Dynamic properties of atomic collective decay in cavity quantum electrodynamics

We theoretically study the collective decay of two atoms trapped in a single mode cavity and we describe the evolution of the population of Dicke states. We show that the collective decay property is strongly dependent on the phase of atomic radiation and the speeding up of collective decay can only be observed in a bad cavity regime. For in-or out-phase case,this occurs due to the quantum interference enhancement, no matter which atom is excited initially. For π/2 phase, the speeding up of collective decay takes place if the first atom is excited at the beginning. However, it disappears due to the quantum interference cancellation if the second atom is excited. Compared with the in-phase and out-phase cases,we also show that the speeding up of collective decay can be significantly enhanced in strong coupling regime for π/2 phase, although one atom is decoupled to the cavity in this condition. The study presented here is helpful to understand the physical mechanism of collective decay in cavity quantum electrodynamics and it provides a useful method to control the collective decay phenomenon via quantum interference effect.

Three-qubit Fredkin gate based on cavity quantum electrodynamics

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.

A scheme for two-photon lasing with two coupled flux qubits in circuit quantum electrodynamics

We theoretically study the system of a superconducting transmission line resonator coupled to two interacting super- conducting flux qubits. It is shown that under certain conditions the resonator mode can be tuned to two-photon resonance between the ground state and the highest excited state while the middle excited states are far-off resonance. Furthermore, we study the steady-state properties of the flux qubits and resonator, such as the photon statistics, the spectrum and squeezing of the resonator, and demonstrate that two-photon laser can be implemented with current experimental technology.

Generalized variational principles for boundary value problem of electromagnetic field in electrodynamics

An expression of the generalized principle of virtual work for the boundary value problem of the linear and anisotropic electromagnetic field is given. Using Chien＇s method, a pair of generalized variational principles （GVPs） are established, which directly leads to all four Maxwell＇s equations, two intensity-potential equations, two constitutive equations, and eight boundary conditions. A family of constrained variational principles is derived sequentially. As additional verifications, two degenerated forms are obtained, equivalent to two known variational principles. Two modified GVPs are given to provide the hybrid finite element models for the present problem.

Effects of Interaction Between Gravitation and Nonlinear Electrodynamics On Scalar Field Evolution

In this paper we investigate the scalar field evolution in the dyadosphere spacetime by using the third-order WKB approximation. We find that the coupling term between the gravitation and the nonlinear electrodynamics makes the scalar field decay more quickly and it also makes the scalar field oscillate more slowly. On the o＇ther words, this coupling term takes effect on the scalar field evolution as a damping factor. At the same time these effects become more obvious for the scalar field with higher angle quantum number.

Circuit quantum electrodynamics with a quadruple quantum dot

In this theoretical work,we describe a mechanism for the coupling between a plane structure consisting of four quantum dots and a resonator.We systematically study the dependence of the quadruple coupling strength and the qubit decoherence rate and point out the optimized operating position of the hybrid system.According to the transmission given by the input-output theory,the signatures in the resonator spectrum are predicted.Furthermore,based on the parameters already achieved in previous works,we prove that the device described in this paper can achieve the strong coupling limit,i.e.,this approach can be used for system extension under the existing technical conditions.Our results show an effective and promotable approach to couple quantum dot structures in plane with the resonator and propose a meaningful extension method.

Quantum electrodynamics in a laser and the electron laser collision

Quantum electrodynamics in a laser is formulated, in which the electron–laser interaction is exactly considered, while the interaction of an electron and a single photon is considered by perturbation. The formulation is applied to the electron– laser collisions. The effect of coherence between photons in the laser is therefore fully considered in these collisions. The possibility of γ-ray laser generation by use of this kind of collision is discussed.

Anomalously Strong Scattering of Spontaneously Produced Laser Radiation in the First Free-Electron Laser and Study of Free-Electron Two-Quantum Stark Lasing in an Electric Wiggler with Quantum-Wiggler Electrodynamics

We calculate the scattering cross section of an electron with respect to the spontaneously produced laser radiation in the first free-electron laser （FEL） with quantum-wiggler electrodynamics （QWD）. The cross section is 1016 times the Thomson cross section, confirming the result obtained by a previous analysis of the experimental data. A QWD calculation show that spontaneous emission in an FEL using only an electric wiggler can be very strong while amplification through net stimulated emission is practically negligible.

Revised Quantum Electrodynamics in a Condensed Form

This theory aims beyond the possibilities being available from the Standard Model. Examples are given by the directly obtained rest masses of the elementary particles, the deduced values of the elementary charge and of the mass of the boson detected by CERN which are close to their experimental data, and by an incorporated spin of the photon.

Scheme for implementing perfect quantum teleportation with four-qubit entangled states 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 ｜Ω/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.

One-step generation of qutrit entanglement via adiabatic passage in cavity quantum electrodynamics

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.

The mechanism of producing energy-polarization entangled photon pairs in the cavity-quantum electrodynamics scheme

We investigate theoretically two photon entanglement processes in a photonic-crystal cavity embedding a quantum dot in tile 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 tile system is analysed by employing the Born Markov master equation, through which the spectra for the system are computed as a fnnction of various parameters. By means of this analysis the photon-reabsorption process in the strong- coupling regime is first observed and analysed from the perspective of radiation spectrum and the optimal parameters for observing energy-entangled photon pairs are identified.

Nonlinear electrodynamics coupled to teleparallel theory of gravity

Using nonlinear electrodynamics coupled to teleparallel theory of gravity, regular charged spherically symmetric solutions are obtained. The nonlinear theory is reduced to the Maxwell one in the weak limit and the solutions correspond to charged spacetimes. One of the obtained solutions contains an arbitrary function which we call general solution since we can generate from it the other solutions. The metric associated with these spacetimes is the same, i.e., regular charged static spherically symmetric black hole. In calculating the energy content of the general solution using the gravitational energy momentum within the framework of the teleparallel geometry, we find that the resulting form depends on the arbitrary function. Using the regularized expression of the gravitational energy-momentum we obtain the value of energy.

Controllable cross-Kerr interaction between microwave photons in circuit quantum electrodynamics

We propose a scheme to enable a controllable cross-Kerr interaction between microwave photons in a circuit quantum electrodynamics （QED） system. In this scheme we use two transmission-line resonators （TLRs） and one superconducting quantum interference device （SQUID） type charge qubit, which acts as an artificial atom. It is shown that in the dispersive regime of the eircuit-QED system, a controllable cross-Kerr interaction can be obtained by properly preparing the initial state of the qubit, and a large cross-phase shift between two microwave fields in the two TLRs can then be reached. Based on this cross-Kerr interaction, we show how to create a macroscopic entangled state between the two TLRs.

Two simple schemes for implementing Toffoli gate via atom-cavity field interaction in cavity quantum electrodynamics

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.

Applications of Galilei Covariant Electrodynamics to VacuumSubstratum Phenomena in Absolute Space and Time

The Galilei covariant generalizations of the EM field equations (1984) (including moving media), Schroedinger, and Dirac (1985, 1993) equations for inertial frames S(w) with substratum velocity w are re- viewed. By G-covariant electrodynamics, physical variables, e.g., rod length, clock rate, particle mass, momentum, and energy are G-invariants, determined by the object velocity v-w= vo=G-inv relative to the substratum frame, So(w=0) [v=object velocity relative to observer in S(w)] Galilean measurements using standard (i) contracted rods and (ii) retarded clocks, anisotropic light propagation, and conservation of EM energy and momentum in IFs S(w) are discussed. Fundamental experiments are formulated which permit measurement of substratum (w) induced EM and charge fields, the substratum velocity w, and verification of the G-invariance of the magnetic field, B= Bo=G-inv. The G-invariant Lagrangian and Hamiltonian of a charged particle in EM fields, and the momentum and energy conservation equations in Particle collisions are given for velocities |v-w|<co. The EM Doppler effects for moving source or moving observer are shown to exhibit measurable substratum effects. The spectral lines from a recoiling atom exhibit superimposed Doppler and substratum (w) shifts. The measurable substratum effects in the (i) aberration of light and (ii) reflection of light from a moving mirror are evaluated. The EM fields of accelerated charges in the substratum flow w are given, and applied to the anisotropic emission of x-rays in IFs S(w). G-covariant electrodynamics is examined for subluminal and superluminal electron velocities. Both the Cerenkov effect in (i) dielectrics for Iv--wl> c(ro) and (ii) vacuum for |v-w| > co are relative to the substratum So, and demonstrate the anisotropy of the vacuum in IFs S(w). G-covariant electrodynamics (relative to substratum) contains Lorentz covariant electrodynamics (relative to observer) in the special case w = 0 (So).

Impacts of Revised Quantum Electrodynamics on Fundamental Physics

A revised quantum electrodynamic theory by the author is reconsidered, in respect to the basic concepts established by M. Planck and H.B.G. Casimir on the Zero Point Energy (ZPE) and by A. Einstein on Special Relativity. Attention is given to the new properties of its field equations and their applications. These equations include results not being available from conventional theory and the Standard Model. This concerns the internal structure of elementary particles, such as the photon, the electron, muon and tauon, the Z boson, and the so called Higgs particle detected in the experiments at the laboratory of CERN. A possible unification of electrodynamics and the strong nuclear force is further provided by the theory. Finally, there are aspects on the expanding universe represented by a new interpretation of dark matter and dark energy in terms of the ZPE.

Principle of Scalar Electrodynamics Phenomena Proof and Theoretical Research

There exist a lot of controversial issues around the subject of SW(Scalar Waves)and the purpose of this white paper is to take an innovative theoretical approach to prove and backup up existence of such phenomena.We basically define this wave as a SLW(Scalar Longitudinal Wave),whose existence derives from the MCE(More Complete Electrodynamic)theory aspect of Maxwell’s classical electrodynamic equations.MCE falls into the QED(Quantum Electrodynamic)aspect of the Maxwell’s equations,in particular out of his four famous classical equations,our interest focuses on the one that is known to us as Faraday’s Law of the Maxwell’s Equation set.

Thermal properties of regular black hole with electric charge in Einstein gravity coupled to nonlinear electrodynamics

We propose a regular spherically symmetric spacetime solution with three parameters in Einstein gravity coupled to nonlinear electrodynamics(NED), which describes the NED black hole with electric charge. It is found that the system enclosed by the horizon of NED spacetime satisfies the first law of thermodynamics. In order to obtain the NED spacetime with only electric charge, the case of two parameters taking the same value is considered. In this case, we express the mass of the NED spacetime as a function of the entropy and electric charge of the NED black hole, give the Smarr-like formula and the approximate Smarr formula for the mass of NED spacetime.

The Universal Expression for the Amplitude Square in Quantum Electrodynamics

The universal expression for the amplitude square ?for any matrix of interaction M is derived. It has obvious covariant form. It allows the avoidance of calculation of products of the Dirac’s matrices traces and allows easy calculation of cross-sections of any different processes with polarized and unpolarized particles.