A Bound on Binding Energies and Mass Renormalization in Models of Quantum Electrodynamics

We study three models of matter coupled to the ultraviolet cutoff, quantized radiation field and to the Coulomb potential of arbitrarily many nuclei. Two are nonrelativistic: the first uses the kinetic energy (p+eA(x))² and the second uses the Pauli–Fierz energy (p+eA(x))²+eB(x). The third, no-pair model, is relativistic and replaces the kinetic energy with the Dirac operator D(A), but restricted to its positive spectral subspace, which is the electron subspace. In each case we are able to give an upper bound to the binding energy–as distinct from the less difficult ground state energy. This implies, for the first time we believe, an estimate, albeit a crude one, of the mass renormalization in these theories.     

Photon Decays in the Radiation-Dominated Universe: Scalar Electrodynamics

The effect of the creation of an arbitrary number of massive pairs by a photon in the spatially flat model of the radiation-dominated Universe is considered. The process added-up probability is calculated within the framework of scalar quantum electrodynamics conformally related to the metric of a curved spacetime. The rate of photon decay in the radiation-dominated universe as well as the mean number of the created particles have been found. Comparison of the rate of the pair creation in the photon decays with the rate of the pair creation in the photon-photon collisions which take place in the Minkowski spacetime has been carried out. The estimates having been made show the number density of the particles created in the processes of the photon decays in the radiation-dominated Universe to be by a factor of 10³⁰ higher than the number density of the particles created from the vacuum of the free scalar field by the gravitational background.     

Off-Shell Propagat ion in a Quark-Gluon Plasma

The off-shell propagation in a quark-gluon plasma is estimated from a quantum transport model beyond the quasi-particle approach. While our ansatz is crude concerning the properties of real quarks and gluons, it nevertheless takes very serious the basic principles of quantum field theory for non-equilibrium states.     

Neutron Star Magnetic Field as for Nonzero Photon Mass

We investigate the neutron star magnetic field by the relative mean-field theory, where the photon effective mass depending on baryon density of charged particles is nonzero. This field is produced by star itself, which is the function of baryon density. The result fits the observations.     

Higher-Order Nonclassicality in Photon Added and Subtracted Qudit States

Higher-order nonclassical properties of r photon added and t photon subtracted qudit states (referred to as rPAQS and tPSQS, respectively) are investigated here to answer: How addition and subtraction of photon can be used to engineer higher-order nonclassical properties of qudit states? To obtain the answer, higher-order moment of relevant bosonic field operators is first obtained and subsequently used to study the higher-order nonclassical properties (e.g., higher-order antibunching, higher-order squeezing, and higher-order sub-Poissonian photon statistics) of the corresponding states. These witnesses establish that rPAQS and tPSQS are highly nonclassical. To quantitatively establish this observation and to make a comparison between rPAQS and tPSQS, volumes of the negative part of Wigner function are computed. Finally, for the sake of verifiability of the obtained results, optical tomograms are also reported. Throughout the study, a particular type of qudit state named as a new generalized binomial state is used as an example.     

Correspondence Between Oscillations and Emitted Photon Closed-Orbits in Spontaneous Emission Rate of an Atom Near a Dielectric Slab

We study the oscillations in the spontaneous emission rate of an atom near a dielectric slab. The emission rate is calculated as a function of system size using quantum electrodynamics. It exhibits multi-periodic oscillations. Four frequencies of the oscillations are extracted by Fourier transforms. They agree with actions of photon closed-orbits going away and returning to the atom. These oscillations are explained as manifestations of quantum interference effects between the emitted photon wave near the atom and the returning photon waves travelling along various closed-orbits.     

High-Fidelity and Low-Cost Hyperparallel Quantum Gates for Photon Systems via Λ-Type Systems

Quantum gates designed with minimized resources overhead have a crucial role in quantum information processing. Here, based on the degrees of freedom (DoFs) of photons and Λ-type atom systems, two high-fidelity and low-cost protocols are presented for realizing polarization-spatial hyperparallel controlled-not (CNOT) and Toffoli gates on photon systems with only two and four two-qubit polarization–polarization swap (P-P-SWAP) gates in each DoF, respectively. Moreover, the quantum gates can be extended feasibly to construct 2m-target-qubit hyperparallel CNOT and 2n-control-qubit Toffoli gates required only 4m and 4n P-P-SWAP gates on $(m+1)$- and $(n+1)$-photon systems, respectively, which dramatically lower the costs and bridge the divide between the theoretical lower bounds and the current optimal syntheses for the photonic quantum computing. Further, the unique auxiliary atom of these quantum gates can be regarded as a temporary quantum memory that requires no initialization and measurement, and is reused within the coherence time, as the state of the atom remains unchanged after the hyperparallel quantum computing.     

Bound States in Quantum Electrodynamics: Theory and Application

The basic methods that have been used for describing bound-state quantum electrodynamics are described and critically discussed. These include the external field approximation, the quasi-potential approaches, the effective potential approach, the Bethe–Salpeter method, and the three-dimensional equations of Lepage and other workers. Other methods less frequently used but of some intrinsic interest such as applications of the Duffin–Kemmer equation are also described. A comparison of the strengths and shortcomings of these various approaches is included.     

Inertial Mass and Vacuum Fluctuations in Quantum Field Theory

Motivated by recent works on the origin of inertial mass, we revisit the relationship between the mass of charged particles and zero-point electromagnetic fields. To this end we first introduce a simple model comprising a scalar field coupled to stochastic or thermal electromagnetic fields. Then we check if it is possible to start from a zero bare mass in the renormalization process and express the finite physical mass in terms of a cut-off. In scalar QED this is indeed possible, except for the problem that all conceivable cut-offs correspond to very large masses. For spin-1/2 particles (QED with fermions) the relation between bare mass and renormalized mass is compatible with the observed electron mass and with a finite cut-off, but only if the bare mass is not zero; for any value of the cut-off the radiative correction is very small.     

Anti-Gravity Effects in the Sachs Theory of Electrodynamics

It is demonstrated to a first approximation that anti-gravity effects can occur in the most general theory of electromagnetism, developed by Sachs [1] from the irreducible representations of the Einstein group.     

Further Support of the Reliability of the Limit on Photon Mass Given by the Rotating Torsion Balance Experiment

We consider there is a vacancy in the plasma in the solar system,and calculate the vector potential produced by the magnetic field frozen in the plasma.The result shows that,in the vacancy,the vector potential produced by the magnetic field frozen in the plasma is much less than the large scale cosmic vector potential.This means if our earth is in such a vacancy,the total vector potential on the surface of the earth is dominated by the cosmic magnetic vector potential,which gives a further support of the reliability of the limit on photon mass given by rotating torsion balance experiment [Phys.Rev.Lett.90(2003) 081801].     

Dynamics of Particles Around a Regular Black Hole with Nonlinear Electrodynamics

We investigate the dynamics of a charged particle being kicked off from its circular orbit around a regular black hole by an incoming massive particle in the presence of magnetic field. The resulting escape velocity, escape energy and the effective potential are analyzed. It is shown that the presence of even a very weak magnetic field helps the charged particles in escaping the gravitational field of the black hole. Moreover the effective force acting on the particle visibly reduces with distance. Thus particle near the black hole will experience higher effective force as compared to when it is far away.     

Further Support of the Reliability of the Limit on Photon Mass Given by the Rotating Torsion Balance Experiment

We consider there is a vacancy in the plasma in the solar system, and calculate the vector potential produced by the magnetic field frozen in the plasma. The result shows that, in the vacancy, the vector potential produced by the magnetic field frozen in the plasma is much less than the large scale cosmic vector potential. This means if our earth is in such a vacancy, the total vector potential on the surface of the earth is dominated by the cosmic magnetic vector potential, which gives a further support of the reliability of the limit on photon mass given by rotating torsion balance experiment [Phys. Rev. Lett. 90 (2003) 081801].     

Electric Black Holes in a Model of Nonlinear Electrodynamics

The electric counterpart of the magnetic black hole solution found in nonlinear electrodynamics (NED) is presented. The electric field emerges regular and confined whereas the spacetime which satisfies all the energy conditions is singular. Our result is in conformation with a theorem proved before about the existence of regular electric black holes. The thermal properties of the black hole including the first law, Smarr's formula, and the thermal stability are investigated. This provides a chance to compare the electric and magnetic types of black holes in a particular model of NED.     

Coherent Controlling Single Photon Asymmetric Transmission in the Atom Chirally Coupled Waveguide System

We theoretically investigate the influences of two coherent driving fields on the asymmetric transmission of single photon in the atom-waveguide system.The atom is considered as a A system.One transition of the atom chirally couples to the waveguide.The other transition is driven by two coherent driving fields.The transmission probabilities for the single photon incidents from the left(T_(lr)) and right(T_(lr)) are given respectively.The calculated results show that one can realize T_(lr)=0(T_(lr)≠0) or T_(lr)=0(T_(lr)≠0) by manipulating the phase difference between the two coherent driving Relds.The influence of the decay rate of the metastable state on the asymmetric transmission is also discussed.     

Photon Wave Mechanics: A De Broglie-Bohm Approach

We compare the de Broglie-Bohm theory for non-relativistic, scalar matter particles with the Majorana-Römer theory of electrodynamics, pointing out the impressive common peculiarities and the role of the spin in both theories. A novel insight into photon wave mechanics is envisaged.     

Electrodynamics in Dirac's Gauge: A Geometrical Equivalence

It is shown that, when classical non-relativistic electrodynamics is formulated in Dirac's gauge A A =const. and the vector potential A interpreted as a velocity field of the vacuum, the motion of a charged particle results from purely inertial effects. A metric is given for particles of a fixed charge to mass ratio.     

Electrodynamics of spin currents in superconductors

In recent work we formulated a new set of electrodynamic equations for superconductors as an alternative to the conventional London equations, compatible with the prediction of the theory of hole superconductivity that superconductors expel negative charge from the interior towards the surface. Charge expulsion results in a macroscopically inhomogeneous charge distribution and an electric field in the interior, and because of this a spin current is expected to exist. Furthermore, we have recently shown that a dynamical explanation of the Meissner effect in superconductors leads to the prediction that a spontaneous spin current exists near the surface of superconductors (spin Meissner effect). In this paper we extend the electrodynamic equations proposed earlier for the charge density and charge current to describe also the space and time dependence of the spin density and spin current. This allows us to determine the magnitude of the expelled negative charge and interior electric field as well as of the spin current in terms of other measurable properties of superconductors. We also provide a `geometric' interpretation of the difference between type I and type II superconductors, discuss how superconductors manage to conserve angular momentum, discuss the relationship between our model and Slater's seminal work on superconductivity, and discuss the magnitude of the expected novel effects for elemental and other superconductors.     

Vacuum-Induced Abelian and Non-Abelian Gauge Potentials in CavityQuantum Electrodynamics

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.