Dissipative Dynamics Of Few-photons Superposition States In Optical Microcavity

In recent years, in quantum information science, quantum cryptography and quantum computing trigered people’s more and more attention, which is closely related to the non-classical effects of quantum state, such as the preparation of quantum states. As everyone knows, to understand the evolution of the quantum state properties contributes to control the quantum stat. Beacusing both of quantum states’Wigner function and density matrix contain probability distribution and phase information, so we to quantum field state Wigner function research is very important.Usually, any selected quantum system is always surrounded by the classical environments. Thus, dissipation of the artificially-prepared quantum sate is one of the central topics in quantum coherence science. Roughly, due to the existence of various dissipations and fluctuations from the environments, any excited quantum state will decay to the ground state and the relevant system finally becomes classical. Under the standard logic, people pay the most attention to calculate either decoherence or decay time of a superposition quantum state, rather than cares on the process of the decoherence or decay. In simulation of the quantum information and quantum computing such processes, the decoherence plays an important role in light field, so we dissipative light field of quantum state research appears very important. Alternatively, in the present work we investigate exactly the dissipative dynamics for a prepared quantum state by calculating its dissipative-dependent Wigner function. And then, we still discuss how the non-classical properties by graphic, such as the anti-bunching effect of photons, changes with the cavity dissipation. At the same time, the non-classical property of quantum optical field has an important meaning in the actual application. Such as quantum communication security system of single photon calls for photons having anti-bunching characteristics; Compression effect to improve signal-to-noise ratio has important value, so we gave out a feasible scheme in the QED cavity to prepare and explore the few-photons superposition state.In our work, we describe how the Wigner function for a few-photon superposed state changes with the cavity’s dissipation. Our numerical results show naturally that the negativity of the Wigner function weakens gradually with the dissipation and the final state of the cavity should be "classical" with positive Wigner function. With the calculated Wigner function we investigate how the non-classical properties, such as the anti-bunching effect of photons, changes with the cavity dissipation. It is surprised that the value of the second-order correlation function g(2)(0)(which serves usually as the standard criterion of a non-classical effect, i. e., g(2)(0)<1implies that the photon is anti-bunching) is a conserved quantity during the dissipative process of the cavity. We prove such an argument analytically by directly solving the relevant master equation and suggest that g(2)(0) is not a good parameter to describe the dissipative-dependent cavity. With an experimentally-demonstrated cavity QED system we propose an approach to test our results, including how to prepare the investigated few-photon superposed state of the cavity and measure its Wigner function. Finally, our conclusions and discussions are given in our work.