Non-Gaussianity and decoherence of generalized photon-added coherent state as a Hermite-excited coherent state

Generalized photon-added coherent state (GPACS) is obtained by repeatedly acting the combination of Bose creation and annihilation operations on the coherent state. It is found that GPACS can be regarded as a Hermite-excited coherent state due to its normalization factor related to a Hermite polynomial. In addition, we adopt the Hilbert-Schmidt distance to quantify the non-Gaussian character of GPACS and discuss the decoherence of GPACS in dissipative channel by studying the loss of nonclassicality in reference of the negativity of Wigner function.     

相干态的小波变换

根据小波变换的量子力学机理, 通过选取不同的系数, 构造出两组新的母小波函数. 在此基础上, 利用正规乘积内积分技术, 推导出相干态和粒子数态的小波变换, 并数值模拟出它们的小波变换图谱.     

Trapped-ion state detection through coherent motion

We demonstrate a general method for state detection of trapped ions that can be applied to a large class of atomic and molecular species. We couple a spectroscopy ion (27Al+) to a control ion (25Mg+) in the same trap and perform state detection through off-resonant laser excitation of the spectroscopy ion that induces coherent motion. The motional amplitude, dependent on the spectroscopy ion state, is measured either by time-resolved photon counting or by resolved sideband excitations on the control ion. The first method provides a simplified way to distinguish clock states in 27Al+, which avoids ground-state cooling and sideband transitions. The second method reduces spontaneous emission and optical pumping on the spectroscopy ion, which we demonstrate by nondestructively distinguishing Zeeman sublevels in the (1)S0 ground state of 27Al+.     

Quantum state measurement using coherent transients

We present the principle and experimental demonstration of time resolved quantum state holography. The quantum state of an excited state interacting with an ultrashort chirped laser pulse is measured during this interaction. This has been obtained by manipulating coherent transients created by the interaction of femtosecond shaped pulses and rubidium atoms.     

Quantum interference between heralded single photon state and coherent state

Balanced homodyne detection has been introduced as a reliable technique of reconstructing the quantum state of a single photon Fock state, which is based on coupling the single photon state and a strong coherent local oscillator in a beam splitter and detecting the field quadrature at the output ports separately. The main challenge associated with a tomographic characterization of the single photon state is mode matching between the single photon state and the local oscillator. Utilizing the heralded single photon generated by the spontaneous parametric process, the multi-mode theoretical model of quantum interference between the single photon state and the coherent state in the fiber beam splitter is established.Moreover, the analytical expressions of the temporal-mode matching coefficient and interference visibility and relationship between the two parameters are shown. In the experimental scheme, the interference visibility under various temporalmode matching coefficients is demonstrated, which is almost accordant with the theoretical value. Our work explores the principle of temporal-mode matching between the single photon state and the coherent photon state, originated from a local oscillator, and could provide guidance for designing the high-performance balanced homodyne detection system.     

增加光子纠缠相干态的统计性质

引入了增加光子纠缠相干态.研究了在纠缠相干态的某个模上加入光子对光场统计性质的影响.由于两个场模间的纠缠,在a模上加入光子不但可以使a模的平均光子数增加,也可以使b模的平均光子数发生变化(增加或减少).加入光子后,光场的亚泊松分布和压缩特征得到明显增强. 关键词： 纠缠 增加光子态 统计性质     

振幅相干态的量子统计性质

对振幅相干态|ψ＞的非经典性质进行了研究，用数值计算的方法讨论了它的振幅压缩性质、亚泊松分布特性和反聚束效应。     

Operator properties of generalized coherent state systems

The main properties of standard quantum mechanical coherent states and the two generalizations of Klauder and of Perelomov are reviewed. For a system of generalized coherent states in the latter sense, necessary and sufficient conditions for existence of a diagonal coherent stable representation for all Hilbert-Schmidt operators are obtained. The main ingredients are Clebsch-Gordan theory and induced representation theory.     

A secure identification system using coherent states

A quantum identification system based on the transformation of polarization of a mesoscopic coherent state is proposed. Physically, an initial polarization state which carries the identity information is transformed into an arbitrary elliptical polarization state. To verify the identity of a communicator, a reverse procedure is performed by the receiver. For simply describing the transformation procedure, the analytical methods of Poincar\'{e} sphere and quaternion are adopted. Since quantum noise provides such a measurement uncertainty for the eavesdropping that the identity information cannot be retrieved from the elliptical polarization state, the proposed scheme is secure.     

The QCD coherent state from asymptotic dynamics

The recently found coherent state operator for soft gluon emission is derived in a simple way from the Faddeev-Kulish approach of asymptotic dynamics. It is argued that this method can be extended to next subleading infrared singularities.     

The sampling theorem and coherent state systems

The Poisson Summation Formula and the sampling theorem for band limited signals, well known in the context of Fourier transformation theory, are analyzed from the perspective of the Zak basis and coherent state systems associated with the Heisenberg-Weyl group. In particular, we rephrase the content of the sampling theorem in terms coherent states and show that this in turn permits extensions, which allow us to make specific statements concerning standard and generalized coherent state systems on von Neumann or finer lattices. The text was submitted by the author in English.     

Nuclear collective rotations and coherent state dynamics

Coherent state dynamics is used to study the time evolution of the quadrupole parameters and to determine the energy spectrum for the two dimensional analogue of the Elliott rotational model. The results are compared in great detail to the exact Schrödinger dynamics.     

Statistical phase properties in a coherent state

The wave function of a harmonic oscillator is investigated under the assumption that the phase plays the role of a generalized coordinate. This wave function makes it possible to obtain all possible statistical information concerning the phase in a coherent state (moments of all orders). It is particularly simple to calculate cos and sin .Odessa State Pedagogical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 7, pp. 748–760, July, 1991.     

Generalized coherent state for soft gluon emission

By using a recursive soft insertion technique, many gluon emission amplitudes are computed to all orders in α_s and leading infrared accuracy. The resulting correlation structure is systematically exponentiated to yield a generalized coherent state operator which satisfies an integral equation where virtual corrections occur as a Sudakov matrix for many parton states. Infrared cancellations for physical quantities, including Drell-Yan processes, are derived on the basis of the unitarity relation for the coherent state. By further assuming strong ordering in emission angles, all known results on coherent effects and multiplicity distributions are easily recovered.     

Euclidean image of the soliton coherent state

A euclidean correspondence of a soliton coherent state is constructed by making use of the Guerra-Ruggiero realization of the euclidean Markov field. As a result, the euclidean image of a soliton coherent state is found to be a gaussian Markov field.     

Quantum interference between a single-photon Fock state and a coherent state

We derive analytical expressions for the single mode quantum field state at the individual output ports of a beam splitter when a single-photon Fock state and a coherent state are incident on the input ports. The output states turn out to be a statistical mixture between a displaced Fock state and a coherent state. Consequently we are able to find an analytical expression for the corresponding Wigner function. Because of the generality of our calculations the obtained results are valid for all passive and lossless optical four port devices. We show further how the results can be adapted to the case of the Mach-Zehnder interferometer. In addition we consider the case for which the single-photon Fock state is replaced with a general input state: a coherent input state displaces each general quantum state at the output port of a beam splitter with the displacement parameter being the amplitude of the coherent state.     

Smart generation of a tripartite GHZ-type state for coherent state qubit

This work describes how to implement probabilistically the entangled state (∣0 0 0〉 + ∣0 1 1〉 + ∣1 0 1〉 + ∣1 1 0〉)/2, for coherent state qubit, using only linear optics and measurements. Its creation is proposed firstly using an ideal lossless setup and secondly considering the decoherence caused by losses in the optical devices. The advantage of our scheme is the absence of single-qubit gates, photons counters and quantum teleportation, resources that are common in coherent state quantum information processing.     

Squeezed coherent state undergoing a continuous nondemolition observation

The time evolution of a squeezed coherent state conditioned by the results of a single and double heterodyne measurement is discussed. The mean values of quadratures as well as the dynamics of quadrature uncertainties have been obtained within the framework of the theory of continuous measurements based on filtration equations. It has been found that while the mean values depend on the measured noise, the uncertainties in the optical quadratures are deterministic. Explicit solutions for the latter have been provided. Finally, a time development of the squeeze parameter for the posterior squeezed coherent state has been found.     

Superfluid state of coherent light in nonlinear waveguides

We establish the photonic superfluid theory in waveguides made of self-defocussing polar crystals. In quantum theory it is shown that photons can sense an attractive effective interaction by exchange of virtual optical phonons. Such an interaction leads to the photonic superfluid state, in which a propagating photon pair consists of a combination of two photons with opposite transverse wave vector and spins. The most important property of the photonic superfluid state is that the system of photon pairs evolves without scattering attenuations. The traveling-wave superfluid state has the squeezing property and the soliton effect.