Non-classical Properties And Decoherence Effects Of Non-gaussian Optical Fields

In recent years, the development of quantum information science makes the experimental and theoretical study on non-classical states describing optical fields as one of popular topics in modern physics. Especially, for non-Gaussian optical fields, since their importance was far more than traditional Gaussian states, constructing all kinds of new non-Gaussian states has been an important research topic in quantum optics. Up to now, physicists have proposed many schemes for obtaining new non-Gaussian states. Among them, adding photons to or subtracting photons from Gaussian quantum states can obtain some new non-Gaussian states. On the other hand, non-Gaussian states as quantum information sources can improve teleportation, quantum storage and quantum cloning,and their non-Gaussianity is crucial for realizing quantum error correction, entanglement distillation and quantum computation on cluster states. However, quantum decoherence is unavoidable in the transmission of non-Gaussian optical fields through the medium since quantum dissipation in this process will deteriorate the degree of non-classicality of these fields. Therefore, the study on quantum features and decoherence effect of non-Gaussian optical fields has become an important research field in quantum theory. Considering the importance of non-Gaussian optical fields in quantum optics and quantum information aspects, this thesis shall study non-classical features of a series of non-Gaussian optical fields and their decoherence effects in different channels. This thesis is organized as follows:1. Based on the exact infinitive operator-sum representation of ρ(t) in the laser channel via the thermal entangled state |τ ? representation, we then present the analytical evolutions of squeezed number states and squeezed thermal states and their Wigner functions and discuss some special cases. Further, we investigate and compare the decoherence behavior of such two states in the laser channel.2. We obtain the normalization factor of multiple-photon-subtracted squeezed vacuum state(MPSSVS) and, analytically and numerically, study its squeezing character, oscillating behavior of photon-number distribution and negativity of Wigner function, and mainly discuss the analytical evolution and decoherence behavior of Wigner function for MPSSVS in thermal channel and phase damping channel. Moreover, we present a comparison between non-classicality and decoherence of MPSSVS and the case of single-photon-subtraction.3. We introduce a new non-Gaussian state: photon-added two-mode squeezed thermal state(PTSTS), and derive the normalization factor of the PTSTS, and discuss the influence of the controlling parameters on some quantum statistical features. According to the partial negativity of Wigner function and its time-evolution in thermal environment, we mainly study the nonclassical features of PTSTS and the effect of decoherence on them. As a non-Gaussianity measure to quantify the non-Gaussian characters of quantum states, we calculate the fidelity of the PTSTS.4. On the basis of the entangled state |η? representation, we derive the analytical formula of Wigner function for the two-variable Hermite polynomial state(THPS) and discuss the nonclassicality of THPS according to the negativity of Wigner function. Moreover, we also use the entangled state |η, τ1, τ2? representation to obtain the optical tomogram of THPS. In terms of Wigner function for THPS in thermal channel, we mainly discuss decoherence features of THPS, and then compare decoherence time of THPS in thermal channel and amplitude dissipative channel.