Quantization Of Electromagnetic Field Research Articles

Electromagnetic field quantization and input–output relation for anisotropic magnetodielectric metamaterial**Project supported by the National Natural Science Foundation of China (Grant No. 11104071).

A phenomenological quantization of electromagnetic field is introduced in the presence of the anisotropic magnetodielectric metamaterial. For a single layer structure with the anisotropic metamaterial, input–output relations of quantized radiation are derived using the Green-function approach. Based on these relations, the reflectance of the linearly polarized wave through this structure is calculated. The results show that different resonant peaks of reflectance appear for different polarized waves and indicate the use of the anisotropic metamaterial as a reflector for a certain polarized wave. Furthermore it is found that such a structure can realize the resonant gap with the increase of the thickness. Finally the effects of the absorption are considered and we find that the above properties do not change with the introduction of the absorption.

Experimental violation of bell-like inequalities by electronic shot noise.

We report measurements of the correlations between electromagnetic field quadratures at two frequencies f1=7 GHz and f1=7.5 GHz of the radiation emitted by a tunnel junction placed at very low temperature and excited at frequency f1+f2. We demonstrate the existence of two-mode squeezing and violation of a Bell-like inequality, thereby proving the existence of entanglement in the quantum shot noise radiated by the tunnel junction.

Canonical quantization of electromagnetic field in the presence of absorbing bi-anisotropic multilayer magnetodielectric media

A bi-anisotropic magnetodielectric medium is modeled by two independent set of three dimensional harmonic oscillators .A fully canonical quantization of electromagnetic field is demonstrated in the presence of a bi-anisotropic magnetodielectric medium. The electric and magnetic polarization fields of the medium are obtained in terms of the dynamical variable modeling the medium. The Heisenberg equations of the system are solved for a multilayer bi-anisotropic magnetodielectric medium.

Unusual Properties of Anisotropic Magnetodielectric Metamaterials

A phenomenological quantization of electromagnetic field is introduced in the presence of the anisotropic magnetodielectric metamaterials. For a single layer structure with the anisotropic metamaterials, input-output relations are derived using the Green-function approach. Based on these relations, the reflectance of the linearly polarized wave through this structure is calculated. The results show different reflectance for different polarized waves and indicate an application of the anisotropic metamaterials to be the reflectors for certain polarized wave. Furthermore it is found that such a structure can realize the resonant gap with the increase of the thickness. Finally the effects of the absorption are considered and we find that the above properties do not change with introduction of the absorption.

Cauchy-Schwarz inequality and particle entanglement

The Glauber-Sudarshan $P$-representation is used in quantum optics to distinguish between semi-classical and genuinely quantum electromagnetic fields. We employ the analog of the $P$-representation to show that the violation of the Cauchy-Schwarz inequality for the second-order correlation function is a proof of entanglement between identical massive bosons. The presented derivation is valid both in systems with fixed and fluctuating number of particles. Thanks to the recent advances in techniques of detecting positions of separate particles, the violation of the Cauchy-Schwarz inequality can be used as a simple entanglement criterion in various many-body quantum systems.

Quantum Brownian motion near a point-like reflecting boundary

The Brownian motion of a test particle interacting with a quantum scalar field in the presence of a perfectly reflecting boundary is studied in (1 + 1)-dimensional flat spacetime. Particularly, the expressions for dispersions in velocity and position of the particle are explicitly derived and their behaviors examined. The results are similar to those corresponding to an electric charge interacting with a quantum electromagnetic field near a reflecting plane boundary, mainly regarding the divergent behavior of the dispersions at the origin (where the boundary is placed), and at the time interval corresponding to a round trip of a light pulse between the particle and the boundary. We close by addressing some effects of allowing the position of the particle to fluctuate.

The C*-algebra of the electromagnetic field

We show that there is a unique C*-algebra for the transverse quantum electromagnetic field obeying the Maxwell equations with any classical charge-current. For nonzero charge, the representation of the C*-algebra differs from the representation with zero charge.

Enhanced resonant force between two entangled identical atoms in a photonic crystal

We consider the resonant interaction energy and force between two identical atoms, one in an excited state and the other in the ground state, placed inside a photonic crystal. The atoms, having the same orientation of their dipole moment, are supposed prepared in their symmetrical state and interact with the quantum electromagnetic field. We consider two specific models of photonic crystals: a one-dimensional model and an isotropic model. We show that in both cases the resonant interatomic force can be strongly enhanced by the presence of the photonic crystal, as a consequence of the modified dispersion relation and density of states, in particular if the transition frequency of the atoms is close to the edge of a photonic gap. Differences between the two models considered of photonic crystal are discussed in detail, as well as comparison with the analogous system of two impurity atoms in a quantum semiconductor wire. A numerical estimate of the effect in a realistic situation is also discussed.

Justification of the single-mode approximation for a finite-duration laser pulse interacting with an electron

The interaction Hamiltonian of an electron and a quasi-monochromatic pulse of a strong quantized electromagnetic field is examined. Canonical transformations of the field variables are found that allow the division of the system's Hamiltonian into two parts. The first one describes the interaction between an electron and a single collective mode of the field. The properties of this mode are defined by the superposition of the modes corresponding to the pulse wave packet. The second part describes the field fluctuations relatively to the collective mode. The field intensity, pulse duration and transversal spread are estimated for which a single-mode approximation can be used for the system's description.

Electromagnetic field quantization in the presence of a rotating body

Starting from a Lagrangian, the electromagnetic field is quantized in the presence of a body rotating along its axis of symmetry. Response functions and fluctuation-dissipation relations are obtained. A general formula for rotational friction and power radiated by a rotating dielectric body is obtained in terms of the dyadic Green's tensor. The Hamiltonian is determined and possible generalizations are discussed. As an example, the rotational friction and power radiated by a spherical dielectric in the vicinity of a semi-infinite dielectric plane is obtained and discussed in some limiting cases.

Dynamical Casimir-Polder interaction between an atom and surface plasmons

We investigate the time-dependent Casimir-Polder potential of a polarizable two-level atom placed near a surface of arbitrary material, after a sudden change in the parameters of the system. Different initial conditions are taken into account. For an initially bare ground-state atom, the time-dependent Casimir-Polder energy reveals how the atom is "being dressed" by virtual, matter-assisted photons. We also study the transient behavior of the Casimir-Polder interaction between the atom and the surface starting from a partially dressed state, after an externally induced change in the atomic level structure or transition dipoles. The Heisenberg equations are solved through an iterative technique for both atomic and field operators in the medium-assisted electromagnetic field quantization scheme. We analyze in particular how the time evolution of the interaction energy depends on the optical properties of the surface, in particular on the dispersion relationof surface plasmon polaritons. The physical significance and the limits of validity of the obtained results are discussed in detail.

Entanglement between qubits due to the atomic coherence

We have investigated the influence of dipole-dipole interaction and initial atomic coherence on the dynamics of two-qubit entanglement. We have considered a model, in which only one atom couples to a quantum electromagnetic field in a finite-Q cavity, since one of them can freely move outside the cavity. We have shown the possibility of disappearance of the entanglement sudden death effect and stabilization of atomic entanglement in the presence of the dipole interaction of qubits.

An exactly solvable model for quantum communications

Information theory establishes the ultimate limits on performance for noisy communication systems. Accurate models of physical communication devices must include quantum effects, but these typically make the theory intractable. As a result, communication capacities--the maximum possible rates of data transmission--are not known, even for transmission between two users connected by an electromagnetic waveguide with Gaussian noise. Here we present an exactly solvable model of communication with a fully quantum electromagnetic field. This gives explicit expressions for all point-to-point capacities of noisy quantum channels, with implications for quantum key distribution and fibre-optic communications. We also develop a theory of quantum communication networks by solving some rudimentary models including broadcast and multiple-access channels. We compare the predictions of our model with the orthodox Gaussian model and in all cases find agreement to within a few bits. At high signal-to-noise ratios, our simple model captures the relevant physics while remaining amenable to exact solution.

Noise spectrum of charge current in a quantum dot system under the irradiation of quantum electromagnetic field

Abstract We have investigated the noise spectrum of a quantum dot (QD) coupled to two normal metal leads under the perturbation of a quantum electromagnetic field (QEMF) by nonequilibrium Greenʼs function method. Current correlation function is determined through making the ensemble average over the lowest SU ( 1 , 1 ) coherent state. The fluctuation of QEMF makes important contribution to the noise by imposing an additional term, and quantum feature of the QEMF is transferred to the shot noise. The total noise of our system is composed of three parts: the thermal noise, the quantum field noise, and the shot noise. The quantum field noise is generated from the QEMF, and it dominates the total noise. The shot noise and quantum field noise belong to different types, and they display quite differently. The stair-like and photon-assisted behaviors are obviously exhibited. The enhancement and suppression of noise can be controlled by adjusting the parameters according to its behaviors.

High-temperature Bose-Einstein condensation of photonlike atom-light polaritons

We propose a method for obtaining a Bose-Einstein condensate of an ideal one-dimensional gas of atom-light polaritons of the lower branch in a trap at high temperatures (on the order of room temperature or higher). The system under consideration is an atomic ensemble that interacts with a single-mode quantum electromagnetic field in the presence of optical collisions with a high-pressure buffer gas. The possibility of using biconical waveguides for revealing the predicted phenomenon is discussed. The dynamics of the polariton condensate in the trap is investigated on the basis of the variational approach.

Electromagnetically induced interference in a superconducting flux qubit

Interaction between quantum two-level systems (qubits) and electromagnetic fields can provide additional coupling channels to qubit states. In particular, the interwell relaxation or Rabi oscillations, resulting, respectively, from the multi- or single-mode interaction, can produce effective crossovers, leading to electromagnetically induced interference in microwave driven qubits. The environment is modeled by a multimode thermal bath, generating the interwell relaxation. Relaxation induced interference, independent of the tunnel coupling, provides deeper understanding to the interaction between the qubits and their environment. It also supplies a useful tool to characterize the relaxation strength as well as the characteristic frequency of the bath. In addition, we demonstrate the relaxation can generate population inversion in a strongly driving two-level system. On the other hand, different from Rabi oscillations, Rabi-oscillation-induced interference involves more complicated and modulated photon exchange thus offers an alternative means to manipulate the qubit, with more controllable parameters including the strength and position of the tunnel coupling. It also provides a testing ground for exploring nonlinear quantum phenomena and quantum state manipulation in qubits either with or without crossover structure.

Ionization and stabilization of an atom in a quantum electromagnetic field

The dynamics of a model atomic system interacting with a quantum electromagnetic field has been investigated. The effect of statistics and average number of photons in a quantum state of the field on the ionization and stabilization of the atomic subsystem has been studied. The formation of a state with the maximum entanglement between the atomic and field subsystems in the case of interaction with a single-photon field has been demonstrated.

Relativistic diffusive motion in thermal electromagnetic fields

We discuss relativistic dynamics in a random electromagnetic field which can be considered as a high temperature limit of the quantum electromagnetic field in a heat bath (cavity) moving with a uniform velocity w. We derive a diffusion approximation for the particle’s dynamics generalizing the diffusion of Schay and Dudley. It is shown that the Jüttner distribution is the equilibrium state of the diffusion.

Quantum bit encoding and information processing with field superposition states in a circuit

Solid-state superconducting devices coupled to coplanar transmission lines offer an exquisite architecture for quantum optical phenomena probing as well as for quantum computation implementation, which is the object of intense theoretical and experimental investigation lately. Under appropriate conditions, the transmission line radiation modes can become strongly coupled to a superconducting device with only two levels—for that reason called an artificial atom or qubit. Employing this system, we propose a two-quantum bit gate encoding, involving quantum electromagnetic field qubit states prepared in a coplanar transmission line capacitively coupled to a single charge qubit. Since dissipative effects are more drastic in the solid-state qubit than in the field one, it can be employed for the storage of information, whose efficiency against the action of an ohmic bath shows that this encoding can be readily implemented with present-day technology. We extend the investigation to generate entanglement between several solid-state qubits and the field qubit through the action of external classical magnetic pulses.

Steady-state correlations of two atoms interacting with a reservoir

We consider two two-level atoms fixed at different positions, driven by a resonant monochromatic laser field, and interacting collectively with the quantum electromagnetic field. A Born-Markov-secular master equation is used to describe the dynamics of the two atoms and the steady-state is obtained analytically for a configuration of the atoms. The steady-state populations of the energy levels of the free atoms, entanglement, quantum and geometric discords and degree of mixedness are calculated analytically as a function of the laser field intensity and the distance between the two atoms. It is found that there is a possibility of considerable steady-state entanglement and left/right quantum discord and that these can be controlled either by increasing/decreasing the intensity of the laser field or by increasing/decreasing the distance between atoms. It is shown that the system of two atoms can be prepared in a separable mixed state with non-zero quantum discord that turns into an $X$-state for high laser field intensities. The behavior and relationships between the different correlations are studied and several limiting cases are investigated.