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. PMID:26684118
Deterministic cavity quantum electrodynamics with trapped ions
We have employed radio-frequency trapping to localize a single 40Ca+-ion in a high-finesse optical cavity. By means of laser Doppler cooling, the position spread of the ion's wavefunction along the cavity axis was reduced to 42 nm, a fraction of the resonance wavelength of ionized calcium (λ = 397 nm). By controlling the position of the ion in the optical field, continuous and completely deterministic coupling of ion and field was realized. The precise three-dimensional location of the ion in the cavity was measured by observing the fluorescent light emitted upon excitation in the cavity field. The single-ion system is ideally suited to implement cavity quantum electrodynamics under cw conditions. To this end we operate the cavity on the D3/2-P1/2 transition of 40Ca+ (λ 866 nm). Applications include the controlled generation of single-photon pulses with high efficiency and two-ion quantum gates
Structure an dynamics in cavity quantum electrodynamics
Much of the theoretical background related to the radiative processes for atoms in the presence of boundaries comes from two often disjoint areas, namely cavity quantum electrodynamics and optical bistability with two-state atoms. While the former of these areas has been associated to a large degree with studies in a perturbative domain of altered associated to a large degree with studies in a perturbative domain of altered emission processes in the presence of boundaries other than those of free space, the latter is often viewed from the perspective of hysteresis cycles and device applications. With the exception of the laser, however, perhaps the most extensive investigations of quantum statistical processes in quantum optics are to be found in the literature on bistability with two-state atoms and on cavity QED. Unfortunately, the degree of overlap of these two areas has not always been fully appreciated. This circumstance is perhaps due in part to the fact that the investigation of dynamical processes in cavity QED has had as its cornerstone the Jaynes-Cummings problem, with extensions to include, for example, small amounts of dissipation. On the other hand, a principle aspect of the bistability literature has been the study of quantum fluctuations in open systems for which dissipation plays a central role, but for which the coherent quantum dynamics of the Haynes-Cummings model are to a large measure lost due to the usual assumption of large system size and weak coupling (as in the standard theory of the laser). 132 refs., 26 figs., 1 tab
Large payload quantum steganography based on cavity quantum electrodynamics
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. (general)
Large payload quantum steganography based on cavity quantum electrodynamics
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.
Cavity Quantum Electrodynamics of Continuously Monitored Bose-Condensed Atoms
Mark D. Lee
2015-09-01
Full Text Available We study cavity quantum electrodynamics of Bose-condensed atoms that are subjected to continuous monitoring of the light leaking out of the cavity. Due to a given detection record of each stochastic realization, individual runs spontaneously break the symmetry of the spatial profile of the atom cloud and this symmetry can be restored by considering ensemble averages over many realizations. We show that the cavity optomechanical excitations of the condensate can be engineered to target specific collective modes. This is achieved by exploiting the spatial structure and symmetries of the collective modes and light fields. The cavity fields can be utilized both for strong driving of the collective modes and for their measurement. In the weak excitation limit the condensate–cavity system may be employed as a sensitive phonon detector which operates by counting photons outside the cavity that have been selectively scattered by desired phonons.
Enhancements to cavity quantum electrodynamics system
Cimmarusti, A D; Norris, D G; Orozco, L A
2011-01-01
We show the planned upgrade of a cavity QED experimental apparatus. The system consists of an optical cavity and an ensemble of ultracold $^{85}$Rb atoms coupled to its mode. We propose enhancements to both. First, we document the building process for a new cavity, with a planned finesse of $\\sim$20000. We address problems of maintaining mirror integrity during mounting and improving vibration isolation. Second, we propose improvements to the cold atom source in order to achieve better optical pumping and control over the flux of atoms. We consider a 2-D optical molasses for atomic beam deflection, and show computer simulation results for evaluating the design. We also examine the possibility of all-optical atomic beam focusing, but find that it requires unreasonable experimental parameters.
Quantum-to-Classical Transition in Cavity Quantum Electrodynamics (QED)
Fink, J M; Studer, P; Bishop, Lev S; Baur, M; Bianchetti, R; Bozyigit, D; Lang, C; Filipp, S; Leek, P J; Wallraff, A
2010-01-01
The quantum properties of electromagnetic, mechanical or any other type of harmonic oscillator can be revealed by investigating its strong coherent coupling to a single quantum two level system in an approach known as cavity 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 system. Here, we study how the classical response of a quantum cavity QED system emerges when its thermal occupation -- or effective temperature -- is raised gradually over 5 orders of magnitude. In this way we explore in detail the continuous cross-over from a quantum response to a classical response in the spirit of Bohr's correspondence principle. We also demonstrate how to extract effective cavity field temperatures from both spectroscopic and time-resolved vacuum Rabi measurements.
Macroscopic quantum electrodynamics of high-Q cavities
In this thesis macroscopic quantum electrodynamics in linear media was applied in order to develop an universally valid quantum theory for the description of the interaction of the electromagnetic field with atomic sources in high-Q cavities. In this theory a complete description of the characteristics of the emitted radiation is given. The theory allows to show the limits of the applicability of the usually applied theory. In order to establish an as possible generally valid theory first the atom-field interaction was studied in the framework of macroscopic quantum electrodynamics in dispersive and absorptive media. In order to describe the electromagnetic field from Maxwell's equations was started, whereby the noise-current densities, which are connected with the absorption of the medium, were included. The solution of these equations expresses the electromagnetic field variables by the noise-current densities by means of Green's tensor of the macroscopic Maxwell equations. The explicit quantization is performed by means of the noise-current densities, whereby a diagonal Hamiltonian is introduced, which then guarantees the time development according to Maxwell's equation and the fulfillment of the fundamental simultaneous commutation relations of the field variables. In the case of the interaction of the medium-supported field with atoms the Hamiltonian must be extended by atom-field interactions energies, whereby the canonical coupling schemes of the minimal or multipolar coupling can be used. The dieelectric properties of the material bodies as well as their shape are coded in the Green tensor of the macroscopic Maxwell equations. As preparing step first the Green tensor was specified in order to derive three-dimensional input-output relations for the electromagnetic field operators on a plane multilayer structure. Such a general dewscription of the electromagnetic field allows the inclusion both of dispersion and absorption of the media and the possible
Measuring the effective phonon density of states of a quantum dot in cavity quantum electrodynamics
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...
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.
Perfect photon absorption in nonlinear regime of cavity quantum electrodynamics
Agarwal, G S; Wang, Liyong; Zhu, Yifu
2016-01-01
It has been shown that perfect photon absorption can occur in the linear excitation regime of cavity quantum electrodynamics (CQED), in which photons from two identical light fields coupled into two ends of the cavity are completely absorbed and result in excitation of the polariton state of the CQED system. The output light from the cavity is totally suppressed by the destructive interference and the polariton state can only decay incoherently back to the ground state. Here we analyze the perfect photon absorption and onset of optical bistability in the nonlinear regime of the CQED and show that the perfect photon absorption persists in the nonlinear regime of the CQED below the threshold of the optical bistability. Therefore the perfect photon absorption is a phenomenon that can be observed in both linear and nonlinear regimes of CQED. Furthermore, our study reveals for the first time that the optical bistability is influenced by the input-light interference and can be manipulated by varying the relative ph...
Cavity quantum electrodynamics with Anderson-localized modes
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren;
2010-01-01
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....
Macroscopic quantum electrodynamics of high-Q cavities
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
Tang, Jing-Wu; Zhao, Guan-Xiang; He, Xiong-Hui
2011-05-01
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.
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. (general)
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
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
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.
Single-shot optical readout of a quantum bit using cavity quantum electrodynamics
Sun, Shuo; Waks, Edo
2016-07-01
We propose a method to perform single-shot optical readout of a quantum bit (qubit) using cavity quantum electrodynamics. We selectively couple the optical transitions associated with different qubit basis states to the cavity and utilize the change in cavity transmissivity to generate a qubit readout signal composed of many photons. We show that this approach enables single-shot optical readout even when the qubit does not have a good cycling transition, which is required for standard resonance fluorescence measurements. We calculate the probability that the measurement detects the correct qubit state using the example of a quantum-dot spin under various experimental conditions and demonstrate that it can exceed 0.99.
Multiparty Quantum Secret Sharing of Classical Message using Cavity Quantum Electrodynamic System
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
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.
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...
Theory and simulation of cavity quantum electro-dynamics in multi-partite quantum complex systems
The cavity quantum electrodynamics of various complex systems is here analyzed using a general versatile code developed in this research. Such quantum multi-partite systems normally consist of an arbitrary number of quantum dots in interaction with an arbitrary number of cavity modes. As an example, a nine-partition system is simulated under different coupling regimes, consisting of eight emitters interacting with one cavity mode. Two-level emitters (e.g. quantum dots) are assumed to have an arrangement in the form of a linear chain, defining the mutual dipole-dipole interactions. It was observed that plotting the system trajectory in the phase space reveals a chaotic behavior in the so-called ultrastrong-coupling regime. This result is mathematically confirmed by detailed calculation of the Kolmogorov entropy, as a measure of chaotic behavior. In order to study the computational complexity of our code, various multi-partite systems consisting of one to eight quantum dots in interaction with one cavity mode were solved individually. Computation run times and the allocated memory for each system were measured. (orig.)
Theory and simulation of cavity quantum electro-dynamics in multi-partite quantum complex systems
Alidoosty Shahraki, Moslem; Khorasani, Sina; Aram, Mohammad Hasan [Sharif University of Technology, School of Electrical Engineering, Tehran (Iran, Islamic Republic of)
2014-05-15
The cavity quantum electrodynamics of various complex systems is here analyzed using a general versatile code developed in this research. Such quantum multi-partite systems normally consist of an arbitrary number of quantum dots in interaction with an arbitrary number of cavity modes. As an example, a nine-partition system is simulated under different coupling regimes, consisting of eight emitters interacting with one cavity mode. Two-level emitters (e.g. quantum dots) are assumed to have an arrangement in the form of a linear chain, defining the mutual dipole-dipole interactions. It was observed that plotting the system trajectory in the phase space reveals a chaotic behavior in the so-called ultrastrong-coupling regime. This result is mathematically confirmed by detailed calculation of the Kolmogorov entropy, as a measure of chaotic behavior. In order to study the computational complexity of our code, various multi-partite systems consisting of one to eight quantum dots in interaction with one cavity mode were solved individually. Computation run times and the allocated memory for each system were measured. (orig.)
Analysis of adiabatic transfer in cavity quantum electrodynamics
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.
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 ...
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.
Vacuum-Induced Abelian and Non-Abelian Gauge Potentials in Cavity Quantum Electrodynamics
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
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.
Preparation of W state in resonant bimodal cavity quantum electrodynamics
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.
Rossi, R., Jr.; de Magalhães, A. R. Bosco; Nemes, M. C.
2008-01-01
We propose an experiment for the observation of the quantum Zeno effect (QZE) in a bipartite system. The setup involves two microwave cavities and a “tunneling” photon, which is observed by the passage of Rydberg atoms. Our proposal allows for the consideration of two types of measurements, namely, sequential observations of the atomic state and its inclusive measurement. In the present system the two processes are shown to lead to the same result in the ideal case. We consider realistic atom-field interaction times, cavity dissipation, and limited detection efficiency. Analytical expressions for the “tunneling” probability are obtained exhibiting a competition between the environment induced exponential decay and the characteristic t2 (for short times) dependence of the QZE. We show that for sufficiently small dissipation constants the effect can be observed with current experimental facilities.
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.
Epitaxial lift-off for solid-state cavity quantum electrodynamics
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
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
Cavity quantum electrodynamics with a Rydberg-blocked atomic ensemble
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 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> and the collectively excited state |E> with a single Rydberg excitation distributed evenly on all atoms. The collectively enhanced coupling of all atoms to the cavity field with coherent coupling strengths which are much larger than the decay rates in the system leads to the strong coupling regime of the resulting 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 that the absence of interactions between remote Rydberg atoms may, due to a combinatorial effect, induce a cavity-assisted excitation blockade whose range is larger than the typical Rydberg dipole-dipole interaction length.
Cavity quantum electrodynamics with a Rydberg-blocked atomic ensemble
Guerlin, Christine; Brion, Etienne; Esslinger, Tilman;
2010-01-01
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......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...... 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> and the...
Teleportation of two-atom entangled state in resonant cavity quantum electrodynamics
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
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%....
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren;
2011-01-01
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
Huisman, S. R.; Frater, E. H.; Korterik, J. P.; Herek, J. L.; Mosk, A. P.; Offerhaus, H. L.; Lagendijk, A.; Stobbe, Søren; Nielsen, Henri Thyrrestrup; Lodahl, Peter; Vos, W. L.; Pinkse, P .W. H.
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...... and these “random cavities” warrants a more detailed investigation....
A nanophotonic probe for quantum electrodynamics in random cavities
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 ...
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.
Perfect photon absorption in the nonlinear regime of cavity quantum electrodynamics
Agarwal, G. S.; Di, Ke; Wang, Liyong; Zhu, Yifu
2016-06-01
It has been shown that perfect photon absorption can occur in the linear excitation regime of cavity quantum electrodynamics (CQED), in which photons from two identical light fields coupled into two ends of the cavity are completely absorbed and result in excitation of the polariton state of the CQED system. The output light from the cavity is totally suppressed by destructive interference and the polariton state can only decay incoherently back to the ground state. Here we analyze perfect photon absorption and the onset of optical bistability in the nonlinear regime of the CQED and show that perfect photon absorption persists in the nonlinear regime of the CQED below the threshold of optical bistability. Therefore perfect photon absorption is a phenomenon that can be observed in both linear and nonlinear regimes of CQED. Furthermore, our study reveals that optical bistability is influenced by input-light interference and can be manipulated by varying the relative phase of the two input fields.
This document consists of translations of the following original papers: (A) the fluctuations of charge connected with the formation of matter from radiation, by W. Heisenberg, Sachsiche Akademie der Wissenschaften; 86:(1934) 317-322; (B) theory of the positron, by P.A.M. Dirac, Report to 7th Solvay Physics Conference, structure and properties of Atomic Nuclei (1934) 203-212; (C) comments on the Dirac theory of the positron, by W. Heisenberg, Zeitschrift fur Physik; 90:(1934) 209-231; and (D) the electrodynamics of the vacuum on the basis of the quantum theory of the electron, by V. Weisskopf, Kongelige Danske Videnskabernes Selskab, Mathematiskfysiske Meddelelser XIV, no. 6 (1936) 3-39. (U.K.)
Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics
Madsen, Kristian Høeg; Lodahl, Peter
2013-01-01
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 Jayn...
Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics
Madsen, K H
2012-01-01
We present detuning-dependent spectral and decay-rate measurements to study the difference between 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-Cummings model, while systematic deviations are observed for the emission spectra. The discrepancy for the spectra is attributed to coupling of other exciton lines to the cavity and interference of different propagation paths towards the detector of the fields emitted by the quantum dot. In contrast, 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 strong coupling. However, time-resolved measurements reveal that the actual coupling strength is significantly smaller than anticipated from the spectral...
Magneto-optical cavity quantum electrodynamics effects in quantum dot - micropillar systems
We report on magneto-optical studies of strongly coupled quantum dot - micropillar cavity systems. Large In0.3Ga0.7As quantum dots (QDs) in the active layer of the micropillar facilitate the observation of strong coupling. In addition, they exhibit a particular large diamagnetic response which is exploited to demonstrate magneto-optical resonance tuning in the strong coupling regime. The magnetic field employed in Faraday configuration induces a transition from strong coupling towards the critical coupling regime which is explained in terms of a magnetic field dependent oscillator strength of the In0.3Ga0.7As QDs. We further study the coherent interaction between spin resolved states of the QDs and microcavity photon modes. A detailed oscillator model is used to extract the associated coupling parameters of the individual spin and cavity modes and reveals an effective coupling between photon modes that is mediated by the exciton spin states.
We report on magneto-optical studies of strongly coupled quantum dot - micropillar cavity systems. Laterally extended In0.3Ga0.7As quantum dots (QDs) in the active layer of a micropillar cavity facilitate the observation of strong coupling. These QDs are characterized by large oscillator strength and they exhibit a large diamagnetic response, which is exploited to demonstrate magneto-optical resonance tuning. In addition, the coherent interaction between spin resolved states of the QDs and microcavity photon modes is studied. We access the spin degree of freedom by applying a non-zero magnetic field in Faraday configuration, so that the spin degeneracy of the QD exciton is lifted, while the resonance tuning of the Zeeman split exciton lines is achieved by temperature variation. A detailed oscillator model is used to extract coupling parameters of the individual spin and cavity modes. Our results demonstrate an effective coupling between photon modes that is mediated by the exciton spin states. We further show simulations of the photon-photon coupling in dependence of the coupling parameters.
Environment-Assisted Speed-up of the Field Evolution in Cavity Quantum Electrodynamics
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 re-population in the optical cavity increases with the coupling strength between the optical cavity mode and this non-Markovian environment (the number of atoms)
Trisetyarso, Agung
2010-01-01
We present the recent works \\cite{trisetyarso01,trisetyarso02} on the application of Darboux transformation on one-dimensional Dirac equation related to the field of Quantum Information and Computation (QIC). The representation of physical system in one-dimensional equation and its transformation due to the Bagrov, Baldiotti, Gitman, and Shamshutdinova (BBGS)-Darboux transformation showing the possibility admitting the concept of relativity and the trade-off of concurrent condition of quantum and classical physics play into the area of QIC. The applications in cavity quantum electrodynamics and on the proposal of quantum transistor are presented.
Bloch-wave engineering of quantum dot-micropillars for cavity quantum electrodynamics experiments
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 ...
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
Li, Jiahua; Yu, Rong; Liu, Jiuyang; Ding, Chunling; Wu, Ying
2016-05-01
We study the probe-field transmission in cavity quantum electrodynamics (cavity-QED) systems with a partially transmitting element (PTE), where the PTE is used to control and tune the amplitude of the weak probe field propagating along a single waveguide channel in the structure. We derive analytic formulas utilized to determine the transmission coefficient of the probe field within the framework of quantum optics. Using experimentally accessible parameters, it is clearly shown that the asymmetric Fano-resonance line shape can be formed and manipulated by means of the added PTE. Furthermore, we reveal that there exists superluminal light with large intensity transmission in the transport spectrum of the waveguide-coupled cavity-QED system. This superluminal-light propagation effect, which exhibits the anomalous phase shift and is characterized by the negative group delay, can be enhanced by properly choosing the system parameters. The obtained results may be used for designing switching, modulation, and sensing for nanophotonic applications and ultrafast on-chip signal processing in telecom applications.
Asymptotic algebra of quantum electrodynamics
Herdegen, Andrzej
2004-01-01
The Staruszkiewicz quantum model of the long-range structure in electrodynamics is reviewed in the form of a Weyl algebra. This is followed by a personal view on the asymptotic structure of quantum electrodynamics.
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.
Quantum Electrodynamics in Photonic Crystal Waveguides
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 in...
Circuit Quantum Electrodynamics
Bishop, Lev S
2010-01-01
Circuit Quantum Electrodynamics (cQED), the study of the interaction between superconducting circuits behaving as artificial atoms and 1-dimensional transmission-line resonators, has shown much promise for quantum information processing tasks. For the purposes of quantum computing it is usual to approximate the artificial atoms as 2-level qubits, and much effort has been expended on attempts to isolate these qubits from the environment and to invent ever more sophisticated control and measurement schemes. Rather than focussing on these technological aspects of the field, this thesis investigates the opportunities for using these carefully engineered systems for answering questions of fundamental physics.
Planar Multilayer Circuit Quantum Electrodynamics
Minev, Z. K.; Serniak, K.; Pop, I. M.; Leghtas, Z.; Sliwa, K.; Hatridge, M.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.
2016-04-01
Experimental quantum information processing with superconducting circuits is rapidly advancing, driven by innovation in two classes of devices, one involving planar microfabricated (2D) resonators, and the other involving machined three-dimensional (3D) cavities. We demonstrate that circuit quantum electrodynamics can be implemented in a multilayer superconducting structure that combines 2D and 3D advantages. We employ standard microfabrication techniques to pattern each layer, and rely on a vacuum gap between the layers to store the electromagnetic energy. Planar qubits are lithographically defined as an aperture in a conducting boundary of the resonators. We demonstrate the aperture concept by implementing an integrated, two-cavity-mode, one-transmon-qubit system.
Minimal Quantum Electrodynamics
Jauregui, R.; Berrondo, M.
1985-01-01
A simple and coherent formulation of quantum electrodynamics is obtained within the general framework of the LSZ field theory. The commutation relations for the interacting fields are obtained rather than being postulated a priori and the current densities fulfill the one particle stability conditions. Thus, the inconsistencies which appear in the canonical formalism are avoided. The resulting spectral representations do not have any ambiguities so that we do not have to introduce the renormalization concept.
Minimal quantum electrodynamics
A simple and coherent formulation of quantum electrodynamics is obtained within the general framework of the LSZ field theory. The commutation relations for the intereacting fields are obtained rather than being postulated a priori and the current densities fulfill the one particle stability conditions. Thus, the inconsistencies which appear in the canonical formalism are avoided. The resulting spectral representations do not have any ambiguities so that we do not have to introduce the ''renormalization'' concept
Minimal Quantum Electrodynamics
A simple and coherent formulation of quantum electrodynamics is obtained within the general framework of the LSZ field theory. The commutation relations for the interacting fields are obtained rather than being postulated a priori and the current densities fulfill the one particle stability conditions. Thus, the inconsistencies which appear in the canonical formalism are avoided. The resulting spectral representations do not have any ambiguities so that we do not have to introduce the renormalization concept
Liu, Siping [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Physics and Electronic Engineering, Hubei University of Arts and Science, Xiangyang 441053 (China); Yu, Rong [Wuhan Institute of Technology, School of Science, Hubei Province Key Laboratory of Intelligent Robot, Wuhan 430073 (China); Li, Jiahua, E-mail: huajia-li@163.com [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Key Laboratory of Fundamental Physical Quantities Measurement of Ministry of Education, Wuhan 430074 (China); Wu, Ying, E-mail: yingwu2@126.com [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)
2014-04-07
Generating entangled states attract tremendous interest as the most vivid manifestation of nonlocality of quantum mechanics and also for emerging applications in quantum information processing (QIP). Here, we propose theoretically a scheme for the deterministic generation of a three-qubit W sate with three semiconductor quantum-dot-molecules (QDMs) trapped in spatially separated cavities connected by optical fibers. The proposed scheme takes full advantage of the voltage-controlled tunnelling effects in QDMs, which induces the quantum coherence and further controls the generation of the W entangled state. The influences of the system parameters and various decoherence processes including spontaneous decay and photon leakage on the fidelity of the W state are discussed in details. Numerical results indicate that our scheme is not only robust against these decoherence factors but also insensitive to the deviation of the system parameters from the ideal conditions. Furthermore, the present scheme can be directly extended to realize an N-qubit W state. Also, this scheme can be generically transferred to other physical systems, including circuit quantum electrodynamics and photonic crystal cavities. The results obtained here may be useful in real experiments for realizing QIP in a solid-state platform.
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
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.
Quantum electrodynamics in a classical approximation, 1
Quantum electrodynamics is formulated in a classical approximation. A quantum mechanical proper-time is employed as a useful parameter, which enables us to elucidate the relationship between quantum electrodynamics and classical electrodynamics. The classical motion of a charged particle is realized as an asymptotic limit of quantum electrodynamics. (author)
Existence of Majorana fermion mode and Dirac equation in cavity quantum electrodynamics
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.
The effect of a permanent dipole moment on the polar molecule cavity quantum electrodynamics
Jing-Yun, Zhao; Li-Guo, Qin; Xun-Ming, Cai; Qiang, Lin; Zhong-Yang, Wang
2016-04-01
A dressed-state perturbation theory beyond the rotating wave approximation (RWA) is presented to investigate the interaction between a two-level electronic transition of polar molecules and a quantized cavity field. Analytical expressions can be explicitly derived for both the ground- and excited-state-energy spectrums and wave functions of the system, where the contribution of permanent dipole moments (PDM) and the counter-rotating wave term (CRT) can be shown separately. The validity of these explicit results is discussed by comparison with the direct numerical simulation. Compared to the CRT coupling, PDM results in the coupling of more dressed states and the energy shift is proportional to the square of the normalized permanent dipole difference, and a greater Bloch–Siegert shift can be produced in the giant dipole molecule cavity QED. In addition, our method can also be extended to the solution of the two-level atom Rabi model Hamiltonian beyond the RWA. Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB01010200), the Hundred Talents Program of the Chinese Academy of Sciences (Grant No. Y321311401), the National Natural Science Foundation of China (Grant Nos. 61475139, 11347147, and 11247014), the National Basics Research Program of China (Grant No. 2013CB329501), and the Zhejiang Provincial Natural Science Foundation (Grant No. LQ13A040006).
The relation between classical and quantum electrodynamics
Mario Bacelar Valente
2012-01-01
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 ex...
Non-relativistic quantum electrodynamics
The book presents a systematic account of non-relativistic quantum electrodynamics. The subject is discussed under the subject headings: classical equations of motion, canonical formalism, canonical quantization, symmetries and conservation laws, interaction of photons and atoms and lastly, path-dependent electrodynamics. (U.K.)
Experimental status of quantum electrodynamics
This review of the experimental status of quantum electrodynamics covers the fine structure constant, the muon g-2 value, the Lamb shift in hydrogen, the finite proton radius, progress in muonium, and positronium. 37 references
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.
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.
Circuit quantum electrodynamics with a nonlinear resonator
Bertet, P; Boissonneault, M; Bolduc, A; Mallet, F; Doherty, A C; Blais, A; Vion, D; Esteve, D
2011-01-01
One of the most studied model systems in quantum optics is a two-level atom strongly coupled to a single mode of the electromagnetic field stored in a cavity, a research field named cavity quantum electrodynamics or CQED. CQED has recently received renewed attention due to its implementation with superconducting artificial atoms and coplanar resonators in the so-called circuit quantum electrodynamics (cQED) architecture. In cQED, the couplings can be much stronger than in CQED due to the design flexibility of superconducting circuits and to the enhanced field confinement in one-dimensional cavities. This enabled the realization of fundamental quantum physics and quantum information processing experiments with a degree of control comparable to that obtained in CQED. The purpose of this chapter is to investigate the situation where the resonator to which the atom is coupled is made nonlinear with a Kerr-type nonlinearity, causing its energy levels to be nonequidistant. The system is then described by a nonlinea...
Quantum Hall Effect in Quantum Electrodynamics
Penin, Alexander A.
2008-01-01
We consider the quantum Hall effect in quantum electrodynamics and find a deviation from the quantum mechanical prediction for the Hall conductivity due to radiative antiscreening of electric charge in an external magnetic field. A weak universal dependence of the von Klitzing constant on the magnetic field strength, which can possibly be observed in a dedicated experiment, is predicted.
The Relation between Classical and Quantum Electrodynamics
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.
Potentialities of Revised Quantum Electrodynamics
Lehnert B.
2013-01-01
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 ...
Renormalizability of generalized quantum electrodynamics
Bufalo, R.; Pimentel, B. M.; Zambrano, G. E. R.
2012-01-01
In this work we present the study of the renormalizability of the Generalized Quantum Electrodynamics ($GQED_{4}$). We begin the article by reviewing the on-shell renormalization scheme applied to $GQED_{4}$. Thereafter, we calculate the explicit expressions for all the counter-terms at one-loop approximation and discuss the infrared behavior of the theory as well. Next, we explore some properties of the effective coupling of the theory which would give an indictment of the validity regime of...
Shu Chang-Gan; Xin Xia; Liu Yu-Min; Yu Zhong-Yuan; Yao Wen-Jie; Wang Dong-Lin; Cao Gui
2012-01-01
We investigate theoretically two photon entanglement processes in a photonic-crystal cavity embedding a quantum dot in the strong-coupling regime.The model proposed by Johne et al.(Johne R,Gippius N A,Pavlovic G,Solnyshkov D D,Shelykh I A and Malpuech G 2008 Phys.Rev.Lett.100 240404),and by Robert et al.(Robert J,Gippius N A and Malpuech G 2009 Phys.Rev.B 79 155317) is modified by considering irreversible dissipation and incoherent continuous pumping for the quantum dot,which is necessary to connect the realistic experiment.The dynamics of the system is analysed by employing the Born-Markov master equation,through which the spectra for the system are computed as a function of various parameters.By means of this analysis the photon-reabsorption process in the strongcoupling regime is first observed and analysed from the perspective of radiation spectrum and the optimal parameters for observing energy-entangled photon pairs are identified.
Scheme for Implementation of Quantum Game in Cavity QED
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.
Scheme for Implementation of Quantum Game in Cavity QED
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.
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.
Offshell quantum electrodynamics
In this paper, we develop the quantum field theory of off-shell electromagnetism, and use it to calculate the Møller scattering cross-section. This calculation leads to qualitative deviations from the usual scattering cross-sections, which are, however, small effects, but may be visible at small angles near the forward direction.
Li, Jiahua [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Key Laboratory of Fundamental Physical Quantities Measurement of Ministry of Education, Wuhan 430074 (China); Yu, Rong, E-mail: yurong321@126.com [School of Science, Hubei Province Key Laboratory of Intelligent Robot, Wuhan Institute of Technology, Wuhan 430073 (China); Ma, Jinyong; Wu, Ying, E-mail: yingwu2@163.com [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)
2014-10-28
The ability to engineer and convert photons between different modes in a solid-state approach has extensive technological implications not only for classical communication systems but also for future quantum networks. In this paper, we put forward a scheme for coherent mode conversion of optical photons by utilizing the intermediate coupling between a single quantum dot and a bimodal photonic crystal microcavity via a waveguide. Here, one mode of the photonic crystal microcavity is coherently driven by an external single-frequency continuous-wave laser field and the two cavity modes are not coupled to each other due to their orthogonal polarizations. The undriven cavity mode is thus not directly coupled to the input driving laser and the only way it can get light is via the quantum dot. The influences of the system parameters on the photon-conversion efficiency are analyzed in detail in the limit of weak probe field and it is found that high photon-conversion efficiency can be achieved under appropriate conditions. It is shown that the cavity dark mode, which is a superposition of the two optical modes and is decoupled from the quantum dot, can appear in such a hybrid optical system. We discuss the properties of the dark mode and indicate that the formation of the dark mode enables the efficient transfer of optical fields between the two cavity modes.
Li, Jiahua; Yu, Rong; Ma, Jinyong; Wu, Ying
2014-10-01
The ability to engineer and convert photons between different modes in a solid-state approach has extensive technological implications not only for classical communication systems but also for future quantum networks. In this paper, we put forward a scheme for coherent mode conversion of optical photons by utilizing the intermediate coupling between a single quantum dot and a bimodal photonic crystal microcavity via a waveguide. Here, one mode of the photonic crystal microcavity is coherently driven by an external single-frequency continuous-wave laser field and the two cavity modes are not coupled to each other due to their orthogonal polarizations. The undriven cavity mode is thus not directly coupled to the input driving laser and the only way it can get light is via the quantum dot. The influences of the system parameters on the photon-conversion efficiency are analyzed in detail in the limit of weak probe field and it is found that high photon-conversion efficiency can be achieved under appropriate conditions. It is shown that the cavity dark mode, which is a superposition of the two optical modes and is decoupled from the quantum dot, can appear in such a hybrid optical system. We discuss the properties of the dark mode and indicate that the formation of the dark mode enables the efficient transfer of optical fields between the two cavity modes.
The ability to engineer and convert photons between different modes in a solid-state approach has extensive technological implications not only for classical communication systems but also for future quantum networks. In this paper, we put forward a scheme for coherent mode conversion of optical photons by utilizing the intermediate coupling between a single quantum dot and a bimodal photonic crystal microcavity via a waveguide. Here, one mode of the photonic crystal microcavity is coherently driven by an external single-frequency continuous-wave laser field and the two cavity modes are not coupled to each other due to their orthogonal polarizations. The undriven cavity mode is thus not directly coupled to the input driving laser and the only way it can get light is via the quantum dot. The influences of the system parameters on the photon-conversion efficiency are analyzed in detail in the limit of weak probe field and it is found that high photon-conversion efficiency can be achieved under appropriate conditions. It is shown that the cavity dark mode, which is a superposition of the two optical modes and is decoupled from the quantum dot, can appear in such a hybrid optical system. We discuss the properties of the dark mode and indicate that the formation of the dark mode enables the efficient transfer of optical fields between the two cavity modes.
Minimal theory of quantum electrodynamics
Within the general framework of the Lehmann-Symanzik-Zimmermann axiomatic field theory, we obtain a simple and coherent formulation of quantum electrodynamics. The definitions of the current densities fulfill the one-particle stability condition, and the commutation relations for the interacting fields are obtained rather than being postulated a priori, thus avoiding the inconsistencies which appear in the canonical formalism. This is possible due to the fact that we use the integral form of the equations of motion in order to compute the propagators and the S matrix. The resulting spectral representations automatically fulfill the correct boundary conditions thus fixing the ubiquitous quasilocal operators in a unique fashion
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
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.
Relativistic Geometry and Quantum Electrodynamics
González-Martin, G R
2000-01-01
Excitations of a relativistic geometry are used to represent the theory of quantum electrodynamics. The connection excitations and the frame excitations reduce, respectively, to the electromagnetic field operator and electron field operator. Because of the inherent geometric algebraic structure these operators obey the standard commutation rules of QED. If we work with excitations, we need to use statistical theory when considering the evolution of microscopic subsystems. The use of classical statistics, in particular techniques of irreversible thermodynamics, determine that the probability of absorption or emission of a geometric excitation is a function of the classical energy density. Emission and absorption of geometric excitations imply discrete changes of certain physical variables, but with a probability determined by its wave energy density. Hence, this geometric theory, without contradicting the fundamental aspects of quantum physics, provides a geometric foundation for the theory.
Renormalizability of generalized quantum electrodynamics
Bufalo, R; Zambrano, G E R; 10.1103/PhysRevD.86.125023
2012-01-01
In this work we present the study of the renormalizability of the Generalized Quantum Electrodynamics ($GQED_{4}$). We begin the article by reviewing the on-shell renormalization scheme applied to $GQED_{4}$. Thereafter, we calculate the explicit expressions for all the counter-terms at one-loop approximation and discuss the infrared behavior of the theory as well. Next, we explore some properties of the effective coupling of the theory which would give an indictment of the validity regime of theory: $m^{2} \\leq k^{2} < m_{P}^{2}$. Afterwards, we make use of experimental data from the electron anomalous magnetic moment to set possible values for the theory free parameter through the one-loop contribution of Podolsky mass-dependent term to Pauli's form factor $F_{2}(q^{2})$.
Potentialities of Revised Quantum Electrodynamics
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.
The physical state space of quantum electrodynamics
Starting from the fact that electrically charged particles are massive we derive a criterion which characterizes the state space of quantum electrodynamics. This criterion clarifies the special role of the electric charge amongst the uncountably many superselection rules in quantum electrodynamics and provides a basis for a general analysis of the infrared problem. Within this framework we establish the existence of asymptotic electromagnetic fields in all charge-sectors, find a general characterization of infraparticles and introduce a notion of asymptotic completeness. (orig.)
On higher order estimates in quantum electrodynamics
Matte, Oliver
2009-01-01
We propose a new method to derive certain higher order estimates in quantum electrodynamics. Our method is particularly convenient in the application to the non-local semi-relativistic models of quantum electrodynamics as it avoids the use of iterated commutator expansions. We re-derive higher order estimates obtained earlier by Fr\\"ohlich, Griesemer, and Schlein and prove new estimates for a non-local molecular no-pair operator.
On Quantum Corrections to Chern-Simons Spinor Electrodynamics
Chaichian, Masud; Fainberg, V Ya
1998-01-01
We make a detailed investigation on the quantum corrections to Abelian Chern-Simons spinor electrodynamics. Starting from Chern-Simons spinor quantum electrodynamics with the Maxwell term $-1/(4\\gamma){\\int}d^3x F_{\\mu\
Dyson-Schwinger equations in quantum electrodynamics
A quantum field theory is completely determined by the knowledge of its Green functions and this thesis is concerned with the Salam and Delbourgo approximation method for the determination of the Green functions. In chapter 2 a Lorentz covariant, canonical formulation for quantum electrodynamics is described. In chapter 3 the definition of the Green functions in quantum electrodynamics is given with a derivation of the Dyson-Schwinger equations. The Ward-Takahashi identities, which are a consequence of current conservation, are derived and finally renormalization is briefly mentioned and the equations for the renormalized quantities are given. The gauge transformations, changing the gauge-parameter, a, discussed in Chapter 2 for the field operators, also have implications for the Green functions, and these are worked out in Chapter 4 for the electron propagator, which is not gauge-invariant. Before developing the main approximation, a simple, non-relativistic model is studied in Chapter 5. It has the feature of being exactly solvable in a way which closely resembles the approximation method of Chapter 6 for relativistic quantum electrodynamics. There the Dyson-Schwinger equations for the electron and photon propagator are studied. In chapter 7, the Johnson-Baker-Willey program of finite quantum electrodynamics is considered, in connection with the Ansatz of Salam and Delbourgo, and the question of a possible fixed point of the coupling constant is considered. In the last chapter, some remarks are made about how the results of the approximation scheme can be improved. (Auth.)
Quantum optics and cavity QED with quantum dots in photonic crystals
Vuckovic, Jelena
2014-01-01
This chapter will primarily focus on the studies of quantum optics with semiconductor, epitaxially grown quantum dots embedded in photonic crystal cavities. We will start by giving brief introductions into photonic crystals and quantum dots, then proceed with the introduction to cavity quantum electrodynamics (QED) effects, with a particular emphasis on the demonstration of these effects on the quantum dot-photonic crystal platform. Finally, we will focus on the applications of such cavity QED effects.
Quantum optics and cavity QED with quantum dots in photonic crystals
Vuckovic, Jelena
2014-01-01
This chapter will primarily focus on the studies of quantum optics with semiconductor, epitaxially grown quantum dots embedded in photonic crystal cavities. We will start by giving brief introductions into photonic crystals and quantum dots, then proceed with the introduction to cavity quantum electrodynamics (QED) effects, with a particular emphasis on the demonstration of these effects on the quantum dot-photonic crystal platform. Finally, we will focus on the applications of such cavity QE...
Electron-photon coupling in mesoscopic quantum electrodynamics
Cottet, A.; Kontos, T.; Douçot, B.
2015-05-01
Understanding the interaction between cavity photons and electronic nanocircuits is crucial for the development of mesoscopic quantum electrodynamics (QED). One has to combine ingredients from atomic cavity QED, such as orbital degrees of freedom, with tunneling physics and strong cavity field inhomogeneities, specific to superconducting circuit QED. It is therefore necessary to introduce a formalism which bridges between these two domains. We develop a general method based on a photonic pseudopotential to describe the electric coupling between electrons in a nanocircuit and cavity photons. In this picture, photons can induce simultaneously orbital energy shifts, tunneling, and local orbital transitions. We study in detail the elementary example of a single quantum dot with a single normal metal reservoir, coupled to a cavity. Photon-induced tunneling terms lead to a nonuniversal relation between the cavity frequency pull and the damping pull. Our formalism can also be applied to multiple quantum dot circuits, molecular circuits, quantum point contacts, metallic tunnel junctions, and superconducting nanostructures enclosing Andreev bound states or Majorana bound states, for instance.
On Calculation of Amplitudes in Quantum Electrodynamics
Karplyuk, Kostyantyn; Zhmudsky, Oleksandr
2012-01-01
A new method of calculation of amplitudes of different processes in quantum electrodynamics is proposed. The method does not use the Feynman technique of trace of product of matrices calculation. The method strongly simplifies calculation of cross sections for different processes. The effectiveness of the method is shown on the cross-section calculation of Coulomb scattering, Compton scattering and electron-positron annihilation.
Massless quantum electrodynamics: a variational study
The variational method was used to study the probable existence of a compound vacuum in quantum electrodynamics. An Ansatz containing a condensate of electron-positron pairs was investigated and an optimization equation for the condensate wave function found. (L.C.J.A.)
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
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 electrodynamic perspective on multiphoton ionization
A fully quantum nonperturbative method is developed to describe multiphoton ionization in intense fields. It is shown that, treating the radiation field with quantum electrodynamic (QED) theory enables the authors to obtain the above-threshold ionization energy distribution spectrum in analytical form firstly. Moreover, in addition to the well-known semiclassical theory, the framework presented here, derived from a QED perspective, provides a new picture of the multiphoton ionization
Applications of conformal symmetry in quantum electrodynamics
Quantum electrodyanmics is a system in which the only scale is provided by the electron mass. A topic of continuing interest has been the structure of this field theory for spatial separations small in comparison to the scale defined by the Compton size ((h/2π)/mc), and one is thus led to consider 'massless' quantum electrodynamics (m equivalent to 0). The classical field equations for massless electrodynamics are invariant under a much larger group of space-time transformations than the massive theory, namely the full fifteen parameter conformal group. However, in contrast to the massive theory where calculations can be formulated in terms of a set of fully Lorentz covariant Green's functions, no fully conformally covariant formalism exists for the massless theory because of complications associated with gauge invariance. The authors present what they regard as the most salient aspects of the conformal symmetry when it is used to simplify calculations. (Auth.)
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.
Circuit quantum electrodynamics with a superconducting quantum point contact
Romero G; Lizuain I.; Shumeiko V.S.; Solano E.; Bergeret F.S.
2012-01-01
We consider a superconducting quantum point contact in a circuit quantum electrodynamics setup. We study three different configurations, attainable with current technology, where a quantum point contact is coupled galvanically to a coplanar waveguide resonator. Furthermore, we demonstrate that the strong and ultrastrong coupling regimes can be achieved with realistic parameters, allowing the coherent exchange between a superconducting quantum point contact and a quantized intracavity field. ©...
Recent advances in bound state quantum electrodynamics
Recent developments are reviewed in four areas of computational quantum electrodynamics: a new relativistic two-body formalism equal in rigor to the Bethe-Salpeter formalism but with strong calculational advantages is discussed; recent work on the computation of the decay rate of bound systems (positronium in particular) is presented; limits on possible composite structure of leptons are discussed; a new multidimensional integration program ('VEGAS') suitable for higher order calculations is presented
Test of quantum electrodynamics at PETRA
Differential cross sections for the reactions e+e → e+e- and e+e- → γγ are given for energies between 27.7 and 31.6 GeV. The results agree with the predictions of standard quantum electrodynamics and set lower limits to the usual cut off parameters of up to 104 GeV. A limit on the Weinberg angle, sin2theta sub(W) 2. (orig.)
Quantum electrodynamics in strong external fields
We review the theoretical description of quantum electrodynamics in the presence of strong and supercritical fields. In particular, the process of the spontaneous vacuum decay accompanied by the observable positron emission in heavy ion collisions is described. Emphasis is put on the proper formulation of many-body aspects in the framework of quantum field theory. The extension of the theory to the description of Bose fields and many-body effects is presented, and the Klein paradox is resolved. Some implications of the theoretical methods developed here are presented concerning non-abelian gauge theories and the quark confinement puzzle. (orig.)
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 ...
Clothed Particles in Quantum Electrodynamics and Quantum Chromodynamics
Shebeko, Alexander
2016-03-01
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.
Clothed Particles in Quantum Electrodynamics and Quantum Chromodynamics
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.
Off-shell quantum electrodynamics
Land, M C
1996-01-01
More than twenty years have passed since the threads of the `proper time formalism' in covariant classical and quantum mechanics were brought together to construct a canonical formalism for the relativistic mechanics of many particles. Drawing on the work of Fock, Stueckelberg, Nambu, Schwinger, and Feynman, the formalism was raised from the status of a purely formal mathematical technique to a covariant evolution theory for interacting particles. In the context of this theory, solutions have been found for the relativistic bound state problem, classical and quantum scattering in relativistic potentials, as well as applications in statistical mechanics. It has been shown that a generalization of the Maxwell theory is required in order that the electromagnetic interaction be well-posed in the theory. The resulting theory of electromagnetism involves a fifth gauge field introduced to compensate for the dependence of the gauge transformation on the invariant time parameter; permitting such dependence relaxes the...
Off-Shell Quantum Electrodynamics
Land, M. C.; Horwitz, L. P.
1996-01-01
More than twenty years have passed since the threads of the `proper time formalism' in covariant classical and quantum mechanics were brought together to construct a canonical formalism for the relativistic mechanics of many particles. Drawing on the work of Fock, Stueckelberg, Nambu, Schwinger, and Feynman, the formalism was raised from the status of a purely formal mathematical technique to a covariant evolution theory for interacting particles. In the context of this theory, solutions have...
New Approach to Quantum Electrodynamics
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
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.
Theoretical analysis of quantum game in cavity QED
Recent years, several ways of implementing quantum games in different physical systems have been presented. In this paper, we perform a theoretical analysis of an experimentally feasible way to implement a two player quantum game in cavity quantum electrodynamic(QED). In the scheme, the atoms interact simultaneously with a highly detuned cavity mode with the assistance of a classical field. So the scheme is insensitive to the influence from the cavity decay and the thermal field, and it does not require the cavity to remain in the vacuum state throughout the procedure. (general)
Gauge independence of transition amplitudes in quantum electrodynamics
Gauge independence of transition amplitudes in quantum electrodynamics is proved in the framework of covariant quantum electrodynamics exploited by Yokoyama. A systematic law of gauge transformation is given for general Green functions in QED. Gauge independence of the wave-function renormalization constant Z2 is also discussed to some extent. (author)
Quantum electrodynamics with arbitrary charge on a noncommutative space
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 Electrodynamics Theory of Laser Assisted Recombination
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.
Pole-factorization theorem in quantum electrodynamics
In quantum electrodynamics a classical part of the S-matrix is normally factored out in order to obtain a quantum remainder that can be treated perturbatively without the occurrence of infrared divergences. However, this separation, as usually performed, introduces spurious large-distance effects that produce an apparent breakdown of the important correspondence between stable particles and poles of the S-matrix, and, consequently, lead to apparent violations of the correspondence principle and to incorrect results for computations in the mesoscopic domain lying between the atomic and classical regimes. An improved computational technique is described that allows valid results to be obtained in this domain, and that leads, for the quantum remainder, in the cases studied, to a physical-region singularity structure that, as regards the most singular parts, is the same as the normal physical-region analytic structure in theories in which all particles have non-zero mass. The key innovations here are to define the classical part in coordinate space, rather than in momentum space, and to define there a separation of the photon-electron coupling into its classical and quantum parts that has the following properties: (1) The contributions from the terms containing only classical couplings can be summed to all orders to give a unitary operator that generates the coherent state that corresponds to the appropriate classical process, and (2) The quantum remainder can be rigorously shown to exhibit, as regards its most singular parts, the normal analytic structure. 22 refs
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
On the finite-temperature quantum electrodynamics of gravitational acceleration
Barton, G.
1989-12-01
The temperature-dependent quantum-electrodynamic corrections to the Helmholtz free energy F of a particle at rest, and to its inertial mass minert, are the same: ΔF=Δminert=πe2(kT)2/3m. By contrast, the correction to the total energy U=F+TS is ΔU=-ΔF. Donoghue, Holstein, and Robinett have pointed out that if (as the equivalence principle appears to imply) weight is proportional to total energy, then the gravitational acceleration of a particle inside a blackbody cavity becomes g(m+ΔU)/(m+ΔF)~=g(1-2ΔF/m)Galilean acceleration g.
Quantum electrodynamical corrections in critical fields
We investigate field-theoretical corrections, such as vacuum polarization and self energy to study their influence on strongly bound electrons in heavy and superheavy atoms. In critical fields (Z≅170) for spontaneous e+e- pair creation the coupling constant of the external field Zα exceeds 1 thereby preventing the ordinary perturbative approach of quantum electrodynamical correction which employs an expansion in Zα. For heavy and superheavy elements radiative corrections have to be treated to all orders in Zα. The dominant effect is provided by the Uehling contribution being visualized by the first diagram on the right hand side. It is linear in the external field and thus of order α(Zα). (orig./HSI)
A new view on quantum electrodynamics
Golovko, V A
2016-01-01
We analyze the equations of quantum electrodynamics and establish that the electron must be described by two bispinors that satisfy two mutually connected Dirac equations. The equations of the electronic and electromagnetic fields are reformulated in terms of c-numbers, which enables one to elucidate the structure of the electron. Although the equations obtained allow only for numerical solution, some characteristics of the electron, in particular its size, can be found at this stage. It is shown also that the Dirac equation should, instead of the mass of the electron, contain a combination involving the electron Compton wavelength. In this case the equations obtained can be used not only for the description of the electron but also for the description of other leptons, which will allow one to find the mass spectrum of leptons.
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...
On the finite-temperature quantum electrodynamics of gravitational acceleration
The temperature-dependent quantum-electrodynamic corrections to the Helmholtz free energy F of a particle at rest, and to its inertial mass minert, are the same: ΔF=Δminert=πe2(kT)2/3m. By contrast, the correction to the total energy U=F+TS is ΔU=-ΔF. Donoghue, Holstein, and Robinett have pointed out that if (as the equivalence principle appears to imply) weight is proportional to total energy, then the gravitational acceleration of a particle inside a blackbody cavity becomes g(m+ΔU)/(m+ΔF)∼g(1-2ΔF/m)< g. However, while F represents the random kinetic energy of (and is thereby localized on) the particle, further analysis now suggests that the entropic energy difference TΔS=ΔU-ΔF is distributed over the cavity uniformly and independently of the particle position. If so, then the gravitational pull on TΔS cannot affect the motion of the particle well within the cavity, so that it will, after all, experience the universal Galilean acceleration g
Quantum Logic Network for Cloning a State Near a Given One Based on Cavity QED
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.
A scheme for implementing quantum clock synchronization algorithm in cavity QED
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
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 electrodynamics (QED) is presented. It is easy to implement this network of cloning machine in the framework of cavity QED and feasible in the experiment. (general)
Plimak, L. I.; Ivanov, Misha; Aiello, A.; Stenholm, S.
2015-01-01
Quantum electrodynamics under conditions of distinguishability of interacting matter entities, and of controlled actions and back-actions between them, is considered. Such "mesoscopic quantum electrodynamics" is shown to share its dynamical structure with the classical stochastic electrodynamics. In formal terms, we demonstrate that all general relations of the mesoscopic quantum electrodynamics may be recast in a form lacking Planck's constant. Mesoscopic quantum electrodynamics is therefore...
Plimak, L. I.; Ivanov, Misha; Aiello, A.; Stenholm, S.
2015-08-01
Quantum electrodynamics under conditions of distinguishability of interacting matter entities, and of controlled actions and back-actions between them, is considered. Such "mesoscopic quantum electrodynamics" is shown to share its dynamical structure with the classical stochastic electrodynamics. In formal terms, we demonstrate that all general relations of the mesoscopic quantum electrodynamics may be recast in a form lacking Planck's constant. Mesoscopic quantum electrodynamics is therefore subject to "doing quantum electrodynamics while thinking classically," allowing one to substitute essentially classical considerations for quantum ones without any loss in generality. Implications of these results for the quantum measurement theory are discussed.
Field, J. H.
2007-01-01
In quantum electrodynamics, the quantitatively most successful theory in the history of science, intercharge forces obeying the inverse square law are due to the exchange of space-like virtual photons. The fundamental quantum process underlying applications as diverse as the gyromagnetic ratio of the electron and electrical machinery is then M{\\o}ller scattering $ee \\to ee$. Analysis of the quantum amplitude for this process shows that the corresponding intercharge force acts instantaneously....
Quantum electrodynamics in a whispering-gallery microcavity coated with a polymer nanolayer
Xiao, Yun-Feng; Xue, Peng; Xiao, Lixin; Li, Yan; Dong, Chun-Hua; Han, Zheng-Fu; Gong, Qihuang
2010-01-01
Quasi-transverse-electric and -transverse-magnetic fundamental whispering gallery modes in a polymer-coated silica microtoroid are theoretically investigated and demonstrated to possess very high-quality factors. The existence of a nanometer-thickness layer not only evidently reduces the cavity mode volume but also draws the maximal electric field's position of the mode to the outside of the silica toroid, where single quantum dots or nanocrystals are located. Both effects result in a strongly enhanced coherent interaction between a single dipole (for example, a single defect center in a diamond crystal) and the quantized cavity mode. Since the coated microtoroid is highly feasible and robust in experiments, it may offer an excellent platform to study strong-coupling cavity quantum electrodynamics, quantum information, and quantum computation.
Quantum electrodynamics in a whispering-gallery microcavity coated with a polymer nanolayer
Quasi-transverse-electric and -transverse-magnetic fundamental whispering gallery modes in a polymer-coated silica microtoroid are theoretically investigated and demonstrated to possess very high-quality factors. The existence of a nanometer-thickness layer not only evidently reduces the cavity mode volume but also draws the maximal electric field's position of the mode to the outside of the silica toroid, where single quantum dots or nanocrystals are located. Both effects result in a strongly enhanced coherent interaction between a single dipole (for example, a single defect center in a diamond crystal) and the quantized cavity mode. Since the coated microtoroid is highly feasible and robust in experiments, it may offer an excellent platform to study strong-coupling cavity quantum electrodynamics, quantum information, and quantum computation.
Quantum electrodynamics of inhomogeneous anisotropic media
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.)
A Way to Revised Quantum Electrodynamics
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.
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.)
Quantum electrodynamics with 1D arti cial atoms
Javadi, Alisa
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...... photons as expected from the theory. The value of g(2)(0) is around 1.08. The results con_rm the observation of an on-chip giant optical nonlinearity and the 1D atom behavior. Another direction in this thesis has been to investigate the e_ect of Anderson localization on the electrodynamics of QDs in PCWs...
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…
Resonator quantum electrodynamics on a microtrap chip
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 ∼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 g0=2π.300 MHz respectively C0=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.
Quantum electrodynamics of high-Z few-electron atoms
A relatively new area in the field of Atomic Physics and Quantum Electrodynamics (QED) is the precise theoretical and experimental study of high-Z few-electron atoms. Comparison of theory and experiment for the transition rates and energy splittings of these systems provides a fundamental test of the theory of strongly bound electrons. This reviews the quantum electrodynamics of high-Z few-electron atoms based on perturbation theory in the Furry bound interaction picture. A complete overview of the theory is given, from the basic equations to the numerical results for the energy splittings, with attention focused on the Lamb shift in two-electron atoms as an example
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...
Applications of the Fokker-Planck equation in circuit quantum electrodynamics
Elliott, Matthew; Ginossar, Eran
2016-01-01
We study exact solutions of the steady state behaviour of several non-linear open quantum systems which can be applied to the field of circuit quantum electrodynamics. Using Fokker-Planck equations in the generalised 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 ana...
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...
On Galilean invariance and nonlinearity in electrodynamics and quantum mechanics
Goldin, G A; Goldin, Gerald A.; Shtelen, Vladimir
2000-01-01
Recent experimental results on slow light heighten interest in nonlinear Maxwell theories. We obtain Galilei covariant equations for electromagnetism by allowing special nonlinearities in the constitutive equations only, keeping Maxwell's equations unchanged. Combining these with linear or nonlinear Schroedinger equations, e.g. as proposed by Doebner and Goldin, yields a Galilean quantum electrodynamics.
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
A Parity Invariant Regularization in 3-D Quantum Electrodynamics
Kimura, Tadahiko
1994-01-01
We regularize the 3-D quantum electrodynamics by a parity invariant Pauli-Villars regularization method. We find that in the perturbation theory the Chern-Simons term is not induced in the massless fermion case and induced in the massive fermion case.
Quantum signalling in cavity QED
Jonsson, Robert H.; Martin-Martinez, Eduardo; Kempf, Achim
2013-01-01
We consider quantum signalling between two-level quantum systems in a cavity, in the pertubative regime of the earliest possible arrival times of the signal. We present two main results: First we find that, perhaps surprisingly, the analogue of amplitude modulated signalling (Alice using her energy eigenstates |g>, |e>, as in the Fermi problem) is generally sub-optimal for communication. Namely, e.g., phase modulated signalling (Alice using, e.g., |+>,|e>-states) overcomes the quantum noise a...
Quantum electrodynamics in finite volume and nonrelativistic effective field theories
Fodor, Z.; Hoelbling, C.; Katz, S. D.; Lellouch, L.; Portelli, A.; Szabo, K. K.; Toth, B. C.
2016-04-01
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.
Dimensional regularization and infrared divergences in quantum electrodynamics
Dimensional continuation was devised as a powerful regularization method for ultraviolet divergences in quantum field theories. Recently it was clear, at least for quantum electrodynamics, that such a method could be employed for factorizing out infrared divergences from the on-shell S-matrix elements. This provides a renormalization scheme on the electron mass-shell without using a gauge violating ''photon mass''. (author)
K\\"all\\'en-Lehmann representation of noncommutative quantum electrodynamics
Bufalo, R.; Cardoso, T. 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...
Path Integral Quantization of Generalized Quantum Electrodynamics
Bufalo, Rodrigo; Pimentel, Bruto Max; Zambrano, German Enrique Ramos
2010-01-01
In this paper, a complete covariant quantization of generalized electrodynamics is shown through the path integral approach. To this goal, we first studied the hamiltonian structure of system following Dirac's methodology and, then, we followed the Faddeev-Senjanovic procedure to obtain the transition amplitude. The complete propagators (Schwinger-Dyson-Fradkin equations) of the correct gauge fixation and the generalized Ward-Fradkin-Takahashi identities are also obtained. Afterwards, an expl...
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
In this paper, a complete covariant quantization of generalized electrodynamics is shown through the path integral approach. To this goal, we first studied the Hamiltonian structure of the system following Dirac's methodology and, then, we followed the Faddeev-Senjanovic procedure to obtain the transition amplitude. The complete propagators (Schwinger-Dyson-Fradkin equations) of the correct gauge fixation and the generalized Ward-Fradkin-Takahashi identities are also obtained. Afterwards, an explicit calculation of one-loop approximations of all Green's functions and a discussion about the obtained results are presented.
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
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
Experiments on two-resonator circuit quantum electrodynamics. A superconducting quantum switch
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 presents the theoretical background, the fabrication techniques and
Deterministic amplification of Schrödinger cat states in circuit quantum electrodynamics
Joo, Jaewoo; Elliott, Matthew; Oi, Daniel K. L.; Ginossar, Eran; Spiller, Timothy P.
2016-02-01
Perfect deterministic amplification of arbitrary quantum states is prohibited by quantum mechanics, but determinism can be achieved by compromising between fidelity and amplification power. We propose a dynamical scheme for deterministically amplifying photonic Schrödinger cat states, which show great promise as a tool for quantum information processing. Our protocol is designed for strongly coupled circuit quantum electrodynamics and utilizes artificial atomic states and external microwave controls to engineer a set of optimal state transfers and achieve high fidelity amplification. We compare analytical results with full simulations of the open, driven Jaynes-Cummings model, using realistic device parameters for state of the art superconducting circuits. Amplification with a fidelity of 0.9 can be achieved for sizable cat states in the presence of cavity and atomic-level decoherence. This tool could be applied to practical continuous-variable information processing for the purification and stabilization of cat states in the presence of photon losses.
Thermal excitation of multi-photon dressed states in circuit quantum electrodynamics
Fink, J M; Baur, M; Bianchetti, R; Filipp, S; Goeppl, M; Leek, P J; Steffen, L; Wallraff, A [Department of Physics, ETH Zurich, CH-8093 Zurich (Switzerland); Blais, A [Departement de Physique, Universite de Sherbrooke, Quebec J1K 2R1 (Canada)], E-mail: jfink@phys.ethz.ch, E-mail: andreas.wallraff@phys.ethz.ch
2009-12-15
The exceptionally strong coupling realizable between superconducting qubits and photons stored in an on-chip microwave resonator allows for the detailed study of matter-light interactions in the realm of circuit quantum electrodynamics (QED). Here we investigate the resonant interaction between a single transmon-type multilevel artificial atom and weak thermal and coherent fields. We explore up to three photon dressed states of the coupled system in a linear response heterodyne transmission measurement. The results are in good quantitative agreement with a generalized Jaynes-Cummings model. Our data indicate that the role of thermal fields in resonant cavity QED can be studied in detail using superconducting circuits.
Thermal excitation of multi-photon dressed states in circuit quantum electrodynamics
The exceptionally strong coupling realizable between superconducting qubits and photons stored in an on-chip microwave resonator allows for the detailed study of matter-light interactions in the realm of circuit quantum electrodynamics (QED). Here we investigate the resonant interaction between a single transmon-type multilevel artificial atom and weak thermal and coherent fields. We explore up to three photon dressed states of the coupled system in a linear response heterodyne transmission measurement. The results are in good quantitative agreement with a generalized Jaynes-Cummings model. Our data indicate that the role of thermal fields in resonant cavity QED can be studied in detail using superconducting circuits.
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$_{d_\\gamma,d_e}$.
Entanglement distillation in circuit quantum electrodynamics
Oppliger, Markus; Heinsoo, Johannes; Salathe, Yves; Potocnik, Anton; Mondal, Mintu; Wallraff, Andreas; Paraoanu, Gheorghe Sorin
Entanglement is an essential resource for quantum information processing, such as quantum error correction, quantum teleportation and quantum communication. Such algorithms perform optimally with maximally entangled states. In practice entangled quantum states are very fragile due to a wide range of decoherence mechanisms. When two parties share degraded entangled states they are still able to generate an entangled state with higher fidelity using local operations and classical communication. This process is commonly referred to as entanglement distillation. Here we demonstrate distillation of highly entangled Bell states from two copies of less entangled states on a four transmon qubit device realized in the circuit-QED architecture. We characterize the output state for different degrees of entanglement at the input with quantum state tomography. A clear improvement of the entanglement measures is observed at the output.
Fixed point structure of quenched, planar quantum electrodynamics
Gauge theories exhibiting a hierarchy of fermion mass scales may contain a pseudo-Nambu-Boldstone boson of spontaneously broken scale invariance. The relation between scale and chiral symmetry breaking is studied analytically in quenched, planar quantum electrodynamics in four dimensions. The model possesses a novel nonperturbative ultraviolet fixed point governing its strong coupling phase which requires the mixing of four fermion operators. 12 refs
The Adler-Bardeen theorem in quantum electrodynamics
A new proof of the Adler-Bardeen theorem in quantum electrodynamics is presented on the basis of three kinds of Ward-Takahashi identities. Among them one is new and essential to the proof. By examining the consistency of these identities with the renormalization group we find three equations for the anomalous dimensions of the operators appearing in the Ward-Takahashi identities. Combination of these three equations immediately yields the Adler-Bardeen theorem. (author)
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...
High-energy limit of quantum electrodynamics beyond Sudakov approximation
Penin, Alexander A.
2015-01-01
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...
Single quantum dot controls a plasmonic cavity's scattering and anisotropy.
Hartsfield, Thomas; Chang, Wei-Shun; Yang, Seung-Cheol; Ma, Tzuhsuan; Shi, Jinwei; Sun, Liuyang; Shvets, Gennady; Link, Stephan; Li, Xiaoqin
2015-10-01
Plasmonic cavities represent a promising platform for controlling light-matter interaction due to their exceptionally small mode volume and high density of photonic states. Using plasmonic cavities for enhancing light's coupling to individual two-level systems, such as single semiconductor quantum dots (QD), is particularly desirable for exploring cavity quantum electrodynamic (QED) effects and using them in quantum information applications. The lack of experimental progress in this area is in part due to the difficulty of precisely placing a QD within nanometers of the plasmonic cavity. Here, we study the simplest plasmonic cavity in the form of a spherical metallic nanoparticle (MNP). By controllably positioning a semiconductor QD in the close proximity of the MNP cavity via atomic force microscope (AFM) manipulation, the scattering spectrum of the MNP is dramatically modified due to Fano interference between the classical plasmonic resonance of the MNP and the quantized exciton resonance in the QD. Moreover, our experiment demonstrates that a single two-level system can render a spherical MNP strongly anisotropic. These findings represent an important step toward realizing quantum plasmonic devices. PMID:26372957
High-energy limit of quantum electrodynamics beyond Sudakov approximation
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
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.
Quantum-electrodynamical approach to the Casimir force problem
Schuller, Frederic
2012-01-01
We derive the Casimir force expression from Maxwell's stress tensor by means of original quantum-electro-dynamical cavity modes. In contrast with similar calculations, our method is straightforward and does not rely on intricate mathematical extrapolation relations.
Entangling distant resonant exchange qubits via circuit quantum electrodynamics
Srinivasa, Vanita; Taylor, Jacob M.; Tahan, Charles
Enabling modularity within a quantum information processing device relies on robust entanglement of coherent qubits at macroscopic distances. To address this challenge, we investigate theoretically 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. By analyzing three specific approaches drawn from circuit quantum electrodynamics and Hartmann-Hahn double resonance techniques for implementing resonator-mediated two-qubit entangling gates in both dispersive and resonant regimes, we show that methods for entangling superconducting qubits map directly to resonant exchange qubits. We also calculate 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 robustness of encoded spin qubits in silicon with the rapid and robust long-range entanglement provided by circuit QED systems.
Multi-qubit circuit quantum electrodynamics
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
Multi-qubit circuit quantum electrodynamics
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
Giant Kerr Nonlinearities in Circuit Quantum Electrodynamics
Rebic, Stojan; Twamley, Jason; Milburn, Gerard J.
2009-01-01
The very small size of optical nonlinearities places wide ranging restrictions on the types of novel physics one can explore. For an ensemble of multi-level systems one can synthesize a large effective optical nonlinearity using quantum coherence effects but such non-linearities are technically extremely challenging to demonstrate at the single atom level. In this work we describe how a single artificial multi-level Cooper Pair Box molecule, interacting with a superconducting microwave coplan...
Casimir effect from macroscopic quantum electrodynamics
Philbin, T G
2011-01-01
The canonical quantization of macroscopic electromagnetism was recently presented in New J. Phys. 12 (2010) 123008. This theory is here used to derive the Casimir effect, by considering the special case of thermal and zero-point fields. The stress-energy-momentum tensor 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.
Modified Maxwell equations in quantum electrodynamics
Harmuth, Henning F; Meffert, Beate
2001-01-01
Divergencies in quantum field theory referred to as "infinite zero-point energy" have been a problem for 70 years. Renormalization has always been considered an unsatisfactory remedy. In 1985 it was found that Maxwell's equations generally do not have solutions that satisfy the causality law. An additional term for magnetic dipole currents corrected this shortcoming. Rotating magnetic dipoles produce magnetic dipole currents, just as rotating electric dipoles in a material like barium titanate produce electric dipole currents. Electric dipole currents were always part of Maxwell's equations. T
Quantum Electrodynamics near a Huttner-Barnett dielectric
Eberlein, Claudia
2012-01-01
We build up a consistent theory of quantum electrodynamics in the presence of macroscopic polarizable media. We use the Huttner-Barnett model of a dispersive and absorbing dielectric medium and formulate the theory in terms of interacting quantum fields. We integrate out the damped polaritons by using diagrammatic techniques and find an exact expression for the displacement field (photon) propagator in the presence of a dispersive and absorbing dielectric half-space. This opens a new route to traceable perturbative calculations of the same kind as in free-space quantum electrodynamics. As a worked-through example we consider the interaction of a neutral atom with a dispersive and absorbing dielectric half-space. For that we use the multipolar coupling $\\boldsymbol{\\mu}\\cdot\\mathbf{D}$ of the atomic dipole moment to the electromagnetic displacement field. We apply the newly developed formalism to calculate the one-loop correction to the atomic electron propagator and find the energy-level shift and changes in ...
Dressed Zeno effect in circuit quantum electrodynamics
Li, Hai-Chao; Ge, Guo-Qin; Feng, Shun-Bin
2014-06-01
We present a theoretical study of the quantum Zeno effect in a driven superconducting charge qubit strongly and ultrastrongly coupled to a transmission line resonator. Using the dressed-state approach, we predict the different dynamics behaviors of the dressed qubit subjected to two opposite projection measurements. We show that, for very frequent measurements, the survival probability of the initial state is of exponential form and the Zeno time of the dressed qubit can be several orders of magnitude longer than that of the bare qubit. For slowly repeated measurements, the detuning of the driving field has significant impact on the measurement dynamics, and by choosing appropriate parameters for the dressed qubit, the Zeno effect can occur in the nonresonant coupling case. Such a Zeno effect is excluded from a usual two-level system.
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.
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.
On bosonization ambiguities of two dimensional quantum electrodynamics
We study bosonization ambiguities in two dimensional quantum electrodynamics in the presence and in the absence of topologically charged gauge fields. The computation of fermionic correlation functions gives us a mechanism to fix the ambiguities in nontrivial topologies, provided that we do not allow changes of sector as we evaluate functional integrals. This removes an infinite arbitrariness from the theory. In the case of trivial topologies, we find upper and lower bounds for the Jackiw-Rajaraman parameter, corresponding to the limiting cases of regularizations which preserve gauge or chiral symmetry. (author). 19 refs
Progress in quantum electrodynamics theory of highly charged ions
Volotka, Andrey V. [Institut fuer Theoretische Physik, Technische Universitaet Dresden, Mommsenstrasse 13, 01062, Dresden (Germany); Department of Physics, St. Petersburg State University, Oulianovskaya 1, Petrodvorets, 198504, St. Petersburg (Russian Federation); Glazov, Dmitry A.; Shabaev, Vladimir M. [Department of Physics, St. Petersburg State University, Oulianovskaya 1, Petrodvorets, 198504, St. Petersburg (Russian Federation); Plunien, Guenter [Institut fuer Theoretische Physik, Technische Universitaet Dresden, Mommsenstrasse 13, 01062, Dresden (Germany)
2013-09-15
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 magnetic moments with heavy ions are discussed. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Renormalization constants and asymptotic behaviour in quantum electrodynamics
Using dimensional regularization a field theory contains at least one parameter less than the dimension of a mass. The Callan-Symanzik equations for the renormalization constants then become soluble entirely in terms of the coefficient functions. Explicit expressions are obtained for all the renormalization constants in Quantum Electrodynamics. At nonexceptional momenta the infrared behaviour and the three leading terms in the asymptotic expansion of any Greens function are controlled by the Callan-Symanzik equations. For the propagators the three leading terms are computed explicitly in terms of functions of α only. The gauge dependence of the electron propagator in momentum space is solved explicitly in all orders of perturbation theory. (Auth.)
Lamb shift in quantum electrodynamics (semiclassical theory)
This paper aims to bring some arguments to the proof of the Barut and Van Huele formula, which gives the Lamb shift in the semi-classical theory model: by shortening the calculation owing to the use of a decomposition of the self-potential of the electron; by eliminating the appeal to a divergent series; by bringing justifications and clarifications on some important points of the proof. The effective calculation of the coefficients of the formula is achieved for some of them, and the general analytical form of these coefficients is explicited. It is also proved that the B. and V.H. formula must give results at least as close to the experiment as those of the Bethe formula, which is obtained in Quantum Theory of Fields. Finally one shows that the B. and V.H. formula provides a justification de facto for the cut-off which is used for associating finite numbers to the divergent integrals of the Bethe formula
Scheme for implementing quantum dense coding with W-class state in cavity QED
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.
Dispersion relations in quantum electrodynamics on the noncommutative Minkowski space
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.)
Dispersion relations in quantum electrodynamics on the noncommutative Minkowski space
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 Φ3 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.)
Relativistic and quantum electrodynamic effects in superheavy elements
Schwerdtfeger, Peter; Pašteka, Lukáš F.; Punnett, Andrew; Bowman, Patrick O.
2015-12-01
The current status of relativistic electronic structure theory for superheavy elements is reviewed. Recent developments in relativistic quantum theory have made it possible to obtain accurate electronic properties for the trans-actinide elements with the aim to predict their chemical and physical behaviour. The role of quantum electrodynamic effects beyond the no-virtual-pair approximation, which is usually neglected in relativistic molecular calculations, is discussed. Changes in periodic trends due to relativistic effects are outlined for the superheavy elements with nuclear charge Z = 111- 120. We also analyse the role of the negative energy states for the electronic stability of superheavy elements beyond the critical nuclear charge (Zcrit ≈ 170), where the 1s state enters the negative energy continuum at - 2mec2.
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.
Digital Quantum Simulation of Spin Models with Circuit Quantum Electrodynamics
Salathé, Y.; Mondal, M.; Oppliger, M.; Heinsoo, J.; Kurpiers, P.; Potočnik, A.; Mezzacapo, Antonio; Las Heras García, Urtzi; Lamata Manuel, Lucas; Solano Villanueva, Enrique Leónidas; Filipp, S.; Wallraff, A.
2015-01-01
Systems of interacting quantum spins show a rich spectrum of quantum phases and display interesting many-body dynamics. Computing characteristics of even small systems on conventional computers poses significant challenges. A quantum simulator has the potential to outperform standard computers in calculating the evolution of complex quantum systems. Here, we perform a digital quantum simulation of the paradigmatic Heisenberg and Ising interacting spin models using a two transmon-qubit circuit...
Quantum Zeno effect in the strong measurement regime of circuit quantum electrodynamics
Slichter, D. H.; Müller, C.; Vijay, R.; Weber, S. J.; Blais, A.; Siddiqi, I.
2016-05-01
We observe the quantum Zeno effect—where the act of measurement slows the rate of quantum state transitions—in a superconducting qubit using linear circuit quantum electrodynamics readout and a near-quantum-limited following amplifier. Under simultaneous strong measurement and qubit drive, the qubit undergoes a series of quantum jumps between states. These jumps are visible in the experimental measurement record and are analyzed using maximum likelihood estimation to determine qubit transition rates. The observed rates agree with both analytical predictions and numerical simulations. The analysis methods are suitable for processing general noisy random telegraph signals.
Inflationary universe from higher derivative quantum gravity coupled with scalar electrodynamics
Myrzakulov, Ratbay; Odintsov, Sergei; Sebastiani, Lorenzo
2016-01-01
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,...
Quantum networks based on cavity QED
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.
Interacting Electrodynamics of Short Coherent Conductors in Quantum Circuits
Altimiras, C.; Portier, F.; Joyez, P.
2016-07-01
When combining lumped mesoscopic electronic components to form a circuit, quantum fluctuations of electrical quantities lead to a nonlinear electromagnetic interaction between the components, which is generally not understood. The Landauer-Büttiker formalism that is frequently used to describe noninteracting coherent mesoscopic components is not directly suited to describe such circuits since it assumes perfect voltage bias, i.e., the absence of fluctuations. Here, we show that for short coherent conductors of arbitrary transmission, the Landauer-Büttiker formalism can be extended to take into account quantum voltage fluctuations similarly to what is done for tunnel junctions. The electrodynamics of the whole circuit is then formally worked out disregarding the non-Gaussianity of fluctuations. This reveals how the aforementioned nonlinear interaction operates in short coherent conductors: Voltage fluctuations induce a reduction of conductance through the phenomenon of dynamical Coulomb blockade, but they also modify their internal density of states, leading to an additional electrostatic modification of the transmission. Using this approach, we can quantitatively account for conductance measurements performed on quantum point contacts in series with impedances of the order of RK=h /e2 . Our work should enable a better engineering of quantum circuits with targeted properties.
External cavity quantum cascade laser
In this paper we review the progress of the development of mid-infrared quantum cascade lasers (QCLs) operated in an external cavity configuration. We concentrate on QCLs based on the bound-to-continuum design, since this design is especially suitable for broadband applications. Since they were first demonstrated, these laser-based tunable sources have improved in performance in terms of output power, duty cycle, operation temperature and tuneability. Nowadays they are an interesting alternative to FTIRs for some applications. They operate at room temperature, feature a high spectral resolution while being small in size. They were successfully used in different absorption spectroscopy techniques. Due to their vast potential for applications in industry, medicine, security and research, these sources enjoy increasing interest within the research community as well as in industry. (topical review)
Are There Topologically Charged States Associated with Quantum Electrodynamics ?
Marino, E C
1994-01-01
We present a formulation of Quantum Electrodynamics in terms of an antisymmetric tensor gauge field. In this formulation the topological current of this field appears as a source for the electromagnetic field and the topological charge therefore acts physically as an electric charge. The charged states of QED lie in the sector where the topological charge is identical to the matter charge. The antisymmetric field theory, however, admits new sectors where the topological charge is more general. These nontrivial, electrically charged, sectors contain massless states orthogonal to the vacuum which are created by a gauge invariant operator and can be interpreted as coherent states of photons. We evaluate the correlation functions of these states in the absence of matter. The new states have a positive definite norm and do interact with the charged states of QED in the usual way. It is argued that if these new sectors are in fact realized in nature then a very intense background electromagnetic field is necessary ...
Effective field theory of quantum gravity coupled to scalar electrodynamics
Ibiapina Bevilaqua, L.; Lehum, A. C.; da Silva, A. J.
2016-05-01
In this work, we use the framework of effective field theory to couple Einstein’s gravity to scalar electrodynamics and determine the renormalization of the model through the study of physical processes below Planck scale, a realm where quantum mechanics and general relativity are perfectly compatible. We consider the effective field theory up to dimension six operators, corresponding to processes involving one-graviton exchange. Studying the renormalization group functions, we see that the beta function of the electric charge is positive and possesses no contribution coming from gravitational interaction. Our result indicates that gravitational corrections do not alter the running behavior of the gauge coupling constants, even if massive particles are present.
Radiative emission of neutrino pair free of quantum electrodynamic backgrounds
A scheme of quantum electrodynamic (QED) background-free radiative emission of a neutrino pair (RENP) is proposed in order to achieve precision determination of neutrino properties so far not accessible. The important point for the background rejection is the fact that the dispersion relation between the wave vector along the propagating direction in the wave guide (and in a photonic-crystal-type fiber) and the frequency is modified by a discretized non-vanishing effective mass. This effective mass acts as a cutoff of allowed frequencies, and one may select the RENP photon energy region free of all macro-coherently amplified QED processes by choosing the cutoff larger than the mass of neutrinos
Nonperturbative renormalization of scalar quantum electrodynamics in d=3
Dimock, J., E-mail: dimock@buffalo.edu [Department of Mathematics, SUNY at Buffalo, Buffalo, New York 14260 (United States)
2015-10-15
For scalar quantum electrodynamics on a three-dimensional toroidal lattice with a fine lattice spacing, we consider the renormalization problem of choosing counter terms depending on the lattice spacing, so that the theory stays finite as the spacing goes to zero. We employ a renormalization group method which analyzes the flow of the mass and the vacuum energy as a problem in discrete dynamical systems. The main result is that counter terms can be chosen so that at the end of the iteration these quantities take preassigned values. No use is made of perturbation theory. The renormalization group transformations are defined with bounded fields, an approximation which can be justified in Balaban’s approach to the renormalization group.
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. PMID:26987436
Higgs-Like Particle due to Revised Quantum Electrodynamics
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
The generation and control of quantum states of spatially-separated qubits distributed in different cavities constitute fundamental tasks in cavity quantum electrodynamics (QED). An interesting question in this context is how to prepare entanglement and realize quantum information transfer between qubits located at different cavities, which are important in large-scale quantum information processing. In this paper, we consider a physical system consisting of two cavities and three qubits. Two of the qubits are placed in two different cavities while the remaining one acts as a coupler, which is used to connect the two cavities. We propose an approach for generating quantum entanglement and implementing quantum information transfer between the two spatially-separated inter-cavity qubits. The quantum operations involved in this proposal are performed by a virtual photon process; thus the cavity decay is greatly suppressed during operations. In addition, to complete these tasks, only one coupler qubit and one operation step are needed. Moreover, there is no need to apply classical pulses, so that the engineering complexity is much reduced and the operation procedure is greatly simplified. Finally, our numerical results illustrate that high-fidelity implementation of this proposal using superconducting phase qubits and one-dimensional transmission line resonators is feasible for current circuit QED implementations. This proposal can also be applied to other types of superconducting qubits, including flux and charge qubits. (paper)
Yang, Chui-Ping; Su, Qi-Ping; Nori, Franco
2013-11-01
The generation and control of quantum states of spatially-separated qubits distributed in different cavities constitute fundamental tasks in cavity quantum electrodynamics (QED). An interesting question in this context is how to prepare entanglement and realize quantum information transfer between qubits located at different cavities, which are important in large-scale quantum information processing. In this paper, we consider a physical system consisting of two cavities and three qubits. Two of the qubits are placed in two different cavities while the remaining one acts as a coupler, which is used to connect the two cavities. We propose an approach for generating quantum entanglement and implementing quantum information transfer between the two spatially-separated inter-cavity qubits. The quantum operations involved in this proposal are performed by a virtual photon process; thus the cavity decay is greatly suppressed during operations. In addition, to complete these tasks, only one coupler qubit and one operation step are needed. Moreover, there is no need to apply classical pulses, so that the engineering complexity is much reduced and the operation procedure is greatly simplified. Finally, our numerical results illustrate that high-fidelity implementation of this proposal using superconducting phase qubits and one-dimensional transmission line resonators is feasible for current circuit QED implementations. This proposal can also be applied to other types of superconducting qubits, including flux and charge qubits.
Quantum Mechanical Description of Raman Scattering from Molecules in Plasmonic Cavities.
Schmidt, Mikolaj K; Esteban, Ruben; González-Tudela, Alejandro; Giedke, Geza; Aizpurua, Javier
2016-06-28
Plasmon-enhanced Raman scattering can push single-molecule vibrational spectroscopy beyond a regime addressable by classical electrodynamics. We employ a quantum electrodynamics (QED) description of the coherent interaction of plasmons and molecular vibrations that reveal the emergence of nonlinearities in the inelastic response of the system. For realistic situations, we predict the onset of phonon-stimulated Raman scattering and a counterintuitive dependence of the anti-Stokes emission on the frequency of excitation. We further show that this QED framework opens a venue to analyze the correlations of photons emitted from a plasmonic cavity. PMID:27203727
Role of the lightmatter coupling strength on nonMarkovian phonon effects in semiconductor cavity QED
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 [1...
Ultrahigh quality factor in a metal-embedded semiconductor microdisk cavity.
Kurosawa, Hiroyuki; Kumano, Hidekazu; Suemune, Ikuo
2015-12-15
We numerically and theoretically investigate electrodynamics of a metal-embedded semiconductor microdisk cavity. The electrodynamics of a cavity mode is discussed from the viewpoint of quantum mechanics, which clarifies the condition for high Q factor. Using numerical calculations, we optimize the cavity structure and show that the Q factor can be increased up to 1,700,000. Our study suggests that the metal-embedded cavity is a promising candidate for cavity quantum electrodynamics (QED) devices. PMID:26670507
Two-resonator circuit quantum electrodynamics: A superconducting quantum switch
Mariantoni, Matteo; Deppe, Frank; Marx, A.; Gross, R.; Wilhelm, F. K.; Solano, E.
2008-09-01
We introduce a systematic formalism for two-resonator circuit QED, where two on-chip microwave resonators are simultaneously coupled to one superconducting qubit. Within this framework, we demonstrate that the qubit can function as a quantum switch between the two resonators, which are assumed to be originally independent. In this three-circuit network, the qubit mediates a geometric second-order circuit interaction between the otherwise decoupled resonators. In the dispersive regime, it also gives rise to a dynamic second-order perturbative interaction. The geometric and dynamic coupling strengths can be tuned to be equal, thus permitting to switch on and off the interaction between the two resonators via a qubit population inversion or a shifting of the qubit operation point. We also show that our quantum switch represents a flexible architecture for the manipulation and generation of nonclassical microwave field states as well as the creation of controlled multipartite entanglement in circuit QED. In addition, we clarify the role played by the geometric interaction, which constitutes a fundamental property characteristic of superconducting quantum circuits without a counterpart in quantum-optical systems. We develop a detailed theory of the geometric second-order coupling by means of circuit transformations for superconducting charge and flux qubits. Furthermore, we show the robustness of the quantum switch operation with respect to decoherence mechanisms. Finally, we propose a realistic design for a two-resonator circuit QED setup based on a flux qubit and estimate all the related parameters. In this manner, we show that this setup can be used to implement a superconducting quantum switch with available technology.
Discretized light-cone quantization: Application to quantum electrodynamics
In this work, a general method for solving quantum field theories, Discretized Light-Cone Quantization (DLCQ), is presented. The method is very straightforward and essentially consists of diagonalizing the light-cone Hamiltonian matrix for the mass spectrum and wavefunctions. This method has been applied successfully in the past to various one space, one time dimensional theories. In each of these past applications, the mass spectrum and wave functions were successfully obtained, and all results agree with previous analytical and numerical work. The success of DLCQ in 1 + 1 dimensions provides the hope of solving theories in three space and one time dimensions. The application to higher dimensions is much more involved than in 1 + 1 dimensions due to the need to introduce ultraviolet and infrared regulators, and invoke a renormalization scheme consistent with gauge invariance and Lorentz invariance. This is in addition to the extra work involved implementing two extra dimensions with their added degrees of freedom. In this paper, I will present the application of DLCQ to 3 + 1 dimensional Quantum Electrodynamics. 24 refs., 43 figs., 2 tabs
Quantum electrodynamics of resonance energy transfer in nanowire systems
Weeraddana, Dilusha; Premaratne, Malin; Andrews, David L.
2016-02-01
Nonradiative resonance energy transfer (RET) provides the ability to transfer excitation energy between contiguous nanowires (NWs) with high efficiency under certain conditions. Nevertheless, the well-established Förster formalism commonly used to represent RET was developed for energy transfer primarily between molecular blocks (i.e., from one molecule, or part of a molecule, to another). Although deviations from Förster theory for functional blocks such as NWs have been studied previously, the role of the relative distance, the orientation of transition dipole moment pairs, and the passively interacting matter on electronic energy transfer are to a large extent unknown. Thus, a comprehensive theory that models RET in NWs is required. In this context, analytical insights to give a deeper and more intuitive understanding of the distance and orientation dependence of RET in NWs is presented within the framework of quantum electrodynamics. Additionally, the influence of an included intermediary on the rate of excitation energy transfer is illustrated, embracing indirect energy transfer rate and quantum interference. The results deliver equations that afford new intuitions into the behavior of virtual photons. In particular, results indicate that RET efficiency in a NW system can be explicitly expedited or inhibited by a neighboring mediator, depending on the relative spacing and orientation of NWs.
Enhancing Quantum Discord in Cavity QED by Applying Classical Driving Field
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.
Quantum gravitational contributions to the beta function of quantum electrodynamics
Full text: Because of the negative mass dimension of the coupling constant perturbative Einstein quantum gravity (EQG) is nonrenormalizable. However, one can still make sense of EQG if it's interpreted as an effective field theory within a low energy expansion of a more fundamental theory. In an effective field theory all interactions compatible with its essential symmetry content are in principle allowed into the Lagrangian and thus it establishes a systematic framework to calculate quantum gravitational effects. This approach has been used to study the asymptotic behavior at high energies of quantum field theories that incorporate the gravitational field. Some studies analyze the asymptotic freedom for the coupling constants of some theories including gravitation near the Planck scale. For example, Robinson and Wilczek suggest that the gravitational field improve the asymptotic freedom of pure Yang-Mills near the Planck scale. Already , a similar calculation in the Maxwell-Einstein theory suggest that such conclusion is gauge dependence. This result was obtained by Pietrykowski. D. Toms say what the effective action is calculated in a gauge-condition independent version of the background field method using dimensional regularization it's argued that the gravitational field plays no role in the beta function of the Yang-Mills coupling. Another calculation done by Ebert, Plefka and Rodigast using conventional diagrammatic methods confirms the result obtained by Toms. In a recent publication, again published by Toms in 2010, claimed that quadratic divergent contributions were responsible to improve asymptotic freedom of fine structure constant by quantum gravity effects by using proper time cutoff regularization and effective action methods. However, the physical reality of the result in Tom's was questioned in recent work. This purpose of this work is to shed light on the origin of such controversies using only a diagrammatic analysis. As an effective model EQG is
The quantum Hall's effect:A quantum electrodynamic phenomenon
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.
Ion-cavity system for quantum networks
Full text: A single atom interacting with a single mode of a cavity allows us to probe the quantum interaction between light and matter. In the context of quantum networks, such a system can provide an interface between stationary and flying qubits, making it possible for single photons to transport quantum information between the network nodes. We study a single 40Ca+ ion trapped inside a high-finesse optical resonator. First, we demonstrate and characterize a single-photon source, in which a vacuum-stimulated Raman process transfers atomic population between two Zeeman states of the ion, creating a single photon in the cavity. We evaluate the photon statistics by measuring the second-order correlation function. Moreover, we obtain the photon temporal profile and investigate the dynamics of the process. Secondly, we perform Raman spectroscopy using the cavity. Residual motion of the ion introduces motional sidebands in the Raman spectrum and thus offers prospects for cavity-assisted cooling. (author)
Nonlinear quantum electrodynamic and electroweak processes in strong laser fields
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.
Effect of laser polarization on quantum electrodynamical cascading
Development of quantum electrodynamical (QED) cascades in a standing electromagnetic wave for circular and linear polarizations is simulated numerically with a 3D PIC-MC code. It is demonstrated that for the same laser energy the number of particles produced in a circularly polarized field is greater than in a linearly polarized field, though the acquiring mean energy per particle is larger in the latter case. The qualitative model of laser-assisted QED cascades is extended by including the effect of polarization of the field. It turns out that cascade dynamics is notably more complicated in the case of linearly polarized field, where separation into the qualitatively different “electric” and “magnetic” regions (where the electric field is stronger than the magnetic field and vice versa) becomes essential. In the “magnetic” regions, acceleration is suppressed, and moreover the high-energy electrons are even getting cooled by photon emission. The volumes of the “electric” and “magnetic” regions evolve periodically in time and so does the cascade growth rate. In contrast to the linear polarization, the charged particles can be accelerated by circularly polarized wave even in “magnetic region.” The “electric” and “magnetic” regions do not evolve in time, and cascade growth rate almost does not depend on time for circular polarization
Quantum Electrodynamics in d =3 from the ɛ Expansion
Di Pietro, Lorenzo; Komargodski, Zohar; Shamir, Itamar; Stamou, Emmanuel
2016-04-01
We study quantum electrodynamics in d =3 coupled to Nf flavors of fermions. The theory flows to an IR fixed point for Nf larger than some critical number Nfc. For Nf≤Nfc, 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 -2 ɛ to study the three-dimensional conformal theory. We compute, in perturbation theory, the IR dimensions of fermion bilinear and quadrilinear operators. For small Nf, a quadrilinear operator can become relevant in the IR and destabilize the fixed point. Therefore, the epsilon expansion can be used to estimate Nfc. 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 -2 ɛ that correspond to the additional conserved currents at d =3 and compute their infrared dimensions.
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. PMID:27081967
Observing different quantum trajectories in cavity QED
Santos, Marcelo França
2011-01-01
The experimental observation of quantum jumps is an example of single open quantum systems that, when monitored, evolve in terms of stochastic trajectories conditioned on measurements results. Here we present a proposal that allows the experimental observation of a much larger class of quantum trajectories in cavity QED systems. In particular, our scheme allows for the monitoring of engineered thermal baths that are crucial for recent proposals for probing entanglement decay and also for entanglement protection. The scheme relies on the interaction of a three-level atom and a cavity mode that interchangeably play the roles of system and probe. If the atom is detected the evolution of the cavity fields follows quantum trajectories and vice-versa.
Quantum Electrodynamics Basis of Classical-Field High-Harmonic Generation Theory
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.
Higher order energy transfer. Quantum electrodynamical calculations and graphical representation
In Chapter 1, a novel method of calculating quantum electrodynamic amplitudes is formulated using combinatorial theory. This technique is used throughout instead of conventional time-ordered methods. A variety of hyperspaces are discussed to highlight isomorphism between a number of A generalisation of Pascal's triangle is shown to be beneficial in determining the form of hyperspace graphs. Chapter 2 describes laser assisted resonance energy transfer (LARET), a higher order perturbative contribution to the well-known process resonance energy transfer, accommodating an off resonance auxiliary laser field to stimulate the migration. Interest focuses on energy exchanges between two uncorrelated molecular species, as in a system where molecules are randomly oriented. Both phase-weighted and standard isotropic averaging are required for the calculations. Results are discussed in terms of a laser intensity-dependent mechanism. Identifying the applied field regime where LARET should prove experimentally significant, transfer rate increases of up to 30% are predicted. General results for three-center energy transfer are elucidated in chapter 3. Cooperative and accretive mechanistic pathways are identified with theory formulated to elicit their role in a variety of energy transfer phenomena and their relative dominance. In multichromophoric the interplay of such factors is analysed with regard to molecular architectures. The alignments and magnitudes of donor and acceptor transition moments and polarisabilities prove to have profound effects on achievable pooling efficiency for linear configurations. Also optimum configurations are offered. In ionic lattices, although both mechanisms play significant roles in pooling and cutting processes, only the accretive is responsible for sensitisation. The local, microscopic level results are used to gauge the lattice response, encompassing concentration and structural effects. (author)
Quantum-electrodynamic influences on the lifetime of metastable states
High-precision lifetime measurements of the metastable 1s22s22p2P03/2 level in boronlike Ar XIV and the 3s22p 2P03/2 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 1s22s22p2P03/2-2P01/2 and 3s23p 2P03/2-2P01/2 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)(+12-5) 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 3σ and 4σ 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.)
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 and noise response where it is found that a soft-spring Duffing self-interaction enables a closer approach to the displacement detection standard quantum limit, as well as cooling closer to the ground state. Next, we make use of a superconducting transmission line formed from an array of dc-SQUIDs for investigating analogue Hawking radiation. Biasing the array with a space-time varying flux modifies the propagation velocity of the transmission line, leading to an effective metric with a horizon. This setup allows for quan...
Phenomenology of the vacuum in quantum electrodynamics and beyond
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
Phenomenology of the vacuum in quantum electrodynamics and beyond
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
Nonlocal quantum cloning via quantum dots trapped in distant cavities
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.
Nonlocal quantum cloning via quantum dots trapped in distant cavities
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. (general)
Microwave Reentrant Cavities for Quantum Devices
Carvalho, Natalia C.; Bourhill, Jeremy; Creedon, Daniel; Goryachev, Maxim; Galliou, Serge; Tobar, Michael
A microwave reentrant cavity is a device able to provide a very sensitive high-Q microwave mode. Its design can be highly advantageous for electromechanical devices and quantum measurements. In this sense, a tuneable device based on a narrow-gap superconducting reentrant cavity is under development. The resonant frequency is able to be fine-tuned over a range larger than 500 MHz at 10 mK with an electrical Q-factor of 105. Such a cavity could possibly accommodate a transmon qubit to control and manipulate its quantum state. We are also working on the investigation of bulk acoustic wave (BAW) resonators in microwave reentrant cavities. BAW resonators offer a promising way to process quantum information through the coupling between microwaves and acoustic phonons. Thus, we are developing a device able to excite phonons through non-linearities and the piezoelectricity of the plano-convex quartz crystal. We will detail our experiments that work towards cooling gram scale phonon resonances to the quantum ground state. Funded by ARC Grant No. CE110001013 (Australia) and National Counsel of Technological and Scientific Development (Brazil).
Macroscopic Quantum Superposition in Cavity Optomechanics.
Liao, Jie-Qiao; Tian, Lin
2016-04-22
Quantum superposition in mechanical systems is not only key evidence for macroscopic quantum coherence, but can also be utilized in modern quantum technology. Here we propose an efficient approach for creating macroscopically distinct mechanical superposition states in a two-mode optomechanical system. Photon hopping between the two cavity modes is modulated sinusoidally. The modulated photon tunneling enables an ultrastrong radiation-pressure force acting on the mechanical resonator, and hence significantly increases the mechanical displacement induced by a single photon. We study systematically the generation of the Yurke-Stoler-like states in the presence of system dissipations. We also discuss the experimental implementation of this scheme. PMID:27152802
Cavity QED Experiments with Ion Coulomb Crystals. Towards quantum memories and photon counters
Trapped and laser cooled atomic ions in the form of Coulomb crystals represent interesting objects for investigation of Cavity Quantum ElectroDynamics (CQED) and related phenomena. First of all, the number and density of atoms in such crystals as well as the shapes of the crystals can relatively easily be controlled. Second, the ion-ion Coulomb repulsion results in an essentially collision-free environment with the prospect of long coherence times. These properties were recently exploited in experiments focused on investigations of the collective coupling of cold ion ensembles to light modes of a Fabry-Perot cavity, as well as in demonstration of cavity Electromagnetically induced Transparency (EIT) and a photon blockade mechanism. The next step of these experiments will be to realize a light storage scheme, partly for demonstrating an efficient photon counting device and partly for eventually establishing a quantum memory for light with both high efficiency and fidelity. (author)
Cavity-assisted quantum bath engineering
Murch, Kater
2013-03-01
In practice, quantum systems are never completely isolated, but instead interact with degrees of freedom in the surrounding environment, eventually leading to decoherence. Precision measurement techniques such as nuclear magnetic resonance and interferometry, as well as envisioned quantum schemes for computation, simulation, and data encryption, rely on the ability to prepare and preserve delicate quantum superpositions and entanglement. The conventional route to long-lived quantum coherence involves minimizing coupling to a dissipative bath. Paradoxically, it is possible to instead engineer specific couplings to a quantum environment that allow dissipation to actually preserve coherence. I will discuss our recent demonstration of quantum bath engineering for a superconducting qubit coupled to a microwave cavity. By tailoring the spectrum of microwave photon shot noise in the cavity, we create a dissipative environment that autonomously relaxes the qubit to an arbitrarily specified coherent superposition of the ground and excited states. In the presence of background thermal excitations, this mechanism increases the state purity and effectively cools the dressed atom state to a low temperature. We envision that future multi-qubit implementations could enable the preparation of entangled many-body states suitable for quantum simulation and computation. This work was supported by the IARPA CSQ program.
Ruggenthaler, Michael; Flick, Johannes; Pellegrini, Camilla; Appel, Heiko; Tokatly, Ilya V.; Rubio, Angel
2014-07-01
In this work, we give a comprehensive derivation of an exact and numerically feasible method to perform ab initio calculations of quantum particles interacting with a quantized electromagnetic field. We present a hierarchy of density-functional-type theories that describe the interaction of charged particles with photons and introduce the appropriate Kohn-Sham schemes. We show how the evolution of a system described by quantum electrodynamics in Coulomb gauge is uniquely determined by its initial state and two reduced quantities. These two fundamental observables, the polarization of the Dirac field and the vector potential of the photon field, can be calculated by solving two coupled, nonlinear evolution equations without the need to explicitly determine the (numerically infeasible) many-body wave function of the coupled quantum system. To find reliable approximations to the implicit functionals, we present the appropriate Kohn-Sham construction. In the nonrelativistic limit, this density-functional-type theory of quantum electrodynamics reduces to the density-functional reformulation of the Pauli-Fierz Hamiltonian, which is based on the current density of the electrons and the vector potential of the photon field. By making further approximations, e.g., restricting the allowed modes of the photon field, we derive further density-functional-type theories of coupled matter-photon systems for the corresponding approximate Hamiltonians. In the limit of only two sites and one mode we deduce the appropriate effective theory for the two-site Hubbard model coupled to one photonic mode. This model system is used to illustrate the basic ideas of a density-functional reformulation in great detail and we present the exact Kohn-Sham potentials for our coupled matter-photon model system.
Cavity mode entanglement in relativistic quantum information
Friis, Nicolai
2013-01-01
A central aim of relativistic quantum information (RQI) is the investigation of quantum information tasks and resources taking into account the relativistic aspects of nature. More precisely, it is of fundamental interest to understand how the storage, manipulation, and transmission of information utilizing quantum systems are influenced by the fact that these processes take place in a relativistic spacetime. In particular, many studies in RQI have been focused on the effects of non-uniform motion on entanglement, the main resource of quantum information protocols. Early investigations in this direction were performed in highly idealized settings that prompted questions as to the practical accessibility of these results. To overcome these limitations it is necessary to consider quantum systems that are in principle accessible to localized observers. In this thesis we present such a model, the rigid relativistic cavity, and its extensions, focusing on the effects of motion on entanglement and applications such...
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.
Mode expansions in the quantum electrodynamics of photonic media with disorder
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...
Cavity-induced quantum cooperative phenomena
Plastina, F.; Falcone, G.; Francica, F.; Liberti, G.; Piperno, F.; Maniscalco, S.
2010-09-01
Two kinds of cooperative effects are discussed for two-level atoms (qubits) interacting with an electromagnetic resonator, both of them concerning Dicke super-radiance. The first is a static, critical phenomenon: the so-called super-radiant phase transition, occurring when a large number of qubits are coupled to a single cavity mode giving rise to a quantum phase transition for a critical value of the interaction strength. The second is a dynamic phenomenon, producing (among other effects) the generation and/or preservation of entanglement between qubits even in the presence of cavity losses.
Cavity-induced quantum cooperative phenomena
Two kinds of cooperative effects are discussed for two-level atoms (qubits) interacting with an electromagnetic resonator, both of them concerning Dicke super-radiance. The first is a static, critical phenomenon: the so-called super-radiant phase transition, occurring when a large number of qubits are coupled to a single cavity mode giving rise to a quantum phase transition for a critical value of the interaction strength. The second is a dynamic phenomenon, producing (among other effects) the generation and/or preservation of entanglement between qubits even in the presence of cavity losses.
Quantum noise in rectangular cavities
In this paper the authors calculate the energy spectrum of vacuum fluctuations for a massless scalar field which satisfies boundary conditions inside a wave guide or a rectangular box. The spectrum is piecewise continuous in the first case and discrete in the second, and exhibits resonances which correspond, as expected, to the energy levels of a particle in a box (with the difference that all these levels are occupied). Since it is known that these fluctuations exhibit a very slow convergence to a Poisson distribution, we conjecture that a realistic detector must find severe quantum vacuum deviations from white noise, except in the non-realistic limit of extremely high frequencies
Quantum noise in rectangular cavities
Villarreal, C.; Jauregui, R.; Hacyan, S.; Cocho, G. (Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Fisica)
1992-10-10
In this paper the authors calculate the energy spectrum of vacuum fluctuations for a massless scalar field which satisfies boundary conditions inside a wave guide or a rectangular box. The spectrum is piecewise continuous in the first case and discrete in the second, and exhibits resonances which correspond, as expected, to the energy levels of a particle in a box (with the difference that all these levels are occupied). Since it is known that these fluctuations exhibit a very slow convergence to a Poisson distribution, we conjecture that a realistic detector must find severe quantum vacuum deviations from white noise, except in the non-realistic limit of extremely high frequencies.
Cavity quantum electrodynamics with three-dimensional photonic bandgap crystals
Vos, W.L.; Woldering, L.A.; Ghulinyan, M.; Pavesi, L.
2015-01-01
This paper is Chapter 8 of the book "Light Localisation and Lasing: Random and Pseudorandom Photonic Structures", edited by Mher Ghulinyan and Lorenzo Pavesi (Cambridge University Press, Cambridge, 2015). It provides an overview of much recent work on 3D photonic crystals with a complete photonic b
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. PMID:27420523
On Galilean invariance and nonlinearity in electrodynamics and quantum mechanics
Goldin, Gerald A.; Shtelen, Vladimir M.
2001-02-01
Recent experimental results such as those on slow light heighten interest in nonlinear Maxwell theories. We obtain Galilei covariant equations for electromagnetism by allowing special nonlinearities in the constitutive equations only, keeping Maxwell's equations unchanged. Combining these with linear or nonlinear Schrödinger equations, e.g., as proposed by Doebner and Goldin, yields a consistent, nonlinear, Galilean Schrödinger-Maxwell electrodynamics.
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...
High brightness angled cavity quantum cascade lasers
A quantum cascade laser (QCL) with an output power of 203 W is demonstrated in pulsed mode at 283 K with an angled cavity. The device has a ridge width of 300 μm, a cavity length of 5.8 mm, and a tilt angle of 12°. The back facet is high reflection coated, and the front facet is anti-reflection coated. The emitting wavelength is around 4.8 μm. In distinct contrast to a straight cavity broad area QCL, the lateral far field is single lobed with a divergence angle of only 3°. An ultrahigh brightness value of 156 MW cm−2 sr−1 is obtained, which marks the brightest QCL to date
High brightness angled cavity quantum cascade lasers
Heydari, D.; Bai, Y.; Bandyopadhyay, N.; Slivken, S.; Razeghi, M., E-mail: razeghi@eecs.northwestern.edu [Center for Quantum Devices, Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, Illinois 60208 (United States)
2015-03-02
A quantum cascade laser (QCL) with an output power of 203 W is demonstrated in pulsed mode at 283 K with an angled cavity. The device has a ridge width of 300 μm, a cavity length of 5.8 mm, and a tilt angle of 12°. The back facet is high reflection coated, and the front facet is anti-reflection coated. The emitting wavelength is around 4.8 μm. In distinct contrast to a straight cavity broad area QCL, the lateral far field is single lobed with a divergence angle of only 3°. An ultrahigh brightness value of 156 MW cm{sup −2 }sr{sup −1} is obtained, which marks the brightest QCL to date.
Inflationary universe from higher derivative quantum gravity coupled with scalar electrodynamics
Myrzakulov, Ratbay; Sebastiani, Lorenzo
2016-01-01
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.