Exotic Smoothness and Noncommutative Spaces. The Model-Theoretical Approach

We give an almost explicit presentation of exotic functions corresponding to some exotic smooth structure on topologically trivial ⁴. The construction relies on the model-theoretic tools from the previous paper. We can formulate unexpected, yet direct connection between localized exotic small R ⁴'s and some noncommutative spaces. The formalism of QM can be interpreted in terms of exotic smooth R ⁴'s localized in spacetime. A new way of looking at the problem of decoherence is suggested. The 4-dimensional spacetime itself has built-in means which may enforce a kind of decoherence.     

General Decoherence Suppression in Three-Level Atom in V- and Ξ-Configurations

In this paper, we present the decoupling bang-bang （BB） twin-born pulses to suppress the genera/deco- herence, both amplitude and phase decoherence, in a three-level atom in V- and Ξ-configurations. We give the exact sequence of periodic twinborn pulses in such systems.     

On Effectiveness of Protocol Creating Maximum Entanglement of Two Charge-Phase Qubits by Cavity Field

We revisit the protocols to create maximally entangled states between two Josephson junction （33） charge phase qubits coupled to a microwave field in a cavity as a quantum data bus. We analyze a novel mechanism of quantum decoherence due to the adiabatic entanglement between qubits and the data bus, the off-resonance microwave field. We show that even if the variable of the data bus can be adiabatically eliminated, the entanglement between the qubits and data bus remains and can decohere the superposition of two-particle state. Fortunately we can construct a decoherencefree subspace of two-dimension to against this adiabatic decoherence. To carry out the analytic study for this decoherence problem, we develop Frohlich transformation to re-derive the effective Hamiltonian of these systems, which is equivalent to that obtained from the adiabatic elimination approach.     

Suppression of Phase and Amplitude Damping Decoherence in a Three-Level Atom in Λ-Configuration Using Bang-Bang Controls

In this paper, we present decoupling bang-bang operations for the suppression of general decoherence, both amplitude and phase damping, in a three-level system in Λ-configuration. We give a program to design a sequence of periodic twinborn pulses to suppress the decoherence in such the system.     

Entanglement in a generalized Jaynes--Cummings model

We investigate the pairwise entanglement and global entanglement in a generalized Jaynes--Cummings model, which can be used to realize Greenberger--Horne--Zeilinger (GHZ) entangled state (Zheng S B 2001 {\it Phys. Rev. Lett.} {\bf 87} 230404). Our results show that the W-type entangled states cannot be generated based on the model. The dependences of entanglement on Rabi frequency $\lambda$ and dipole--dipole coupling strength ${\it \Omega}$ are given. It is found that there exists the quantum phase transition when $\lambda={\it \Omega}$. For typical experimental data, the critical temperature for pairwise entanglement is on the order of $10^{-6}$\,K. Based on these results, two strategies that overcome decoherence are proposed.     

Influence of Intrinsic Decoherence on Entanglement in Two-Qubit Quantum Heisenberg XYZ Chain

Taking the intrinsic decoherence effect into account, we investigate the time evolution of entanglement for two-qubit XYZ Heisenberg model in an external uniform magnetic field. Concurrence, the measurement of entanglement,is calculated. We show how the intrinsic decoherence modifies the time evolution of the entanglement and find that at short-time case, concurrence is oscillating as increasing magnetic field, which implies that entanglement may be enhanced or weakened in some time regions.     

基于量子点接触的开放双量子点系统电子转移特性

基于量子点接触探测器(QPC)理论上研究了双量子点(DQD)系统在耗散环境和纯退相环境影响下的电子转移特性.结果表明,耗散环境中探测器导致的退相干会增大平均电流和Fano factor随时间演化的值,并观察到量子芝诺效应的存在.在对称的DQD情况下,弛豫减小了平均电流随时间演化的震荡振幅.在非对称的DQD情况下,弛豫降低了Fano factor随时间演化的峰值.纯退相环境中测量会阻碍共隧穿过程中不同电流通道之间的转换,导致Fano factor的极高值.在对称的DQD情况下,增大纯退相速率会提高Fano factor.在非对称的DQD情况下,动力学随时间的演化对纯退相环境不敏感.另外,还发现探测器内n个电子的转移几率只受QPC与DQD耦合的影响.我们的结论可以为实验工作者研究电子输运特性提供理论参考.     

Effects of Quantum Correction on Dynamical Phase Transition in a Single Species Bosonic Josephson Junction

In this paper,by employing Bogliubov backreaction method,we investigate quantum correction effects on dynamical phase transition in a single species bosonic Josephson junction induced by increasing nonlinear interaction.Compared with mean field theory results,we find that the transition point is shifted.The dynamical phase transition is accompanied by a change of the entanglement entropy,which is found to reach a maximum at the transition point of the mean field theory.     

No-signaling non-unitary modification of quantum dynamics within a deterministic model of quantization

We have developed in the previous works a statistical model of quantum fluctuation based on a chaotic deviation from infinitesimal stationary action which is constrained by the principle of Locality to have a unique exponential distribution up to a parameter that determines its average. The unitary Schrödinger time evolution with Born’s statistical interpretation of the wave function is recovered as a specific case when the average deviation from infinitesimal stationary action is given by ?/2$?/2$ for all the time. This naturally suggests a possible generalization of the quantum dynamics and statistics by allowing the average deviation fluctuates effectively randomly around ?/2$?/2$ with a finite yet very small width and a finite time scale. We shall show that averaging over such fluctuation will lead to a non-unitary average-energy-conserving time evolution providing an intrinsic mechanism of decoherence in energy basis in the macroscopic regime. A possible cosmological origin of the fluctuation is suggested. Coherence and decoherence are thus explained as two features of the same statistical model corresponding to microscopic and macroscopic regimes, respectively. Moreover, noting that measurement-interaction can be treated in equal footing as the other types of interaction, the objective locality of the model is argued to imply no-signaling between a pair of arbitrarily separated experiments.     

Entanglement dynamics of two qubits coupled by Heisenberg XY interaction under a nonuniform magnetic field in a spin bath

This paper investigates the entanglement dynamics of a Heisenberg XY model for a two-spin system in the presence of a nonuniform magnetic field.The master equations and the concurrence evolution equations for the initial α state are derived and analysed.It is shown that for the symmetric initial α state,only the nonuniform field can play a role in entanglement dynamics while the uniform field and the bath will not play such a role.For the asymmetric α state,the nonuniform field leads to the beat pattern oscillation of the concurrence evolution.The inhomogeneity of the field can enhance the entanglement by suppressing the decoherence effects of both the spin-orbit interaction and the spin bath.