Bao-Long Liang

A new kind of nonlinear coherent states and their properties

Abstract A new kind of nonlinear coherent states, i.e. the k eigenstates of the powers (k ≥ 3) of the generalized annihilation operator of f-oscillators, are constructed using the inverse operators of the boson annihilation and creation operators. The set of these states may form a complete quantum mechanics representation. Using newly defined higher order squeezing and an antibunching, the properties of the Mth-order squeezing and the antibunching effect of the k states are investigated. The results show that the Mth-order [M = (n + 1/2)k; n = 0, 1, 2, …] squeezing effects exist in all of the k states when k is even and the antibunching effect exists in all of the k states.

QUANTIZATION FOR THE MESOSCOPIC RLC CIRCUIT AND ITS THERMAL EFFECT BY VIRTUE OF GHFT

The mesoscopic single RLC (resistance-inductance-capacitance) circuit and the RLC circuit including complicated coupling are quantized by employing Diracs standard canonical quantization method. The thermal effects for the systems are investigated by virtue of GHFT (the generalized Hellmann–Feynman theorem). The results distinctly show the effect of temperature on the quantum fluctuation.

The construction, properties and applications of a new bipartite coherent-entangled state in the two-mode Fock space

Using the technique of integration within an ordered product (IWOP) of operators, we find a new kind of bipartite coherent-entangled state (CES) that exhibits both coherent state and entangled state properties. The set of CESs makes up a complete and partly nonorthogonal representation. Using an asymmetric beamsplitter we propose a simple experimental scheme for producing the CES. Finally, we present some new quantum states related to the CES and some applications of the CES to quantum optics.

New parameterized entangled state representation and its applications

By virtue of the technique of integral within an ordered product of operators, we construct a new parameterized entangled state |τs, r and prove the set of |τs, r making up a new complete and orthogonal representation. As applications, we use the state |τs, r representation to derive a two-mode entangled Fresnel operator, to formulate quantum correspondence theory of the classical circular harmonic correlator, and to develop quantum tomography of entangled systems.

DECOHERENCE DYNAMICS OF A FLUX QUBIT RESPECTIVELY COUPLED TO A BOSON BATH AND A SPIN BATH

In this paper, we investigate the dynamical evolution and the decoherence of a single flux qubit due to its coupling with the external environment bath. We consider two typical baths: boson bath and spin bath. It is shown that, at low but finite temperature, if the two typical baths have smooth and continuous spectrum, the dynamics of the system is in general non-Markovian though of finite memory time. Most important of all, affected by the external environment bath, the flux qubit exhibits resonance of the coherence of the qubit. Comparing with the spin bath, the boson baths destruction of the coherence is more serious.

QUANTUM EFFECTS OF A DOMAIN WALL IN THE FERROMAGNETIC SYSTEM

Starting from the classical equation of the motion of a domain wall in the ferromagnetic systems, the quantum energy levels of the wall and the corresponding eigenfunctions in the case of considering damping term are given by using the canonical quantization method and unitary transformation. The quantum fluctuations of displacement and momentum of the moving wall has also been given as well as the uncertain relation.

OPERATOR JOSEPHSON EQUATION FOR A JOSEPHSON JUNCTION CONNECTED INTO A MESOSCOPIC LC CIRCUIT

We find that when a single Josephson junction is inserted into a mesoscopic LC circuit, the operator Josephson equation is modified accompanying with the modification of Farady equation describing the inductance. By virtue of the entangled state representation and using the appropriate phase operator in bosonic form we derive the modified equations.

Quantum superimposing multiple cloning-cum-complementing machine

We prove that the nonorthogonal states randomly selected from a set can evolve into a linear superposition of multiple original and orthogonal complementing states with failure branch if and only if the input states are linearly independent. The results for a single-input state are also generalized into the case of several copies of an input state.