu
2016-01-01
We theoretically explore manipulation of interactions between excited and ground state atoms at nanoscale separations by cavity quantum electrodynamics (CQED). We develop an adiabatic molecular dressed state formalism and show that it is possible to generate Fano-Feshbach resonances between ground and long-lived excited-state atoms inside a cavity. The resonances are shown to arise due to non-adiabatic coupling near a pseudo-crossing between the dressed state potentials. We illustrate our results with a model study using fermionic $^{171}$Yb atoms in a two-modal cavity. Our study is important for manipulation of interatomic interactions at low energy by cavity field.
Sarkar, Sujit
2014-01-01
Quantum simulation aims to simulate a quantum system using a controble laboratory system that underline the same mathematical model. Cavity QED lattice system is that prescribe system to simulate the relativistic quantum effect. We quantum simulate the Dirac fermion mode, Majorana fermion mode and Majorana-Weyl fermion mode and a crossover between them in cavity QED lattice. We also present the different analytical relations between the field operators for different mode excitations.
Long-distance quantum state transfer through cavity-assisted interaction
Institute of Scientific and Technical Information of China (English)
Li Yu-Ning; Mei Feng; Yu Ya-Fei; and Zhang Zhi-Ming
2011-01-01
We propose a scheme for long-distance quantum state transfer between different atoms based on cavity-assisted interactions.In our scheme,a coherent optical pulse sequentially interacts with two distant atoms trapped in separated cavities. Through the measurement of the state of the first atom and the homodyne detection of the final output coherent light,the quantum state can be transferred into the second atom with a success probability of unity and a fidelity of unity.In addition,our scheme neither requires the high-Q cavity working in the strong coupling regime nor employs the single-photon quantum channel,which greatly relaxes the experimental requirements.
Vacuum Rabi splitting in a plasmonic cavity at the single quantum emitter limit.
Santhosh, Kotni; Bitton, Ora; Chuntonov, Lev; Haran, Gilad
2016-06-13
The strong interaction of individual quantum emitters with resonant cavities is of fundamental interest for understanding light-matter interactions. Plasmonic cavities hold the promise of attaining the strong coupling regime even under ambient conditions and within subdiffraction volumes. Recent experiments revealed strong coupling between individual plasmonic structures and multiple organic molecules; however, strong coupling at the limit of a single quantum emitter has not been reported so far. Here we demonstrate vacuum Rabi splitting, a manifestation of strong coupling, using silver bowtie plasmonic cavities loaded with semiconductor quantum dots (QDs). A transparency dip is observed in the scattering spectra of individual bowties with one to a few QDs, which are directly counted in their gaps. A coupling rate as high as 120 meV is registered even with a single QD, placing the bowtie-QD constructs close to the strong coupling regime. These observations are verified by polarization-dependent experiments and validated by electromagnetic calculations.
Scheme for Remote Implementation of Partially Unknown Quantum Operation of Two Qubits in Cavity QED
Institute of Scientific and Technical Information of China (English)
QIU Liang; WANG An-Min
2008-01-01
By constructing the recovery operations of the protocol of remote implementation of partially unknown quantum operation of two qubits [An-Min Wang: Phys. Rev. A 74 (2006) 032317] with two-qubit Cnot gate and single qubit logic gates, we present a scheme to implement it in cavity QED. Long-lived Rydberg atoms are used as qubits, and the interaction between the atoms and the field of cavity is a nonresonant one. Finally, we analyze the experimental feasibility of this scheme.
Chulhai, Dhabih V; Jensen, Lasse
2014-10-01
Raman optical activity has proven to be a powerful tool for probing the geometry of small organic and biomolecules. It has therefore been expected that the same mechanisms responsible for surface-enhanced Raman scattering may allow for similar enhancements in surface-enhanced Raman optical activity (SEROA). However, SEROA has proved to be an experimental challenge and mirror-image SEROA spectra of enantiomers have so far not been measured. There exists a handful of theories to simulate SEROA, all of which treat the perturbed molecule as a point-dipole object. To go beyond these approximations, we present two new methods to simulate SEROA: the first is a dressed-tensors model that treats the molecule as a point-dipole and point-quadrupole object; the second method is the discrete interaction model/quantum mechanical (DIM/QM) model, which considers the entire charge density of the molecule. We show that although the first method is acceptable for small molecules, it fails for a medium-sized one such as 2-bromohexahelicene. We also show that the SEROA mode intensities and signs are highly sensitive to the nature of the local electric field and gradient, the orientation of the molecule, and the surface plasmon frequency width. Our findings give some insight into why experimental SEROA, and in particular observing mirror-image SEROA for enantiomers, has been difficult.
Quantum phase gate based on electromagnetically induced transparency in optical cavities
Borges, Halyne S.; Villas-Bôas, Celso J.
2016-11-01
We theoretically investigate the implementation of a quantum controlled-phase gate in a system constituted by a single atom inside an optical cavity, based on the electromagnetically induced transparency effect. First we show that a probe pulse can experience a π phase shift due to the presence or absence of a classical control field. Considering the interplay of the cavity-EIT effect and the quantum memory process, we demonstrated a controlled-phase gate between two single photons. To this end, first one needs to store a (control) photon in the ground atomic states. In the following, a second (target) photon must impinge on the atom-cavity system. Depending on the atomic state, this second photon will be either transmitted or reflected, acquiring different phase shifts. This protocol can then be easily extended to multiphoton systems, i.e., keeping the control photon stored, it may induce phase shifts in several single photons, thus enabling the generation of multipartite entangled states. We explore the relevant parameter space in the atom-cavity system that allows the implementation of quantum controlled-phase gates using the recent technologies. In particular, we have found a lower bound for the cooperativity of the atom-cavity system which enables the implementation of phase shift on single photons. The induced shift on the phase of a photonic qubit and the controlled-phase gate between single photons, combined with optical devices, enable one to perform universal quantum computation.
Bloch Oscillations of Cold Atoms in a Cavity: Effects of Quantum Noise
Venkatesh, B Prasanna
2013-01-01
In this communication we extend our theory of Bloch oscillations of cold atoms inside an optical cavity [Venkatesh et al., Phys. Rev. A 80, 063834 (2009)] to include the effects of quantum noise. By solving the coupled dynamics of linearized fluctuations about the atomic and optical meanfields, we are able to include the effects of quantum measurement backaction upon the atoms and ultimately examine how this influences the signal-to-noise ratio of a measurement of external forces using this system. One of the hurdles we overcome along the way is the proper treatment of fluctuations about time-dependent meanfields in the cold atom cavity-QED context.
Capture cavity cryomodule for quantum beam experiment at KEK superconducting RF test facility
Tsuchiya, K.; Hara, K.; Hayano, H.; Kako, E.; Kojima, Y.; Kondo, Y.; Nakai, H.; Noguchi, S.; Ohuchi, N.; Terashima, A.; Horikoshi, A.; Semba, T.
2014-01-01
A capture cavity cryomodule was fabricated and used in a beam line for quantum beam experiments at the Superconducting RF Test Facility (STF) of the High Energy Accelerator Research Organization in Japan. The cryomodule is about 4 m long and contains two nine-cell cavities. The cross section is almost the same as that of the STF cryomodules that were fabricated to develop superconducting RF cavities for the International Linear Collider. An attempt was made to reduce the large deflection of the helium gas return pipe (GRP) that was observed in the STF cryomodules during cool-down and warm-up. This paper briefly describes the structure and cryogenic performance of the captures cavity cryomodule, and also reports the measured displacement of the GRP and the cavity-containing helium vessels during regular operation.
Capture cavity cryomodule for quantum beam experiment at KEK superconducting RF test facility
Energy Technology Data Exchange (ETDEWEB)
Tsuchiya, K.; Hara, K.; Hayano, H.; Kako, E.; Kojima, Y.; Kondo, Y.; Nakai, H.; Noguchi, S.; Ohuchi, N.; Terashima, A. [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Horikoshi, A.; Semba, T. [Hitachi, Ltd., Hitachi Works, Hitachi, Ibaraki 317-8511 (Japan)
2014-01-29
A capture cavity cryomodule was fabricated and used in a beam line for quantum beam experiments at the Superconducting RF Test Facility (STF) of the High Energy Accelerator Research Organization in Japan. The cryomodule is about 4 m long and contains two nine-cell cavities. The cross section is almost the same as that of the STF cryomodules that were fabricated to develop superconducting RF cavities for the International Linear Collider. An attempt was made to reduce the large deflection of the helium gas return pipe (GRP) that was observed in the STF cryomodules during cool-down and warm-up. This paper briefly describes the structure and cryogenic performance of the captures cavity cryomodule, and also reports the measured displacement of the GRP and the cavity-containing helium vessels during regular operation.
Lin, G W; Huang, T; Lin, X M; Wang, Z Y; Gong, S Q
2012-01-01
We propose a technique for quantum nondemolition (QND) measurement and preparation of fock states by dynamics of electromagnetically induced transparency (EIT). An atomic medium trapped in an optical cavity is driven by two continuous-wave classical fields under steady-state EIT. The weak coherent fields are sequently injected into the cavity. During the process of photons passing through the cavity, a measurement on the changes of absorption loss of the probe field will be used for QND measurement of the small photon number, and thus create photon fock states, in particular single-photon states, in a heralded way.
Institute of Scientific and Technical Information of China (English)
Wu Xi; Chen Zhi-Hua; Zhang Yong; Chen Yue-Hua; Ye Ming-Yong; Lin Xiu-Min
2011-01-01
Schemes are presented for realizing quantum controlled phase gate and preparing an N-qubit W-like state, which are based on the large-detuned interaction among three-state atoms, dual-mode cavity and a classical pulse. In particular, a class of W states that can be used for perfect teleportation and superdense coding is generated by only one step.Compared with the previous schemes, cavity decay is largely suppressed because the cavity is only virtually excited and always in the vacuum state and the atomic spontaneous emission is strongly restrained due to a large atom-field detuning.
Cavity-Based Single-Atom Quantum Memory
Dilley, Jerome; Shore, Bruce W; Kuhn, Axel
2011-01-01
We show how to capture a single photon of arbitrary temporal shape with one atom coupled to an optical cavity. Our model applies to Raman transitions in three-level atoms with one branch of the transition controlled by a (classical) laser pulse, and the other coupled to the cavity. Photons impinging on the cavity normally exhibit partial reflection, transmission, and/or absorption by the atom. Only a control pulse of suitable temporal shape ensures impedance matching throughout the pulse, resulting in complete state mapping from photon to atom. For most possible photon shapes, we derive an unambiguous analytic expression for the temporal shape of the required control pulse. The process is subject to some inherent limitations, which we also discuss briefly.
Implementation of n-qubit Deutsch-Jozsa algorithm using resonant interaction in cavity QED
Institute of Scientific and Technical Information of China (English)
Wang Hong-Fu; Zhang Shou
2008-01-01
We propose a scheme to implement the n-qubit Deutsch-Jozsa algorithm based on resonant interaction between the atoms and a single-mode cavity. In the scheme, the resonant transitions between two ground states and one excited state of an atom are changed alternately by adjusting the cavity frequency appropriately, and the operations required to complete the algorithm can be significantly simplified following the increment of the number of qubits. The implementation of the scheme in experiment would show the full power of quantum algorithm and would be significative and important for more complicated quantum algorithm in cavity quantum electrodynamics.
Li, Tao; Long, Gui-Lu
2016-08-01
We propose an effective, scalable, hyperparallel photonic quantum computation scheme in which photonic qubits are hyperencoded both in the spatial degrees of freedom (DOF) and the polarization DOF of each photon. The deterministic hyper-controlled-not (hyper-cnot) gate on a two-photon system is attainable with our interesting interface between the polarized photon and the collective spin wave (magnon) of an atomic ensemble embedded in a double-sided optical cavity, and it doubles the operations in the conventional quantum cnot gate. Moreover, we present a compact hyper-cnotN gate on N +1 hyperencoded photons with only two auxiliary cavity-magnon systems, not more, and it can be faithfully constituted with current experimental techniques. Our proposal enables various applications with the hyperencoded photons in quantum computing and quantum networks.
Dispersive readout of valley splittings in cavity-coupled silicon quantum dots
Burkard, Guido; Petta, J. R.
2016-11-01
The band structure of bulk silicon has a sixfold valley degeneracy. Strain in the Si/SiGe quantum well system partially lifts the valley degeneracy, but the materials factors that set the splitting of the two lowest lying valleys are still under intense investigation. Using cavity input-output theory, we propose a method for accurately determining the valley splitting in Si/SiGe double quantum dots embedded in a superconducting microwave resonator. We show that low lying valley states in the double quantum dot energy level spectrum lead to readily observable features in the cavity transmission. These features generate a "fingerprint" of the microscopic energy level structure of a semiconductor double quantum dot, providing useful information on valley splittings and intervalley coupling rates.
A scheme for conditional quantum phase gate via bimodal cavity and a Λ-type three-level atom
Institute of Scientific and Technical Information of China (English)
Cai Jian-Wu; Fang Mao-Fa; Liao Xiang-Ping; Zheng Xiao-Juan
2006-01-01
We propose a scheme to implement a two-qubit conditional quantum phase gate for the intracavity field via a single three-level Λ-type atom driven by two modes in a high-Q cavity. The quantum information is encoded on the Fock states of the bimodal cavity. The gate's averaged fidelity is expected to reach 99.8%.
PT-symmetric quantum oscillator in an optical cavity
Longhi, Stefano
2016-01-01
The quantum harmonic oscillator with parity-time ($\\mathcal{PT}$) symmetry, obtained from the ordinary (Hermitian) quantum harmonic oscillator by an imaginary displacement of the spatial coordinate, provides an important and exactly-solvable model to investigate non-Hermitian extension of the Ehrenfest theorem. Here it is shown that transverse light dynamics in an optical resonator with off-axis longitudinal pumping can emulate a $\\mathcal{PT}$-symmetric quantum harmonic oscillator, providing an experimentally accessible system to investigate non-Hermitian coherent state propagation.
Holonomic quantum computation with superconducting charge-phase qubits in a cavity
Energy Technology Data Exchange (ETDEWEB)
Feng Zhibo [National Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093 (China) and Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China)], E-mail: zbfeng010@163.com; Zhang Xinding [Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China)
2008-03-03
We theoretically propose a feasible scheme to realize holonomic quantum computation with charge-phase qubits placed in a microwave cavity. By appropriately adjusting the controllable parameters, each charge-phase qubit is set as an effective four-level subsystem, based on which a universal set of holonomic quantum gates can be realized. Further analysis shows that our system is robust to the first-order fluctuation of the gate charges, and the intrinsic leakages between energy levels can be ignored.
Ultrafast photon-photon interaction in a strongly coupled quantum dot-cavity system
Englund, Dirk; Bajcsy, Michal; Faraon, Andrei; Petroff, Pierre; vuckovic, Jelena
2011-01-01
We study dynamics of the interaction between two weak light beams mediated by a strongly coupled quantum dot-photonic crystal cavity system. First, we perform all optical switching of a weak continuous-wave signal with a pulsed control beam, and then perform switching between two pulsed beams (40ps pulses) at the single photon level. Our results show that the quantum dot-nanocavity system creates strong, controllable interactions at the single photon level.
Cencek, Wojciech; Przybytek, Michał; Komasa, Jacek; Mehl, James B; Jeziorski, Bogumił; Szalewicz, Krzysztof
2012-06-14
The adiabatic, relativistic, and quantum electrodynamics (QED) contributions to the pair potential of helium were computed, fitted separately, and applied, together with the nonrelativistic Born-Oppenheimer (BO) potential, in calculations of thermophysical properties of helium and of the properties of the helium dimer. An analysis of the convergence patterns of the calculations with increasing basis set sizes allowed us to estimate the uncertainties of the total interaction energy to be below 50 ppm for interatomic separations R smaller than 4 bohrs and for the distance R = 5.6 bohrs. For other separations, the relative uncertainties are up to an order of magnitude larger (and obviously still larger near R = 4.8 bohrs where the potential crosses zero) and are dominated by the uncertainties of the nonrelativistic BO component. These estimates also include the contributions from the neglected relativistic and QED terms proportional to the fourth and higher powers of the fine-structure constant α. To obtain such high accuracy, it was necessary to employ explicitly correlated Gaussian expansions containing up to 2400 terms for smaller R (all R in the case of a QED component) and optimized orbital bases up to the cardinal number X = 7 for larger R. Near-exact asymptotic constants were used to describe the large-R behavior of all components. The fitted potential, exhibiting the minimum of -10.996 ± 0.004 K at R = 5.608 0 ± 0.000 1 bohr, was used to determine properties of the very weakly bound (4)He(2) dimer and thermophysical properties of gaseous helium. It is shown that the Casimir-Polder retardation effect, increasing the dimer size by about 2 Å relative to the nonrelativistic BO value, is almost completely accounted for by the inclusion of the Breit-interaction and the Araki-Sucher contributions to the potential, of the order α(2) and α(3), respectively. The remaining retardation effect, of the order of α(4) and higher, is practically negligible for the bound
Energy Technology Data Exchange (ETDEWEB)
Brenner, G.
2007-07-17
High-precision lifetime measurements of the metastable 1s{sup 2}2s{sup 2}2p{sup 2}P{sup 0}{sub 3/2} level in boronlike Ar XIV and the 3s{sup 2}2p {sup 2}P{sup 0}{sub 3/2} level in aluminumlike Fe XIV were performed at the Heidelberg electron beam ion trap (HD-EBIT). The lifetimes were inferred by monitoring their optical decay curves resulting from the magnetic dipole (M1) transition 1s{sup 2}2s{sup 2}2p{sup 2}P{sup 0}{sub 3/2}-{sup 2}P{sup 0}{sub 1/2} and 3s{sup 2}3p {sup 2}P{sup 0}{sub 3/2}-{sup 2}P{sup 0}{sub 1/2} to the ground state configuration with transition wavelengths of 441.256 nm and 530.29 nm, respectively. Possible systematic error sources were investigated by studying the dependence of the decay times of the curves on various trapping conditions with high statistical significance. A new trapping scheme for lifetime measurements at an EBIT has been applied and allowed to reach an unprecedented precision in the realm of lifetime determinations on highly charged ions. The results of 9.573(4)({sup +12}{sub -5}) ms (stat)(syst) for Ar XIV and 16.726(10)(+17) ms (stat)(syst) for Fe XIV with a relative accuracy of 0.14% and 0.13%, respectively, make these measurements for the first time sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM). The results, improving the accuracy of previous measurements by factors of 10 and 6, respectively, show a clear discrepancy of about 3{sigma} and 4{sigma} to the trend of existing theoretical models, which in almost all cases predict a shorter lifetime, when adjusted for the EAMM. The obvious disagreement between experimental results and the predictions points at the incompleteness of the theoretical models used. (orig.)
Non-classical light generated by quantum-noise-driven cavity optomechanics.
Brooks, Daniel W C; Botter, Thierry; Schreppler, Sydney; Purdy, Thomas P; Brahms, Nathan; Stamper-Kurn, Dan M
2012-08-23
Optomechanical systems, in which light drives and is affected by the motion of a massive object, will comprise a new framework for nonlinear quantum optics, with applications ranging from the storage and transduction of quantum information to enhanced detection sensitivity in gravitational wave detectors. However, quantum optical effects in optomechanical systems have remained obscure, because their detection requires the object’s motion to be dominated by vacuum fluctuations in the optical radiation pressure; so far, direct observations have been stymied by technical and thermal noise. Here we report an implementation of cavity optomechanics using ultracold atoms in which the collective atomic motion is dominantly driven by quantum fluctuations in radiation pressure. The back-action of this motion onto the cavity light field produces ponderomotive squeezing. We detect this quantum phenomenon by measuring sub-shot-noise optical squeezing. Furthermore, the system acts as a low-power, high-gain, nonlinear parametric amplifier for optical fluctuations, demonstrating a gain of 20 dB with a pump corresponding to an average of only seven intracavity photons. These findings may pave the way for low-power quantum optical devices, surpassing quantum limits on position and force sensing, and the control and measurement of motion in quantum gases.
Measurement-induced chaos and quantum state discrimination in an iterated Tavis-Cummings scheme
Torres, Juan Mauricio; Bernád, József Zsolt; Alber, Gernot; Kálmán, Orsolya; Kiss, Tamás
2016-01-01
A cavity quantum electrodynamical scenario is proposed for implementing a Schr\\"odinger microscope capable of amplifying differences between non orthogonal atomic quantum states. The scheme involves an ensemble of identically prepared two-level atoms interacting pairwise with a single mode of the radiation field as described by the Tavis-Cummings model. By repeated measurements of the cavity field and of one atom within each pair a measurement-induced nonlinear quantum transformation of the r...
Influences of strong exciton-phonon interaction on two coupled quantum dots within cavity QED
Energy Technology Data Exchange (ETDEWEB)
Yuan Xiaozhong [Department of Physics, Institute of Quantum Optics and Quantum Information, Shanghai Jiao Tong University, Shanghai 200240 (China)]. E-mail: yxz@sjtu.edu.cn; Zhu Kadi [Department of Physics, Institute of Quantum Optics and Quantum Information, Shanghai Jiao Tong University, Shanghai 200240 (China); Li Waisang [Department of Electronic and Information Engineering, Hong Kong Polytechnic University, Hong Kong (China)
2004-08-30
For two coupled quantum dots within cavity QED, we show that the exciton-phonon interaction reduces the Rabi frequency and Foerster interaction even at absolute zero temperature. The exciton-phonon interaction also makes an additional contribution to the static exciton-exciton dipole interaction energy.
Influences of strong exciton-phonon interaction on two coupled quantum dots within cavity QED
Yuan, Xiao-Zhong; Zhu, Ka-Di; Li, Wai-Sang
2004-08-01
For two coupled quantum dots within cavity QED, we show that the exciton-phonon interaction reduces the Rabi frequency and Förster interaction even at absolute zero temperature. The exciton-phonon interaction also makes an additional contribution to the static exciton-exciton dipole interaction energy.
Observation of Non-Markovian Dynamics of a Single Quantum Dot in a Micropillar Cavity
DEFF Research Database (Denmark)
Madsen, Kristian Høeg; Ates, Serkan; Lund-Hansen, Toke;
2011-01-01
We measure the detuning-dependent dynamics of a quasiresonantly excited single quantum dot coupled to a micropillar cavity. The system is modeled with the dissipative Jaynes-Cummings model where all experimental parameters are determined by explicit measurements. We observe non-Markovian dynamics...
Classical correlation and quantum discord mediated by cavity in two coupled qubits
Wang, Cheng-Zhi; Li, Chun-Xian; Nie, Liu-Ying; Li, Jiang-Fan
2011-01-01
We study the dynamics of classical correlation and quantum discord of two coupled two-level atoms interacting with a cavity initially in vacuum, coherent and thermal equilibrium states, respectively. The interplay between the atom-atom coupling and mean number of photons is considered. We find that,
Hidden Markov Model of atomic quantum jump dynamics in an optically probed cavity
DEFF Research Database (Denmark)
Gammelmark, S.; Molmer, K.; Alt, W.
2014-01-01
We analyze the quantum jumps of an atom interacting with a cavity field. The strong atom- field interaction makes the cavity transmission depend on the time dependent atomic state, and we present a Hidden Markov Model description of the atomic state dynamics which is conditioned in a Bayesian......, the atomic state is determined in a Bayesian manner from the measurement data, and we present an iterative protocol, which determines both the atomic state and the model parameters. As a new element in the treatment of observed quantum systems, we employ a Bayesian approach that conditions the atomic state...... manner on the detected signal. We suggest that small variations in the observed signal may be due to spatial motion of the atom within the cavity, and we represent the atomic system by a number of hidden states to account for both the small variations and the internal state jump dynamics. In our theory...
Quantum Dot Cavity-QED in the Presence of Strong Electron-Phonon Interactions
Wilson-Rae, I
2001-01-01
A quantum dot strongly coupled to a single high finesse optical microcavity mode constitutes a new fundamental system for quantum optics. Here, the effect of exciton-phonon interactions on reversible quantum-dot cavity coupling is analysed without making Born-Markov approximation. The analysis is based on techniques that have been used to study the ``spin boson'' Hamiltonian. Observability of vacuum-Rabi splitting depends on the strength and the frequency dependence of the spectral density function characterizing the interactions with phonons, both of which can be influenced by phonon confinement.
Lee, Mark D.; Ruostekoski, Janne
2014-08-01
We formulate computationally efficient classical stochastic measurement trajectories for a multimode quantum system under continuous observation. Specifically, we consider the nonlinear dynamics of an atomic Bose-Einstein condensate contained within an optical cavity subject to continuous monitoring of the light leaking out of the cavity. The classical trajectories encode within a classical phase-space representation a continuous quantum measurement process conditioned on a given detection record. We derive a Fokker-Planck equation for the quasiprobability distribution of the combined condensate-cavity system. We unravel the dynamics into stochastic classical trajectories that are conditioned on the quantum measurement process of the continuously monitored system. Since the dynamics of a continuously measured observable in a many-atom system can be closely approximated by classical dynamics, the method provides a numerically efficient and accurate approach to calculate the measurement record of a large multimode quantum system. Numerical simulations of the continuously monitored dynamics of a large atom cloud reveal considerably fluctuating phase profiles between different measurement trajectories, while ensemble averages exhibit local spatially varying phase decoherence. Individual measurement trajectories lead to spatial pattern formation and optomechanical motion that solely result from the measurement backaction. The backaction of the continuous quantum measurement process, conditioned on the detection record of the photons, spontaneously breaks the symmetry of the spatial profile of the condensate and can be tailored to selectively excite collective modes.
Quantum logic operations on two distant atoms trapped in two optical-fibre-connected cavities
Institute of Scientific and Technical Information of China (English)
Zhang Ying-Qiao; Zhang Shou; Yeon Kyu-Hwang; Yu Seong-Cho
2011-01-01
Based on the coupling of two distant three-level atoms in two separate optical cavities connected with two optical fibres,schemes on the generation of several two-qubit logic gates are discussed under the conditions of △ =δ -2v cos πk/2 (》) g/2 and (v～ g).Discussion and analysis of the fidelity,gate time and experimental setups show that our schemes are feasible with current optical cavity,atomic trap and optical fibre techniques.Moreover,the atom-cavityfibre coupling can be used to generate an N-qubit nonlocal entanglement and transfer quantum information among N distant atoms by arranging N atom-cavity assemblages in a line and connecting each two adjacent cavities with two optical fibres.
Cavity-photon contribution to the effective interaction of electrons in parallel quantum dots
Energy Technology Data Exchange (ETDEWEB)
Gudmundsson, Vidar [Science Institute, University of Iceland, Reykjavik (Iceland); Sitek, Anna [Science Institute, University of Iceland, Reykjavik (Iceland); Department of Theoretical Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Technology (Poland); Abdullah, Nzar Rauf [Science Institute, University of Iceland, Reykjavik (Iceland); Physics Department, Faculty of Science and Science Education, School of Science, University of Sulaimani, Kurdistan Region (Iraq); Tang, Chi-Shung [Department of Mechanical Engineering, National United University, Miaoli (China); Manolescu, Andrei [School of Science and Engineering, Reykjavik University (Iceland)
2016-05-15
A single cavity photon mode is expected to modify the Coulomb interaction of an electron system in the cavity. Here we investigate this phenomena in a parallel double quantum dot system. We explore properties of the closed system and the system after it has been opened up for electron transport. We show how results for both cases support the idea that the effective electron-electron interaction becomes more repulsive in the presence of a cavity photon field. This can be understood in terms of the cavity photons dressing the polarization terms in the effective mutual electron interaction leading to nontrivial delocalization or polarization of the charge in the double parallel dot potential. In addition, we find that the effective repulsion of the electrons can be reduced by quadrupolar collective oscillations excited by an external classical dipole electric field. (copyright 2015 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Statistics of quantum transport in weakly nonideal chaotic cavities.
Rodríguez-Pérez, Sergio; Marino, Ricardo; Novaes, Marcel; Vivo, Pierpaolo
2013-11-01
We consider statistics of electronic transport in chaotic cavities where time-reversal symmetry is broken and one of the leads is weakly nonideal; that is, it contains tunnel barriers characterized by tunneling probabilities Γ(i). Using symmetric function expansions and a generalized Selberg integral, we develop a systematic perturbation theory in 1-Γ(i) valid for an arbitrary number of channels and obtain explicit formulas up to second order for the average and variance of the conductance and for the average shot noise. Higher moments of the conductance are considered to leading order.
Quantum chaos and fractals with atoms in cavities
Uleysky, M; Prants, S V
2002-01-01
We study the coupled translational, electronic, and field dynamics of the combined system "a two-level atom + a single-mode quantized field + a standing-wave ideal cavity". We derive Hamilton -- Schr\\"odinger equations for probability amplitudes and averaged position and momentum of a point-like atom interacting with the quantized field in a standing-wave cavity. They constitute, in general, an infinite-dimensional set of equations with an infinite number of integrals of motion which may be reduced to a dynamical system with four degrees of freedom if the quantized field is supposed to be initially prepared in a Fock state. This system is found to produce semiquantum chaos with positive values of the maximal Lyapunov exponent. At large values of detuning $|\\delta|\\gg 1$, the Rabi atomic oscillations are usually shallow, and the dynamics is found to be almost regular. The Doppler -- Rabi resonance, deep Rabi oscillations that may occur at any large value of $|\\delta|$ to be equal to $|\\alpha p_0|$, is found nu...
Zangwill, Andrew
2013-01-01
An engaging writing style and a strong focus on the physics make this comprehensive, graduate-level textbook unique among existing classical electromagnetism textbooks. Charged particles in vacuum and the electrodynamics of continuous media are given equal attention in discussions of electrostatics, magnetostatics, quasistatics, conservation laws, wave propagation, radiation, scattering, special relativity and field theory. Extensive use of qualitative arguments similar to those used by working physicists makes Modern Electrodynamics a must-have for every student of this subject. In 24 chapters, the textbook covers many more topics than can be presented in a typical two-semester course, making it easy for instructors to tailor courses to their specific needs. Close to 120 worked examples and 80 applications boxes help the reader build physical intuition and develop technical skill. Nearly 600 end-of-chapter homework problems encourage students to engage actively with the material. A solutions manual is availa...
Quantum aspects of cavity optomechanics with atomic ensembles and ensemble arrays
Stamper-Kurn, Dan
2012-06-01
While the motion of a many-atom ensemble of atoms interacting strongly with a single mode of an optical resonator can be devilishly complicated, under favorable conditions, the cavity can be made to interact with and to sense just one, or just a few, normal modes of the gaseous system. This leads to an atoms-based realization of cavity optomechanics, directly analogous to experiments in which one seeks to observe the motion of suspended mirrors, cantilevers, and membranes at the quantum limits of precision. I will discuss our progress toward demonstrating and understanding the distinctively quantum mechanical aspects of both the ``opto'' and ``mechanical'' portions of cavity optomechanical systems. Specifically, I will report on the observation of the ponderomotive squeezing of light by a mechanical oscillator, and of strong motional sideband asymmetry that demonstrates the quantization of collective atomic motion and quantifies the energy flux into the mechanical system due to quantum measurement backaction. I will conclude by describing our approach to realizing strong cavity coupling to a multi-mode mechanical system, specifically to an array of distinguishable mechanical oscillators. [4pt] The work reported in this talk was performed in collaboration with members of my research group, including Thierry Botter, Nathaniel Brahms, Daniel Brooks, Thomas Purdy and Sydney Schreppler, and was supported by the AFOSR and NSF.
Efficient and long-lived quantum memory with cold atoms inside a ring cavity
Bao, Xiao-Hui; Dietrich, Peter; Rui, Jun; Dück, Alexander; Strassel, Thorsten; Li, Li; Liu, Nai-Le; Zhao, Bo; Pan, Jian-Wei; 10.1038/nphys2324
2012-01-01
Quantum memories are regarded as one of the fundamental building blocks of linear-optical quantum computation and long-distance quantum communication. A long standing goal to realize scalable quantum information processing is to build a long-lived and efficient quantum memory. There have been significant efforts distributed towards this goal. However, either efficient but short-lived or long-lived but inefficient quantum memories have been demonstrated so far. Here we report a high-performance quantum memory in which long lifetime and high retrieval efficiency meet for the first time. By placing a ring cavity around an atomic ensemble, employing a pair of clock states, creating a long-wavelength spin wave, and arranging the setup in the gravitational direction, we realize a quantum memory with an intrinsic spin wave to photon conversion efficiency of 73(2)% together with a storage lifetime of 3.2(1) ms. This realization provides an essential tool towards scalable linear-optical quantum information processing.
Impurity-free quantum well intermixing for large optical cavity high-power laser diode structures
Kahraman, Abdullah; Gür, Emre; Aydınlı, Atilla
2016-08-01
We report on the correlation of atomic concentration profiles of diffusing species with the blueshift of the quantum well luminescence from both as-grown and impurity free quantum wells intermixed on actual large optical cavity high power laser diode structures. Because it is critical to suppress catastrophic optical mirror damage, sputtered SiO2 and thermally evaporated SrF2 were used both to enhance and suppress quantum well intermixing, respectively, in these (Al)GaAs large optical cavity structures. A luminescence blueshift of 55 nm (130 meV) was obtained for samples with 400 nm thick sputtered SiO2. These layers were used to generate point defects by annealing the samples at 950 °C for 3 min. The ensuing Ga diffusion observed as a shifting front towards the surface at the interface of the GaAs cap and AlGaAs cladding, as well as Al diffusion into the GaAs cap layer, correlates well with the observed luminescence blue shift, as determined by x-ray photoelectron spectroscopy. Although this technique is well-known, the correlation between the photoluminescence peak blue shift and diffusion of Ga and Al during impurity free quantum well intermixing on actual large optical cavity laser diode structures was demonstrated with both x ray photoelectron and photoluminescence spectroscopy, for the first time.
Institute of Scientific and Technical Information of China (English)
WANG Yi-Min; ZHOU Yan-Li; LIANG Lin-Mei; LI Cheng-Zu
2009-01-01
We propose a feasible scheme to achieve universal quantum gate operations in decoherence-free subspace with superconducting charge qubits placed in a microwave cavity.Single-logic-qubit gates can be realized with cavity assisted interaction, which possesses the advantages of unconventional geometric gate operation.The two-logic-qubit controlled-phase gate between subsystems can be constructed with the help of a variable electrostatic transformer, The collective decoherence can be successfully avoided in our well-designed system.Moreover, GHZ state for logical qubits can also be easily produced in this system.
Entanglement and quantum state transfer between two atoms trapped in two indirectly coupled cavities
Zheng, Bin; Shen, Li-Tuo; Chen, Ming-Feng
2016-05-01
We propose a one-step scheme for implementing entanglement generation and the quantum state transfer between two atomic qubits trapped in two different cavities that are not directly coupled to each other. The process is realized through engineering an effective asymmetric X-Y interaction for the two atoms involved in the gate operation and an auxiliary atom trapped in an intermediate cavity, induced by virtually manipulating the atomic excited states and photons. We study the validity of the scheme as well as the influences of the dissipation by numerical simulation and demonstrate that it is robust against decoherence.
Quantum optics and cavity QED Quantum network with individual atoms and photons
Directory of Open Access Journals (Sweden)
Rempe G.
2013-08-01
Full Text Available Quantum physics allows a new approach to information processing. A grand challenge is the realization of a quantum network for long-distance quantum communication and large-scale quantum simulation. This paper highlights a first implementation of an elementary quantum network with two fibre-linked high-finesse optical resonators, each containing a single quasi-permanently trapped atom as a stationary quantum node. Reversible quantum state transfer between the two atoms and entanglement of the two atoms are achieved by the controlled exchange of a time-symmetric single photon. This approach to quantum networking is efficient and offers a clear perspective for scalability. It allows for arbitrary topologies and features controlled connectivity as well as, in principle, infinite-range interactions. Our system constitutes the largest man-made material quantum system to date and is an ideal test bed for fundamental investigations, e.g. quantum non-locality.
Quantum-coherent coupling of a mechanical oscillator to an optical cavity mode.
Verhagen, E; Deléglise, S; Weis, S; Schliesser, A; Kippenberg, T J
2012-02-01
Optical laser fields have been widely used to achieve quantum control over the motional and internal degrees of freedom of atoms and ions, molecules and atomic gases. A route to controlling the quantum states of macroscopic mechanical oscillators in a similar fashion is to exploit the parametric coupling between optical and mechanical degrees of freedom through radiation pressure in suitably engineered optical cavities. If the optomechanical coupling is 'quantum coherent'--that is, if the coherent coupling rate exceeds both the optical and the mechanical decoherence rate--quantum states are transferred from the optical field to the mechanical oscillator and vice versa. This transfer allows control of the mechanical oscillator state using the wide range of available quantum optical techniques. So far, however, quantum-coherent coupling of micromechanical oscillators has only been achieved using microwave fields at millikelvin temperatures. Optical experiments have not attained this regime owing to the large mechanical decoherence rates and the difficulty of overcoming optical dissipation. Here we achieve quantum-coherent coupling between optical photons and a micromechanical oscillator. Simultaneously, coupling to the cold photon bath cools the mechanical oscillator to an average occupancy of 1.7 ± 0.1 motional quanta. Excitation with weak classical light pulses reveals the exchange of energy between the optical light field and the micromechanical oscillator in the time domain at the level of less than one quantum on average. This optomechanical system establishes an efficient quantum interface between mechanical oscillators and optical photons, which can provide decoherence-free transport of quantum states through optical fibres. Our results offer a route towards the use of mechanical oscillators as quantum transducers or in microwave-to-optical quantum links.
Lazur, V. Yu.; Myhalyna, S. I.; Reity, O. K.
The problem of interaction of two quasimolecular electrons located at an arbitrary distance from each other and near different atoms (nuclei) is solved. The interaction is considered as a second-order effect of quantum electrodynamics in the coordinate representation. It is shown that a consistent account for the natural condition of the interaction symmetry with respect to both electrons leads to an additional contribution to the relativistic interaction of the two quasimolecular electrons compared with both the standard Breit operator and the generalized Breit operator known previously. The generalized Breit-Pauli operator and the operator of electric dipole-dipole interaction of two quasimolecular electrons located at an arbitrary distance from each other are obtained. Modern methods of accounting for the relativistic and correlative effects in the problem of ion-atom interactions are discussed.
Semi-classical Electrodynamics
Lestone, John
2016-03-01
Quantum electrodynamics is complex and its associated mathematics can appear overwhelming for those not trained in this field. We describe semi-classical approaches that can be used to obtain a more intuitive physical feel for several QED processes including electro-statics, Compton scattering, pair annihilation, the anomalous magnetic moment, and the Lamb shift, that could be taught easily to undergraduate students. Any physicist who brings their laptop to the talk will be able to build spread sheets in less than 10 minutes to calculate g/2 =1.001160 and a Lamb shift of 1057 MHz.
Quantum-dot nano-cavity lasers with Purcell-enhanced stimulated emission
DEFF Research Database (Denmark)
Gregersen, Niels; Skovgård, Troels Suhr; Lorke, Michael;
2012-01-01
We present a rate equation model for quantum-dot light-emitting devices that take into account Purcell enhancement of both spontaneous emission and stimulated emission as well as the spectral profile of the optical and electronic density-of-states. We find that below threshold the b-factor in a q......We present a rate equation model for quantum-dot light-emitting devices that take into account Purcell enhancement of both spontaneous emission and stimulated emission as well as the spectral profile of the optical and electronic density-of-states. We find that below threshold the b......-factor in a quantum-dot nanolaser depends strongly on the pump. For quantum dots with linewidth comparable to that of the cavity, we then show that an otherwise non-lasing device can lase due to Purcell enhancement of the stimulated emission. Finally, we compare the rate equation model to a microscopic model...
Backaction-limited cavity-sideband spectroscopy of quantum collective motion
Brahms, Nathan; Schreppler, Sydney; Brooks, Daniel W C; Stamper-Kurn, Dan M
2011-01-01
The motion of sub-atomic particles is characteristically quantum mechanical in nature. In contrast, quantum aspects of the motion of massive, many-atom objects are typically obscured by high phonon occupation and thermal noise. This contrast is now diminishing, owing to research efforts to bring the control and measurement of macroscopic motion fully into the quantum regime, using objects with masses from attograms to kilograms. This achievement will be critical for constructing force detectors sensitive to gravitational waves, verifying the correspondence principle at macroscopic scales, and realizing protocols that mechanically store and exchange quantum information. Here, we directly observe the quantization of the collective motion of an ultracold atomic ensemble by measuring the inability of a 0.6 attogram centre-of-mass mode to emit energy from its ground state. Moreover, the optical output of our strongly coupled cavity-optomechanical system contains a spectroscopic record of the energy exchanged betwe...
Yang, Wanli; An, Jun-Hong; Zhang, Chengjie; Feng, Mang; Oh, C. H.
2014-03-01
We investigate the non-Markovian dynamics of quantum correlation between two initially entangled nitrogen-vacancy centers (NVC) embedded in photonic crystal cavities (PCC). We find that a finite quantum correlation is preserved even asymptotically when the transition frequency ofthe NVC is within the band gap of the PCC, which is quantitatively different from the result of approaching zero under the Born-Markovian approximation. In addition, once the transition frequency of NVC is far beyond the bad gap of the PCC, the quantum correlation initially prepared in NVC will be fully transferred to the reservoirs in the long-time limit. Our result reveals that the interplay between the non-Markovian effect of the structured reservoirs and the existence of emitter-field bound state plays an essential role in such quantum correlation preservation. This feature may open new perspectives for devising active decoherence-immune solid-state optical devices.
Institute of Scientific and Technical Information of China (English)
Li Peng-Bo; Li Fu-Li
2011-01-01
A protocol is proposed to generate atomic entangled states and implement quantum information transfer in a cavity quantum electrodynamics system. It utilizes Raman transitions or stimulated Raman adiabatic passages between two systems to entangle the ground states of two three-state A-type atoms trapped in a single mode cavity. It does not need the measurements on cavity field nor atomic detection and can be implemented in a deterministic fashion. Since the present protocol is insensitive to both cavity decay and atomic spontaneous emission,it may have some interesting applications in quantum information processing.
A simple scheme for generating multi-atom GHZ state via cavity QED
Institute of Scientific and Technical Information of China (English)
Wang Jun; Yu Long-Bao; Ye Liu
2007-01-01
This paper proposes a simple scheme for generating a three-atom GHZ state via cavity quantum electrodynamics (QED). The task can be achieved through the interaction between two EPR states, which can be prepared easily with current technology. In this scheme, the cavity field is only virtually excited during the interaction process, and no quantum information transfer between the atoms and the cavity is required. Thus it greatly prolongs the efficient decoherent time. Moreover, this scheme is also applicable for generating an .N-atom GHZ state.
Teleportation of a two-atom entangled state using a single EPR pair in cavity QED
Institute of Scientific and Technical Information of China (English)
Ji Xin; Li Ke; Zhang Shou
2006-01-01
We propose a scheme for teleporting a two-atom entangled state in cavity quantum electrodynamics(QED).In the scheme,we choose a single Einstein-Podolsky-Rosen (EPR) pair as the quantum channel which is shared by the sender and the receiver.By using the atom-cavity-field interaction and introducing an additional atom,we can teleport the two-atom entangled state successfully with a probability of 1.0.Moreover,we show that the scheme is insensitive to cavity decay and thermal field.
Quantum entanglement and teleportation in pulsed cavity optomechanics
Energy Technology Data Exchange (ETDEWEB)
Hofer, Sebastian G. [Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna (Austria); Institute for Theoretical Physics, Institute for Gravitational Physics, Leibniz University Hannover, Callinstrasse 38, 30167 Hannover (Germany); Wieczorek, Witlef; Aspelmeyer, Markus [Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna (Austria); Hammerer, Klemens [Institute for Theoretical Physics, Institute for Gravitational Physics, Leibniz University Hannover, Callinstrasse 38, 30167 Hannover (Germany)
2011-11-15
Entangling a mechanical oscillator with an optical mode is an enticing and yet a very challenging goal in cavity optomechanics. Here we consider a pulsed scheme to create Einstein-Podolsky-Rosen-type entanglement between a traveling-wave light pulse and a mechanical oscillator. The entanglement can be verified unambiguously by a pump-probe sequence of pulses. In contrast to schemes that work in a steady-state regime under a continuous-wave drive, this protocol is not subject to stability requirements that normally limit the strength of achievable entanglement. We investigate the protocol's performance under realistic conditions, including mechanical decoherence, in full detail. We discuss the relevance of a high mechanical Qf product for entanglement creation and provide a quantitative statement on which magnitude of the Qf product is necessary for a successful realization of the scheme. We determine the optimal parameter regime for its operation and show it to work in current state-of-the-art systems.
Long-distance entanglement and quantum communication in coupled cavity arrays
Giampaolo, S M
2009-01-01
We introduce quantum spin models that allow for long-distance end-to-end entanglement and long-distance, high-fidelity teleportation, even at moderately high temperatures. We show how these models, that realize an optimal compromise between scalability and resilience to decoherence, can be implemented in simply engineered arrays of coupled optical cavities. We demonstrate how the latter can be used to realize a quasi-deterministic scheme of long-distance quantum communication with high success rate, without direct projection on Bell states and Bell measurements.
Two-Qubit Geometric Phase Gate for Quantum Dot Spins using Cavity Polariton Resonance
Puri, Shruti; Yamamoto, Yoshihisa
2012-01-01
We describe a design to implement a two-qubit geometric phase gate, by which a pair of electrons confined in adjacent quantum dots are entangled. The entanglement is a result of the Coulomb exchange interaction between the optically excited exciton-polaritons and the localized spins. This optical coupling, resembling the electron-electron Ruderman-Kittel-Kasuya-Yosida (RKKY) inter- actions, offers high speed, high fidelity two-qubit gate operation with moderate cavity quality factor Q. The errors due to the finite lifetime of the polaritons can be minimized by optimizing the optical pulse parameters (duration and energy). The proposed design, using electrostatic quantum dots, maximizes entanglement and ensures scalability.
Encoding quantum information in a stabilized manifold of a superconducting cavity
Touzard, S.; Leghtas, Z.; Mundhada, S. O.; Axline, C.; Reagor, M.; Chou, K.; Blumoff, J.; Sliwa, K. M.; Shankar, S.; Frunzio, L.; Schoelkopf, R. J.; Mirrahimi, M.; Devoret, M. H.
In a superconducting Josephson circuit architecture, we activate a multi-photon process between two modes by applying microwave drives at specific frequencies. This creates a pairwise exchange of photons between a high-Q cavity and the environment. The resulting open dynamical system develops a two-dimensional quasi-energy ground state manifold. Can we encode, protect and manipulate quantum information in this manifold? We experimentally investigate the convergence and escape rates in and out of this confined subspace. Finally, using quantum Zeno dynamics, we aim to perform gates which maintain the state in the protected manifold at all times. Work supported by: ARO, ONR, AFOSR and YINQE.
Realization of quantum gates with multiple control qubits or multiple target qubits in a cavity
Waseem, Muhammad; Irfan, Muhammad; Qamar, Shahid
2015-06-01
We propose a scheme to realize a three-qubit controlled phase gate and a multi-qubit controlled NOT gate of one qubit simultaneously controlling n-target qubits with a four-level quantum system in a cavity. The implementation time for multi-qubit controlled NOT gate is independent of the number of qubit. Three-qubit phase gate is generalized to n-qubit phase gate with multiple control qubits. The number of steps reduces linearly as compared to conventional gate decomposition method. Our scheme can be applied to various types of physical systems such as superconducting qubits coupled to a resonator and trapped atoms in a cavity. Our scheme does not require adjustment of level spacing during the gate implementation. We also show the implementation of Deutsch-Joza algorithm. Finally, we discuss the imperfections due to cavity decay and the possibility of physical implementation of our scheme.
Energy Technology Data Exchange (ETDEWEB)
Turčinková, Dana; Scalari, Giacomo; Beck, Mattias; Faist, Jérôme [ETH Zurich, Institute for Quantum Electronics, Auguste-Piccard-Hof 1, 8093 Zurich (Switzerland); Amanti, Maria Ines [ETH Zurich, Institute for Quantum Electronics, Auguste-Piccard-Hof 1, 8093 Zurich (Switzerland); Univ. Paris Diderot, Lab. Matererk iaux et Phenomenes Quantiques, F-75205 Paris (France)
2015-03-30
The continuous electrical tuning of a single-mode terahertz quantum cascade laser operating at a frequency of 3 THz is demonstrated. The devices are based on a two-section interdigitated third-order distributed feedback cavity. The lasers can be tuned of about 4 GHz at a constant optical output power of 0.7 mW with a good far-field pattern.
Improving the Efficiency of an Ideal Heat Engine: The Quantum Afterburner
Scully, Marlan O.
2001-01-01
By using a laser and maser in tandem, it is possible to obtain laser action in the hot exhaust gases involved in heat engine operation. Such a "quantum afterburner" involves the internal quantum states of working gas atoms or molecules as well as the techniques of cavity quantum electrodynamics and is therefore in the domain of quantum thermodynamics. As an example, it is shown that Otto cycle engine performance can be improved beyond that of the "ideal" Otto heat engine.
Quantum Bayesian rule for weak measurements of qubits in superconducting circuit QED
Wang, Peiyue; Qin, Lupei; Li, Xin-Qi
2014-01-01
Compared with the quantum trajectory equation, the quantum Bayesian approach has the advantage of being more efficient to infer quantum state under monitoring, based on the integrated output of measurement. For weak measurement of qubits in circuit quantum electrodynamics(cQED), properly accounting for the measurement backaction effects within the Bayesian framework is an important problem of current interest.Elegant work towards this task was carried out by Korotkov in "bad-cavity" and weak-...
Meystre, Pierre
2007-01-01
Elements of Quantum Optics gives a self-contained and broad coverage of the basic elements necessary to understand and carry out research in laser physics and quantum optics, including a review of basic quantum mechanics and pedagogical introductions to system-reservoir interactions and to second quantization. The text reveals the close connection between many seemingly unrelated topics, such as probe absorption, four-wave mixing, optical instabilities, resonance fluorescence and squeezing. It also comprises discussions of cavity quantum electrodynamics and atom optics. The 4th edition includes a new chapter on quantum entanglement and quantum information, as well as added discussions of the quantum beam splitter, electromagnetically induced transparency, slow light, and the input-output formalism needed to understand many problems in quantum optics. It also provides an expanded treatment of the minimum-coupling Hamiltonian and a simple derivation of the Gross-Pitaevskii equation, an important gateway to rese...
Collective strong coupling of cold potassium atoms in a ring cavity
Culver, Robert; Megyeri, Balázs; Pahwa, Komal; Mudarikwa, Lawrence; Holynski, Michael; Courteille, Philippe W; Goldwin, Jon
2016-01-01
We present experiments on ensemble cavity quantum electrodynamics with cold potassium atoms in a high-finesse ring cavity. Potassium-39 atoms are cooled in a two-dimensional magneto-optical trap, and transferred to a three-dimensional trap which intersects the cavity mode. The apparatus is described in detail and the first observations of strong coupling with potassium atoms are presented. Collective strong coupling of atoms and light is demonstrated via the splitting of the cavity transmission spectrum and the avoided crossing of the normal modes.
Numerical and Experimental Study of the Q Factor of High-Q Micropillar Cavities
DEFF Research Database (Denmark)
Gregersen, Niels; Reitzenstein, S.; Kistner, C.;
2010-01-01
to the effective reflectivity of the fundamental mode arising from coupling to scattering channels involving higher-order cavity modes and propagating Bloch modes in the distributed Bragg reflectors (DBRs). We show how these weak contributions lead to strong variations of the Q factor, and we relate the average......Micropillar cavities are potential candidates for high-efficiency single-photon sources and are testbeds for cavity quantum electrodynamics experiments. In both applications a high quality (Q) factor is desired. It was recently shown that the Q of high-Q semiconductor micropillar cavities exhibit...
DEFF Research Database (Denmark)
Breuer, Stefan; Elsässer, Wolfgang; McInerney, J.G.
2010-01-01
We have investigated experimentally the pulse train (mode beating) stability of a monolithic mode-locked multi-section quantum-dot laser with an added passive auxiliary optical fiber cavity. Addition of the weakly coupled (Â¿ -24dB) cavity reduces the current-induced shift dÂ¿/dI of the principal...
DEFF Research Database (Denmark)
Settnes, Mikkel; Nielsen, Per Kær; Lund, Anders Mølbjerg;
2013-01-01
We show that Auger processes involving wetting layer transitions mediate emission from a cavity that is detuned from a quantum dot by even tens of meV. The wetting layer thus acts as a reservoir, which by Coulomb scattering can supply or absorb the energy difference between emitter and cavity. We...
Trojan Wave Packets in the Quantum Cavity within the Extended Jaynes-Cummings Model
Kalinski, Matt
2016-05-01
Some time ago we have developed the theory of the Trojan Wave Packets (TWP) in the classical strong Circularly Polarized electromagnetic field in terms of the Mathieu generating functions. We have discovered that by the proper partitioning of the Coulomb spectrum i.e. by considering the deviation from the circularity and the vertical tilt of the undressed states as the new quantum numbers we can reduce the problem to the problem of several non-interacting quantum pendula for the Stark-Zeeman field dressed states. The TWP in the infinite physical space however turned out to be weakly unstable due to the spontaneous emission. Here we develop the theory in which the TWP is truly eternal when the electromagnetic interactions are considered quantum and the field is confined by the perfect quantum cavity boundary conditions. First we extend the Jaynes-Cummings (JC) model from the two to the infinite number of levels interacting with the one or two perfectly resonant quantum modes of the electromagnetic field. Similarly the model of JC and our previous pendular model the dressed electron-field eigenstates are constructed within the weakly interacting manifolds. Superpositions of those states are possible with the quantum electron density moving on the circular trajectories.
Quantum Key Distribution Based on a Weak-Coupling Cavity QED Regime
Institute of Scientific and Technical Information of China (English)
李春燕; 李岩松
2011-01-01
We present a quantum key distribution scheme using a weak-coupling cavity QED regime based on quantum dense coding.Hybrid entanglement states of photons and electrons are used to distribute information.We just need to transmit photons without storing them in the scheme.The electron confined in a quantum dot,which is embedded in a microcavity,is held by one of the legitimate users throughout the whole communication process.Only the polarization of a single photon and spin of electron measurements are applied in this protocol,which are easier to perform than collective-Bell state measurements.Linear optical apparatus,such as a special polarizing beam splitter in a circular basis and single photon operations,make it more flexible to realize under current technology.Its efficiency will approach 100％ in the ideal case.The security of the scheme is also discussed.%We present a quantum key distribution scheme using a weak-coupling cavity QED regime based on quantum dense coding. Hybrid entanglement states of photons and electrons are used to distribute information. We just need to transmit photons without storing them in the scheme. The electron confined in a quantum dot, which is embedded in a microcavity, is held by one of the legitimate users throughout the whole communication process. Only the polarization of a single photon and spin of electron measurements are applied in this protocol, which are easier to perform than collective-Bell state measurements. Linear optical apparatus, such as a speciai polarizing beam splitter in a circular basis and single photon operations, make it more flexible to realize under current technology. Its efficiency will approach 100% in the ideal case. The security of the scheme is also discussed.
Probing biological light-harvesting phenomena by optical cavities
Caruso, Filippo; Solano, Enrique; Huelga, Susana F; Aspuru-Guzik, Alán; Plenio, Martin B
2011-01-01
We propose a driven optical cavity quantum electrodynamics (QED) set up aimed at directly probing energy transport dynamics in photosynthetic biomolecules. We show that detailed information concerning energy transfer paths and delocalization of exciton states can be inferred (and exciton energies estimated) from the statistical properties of the emitted photons. This approach provides us with a novel spectroscopic tool for the interrogation of biological systems in terms of quantum optical phenomena which have been usually studied for atomic or solid-state systems, e.g. trapped atoms and semiconductor quantum dots.
Bubin, Sergiy; Komasa, Jacek; Stanke, Monika; Adamowicz, Ludwik
2010-03-21
We present very accurate quantum mechanical calculations of the three lowest S-states [1s(2)2s(2)((1)S(0)), 1s(2)2p(2)((1)S(0)), and 1s(2)2s3s((1)S(0))] of the two stable isotopes of the boron ion, (10)B(+) and (11)B(+). At the nonrelativistic level the calculations have been performed with the Hamiltonian that explicitly includes the finite mass of the nucleus as it was obtained by a rigorous separation of the center-of-mass motion from the laboratory frame Hamiltonian. The spatial part of the nonrelativistic wave function for each state was expanded in terms of 10,000 all-electron explicitly correlated Gaussian functions. The nonlinear parameters of the Gaussians were variationally optimized using a procedure involving the analytical energy gradient determined with respect to the nonlinear parameters. The nonrelativistic wave functions of the three states were subsequently used to calculate the leading alpha(2) relativistic corrections (alpha is the fine structure constant; alpha=1/c, where c is the speed of light) and the alpha(3) quantum electrodynamics (QED) correction. We also estimated the alpha(4) QED correction by calculating its dominant component. A comparison of the experimental transition frequencies with the frequencies obtained based on the energies calculated in this work shows an excellent agreement. The discrepancy is smaller than 0.4 cm(-1).
Bubin, Sergiy; Komasa, Jacek; Stanke, Monika; Adamowicz, Ludwik
2010-03-01
We present very accurate quantum mechanical calculations of the three lowest S-states [1s22s2(S10), 1s22p2(S10), and 1s22s3s(S10)] of the two stable isotopes of the boron ion, B10+ and B11+. At the nonrelativistic level the calculations have been performed with the Hamiltonian that explicitly includes the finite mass of the nucleus as it was obtained by a rigorous separation of the center-of-mass motion from the laboratory frame Hamiltonian. The spatial part of the nonrelativistic wave function for each state was expanded in terms of 10 000 all-electron explicitly correlated Gaussian functions. The nonlinear parameters of the Gaussians were variationally optimized using a procedure involving the analytical energy gradient determined with respect to the nonlinear parameters. The nonrelativistic wave functions of the three states were subsequently used to calculate the leading α2 relativistic corrections (α is the fine structure constant; α =1/c, where c is the speed of light) and the α3 quantum electrodynamics (QED) correction. We also estimated the α4 QED correction by calculating its dominant component. A comparison of the experimental transition frequencies with the frequencies obtained based on the energies calculated in this work shows an excellent agreement. The discrepancy is smaller than 0.4 cm-1.
Thermoelectric energy harvesting with quantum dots.
Sothmann, Björn; Sánchez, Rafael; Jordan, Andrew N
2015-01-21
We review recent theoretical work on thermoelectric energy harvesting in multi-terminal quantum-dot setups. We first discuss several examples of nanoscale heat engines based on Coulomb-coupled conductors. In particular, we focus on quantum dots in the Coulomb-blockade regime, chaotic cavities and resonant tunneling through quantum dots and wells. We then turn toward quantum-dot heat engines that are driven by bosonic degrees of freedom such as phonons, magnons and microwave photons. These systems provide interesting connections to spin caloritronics and circuit quantum electrodynamics.
Novel laser machining of optical fibers for long cavities with low birefringence
Takahashi, Hiroki; Orucevic, Fedja; Noguchi, Atsushi; Kassa, Ezra; Keller, Matthias
2015-01-01
We present a novel method of machining optical fiber surfaces with a CO${}_2$ laser for use in Fiber-based Fabry-Perot Cavities (FFPCs). Previously FFPCs were prone to large birefringence and limited to relatively short cavity lengths ($\\le$ 200 $\\mu$m). These characteristics hinder their use in some applications such as cavity quantum electrodynamics with trapped ions. We optimized the laser machining process to produce large, uniform surface structures. This enables the cavities to achieve high finesse even for long cavity lengths. By rotating the fibers around their axis during the laser machining process the asymmetry resulting from the laser's transverse mode profile is eliminated. Consequently we are able to fabricate fiber mirrors with a high degree of rotational symmetry, leading to remarkably low birefringence. Through measurements of the cavity finesse over a range of cavity lengths and the polarization dependence of the cavity linewidth, we confirmed the quality of the produced fiber mirrors for us...
X-ray quantum optics with Moessbauer nuclei in thin-film cavities
Energy Technology Data Exchange (ETDEWEB)
Heeg, Kilian Peter
2014-12-09
In this thesis thin-film cavities with embedded Moessbauer nuclei probed by near-resonant X-ray light are studied from a quantum optical perspective. A theoretical framework is developed and compact expressions for the observables are derived for the linear excitation regime, which is encountered in current experiments. Even advanced cavity layouts can be modeled in excellent agreement with the results of previous experiments and semi-classical approaches. In the absence of magnetic hyperfine splitting, the spectral response of the system is found to be formed by tunable Fano profiles. An experimental implementation of this line shape control allows to extract spectroscopic signatures with high precision and to reconstruct the phase of the nuclear transition in good agreement with the theoretical predictions. The alignment of medium magnetization and polarization control of the X-rays enable to engineer advanced quantum optical level schemes, in which vacuum induced coherence effects are predicted and successfully demonstrated in an experiment. Furthermore, it is shown that group velocity control for x-ray pulses can be achieved in the cavity. A scheme for its observation is proposed and then employed to experimentally confirm sub-luminal X-ray propagation. Finally, non-linear effects, which could become accessible with future light sources, are explored and a non-linear line shape control mechanism is discussed.
Quantum Noise Limits in White-Light-Cavity-Enhanced Gravitational Wave Detectors
Zhou, Minchuan; Shahriar, Selim M
2014-01-01
Previously, we had proposed a gravitational wave detector that incorporates the white light cavity (WLC) effect using a compound cavity for signal recycling (CC-SR). Here, we first calculate the quantum noise (QN) limited sensitivity curves for this design, and find that the broadening of sensitivity predicted by the classical analysis is also present in these curves, but is somewhat reduced. Furthermore, we find that the curves always stay above the standard quantum limit (SQL). To circumvent this limitation, we modify the dispersion to compensate the non-linear phase variation produced by the opto-mechanical (OM) resonance effects by making use of the single sideband approximation (SSA). We find that the resonance dips in the resulting QN curves entails a 14 times higher sensitivity-bandwidth product compared to the highest sensitivity result presented by Bunanno and Chen. We also present a simpler scheme (WLC-SR) where a dispersion medium is inserted in the SR cavity. Compared to the highest sensitivity re...
Exciton dynamics in a site-controlled quantum dot coupled to a photonic crystal cavity
Energy Technology Data Exchange (ETDEWEB)
Jarlov, C., E-mail: clement.jarlov@epfl.ch; Lyasota, A.; Ferrier, L.; Gallo, P.; Dwir, B.; Rudra, A.; Kapon, E. [Laboratory of Physics of Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)
2015-11-09
Exciton and cavity mode (CM) dynamics in site-controlled pyramidal quantum dots (QDs), integrated with linear photonic crystal membrane cavities, are investigated for a range of temperatures and photo-excitation power levels. The absence of spurious multi-excitonic effects, normally observed in similar structures based on self-assembled QDs, permits the observation of effects intrinsic to two-level systems embedded in a solid state matrix and interacting with optical cavity modes. The coupled exciton and CM dynamics follow the same trend, indicating that the CM is fed only by the exciton transition. The Purcell reduction of the QD and CM decay times is reproduced well by a theoretical model that includes exciton linewidth broadening and temperature dependent non-radiative processes, from which we extract a Purcell factor of 17 ± 5. For excitation powers above QD saturation, we show the influence of quantum wire barrier states at short delay time, and demonstrate the absence of multiexcitonic background emission.
A novel experiment for coupling a Bose-Einstein condensate with two crossed cavity modes
Leonard, Julian; Morales, Andrea; Zupancic, Philip; Donner, Tobias; Esslinger, Tilman
2015-05-01
Over the last decade, combining cavity quantum electrodynamics and quantum gases made it possible to explore the coupling of quantized light fields to coherent matter waves, leading e.g. to new optomechanical phenomena and the realization of quantum phase transitions. Triggered by the interest to study setups with more complex cavity geometries, we built a novel, highly flexible experimental system for coupling a Bose-Einstein condensate (BEC) with optical cavities, which allows to switch the cavity setups by means of an interchangeable science platform. report on our latest results on coupling a Bose-Einstein condensate with two crossed cavity modes intersecting under an angle of 60°. The mirrors have been machined in a way to spatially approach them, thus obtaining maximum single atom coupling rates of several MHz. This setup will allow the study of self-ordered phases in different lattice shapes, such as hexagonal and triangular geometries.
Boi, Luciano
2011-01-01
A vacuum, classically understood, contains nothing. The quantum vacuum, on the other hand, is a seething cauldron of nothingness: particle pairs going in and out of existence continuously and rapidly while exerting influence over an enormous range of scales. Acclaimed mathematical physicist and natural philosopher Luciano Boi expounds the quantum vacuum, exploring the meaning of nothingness and its relationship with physical reality. Boi first provides a deep analysis of the interaction between geometry and physics at the quantum level. He next describes the relationship between the microscopic and macroscopic structures of the world. In so doing, Boi sheds light on the very nature of the universe, stressing in an original and profound way the relationship between quantum geometry and the internal symmetries underlying the behavior of matter and the interactions of forces. Beyond the physics and mathematics of the quantum vacuum, Boi offers a profoundly philosophical interpretation of the concept. Plato and...
Wang, Lei; Jia, Zhi-Wei; Zhao, Yue; Liu, Chuan-Wei; Liu, Ying-Hui; Zhai, Shen-Qiang; Zhuo, Ning; Liu, Feng-Qi; Xu, Xian-Gang
2016-01-01
Diffraction coupled arrays of quantum cascade laser are presented. The phase-locked behavior is achieved through monolithic integration of a Talbot cavity at one side of the laser array. The principle is based on fractional Talbot effect. By controlling length of Talbot cavity to be a quarter of Talbot distance (Zt/4), in-phase mode operation is selected. Measured far-field radiation patterns reflect stable in-phase mode operation under different injection currents, from threshold current to full power current. Diffraction-limited performance is shown from the lateral far-field, where three peaks can be obtained and main peak and side peak interval is 10.5{\\deg}. The phase-locked arrays with in-phase mode operation may be a feasible solution to get higher output power and maintain well beam quality meanwhile.
Tunable single and dual mode operation of an external cavity quantum-dot injection laser
Energy Technology Data Exchange (ETDEWEB)
Biebersdorf, A [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Lingk, C [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); De Giorgi, M [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Feldmann, J [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet, Amalienstrasse 54, D-80799 Munich (Germany); Sacher, J [Sacher Lasertechnik GmbH, Hannah Arendt Strasse 3-7, D-35037 Marburg (Germany); Arzberger, M [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Ulbrich, C [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Boehm, G [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Amann, M-C [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Abstreiter, G [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany)
2003-08-21
We investigate quantum-dot (QD) lasers in an external cavity using Littrow and Littman configurations. Here, we report on a continuously tunable QD laser with a broad tuning range from 1047 to 1130 nm with high stability and efficient side mode suppression. The full-width at half-maximum of the laser line is 0.85 nm determined mainly by the quality of the external grating. This laser can be operated in a dual-mode modus, where the mode-spacing can be tuned continuously between 1.1 and 34 nm. Simultaneous emission of the two laser modes is shown by sum frequency generation experiments.
Energy Technology Data Exchange (ETDEWEB)
Bernacki, Bruce E.; Phillips, Mark C.
2010-05-01
We describe experimental results on the detection of explosives residues using active hyperspectral imaging by illumination of the target surface using an external cavity quantum cascade laser (ECQCL) and imaging using a room temperature microbolometer camera. The active hyperspectral imaging technique forms an image hypercube by recording one image for each tuning step of the ECQCL. The resulting hyperspectral image contains the full absorption spectrum produced by the illumination laser at each pixel in the image which can then be used to identify the explosive type and relative quantity using spectral identification approaches developed initially in the remote sensing community.
Cavity QED quantum phase gates for a single longitudinal mode of the intracavity field
García-Maraver, R.; Corbalán, R.; Eckert, K.; Rebić, S.; Artoni, M.; Mompart, J.
2004-12-01
A single three-level atom driven by a longitudinal mode of a high- Q cavity is used to implement two-qubit quantum phase gates for the intracavity field. The two qubits are associated with the zero- and one-photon Fock states of each of the two opposite circular polarization states of the field. The three-level atom mediates the conditional phase gate provided the two polarization states and the atom interact in a V-type configuration and the two-photon resonance condition is satisfied. Microwave and optical implementations are discussed with gate fidelities being evaluated against several decoherence mechanisms such as atomic velocity fluctuations or the presence of a weak magnetic field. The use of coherent states for both polarization states is investigated to assess the entanglement capability of the proposed quantum gates.
Feedback in a cavity QED system for control of quantum beats
Directory of Open Access Journals (Sweden)
Cimmarusti A.D.
2013-08-01
Full Text Available Conditional measurements on the undriven mode of a two-mode cavity QED system prepare a coherent superposition of ground states which generate quantum beats. The continuous system drive induces decoherence through the phase interruptions from Rayleigh scattering, which manifests as a decrease of the beat amplitude and an increase of the frequency of oscillation. We report recent experiments that implement a simple feedback mechanism to protect the quantum beat. We continuously drive the system until a photon is detected, heralding the presence of a coherent superposition. We then turn off the drive and let the superposition evolve in the dark, protecting it against decoherence. At a later time we reinstate the drive to measure the amplitude, phase, and frequency of the beats. The amplitude can increase by more than fifty percent, while the frequency is unchanged by the feedback.
Quantum simulation of 2D topological physics in a 1D array of optical cavities.
Luo, Xi-Wang; Zhou, Xingxiang; Li, Chuan-Feng; Xu, Jin-Shi; Guo, Guang-Can; Zhou, Zheng-Wei
2015-07-06
Orbital angular momentum of light is a fundamental optical degree of freedom characterized by unlimited number of available angular momentum states. Although this unique property has proved invaluable in diverse recent studies ranging from optical communication to quantum information, it has not been considered useful or even relevant for simulating nontrivial physics problems such as topological phenomena. Contrary to this misconception, we demonstrate the incredible value of orbital angular momentum of light for quantum simulation by showing theoretically how it allows to study a variety of important 2D topological physics in a 1D array of optical cavities. This application for orbital angular momentum of light not only reduces required physical resources but also increases feasible scale of simulation, and thus makes it possible to investigate important topics such as edge-state transport and topological phase transition in a small simulator ready for immediate experimental exploration.
Active mode locking of quantum cascade lasers operating in external ring cavity
Revin, D G; Wang, Y; Cockburn, J W; Belyanin, A
2015-01-01
Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode locked operation remains a challenge despite dedicated effort. Here we report the first demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents of a standard commercial laser chip.
Cavity QED quantum phase gates for a single longitudinal mode of the intracavity field
García-Maraver, R; Eckert, K; Rebic, S; Artoni, M; Mompart, J
2004-01-01
A single three-level atom driven by a longitudinal mode of a high-Q cavity is used to implement two-qubit quantum phase gates for the intracavity field. The two qubits are associated to the zero-and one-photon Fock states of each of the two opposite circular polarization states of the field. The three-level atom yields the conditional phase gate provided the two polarization states and the atom interact in a $V$-type configuration and the two photon resonance condition is fulfilled. Microwave and optical implementations are discussed with gate fidelities being evaluated against several decoherence mechanisms such as atomic velocity fluctuations or the presence of a weak magnetic field. The use of coherent states for both polarization states is investigated to assess the entanglement capability of the proposed quantum gates.
Seeing Wave-Particle Superposition with Cavity Input-Output Process
Min, Rui
2016-10-01
We present an experimental protocol to implement quantum delay-choice experiment in the context of cavity input-output process. In our protocol, the single-atom is employed as ancillary qubit to test the wave-particle feature of a single photon. With the cavity input-output process, we show that the controlled phase shift gate between single-atom and single-photon can be naturally used to generate the controlled Hadamard gate, which thus allows us to construct the quantum circuit for realizing the quantum delay-choice experiment. We also demonstrate the photonic wavelike and particlelike states can be simultaneously observed in our platform. Our protocol may open a new prospect using cavity quantum electrodynamics system to study some counterintuitive fundamental phenomenons in quantum mechanics.
Hu, Zixuan; Ratner, Mark A; Seideman, Tamar
2014-12-14
We develop a numerical approach for simulating light-induced charge transport dynamics across a metal-molecule-metal conductance junction. The finite-difference time-domain method is used to simulate the plasmonic response of the metal structures. The Huygens subgridding technique, as adapted to Lorentz media, is used to bridge the vastly disparate length scales of the plasmonic metal electrodes and the molecular system, maintaining accuracy. The charge and current densities calculated with classical electrodynamics are transformed to an electronic wavefunction, which is then propagated through the molecular linker via the Heisenberg equations of motion. We focus mainly on development of the theory and exemplify our approach by a numerical illustration of a simple system consisting of two silver cylinders bridged by a three-site molecular linker. The electronic subsystem exhibits fascinating light driven dynamics, wherein the charge density oscillates at the driving optical frequency, exhibiting also the natural system timescales, and a resonance phenomenon leads to strong conductance enhancement.
Energy Technology Data Exchange (ETDEWEB)
Cao, Xiufeng, E-mail: xfcao@xmu.edu.cn [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China); Advanced Science Institute, RIKEN, Wako-shi 351-0198 (Japan); Ai, Qing; Sun, Chang-Pu [Advanced Science Institute, RIKEN, Wako-shi 351-0198 (Japan); Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Nori, Franco [Advanced Science Institute, RIKEN, Wako-shi 351-0198 (Japan); Physics Department, The University of Michigan, Ann Arbor, MI 48109-1040 (United States)
2012-01-09
We propose a strategy to demonstrate the transition from the quantum Zeno effect (QZE) to the anti-Zeno effect (AZE) using a superconducting qubit coupled to a transmission line cavity, by varying the central frequency of the cavity mode. Our results are obtained without the rotating wave approximation (RWA), and the initial state (a dressed state) is easy to prepare. Moreover, we find that in the presence of both qubit's intrinsic bath and the cavity bath, the emergence of the QZE and the AZE behaviors relies not only on the match between the qubit energy-level-spacing and the central frequency of the cavity mode, but also on the coupling strength between the qubit and the cavity mode. -- Highlights: ► We propose how to demonstrate the transition from Zeno effect to anti-Zeno effect. ► Our results are beyond the RWA, and the initial state is easy to prepare. ► The case of both qubit's intrinsic bath and cavity bath coexist is also studied.
Mullin, Jonathan; Schatz, George C
2012-03-01
A multiscale method is presented that allows for evaluation of plasmon-enhanced optical properties of nanoparticle/molecule complexes with no additional cost compared to standard electrodynamics (ED) and linear response quantum mechanics (QM) calculations for the particle and molecule, respectively, but with polarization and orientation effects automatically described. The approach first calculates the total field of the nanoparticle by ED using the finite difference time domain (FDTD) method. The field intensity in the frequency domain as a function of distance from the nanoparticle is calculated via a Fourier transform. The molecular optical properties are then calculated with QM in the frequency domain in the presence of the total field of the nanoparticle. Back-coupling due to dipolar reradiation effects is included in the single-molecule plane wave approximation. The effects of polarization and partial orientation averaging are considered. The QM/ED method is evaluated for the well-characterized test case of surface-enhanced Raman scattering (SERS) of pyridine bound to silver, as well as for the resonant Raman chromophore rhodamine 6G. The electromagnetic contribution to the enhancement factor is 10(4) for pyridine and 10(2) for rhodamine 6G.
Chantler, C T; Kinnane, M N; Gillaspy, J D; Hudson, L T; Payne, A T; Smale, L F; Henins, A; Pomeroy, J M; Tan, J N; Kimpton, J A; Takacs, E; Makonyi, K
2012-10-12
We report a new test of quantum electrodynamics (QED) for the w (1s2p(1)P(1)→1s(2)(1)S(0)) x-ray resonance line transition energy in heliumlike titanium. This measurement is one of few sensitive to two-electron QED contributions. Systematic errors such as Doppler shifts are minimized in our experiment by trapping and stripping Ti atoms in an electron beam ion trap and by applying absolute wavelength standards to calibrate the dispersion function of a curved-crystal spectrometer. We also report a more general systematic discrepancy between QED theory and experiment for the w transition energy in heliumlike ions for Z>20. When all of the data available in the literature for Z=16-92 are taken into account, the divergence is seen to grow as approximately Z(3) with a statistical significance on the coefficient that rises to the level of 5 standard deviations. Our result for titanium alone, 4749.85(7) eV for the w line, deviates from the most recent ab initio prediction by 3 times our experimental uncertainty and by more than 10 times the currently estimated uncertainty in the theoretical prediction.
Nanocatalysts by Quantum Electrodynamics Induced Electromagnetic Radiation%量子电动学诱导电磁辐射研究纳米催化剂
Institute of Scientific and Technical Information of China (English)
Thomas V. PREVENSLIK
2008-01-01
Gold has been regarded as a poor heterogeneous catalyst because it is generally considered a nonreactive metal. But as nanocatalysts, gold and other metals somehow significantly enhance reactivity. It is generally thought chemical bonds of reactants are weakened by adsorption to nanocatalysts thereby allowing reactions to proceed more rapidly, but how this reaction proceeds to completion is not well understood. Here gold nanocatalysts are treated as unsupported nanoparticles (NPs) in a solution of reactant molecules from which extensions are made to gold NPs supported on titanium dioxide. Whether the NPs are supported or unsupported, enhanced catalytic reactivity depends on absorbed thermal kT (k is Boltzmann′s constant and T is absolute temperature) energy accumulated from prior collisions of reactant molecules. The accumulated kT energy is treated as electromagnetic thereby allowing frequency up-conversion by quantum electrodynamics (QED) to the confinement frequency of the NP, typically beyond the vacuum ultraviolet (VUV). By this theory, the chemical reaction of reactant molecules having bonds weakened by adsorption is completed by QED induced VUV photolysis.
Institute of Scientific and Technical Information of China (English)
SONG Ke-Hui; ZHOU Zheng-Wei; GUO Guang-Can
2006-01-01
We present a scheme to realize geometric phase-shift gate for two superconducting quantum interference device (SQUID) qubits coupled to a single-mode microwave field. The geometric phase-shift gate operation is performed transitions during the gate operation. Thus, the docoherence due to energy spontaneous emission based on the levels of SQUIDs are suppressed. The gate is insensitive to the cavity decay throughout the operation since the cavity mode is displaced along a circle in the phase space, acquiring a phase conditional upon the two lower flux states of the SQUID qubits, and the cavity mode is still in the original vacuum state. Based on the SQUID qubits interacting with the cavity mode, our proposed approach may open promising prospects for quantum logic in SQUID-system.
Trace-gas sensing using the compliance voltage of an external cavity quantum cascade laser
Energy Technology Data Exchange (ETDEWEB)
Phillips, Mark C.; Taubman, Matthew S.
2013-06-04
Quantum cascade lasers (QCLs) are increasingly being used to detect, identify, and measure levels of trace gases in the air. External cavity QCLs (ECQCLs) provide a broadly-tunable infrared source to measure absorption spectra of chemicals and provide high detection sensitivity and identification confidence. Applications include detecting chemical warfare agents and toxic industrial chemicals, monitoring building air quality, measuring greenhouse gases for atmospheric research, monitoring and controlling industrial processes, analyzing chemicals in exhaled breath for medical diagnostics, and many more. Compact, portable trace gas sensors enable in-field operation in a wide range of platforms, including handheld units for use by first responders, fixed installations for monitoring air quality, and lightweight sensors for deployment in unmanned aerial vehicles (UAVs). We present experimental demonstration of a new chemical sensing technique based on intracavity absorption in an external cavity quantum cascade laser (ECQCL). This new technique eliminates the need for an infrared photodetector and gas cell by detecting the intracavity absorption spectrum in the compliance voltage of the laser device itself. To demonstrate and characterize the technique, we measure infrared absorption spectra of chemicals including water vapor and Freon-134a. Sub-ppm detection limits in one second are achieved, with the potential for increased sensitivity after further optimization. The technique enables development of handheld, high-sensitivity, and high-accuracy trace gas sensors for in-field use.
Dual Quantum Electrodynamics Dyon-Dyon and Charge-Monopole Scattering in a High-Energy Approximation
Gamberg, L P; Gamberg, Leonard; Milton, Kimball A.
2000-01-01
We develop the quantum field theory of electron-point magnetic monopole interactions and more generally, dyon-dyon interactions, based on the original string-dependent ``nonlocal'' action of Dirac and Schwinger. We demonstrate that a viable nonperturbative quantum field theoretic formulation can be constructed that results in a string {\\em independent} cross section for monopole-electron and dyon-dyon scattering. Such calculations can be done only by using nonperturbative approximations such as the eikonal and not by some mutilation of lowest-order perturbation theory.
A grating-coupled external cavity InAs/InP quantum dot laser with 85-nm tuning range
Wei, Heng; Jin, Peng; Luo, Shuai; Ji, Hai-Ming; Yang, Tao; Li, Xin-Kun; Wu, Jian; An, Qi; Wu, Yan-Hua; Chen, Hong-Mei; Wang, Fei-Fei; Wu, Ju; Wang, Zhan-Guo
2013-09-01
The optical performance of a grating-coupled external cavity laser based on InAs/InP quantum dots is investigated. Continuous tuning from 1391 nm to 1468 nm is realized at an injection current of 1900 mA. With the injection current increasing to 2300 mA, the tuning is blue shifted to some extent to the range from 1383 nm to 1461 nm. By combining the effect of the injection current with the grating tuning, the total tuning bandwidth of the external cavity quantum-dot laser can reach up to 85 nm. The dependence of the threshold current on the tuning wavelength is also presented.
Simplified realization of two-qubit quantum phase gate with four-level systems in cavity QED
Yang, Chui-Ping; Chu, Shih-I.; Han, Siyuan
2004-10-01
We propose a method for realizing two-qubit quantum phase gate with 4-level systems in cavity QED. In this proposal, the two logical states of a qubit are represented by the two lowest levels of each system, and two intermediate levels of each system are utilized to facilitate coherent control and manipulation of quantum states of the qubits. The present method does not involve cavity-photon population during the operation. In addition, we show that the gate can be achieved using only two-step operations.
Institute of Scientific and Technical Information of China (English)
ZHAN Zhi-Ming
2008-01-01
We put forward a simple scheme for one-step realization of a two-qubit SWAP gate with SQUIDs (super-conducting quantum-interference devices) in cavity QED via Raman transition. In this scheme, the cavity field is only virtually excited and thus the cavity decay is suppressed. The SWAP gate is realized by using only two lower flux states of the SQUID system and the excited state would not be excited. Therefore, the effect of decoherence caused from the levels of the SQUID system is possibly minimized. The scheme can also be used to implement the SWAP gate with atoms.
Simplified Scheme for Cloning and Telecloing Quantum States near a Given State
Institute of Scientific and Technical Information of China (English)
郑仕标
2003-01-01
We describe a simple protocol to produce two approximate copiers of an input state in the neighbourhood of a particular state. We show that the scheme can be realized within the framework of cavity quantum electrodynamics. We also present a scheme for telecloning this kind of states.
$\\hbar$ as a Physical Constant of Classical Optics and Electrodynamics
Tremblay, Real; Allen, Claudine Ni
2015-01-01
The Planck constant ($\\hbar$) plays a pivotal role in quantum physics. Historically, it has been proposed as postulate, part of a genius empirical relationship $E=\\hbar \\omega$ in order to explain the intensity spectrum of the blackbody radiation for which classical electrodynamic theory led to an unacceptable prediction: The ultraviolet catastrophe. While the usefulness of the Planck constant in various fields of physics is undisputed, its derivation (or lack of) remains unsatisfactory from a fundamental point of view. In this paper, the analysis of the blackbody problem is performed with a series expansion of the electromagnetic field in terms of TE, TM modes in a metallic cavity with small losses, that leads to developing the electromagnetic fields in a \\textit{complete set of orthonormal functions}. This expansion, based on coupled power theory, maintains both space and time together enabling modeling of the blackbody's evolution toward equilibrium. Reaching equilibrium with a multimodal waveguide analysi...
Wang, Guan-Yu; Li, Tao; Deng, Fu-Guo
2015-04-01
Quantum entanglement is the key resource in quantum information processing, especially in quantum communication network. However, affected by the environment noise, the maximally entangled states usually collapse into nonmaximally entangled ones or even mixed states. Here we present two high-efficiency schemes to complete the entanglement concentration of nonlocal two-atom systems. Our first scheme is used to concentrate the nonlocal atomic systems in the partially entangled states with known parameters, and it has the optimal success probability. The second scheme is used to concentrate the entanglement of the nonlocal two-atom systems in the partially entangled states with unknown parameters. Compared with the other schemes for the entanglement concentration of atomic systems, our two protocols are more efficient and practical. They require only an ancillary single photon to judge whether they succeed or not, and they work in a heralded way with detection inefficiency and absence of sophisticated single-photon detectors in practical applications. Moreover, they are insensitive to both the cavity decay and atomic spontaneous emission.
Fano-resonance induced strong-coupling of a hyperbolic cavity to a quantum emitter
Hasan, Mehedi; Belov, Pavel
2015-01-01
Light-matter interaction is studied for an open quantum system in the strong-coupling regime. A quantum dot and a hyperbolic cavity of spherical geometry is shown to couple light with large Rabi frequency and the role of Fano resonance is shown in the coupling mechanism. High Purcell factor and large Lamb shift are outlined. In the near-field spectrum, two distinct anti-crossings are evident, namely -- the one near the epsilon near zero (ENZ) frequency (from the effective medium description) which is detectable in the far-field, and the second anti-crossing is a pseudomode that does not appear in the far-field spectrum. This delineates the phenomenon `farfield propagating large Purcell factor'. Finally, we remark the fidelity of the strong-coupling, i.e. how prone the strong-coupling with respect to the loss mechanisms. This study on strong-coupling will have applications for spectroscopy, control over chemical reaction rate, microcavity, and in quantum information technology.
Miyazono, Evan; Craiciu, Ioana; Kindem, Jonathan M; Faraon, Andrei
2016-01-01
Erbium dopants in crystals exhibit highly coherent optical transitions well suited for solid-state optical quantum memories operating in the telecom band. Here we demonstrate coupling of erbium dopant ions in yttrium orthosilicate to a photonic crystal cavity fabricated directly in the host crystal using focused ion beam milling. The coupling leads to reduction of the photoluminescence lifetime and enhancement of the optical depth in microns-long devices, which will enable on-chip quantum memories.
Nakamura, Satoshi; Goto, Hayato; Kujiraoka, Mamiko; Ichimura, Kouichi
2016-12-01
We propose a scheme for frequency-domain quantum computation (FDQC) in which the errors due to crosstalk are suppressed using extra physical systems coupled to a cavity. FDQC is a promising method to realize large-scale quantum computation, but crosstalk is a major problem. When physical systems employed as qubits satisfy specific resonance conditions, gate errors due to crosstalk increase. In our scheme, the errors are suppressed by controlling the resonance conditions using extra physical systems.
Energy Technology Data Exchange (ETDEWEB)
Miyazono, Evan; Zhong, Tian; Craiciu, Ioana; Kindem, Jonathan M.; Faraon, Andrei, E-mail: faraon@caltech.edu [T. J. Watson Laboratory of Applied Physics, California Institute of Technology, 1200 E California Blvd, Pasadena, California 91125 (United States)
2016-01-04
Erbium dopants in crystals exhibit highly coherent optical transitions well suited for solid-state optical quantum memories operating in the telecom band. Here, we demonstrate coupling of erbium dopant ions in yttrium orthosilicate to a photonic crystal cavity fabricated directly in the host crystal using focused ion beam milling. The coupling leads to reduction of the photoluminescence lifetime and enhancement of the optical depth in microns-long devices, which will enable on-chip quantum memories.
Characterization and Dynamic Analysis of Long-Cavity Multi-Section Gain- Levered Quantum-Dot Lasers
2013-03-01
linewidth-enhancement factor to values greater than one [19]. This is combined with the original quantum-dot emission wavelength being blueshifted ...16]. Figure 12: Blueshift of the quantum-dot emission due to state filling. Each spectrum is marked with the corresponding laser cavity length...distinct second peak near 1222 nm. This spectral feature continues to blueshift as biasing is increased to 500 mA. The fundamental spectral feature widens
Low-energy electrodynamics of novel spin excitations in the quantum spin ice Yb₂Ti₂O₇.
Pan, LiDong; Kim, Se Kwon; Ghosh, A; Morris, Christopher M; Ross, Kate A; Kermarrec, Edwin; Gaulin, Bruce D; Koohpayeh, S M; Tchernyshyov, Oleg; Armitage, N P
2014-09-18
In condensed matter systems, formation of long-range order (LRO) is often accompanied by new excitations. However, in many geometrically frustrated magnetic systems, conventional LRO is suppressed, while non-trivial spin correlations are still observed. A natural question to ask is then what is the nature of the excitations in this highly correlated state without broken symmetry? Frequently, applying a symmetry breaking field stabilizes excitations whose properties reflect certain aspects of the anomalous state without LRO. Here we report a THz spectroscopy study of novel excitations in quantum spin ice Yb2Ti2O7 under a directed magnetic field. At large positive fields, both right- and left-handed magnon and two-magnon-like excitations are observed. The g-factors of these excitations are dramatically enhanced in the low-field limit, showing a crossover of these states into features consistent with the quantum string-like excitations proposed to exist in quantum spin ice in small fields.
Realization of collective strong coupling with ion Coulomb crystals in an optical cavity
DEFF Research Database (Denmark)
Herskind, Peter Fønss; Dantan, Aurélien; Marler, Joan;
2009-01-01
quantum-information-processing networks 11, 12 hence requires devices to efficiently couple photons and stationary qubits. Here, we present the first CQED experiments demonstrating that the collective strong-coupling regime 2 can be reached in the interaction between a solid in the form of an ion Coulomb......Cavity quantum electrodynamics (CQED) focuses on understanding the interactions between matter and the electromagnetic field in cavities at the quantum level 1, 2 . In the past years, CQED has attracted attention 3, 4, 5, 6, 7, 8, 9 especially owing to its importance for the field of quantum...... information 10 . At present, photons are the best carriers of quantum information between physically separated sites 11, 12 and quantum-information processing using stationary qubits 10 is most promising, with the furthest advances having been made with trapped ions 13, 14, 15 . The implementation of complex...
Mekhov, Igor B.; Ritsch, Helmut
2012-05-01
Although the study of ultracold quantum gases trapped by light is a prominent direction of modern research, the quantum properties of light were widely neglected in this field. Quantum optics with quantum gases closes this gap and addresses phenomena where the quantum statistical natures of both light and ultracold matter play equally important roles. First, light can serve as a quantum nondemolition probe of the quantum dynamics of various ultracold particles from ultracold atomic and molecular gases to nanoparticles and nanomechanical systems. Second, due to the dynamic light-matter entanglement, projective measurement-based preparation of the many-body states is possible, where the class of emerging atomic states can be designed via optical geometry. Light scattering constitutes such a quantum measurement with controllable measurement back-action. As in cavity-based spin squeezing, the atom number squeezed and Schrödinger cat states can be prepared. Third, trapping atoms inside an optical cavity, one creates optical potentials and forces, which are not prescribed but quantized and dynamical variables themselves. Ultimately, cavity quantum electrodynamics with quantum gases requires a self-consistent solution for light and particles, which enriches the picture of quantum many-body states of atoms trapped in quantum potentials. This will allow quantum simulations of phenomena related to the physics of phonons, polarons, polaritons and other quantum quasiparticles.
Wei, Hai-Rui; Deng, Fu-Guo
2014-12-18
Quantum logic gates are the key elements in quantum computing. Here we investigate the possibility of achieving a scalable and compact quantum computing based on stationary electron-spin qubits, by using the giant optical circular birefringence induced by quantum-dot spins in double-sided optical microcavities as a result of cavity quantum electrodynamics. We design the compact quantum circuits for implementing universal and deterministic quantum gates for electron-spin systems, including the two-qubit CNOT gate and the three-qubit Toffoli gate. They are compact and economic, and they do not require additional electron-spin qubits. Moreover, our devices have good scalability and are attractive as they both are based on solid-state quantum systems and the qubits are stationary. They are feasible with the current experimental technology, and both high fidelity and high efficiency can be achieved when the ratio of the side leakage to the cavity decay is low.
External cavity-quantum cascade laser (EC-QCL) spectroscopy for protein analysis in bovine milk.
Kuligowski, Julia; Schwaighofer, Andreas; Alcaráz, Mirta Raquel; Quintás, Guillermo; Mayer, Helmut; Vento, Máximo; Lendl, Bernhard
2017-04-22
The analytical determination of bovine milk proteins is important in food and non-food industrial applications and yet, rather labour-intensive wet-chemical, low-throughput methods have been employed since decades. This work proposes the use of external cavity-quantum cascade laser (EC-QCL) spectroscopy for the simultaneous quantification of the most abundant bovine milk proteins and the total protein content based on the chemical information contained in mid-infrared (IR) spectral features of the amide I band. Mid-IR spectra of protein standard mixtures were used for building partial least squares (PLS) regression models. Protein concentrations in commercial bovine milk samples were calculated after chemometric compensation of the matrix contribution employing science-based calibration (SBC) without sample pre-processing. The use of EC-QCL spectroscopy together with advanced multivariate data analysis allowed the determination of casein, α-lactalbumin, β-lactoglobulin and total protein content within several minutes.