Phase properties of superposed squeezed states

The phase properties of the superposed squeezed states are studied. The superposed squeezed states are obtained by inserting two squeezers in a Mach-Zehnder interferometer one for each arm. The visibility of the states as a measure of the coherence of the generated photons in the nonlinear interferometer is analyzed. And the mean-square phase fluctuations are also considered to analyze the phase properties of the superposed squeezed states. The quantities are obtained as a function of gain and the input phase, when the amplified input is a coherent state, a number state, a thermal state, a displaced number state, or a coherent thermal state.     

Phase properties of squeezed states of light

Recently introduced unitary and hermitian phase operators are used to examine the phase properties of squeezed states of light with particular reference to the squeezed vacuum. The results differ markedly from previous calculations involving the Susskind and Glogower operators. The new formalism allows the construction of a phase probability density which, on a polar diagram, is a circle for the vacuum state, becomes elliptical with gentle squeezing and collapses to a line through the origin for full squeezing. This probability density together with the calculation of expectation values of various trigonometrical functions of phase show how squeezing impresses phase information onto the vacuum.     

Phase properties of squeezed states of light

A systematic investigation for the phase properties of squeezed states has been given using a phase operator formalism. Exact general results are derived and are used for discussing some special cases.     

Statistical properties for a class of nonlinear squeezed states

Theoretical investigations of dynamical behavior in optical parametric oscillators (OPO) have generally assumed that the cavity detunings of the interacting fields are controllable parameters. However, OPOs are known to experience mode hops, where the system jumps to the mode of lowest cavity detuning. We note that this phenomenon significantly limits the range of accessible detunings and thus may prevent instabilities predicted to occur above a minimum detuning from being evidenced experimentally. As a simple example among a number of instability mechanisms possibly affected by this limitation, we discuss the Hopf bifurcation leading to periodic behavior in the monomode mean-field model of a triply resonant OPO and show that it probably can be observed only in very specific setups.     

Nonclassicality of photon-added squeezed vacuum states

By applying the bosonic creation operator to squeezed vacuum states, this paper introduces a new kind of quantum states: photon-added squeezed vacuum states. It also presents an experimental approach to prepare these states, and investigates their quantum statistical properties by the numerical method. The results indicate that these states reveal some interesting non-classical properties, such as anti-bunching effects, squeezing effects and negativities of the relevant Wigner functions.     

The nonlinear squeezed one-photon states and their nonclassical properties

By virtue of the technique of integration within an ordered product (IWOP) of operators and the properties of the inverses of annihilation and creation operators of f-oscillator, this paper obtains two new types of squeezed operators and f-analogues of squeezed one-photon states, which are quite different from ones constructed by Song and Fan ({Phys. Lett.} A {294} (2002) 66). Subsequently, some nonclassical properties of the states are investigated in detail.     

Realistic teleportation of coherent states using squeezed vacuum states

This paper presents a realistic scheme for the teleportation of coherent states in which a two-mode squeezed vacuum state serves as the quantum channel and the position-sum and momentum-difference of two local modes serve as the measuring observables. The average fidelity of the teleportation of coherent states is derived for finite squeezing parameters and it turns out that fidelity greater than 1/2 cannot be achieved by using a classical channel alone and the probability distribution of the measurement result is a Gaussian distribution around the unknown parameter of the input coherent state with a width given by the squeezing parameter.     

Quantum teleportation of entangled squeezed vacuum states

An optical scheme for probabilistic teleporting entangled squeezed vacuum states (SVS) is proposed. In this scheme, the teieported state is a bipartite entangled SVS, and the quantum channel is a tripartite entangled SVS. The process of the teleportation is achieved by using a 50/50 symmetric beamsplitter and photon detectors with the help of classical information.     

Generation of cluster-type entangled squeezed vacuum states

We present a scheme to prepare cluster-type entangled squeezed vacuum states （CTESVS） by considering the two-photon interaction between a two-level atom and a high-quality cavity, driven by a strong classical field. After the realization of simple atomic measurements, the generation of CTESVS in four separate cavities is accomplished within the cavity decay time. In the case of large atom=cavity detuning, the scheme is immune to the effect of atomic spontaneous emission.     

Two-mode squeezed vacuum states in tomographic-probability representation

The two-mode quantum electromagnetic field in the vacuum squeezed state is considered in the tomographic-probability representation. The symplectic, center-of-mass, and photon-number tomograms for the two-mode vacuum squeezed state are obtained explicitly. The expressions for photon statistics of the squeezed light are reconsidered using the state tomograms, and some new integral relations are found for one and multimode orthogonal polynomials.     

Generation of bright squeezed vacuum in the Karassiov states

We suggest an experimental procedure allowing one to prepare squeezed vacuum in a special type of generalized Bell states, first introduced by V.P. Karassiov. We present the first results on the experimental generation of such states and observation of their polarization properties.     

Charged two-dimensional magnetoexciton and two-mode squeezed vacuum states

A novel unitary transformation of the Hamiltonian that allows one to partially separate the center-of-mass motion for charged electron-hole systems in a magnetic field is presented. The two-mode squeezed oscillator states that appear at the intermediate stage of the transformation are used for constructing a trial wave function of a two-dimensional charged magnetoexciton.     

光压缩态的相位涨落

本文对光场压缩态的相位涨落进行了计算,得出(△cos(?))~2和(△sin(?))~2的表达式.压缩分量的涨落与相位涨落同时压缩.     

Entanglement swapping of continuous variable using squeezed vacuum states

We present a realistic scheme for the entanglement swapping of continuous variable, in which a two-mode squeezed vacuum state serves as a quantum channel. The position sum and momentum difference of two local modes are measured. By taking the input entangled state also as a two-mode squeezed vacuum state, we investigate the average fidelity and the von Neumann entropy of the output state. The results show that the perfect teleportation can be achieved by increasing the squeezing of the quantum channel and that any nonzero squeezing in both the quantum channel and the input entangled state is sufficient to swap the entanglement.     

Arbitrated quantum signature scheme with continuous-variable squeezed vacuum states

We propose an arbitrated quantum signature(AQS) scheme with continuous variable(CV) squeezed vacuum states,which requires three parties, i.e., the signer Alice, the verifier Bob and the arbitrator Charlie trusted by Alice and Bob, and three phases consisting of the initial phase, the signature phase and the verification phase. We evaluate and compare the original state and the teleported state by using the fidelity and the beam splitter(BS) strategy. The security is ensured by the CV-based quantum key distribution(CV-QKD) and quantum teleportation of squeezed states. Security analyses show that the generated signature can be neither disavowed by the signer and the receiver nor counterfeited by anyone with the shared keys. Furthermore, the scheme can also detect other manners of potential attack although they may be successful.Also, the integrality and authenticity of the transmitted messages can be guaranteed. Compared to the signature scheme of CV-based coherent states, our scheme has better encoding efficiency and performance. It is a potential high-speed quantum signature scheme with high repetition rate and detection efficiency which can be achieved by using the standard off-the-shelf components when compared to the discrete-variable(DV) quantum signature scheme.     

Nonclassical and non-Gaussian properties of states generated by the superposed photon added-and-subtracted operation on squeezed vacuum

A new kind of non-Gaussian quantum state is constructed by operating the superposed operator (SO) (cos θaa^† + sin θa^†a) on a squeezed vacuum state (SVS) S(r)|0〉. It is found that the SOSVS is just a superposition state between S(r)|0〉 and S(r)|2〉 with only even numbers of photons. The nonclassicality is investigated by exploring the negativity of Wigner function (WF) and the sub-Poissonian distribution of Mandel's Q-parameter. The non-Guassianity is exhibited via the fidelity between the SOSVS and the SVS and the marginal distribution of its Wigner function. It is found that such SO on the SVS can enhance the nonclassicality and change the non-Gaussianity of the SOSVS. This provides the possibility of generating quantum states with specific nonclassical and non-Gaussian properties.     

Analytical investigation on interactions among squeezed vacuum and coherent state,coherent vacuum and squeezed state,and among phase squeezed and amplitude squeezed states of light

Squeezed state of light has drawn an enormous attention in information processing and digital communication since it has broken the quantum limit of noise. Here we have analytically investigated the interactions among coherent and vacuum squeezed states of light, interaction among coherent vacuum and squeezed states of light, and that between phase and amplitude squeezed states of light signals. Hence we established the nature of the resulting interaction with the help of photon statistics.     

利用双模压缩真空态实现量子态的远程传输

借助于双模压缩真空态在EPR纠缠态表象中的表示，研究了用双模压缩真空态作为量子通道 实现任意的单模和双模量子态的远程传输. 关键词： 量子隐形传态 EPR纠缠态 压缩真空态     

Comparison of nonclassicality between photon-added and photon-subtracted squeezed vacuum states

In this paper, we introduce photon-added and photon-subtracted squeezed vacuum state (PASV and PSSV) and obtain their normalized factors, which have the similar forms involved in Lengendre polynomials. Moreover, we give the compact expressions of Wigner function, which are related to single-variable Hermite polynomials. Especially, we compare their nonclassicality in terms of Mandel Q-factor and the negativity of Wigner function.