arXiv subjects

Jian-Qi Shen

Publications and source records attributed to Jian-Qi Shen.

15 recordsLinked to original sources

arXiv2004

Explicit formula for the external driving field used to eliminate the decoherence of a two-state system coupled to a noise field

The elimination of decoherence of a multiphoton two-state quantum system by using an appropriate external driving field is considered. The multiphoton process caused by the noise field has a supersymmetric Lie algebraic structure. The time-evolution equations for the off-diagonal elements of the density operator of the two-state system are derived in the interaction picture. A simple explicit formula is given for the time-dependent external driving field used to eliminate the decoherence of the multiphoton two-state system.

quant-ph↗

arXiv2004

Influence of the signal light on the transient optical properties of a four-level EIT medium

General formulae for the transient evolution of the susceptibility (absorption) induced by the quantum interference effect in a four-level N-type EIT medium is presented. The influence of the signal light on the transient susceptibility for the probe beam is studied for two typical cases when the strength of the coupling beam is much greater or less than that of the signal field. An interesting level reciprocity relationship between these two cases is found.

quant-ph↗

arXiv2003

The su(n) Lie algebraic structures in the Pegg-Barnett quantization formulation

We investigate the oscillator algebra of the Pegg-Barnett oscillator with a finite-dimensional number-state space and show that it possesses the su($n$) Lie algebraic structure. In addition, a so-called supersymmetric Pegg-Barnett oscillator is suggested, and the related topics such as the algebraic structure and particle occupation number of the Pegg-Barnett oscillator are briefly discussed.

quant-ph↗

arXiv2003

Monomode photon spin operators projected onto the fixed frame and quantum-vacuum geometric phases of photons inside a noncoplanar optical fibre

The propagation of monomode photons inside a coiled optical fibre was regarded as a time-dependent quantum evolution process, which gives rise to a geometric phase. It is well known that the investigation of non-adiabatic geometric phases ought to be performed only in the Schrödinger picture. So, the projections of photon spin operators onto the fixed frame of reference is discussed in this paper. In addition, we also treat the non-normal-order spin operators and consider the potential effects (e.g., quantum-vacuum geometric phases) of quantum fluctuation fields arising in a curved optical fibre. The quantum-vacuum geometric phase, which is of physical interest, can be deducted by using the operator normal product, and the doubt of validity and universality for the normal-normal procedure applied to time-dependent quantum systems is thus proposed. In the Appendix, the discussion of possible experimental realizations of quantum-vacuum geometric phases is briefly presented.

quant-ph↗

arXiv2003

Neutron-gravity interferometry experiment: testing Earth's rotating frequency fluctuations via neutron Berry's phases due to spin-rotation couplings

Neutron spin can be coupled to the Earth's rotating frequency. Once if the Earth's rotating frequency is time-dependent, then the neutron will acquire a Berry's topological phase (cyclic adiabatic geometric phase). So, a potential method to investigate the Earth's time-varying rotating frequency by measuring the phase difference between geometric phases of neutron spin polarized vertically down and up is proposed.

physics.geo-ph↗

arXiv2003

Exact solutions to the time-dependent supersymmetric muliphoton Jaynes-Cummings model and the Chiao-Wu model

By using both the Lewis-Riesenfeld invariant theory and the invariant-related unitary transformation formulation, the present paper obtains the exact solutions to the time-dependent supersymmetric two-level multiphoton Jaynes-Cummings model and the Chiao-Wu model that describes the propagation of a photon inside the optical fiber. On the basis of the fact that the two-level multiphoton Jaynes-Cummings model possesses the supersymmetric structure, an invariant is constructed in terms of the supersymmetric generators by working in the sub-Hilbert-space corresponding to a particular eigenvalue of the conserved supersymmetric generators (i.e., the time-independent invariant). By constructing the effective Hamiltonian that describes the interaction of the photon with the medium of the optical fiber, it is further verified that the particular solution to the Schrödinger equation is the eigenfunction of the second-quantized momentum operator of photons field. This, therefore, means that the explicit expression (rather than the hidden form that involves the chronological product) for the time-evolution operator of wave function is obtained by means of the invariant theories.

quant-ph↗

arXiv2003

Geometric Phase of electrons due to the Spin-rotation Coupling in Rotating C$_{60}$ Molecules

The rapidly rotational motion of C$_{60}$ molecules provides us with an ingenious way to test Mashhoon's spin-rotation coupling. The spin-rotation coupling of electrons in the rotating C$_{60}$ molecule is considered in the present letter. It is shown that the intrinsic spin (gravitomagnetic moment) of the electron that can be coupled to the time-dependent rotating frequency of rotating frame of reference (C$_{60}$ molecule) results in a geometric phase, which may be measured through the electronic energy spectra of C$_{60}$ molecules.

quant-ph↗

arXiv2003

Frequency-independent effective rest mass of photons in the 2TDLM model

A physically interesting {\it effective rest mass} of photons in electromagnetic media, which is independent of wave frequency $ω$, is defined in the present paper. It is verified that this frequency-independent effective rest mass of photons can be easily read off from the optical refractive index squared $n^{2}(ω) $ of commonly-seen electromagnetic media. As an illustrative example, we extract the frequency-independent effective rest mass of photons from $n^{2}(ω) $ in the {\it two time derivative Lorentz material} (2TDLM) model. The connection between effective rest mass and electromagnetic parameters of electric permittivity ($ε$) and magnetic permeability ($μ$) in left-handed media is also briefly discussed.

cond-mat.mtrl-sci↗

arXiv2003

Gravitational Effects Associated With Gravitomagnetic Fields

Several relativistic quantum gravitational effects such as spin-rotation coupling, gravitomagnetic charge and gravitational Meissner effect are investigated in the present letter. The field equation of gravitomagnetic matter is suggested and a static spherically symmetric solution of this equation is offered. With foreseeable improvements in detecting and measuring technology, it is possible for us to investigate quantum mechanics in weak-gravitational fields. The potential implications of these gravitational effects (or phenomena) to some problems are briefly discussed.

gr-qc↗

arXiv2003

Geometric Phase and Helicity Inversion of Photons Propagating inside a Noncoplanarly Curved Optical Fiber

The Letter presents an exact expression for the non-adiabatic non-cyclic geometric phase of photons propagating inside a noncoplanarly curved optical fiber by using the Lewis-Riesenfeld invariant theory. It is shown that the helicity inversion of photons arises in the curved fiber. Since we have exactly solved the time-dependent Schrödinger equation that governs the propagation of photons in a curved fiber and, moreover, the chronological product is not involved in this exact solution, our formulation therefore has several advantages over other treatments based on the classical Maxwell's theory and the Berry's adiabatic quantum theory. The potential application of helicity inversion of photons to information science is briefly suggested.

quant-ph↗

arXiv2003

Exact time-dependent decoherence factor and its adiabatic classical limit

The present paper finds the complete set of exact solutions of the general time-dependent dynamical models for quantum decoherence, by making use of the Lewis-Riesenfeld invariant theory and the invariant-related unitary transformation formulation. Based on this, the general explicit expression for the decoherence factor is then obtained and the adiabatic classical limit of an illustrative example is discussed. The result (i.e., the adiabatic classical limit) obtained in this paper is consistent with what obtained by other authors, and futhermore we obtain the more general results concerning the time-dependent non-adiabatic quantum decoherence. It is shown that the invariant theory is appropriate for treating both the time-dependent quantum decoherence and the geometric phase factor.

quant-ph↗

arXiv2003

An approach to exact solutions of the time-dependent supersymmetric two-level three-photon Jaynes-Cummings model

By utilizing the property of the supersymmetric structure in the two-level multiphoton Jaynes-Cummings model, an invariant is constructed in terms of the supersymmetric generators by working in the sub-Hilbert-space corresponding to a particular eigenvalue of the conserved supersymmetric generators. We obtain the exact solutions of the time-dependent Schrödinger equation which describes the time-dependent supersymmetric two-level three-photon Jaynes-Cummings model (TLTJCM) by using the invariant-related unitary transformation formulation. The case under the adiabatic approximation is also discussed. Keywords: Supersymmetric Jaynes-Cummings model; exact solutions; invariant theory; geometric phase factor; adiabatic approximation

math-ph↗

arXiv2003

Dynamics of Gravitomagnetic Charge

The physically interesting gravitational analogue of magnetic monopole in electrodynamics is considered in the present paper. The author investigates the field equation of gravitomagnetic matter, and the exact static cylindrically symmetric solution of field equation as well as the motion of gravitomagnetic charge in gravitational fields. Use is made of the mechanism of gravitational Meissner effect, a potential interpretation of anomalous, constant, acceleration acting on the Pioneer 10/11, Galileo and Ulysses spacecrafts is also suggested.

gr-qc↗

arXiv2003

Gravitomagnetic Field and Time-Dependent Spin-Rotation Coupling

The Kerr metric of spherically symmetric gravitational field is analyzed through the coordinate transformation from the rotating frame to fixing frame, and consequently that the inertial force field (with the exception of the centrifugal force field) in the rotating system is one part of its gravitomagnetic field is verified. We investigate the spin-rotation coupling and, by making use of Lewis-Riesenfeld invariant theory, we obtain exact solutions of the Schrödinger equation of a spinning particle in a time-dependent rotating reference frame. A potential application of these exact solutions to the investigation of Earth$^{,}$s rotating frequency fluctuation by means of neutron-gravity interferometry experiment is briefly discussed in the present paper.

quant-ph↗

arXiv2002

Exact solutions of time-dependent three-generator systems

There exist a number of typical and interesting systems or models which possess three-generator Lie-algebraic structure in atomic physics, quantum optics, nuclear physics and laser physics. The well-known fact that all simple 3-generator algebras are either isomorphic to the algebra $sl(2,C)$ or to one of its real forms enables us to treat these time-dependent quantum systems in a unified way. By making use of the Lewis-Riesenfeld invariant theory and the invariant-related unitary transformation formulation, the present paper obtains exact solutions of the time-dependent Schrödinger equations governing various three-generator quantum systems. For some quantum systems whose time-dependent Hamiltonians have no quasialgebraic structures, we show that the exact solutions can also be obtained by working in a sub-Hilbert-space corresponding to a particular eigenvalue of the conserved generator (i.e., the time-independent invariant that commutes with the time-dependent Hamiltonian). The topological property of geometric phase factors in time-dependent systems is briefly discussed.

quant-ph↗