Quantum properties of nonclassical states generated by an optomechanical system with catalytic quantum scissors

A scheme is proposed to investigate the non-classical states generated by a quantum scissors device (QSD) operating on the the cavity mode of an optomechanical system. When the catalytic QSD acts on the cavity mode of the optomechanical system, the resulting state contains only the vacuum, single-photon and two-photon states depending upon the coupling parameter of the optomechanical system as well as the transmission coefficients of beam splitters (BSs). Especially, the output state is just a class of multicomponent cat state truncations at time t=2π by choosing the appropriate value of coupling parameter. We discuss the success probability of such a state and the fidelity between the output state and input state via QSD. Then the linear entropy is used to investigate the entanglement between the two subsystems, finding that QSD operation can enhance their entanglement degree. Furthermore, we also derive the analytical expression of the Wigner function (WF) for the cavity mode via QSD and numerically analyze the WF distribution in phase space at time t=2π. These results show that the high non-classicality of output state can always be achieved by modulating the coupling parameter of the optomechanical system as well as the transmittance of BSs.     

New equation for deriving pure state density operators by Weyl correspondence and Wigner operator

By virtue of the completeness of Wigner operator and Weyl correspondence we construct a general equation for deriving pure state density operators. Several important examples are considered as the applications of this equation, which shows that our approach is effective and convenient for deducing these entangled state representations.     

再谈相干态在算符编序中的应用

利用广义Weyl对应导出了相干态密度算符的S-编序表示.通过此表示并结合S-编序内的算符积分技术,导出了若干量子玻色算符的S-编序形式(包含了正规编序、Weyl编序和反正规编序).此方法进一步推广了相干态在算符编序中的应用.     

双光力诱导透明窗口的可调特性

提出一个杂化腔光力系统理论方案,利用两纳米机械振子间的库仑耦合作用实现弱探测光的双光力诱导透明窗口.研究边带可分辨区域和红失谐情况下双光力诱导透明窗口的可调特性.数值计算表明:两纳米振子间的库仑作用可有效地使单光力诱导透明窗口劈裂为双透明窗口.随着库仑耦合强度的增大,两透明窗口间的距离对称性地拉大;其次,光力腔衰减率的改变对两透明窗口的位置和深度无影响,仅对两透明窗口的宽度产生细微改变,测量精度可在坏腔情形下得到很好的保持;另外,仅增加参量放大器的非线性增益参量将使两透明窗口变宽,而引入驱动参量放大器的光场相位,利用相位匹配可以产生比空腔情形更加狭窄陡峭的双透明窗口,可用于比空腔情况更加精密的测量.     

量子相空间分布函数与压缩相干态表示间的变换关系

基于Husimi算符具有压缩相干态投影子形式, 首先介绍了一个新的量子算符表示, 即压缩相干态表示.当高斯展宽参数κ = 1时, 该函数约化为通常的P函数. 作为例子, 研究了热态的压缩相干态表示, 通过图示说明了压缩相干态表示与P函数的区别. 为更好地在量子光学问题中使用该表示, 我们揭示了压缩相干态表示与Wigner函数、Q函数以及Husimi函数间的积分变换关系.     

奇偶二项式光场态的小波变换

利用有序算符内积分方法,小波变换可以表示为被转换态矢|f〉在压缩平移算符U(μ,s)作用下向母小波态矢〈ψ|转换的矩阵元〈ψ|U(μ,s)|f〉. 在此基础上,计算了奇、偶二项式态的小波变换,得到小波变换谱. 结果表明,小波变换谱可以起到识别这些量子力学态的作用,具有直观易辨的优点. 关键词： 小波变换 奇偶二项式态 有序算符内积分     

Enhancing stationary entanglement between two optomechanical oscillators by Coulomb interaction with Kerr medium

We theoretically study the stationary entanglement of two charged nanomechanical oscillators coupling via Coulomb interaction in an optomechanical system with an additional Kerr medium. We show that the degree of entanglement between two nanomechanical oscillators is suppressed by Kerr interaction due to photon blockade and enhanced by Coulomb coupling strength. We also show other parameters for adjusting and obtaining entanglement, such as the driving power and the frequencies of the two oscillators, and the entanglement is robust against temperature. Our study proves a way for adjusting stationary entanglement between two optomechanical oscillators by Coulomb interaction and Kerr medium.     

Pseudo-Classical Partition Function of Spin One-Half Derived by Coherent State Method

Using the bosonic coherent state representation and the Schwinger bosonic operator realization of angular momentum we find the formula for the quantum Hamiltonian H =iaiUijUjl a1 for SU（2） rotation U, in this way we further specify the angular velocity w, iUU = （1/2）σ·ω, where σ is the Pauli matrix. Though the spin as a quantum observable has no classical correspondence, we may still mimic it as a rigid body rotation characterized by 3 Euler angles, and calculate its Pseudo-classical rotational partition function of spin one-half.