We study the photon-number distributions (PND) of non-Gaussian states generated by subtracting m photons from or adding m photons to a displacement squeezed thermal state (DSTS). Compared with the PND of DSTS, PND of both m-photon-subtracted DSTS (PSDSTS) and m-photon-added DSTS (PADSTS) are modulated by a factor that is a monotonically increasing function of n, the photonnumber in the resulting non-Gaussian states. And the photon subtraction or addition essentially shifts the PND. We further demonstrate that both PND are periodic functions of the compound phase ϕ−θ/2 involved in complex squeezing and displacement parameters with a period πand exhibit more remarkable oscillations than that of DSTS. In the case of small squeezing and weak coherence, we investigate the negativity of Mandel’s Q parameter and the properties of PND of both PSDSTS and PADSTS. Our results indicate that generating new photon-number-controllable nonclassical states from a squeezed light with coherent component is effective by multiple-photon subtraction or addition when ϕ−θ/2=π/2.
We study the photon-number distributions (PND) of non-Gaussian states generated by subtracting m photons from or adding m photons to a displacement squeezed thermal state (DSTS). Compared with the PND of DSTS, PND of both m-photon-subtracted DSTS (PSDSTS) and m-photon-added DSTS (PADSTS) are modulated by a factor that is a monotonically increasing function of n, the photonnumber in the resulting non-Gaussian states. And the photon subtraction or addition essentially shifts the PND. We further demonstrate that both PND are periodic functions of the compound phase ϕ−θ/2 involved in complex squeezing and displacement parameters with a period πand exhibit more remarkable oscillations than that of DSTS. In the case of small squeezing and weak coherence, we investigate the negativity of Mandel’s Q parameter and the properties of PND of both PSDSTS and PADSTS. Our results indicate that generating new photon-number-controllable nonclassical states from a squeezed light with coherent component is effective by multiple-photon subtraction or addition when ϕ−θ/2=π/2.
We introduce the photon-subtracted squeezed coherent state (PSSCS), which is theoretically constructed by repeatedly subtracting photons from the squeezed coherent state (SCS) with squeezing parameter r and displacement amplitude α=|α|eiφ. Employing the normal ordering form of density operator of the SCS, we study the nonclassicality of the PSSCS by analyzing Mandel’s Q-parameter, quadratures squeezing, photon-number distribution (PND), and Wigner function (WF). We find that the PND in a PSSCS is a periodic function of φ with a period π and exhibits more remarkable oscillations than that of a SCS in the case of strong squeezing. The partial negative region of the WF is sensitive to r and |α|. The fidelity between PSSCS and SCS is analyzed, which manifests that larger photon subtraction number may result in lower fidelity. By virtue of the thermal entangled state representation the decoherence of the PSSCS in thermal environment is studied through the time evolution of the WF. The negative volume of the WF gradually diminishes with the increase of evolution time and thermal photon number, respectively. The study of the PSSCS shows that generating new photon-number-controllable nonclassical states from a weak coherent light may be realized by subtracting suitable photons from a SCS.
We investigate the nonclassical properties of multiple-photon-added displaced squeezed thermal states (PADSTSs). Particularly, we study the dependence of those nonclassical properties on the compound phase ϕ−θ/2 involved in squeezing and displacement parameters. We find that the Mandel Q parameter, the quadrature squeezing, the negative volume of the Wigner function, and the fidelity between PADSTSs and displaced squeezed thermal states (DSTSs) are all periodic functions of ϕ−θ/2 with a period π. Without considering the displacement parameter, these quantities are all phase independent. Finally, we investigate the non-Gaussianity of PADSTSs according to the fidelity between PADSTSs and DSTSs and find that non-Gaussianity and nonclassicality have similar behavior. Thus, the non-Gaussianity induced by the photon-addition operation is essentially nonclassical.
We investigate the nonclassical properties of the photon-added-then-subtracted coherent squeezed state (PASCSS) via the sub-Poissonian statistics, the photon-number distribution, and the negativity of the Wigner function. It is found that the PASCSS is a superposition state of D (β) S (ζ)|0〉, D (β) S (ζ)|1〉, and D (β) S (ζ)|2〉. We find that the Mandel Q parameter, the photon-number distribution, and the negative volume of the Wigner function of the PASCSS are all periodic functions of the compound φ − θ/2 with a period π involved with squeezing and displacement parameters.
Abstract The nonclassicality is the prerequisite for quantum states to be applied into quantum information, especially for quantum metrology. Here we theoretically investigate the non-classical properties of the non-Gaussian state generated by repeatedly operating a number-conserving generalized superposition of products (GSP), i.e., ( s 1 aa † + t 1 a † a ) m with s 1 2 + t 1 2 = 1 , on the squeezed thermal state (STS), in terms of second-order correlation function, Mandel’s Q parameter, quadrature squeezing and Wigner function (WF). It is shown that, compared to the cases of the STS, the GSP-STS with the high-order GSP operations ( m > 1) at the small-squeezing levels can be beneficial to the existence of the photon-antibunching effect, the sub-Poissonian distribution and the partial negativity of the WF, apart from the quadrature squeezing. In addition, for the case of m = 1, we also compare with the non-classical properties of several different non-Gaussian resources, involving the photon-subtracted-then-added (PSTA) STS, the GSP-STS and the photon-added-then-subtracted (PATS) STS. It is found that the PSTA-STS with respect to the sub-Poissonian distribution and the partial negativity of the WF has a better performance than others. Significantly, the generated GSP-STS has an obvious advantage of showing the photon-antibunching effects, compared to the PSTA-STS and the PATS-STS, which means that our scheme may have an excellent guidance for the practical implementations in quantum information.
We investigate the nonclassical properties of the photon-added-then-subtracted coherent squeezed state(PASCSS) via the sub-Poissonian statistics,the photon-number distribution,and the negativity of the Wigner function.It is found that the PASSCS is a superposition state of D(β)S(ζ)|0>,D(β)S(ζ)|1>,and D(β)S(ζ)|2>.We find that the Mandel Q parameter,the photon-number distribution,and the negative volume of the Wigner function of the PASCSS are all periodic functions of the compound φ-θ/2 with a period π involved with squeezing and displacement parameters.
We put forward the photon-added squeezing-enhanced thermal states (PASETS) theoretically by adding photon to the squeezed enhancing thermal states (SETS) repeatedly. Based on the normally ordered density operator of PASETS, we investigate the nonclassical behavior of the PASETS by evaluating, both analytically and numerically, Mandel's Q-parameter, photon-number distribution (PND), and Wigner function (WF). It is found that smaller squeezing parameter r and thermal photon number nc can lead to more chance of the appearance of sub-Poissonian statistics. And it is shown that the PND of PASETS exhibit more remarkable oscillations than that of SETS in stronger squeezing case. The WF exhibit partial negativity in phase space and the squeezing parameter r can result in both squeezing and rotating effect. By investigating the fidelity between PASETS and SETS shows that the fidelity tender to steady values in the high value of squeezing parameter or thermal photon number. In addition, the decoherence effect on the PASETS is examined by the time-evolution of the analytical WF in thermal channel. The results show that the PASETS shall lose nonclassicality and non-Gaussianity and reduce to classical states with Gaussian distribution after sufficient time interaction with the thermal noise. And larger photon-added number or thermal photon number shall render shorter decoherence time.