Generation of stable entanglement between two cavity mirrors by squeezed-reservoir engineering

The generation of quantum entanglement of macroscopic or mesoscopic bodies in mechanical motion is generally bounded by the thermal fluctuation exerted by their environments. Here we propose a scheme to establish stationary entanglement between two mechanically oscillating mirrors of a cavity. It is revealed that, by applying a broadband squeezed laser acting as a squeezed-vacuum reservoir to the cavity, a stable entanglement between the mechanical mirrors can be generated. Using the adiabatic elimination and master equation methods, we analytically find that the generated entanglement is essentially determined by the squeezing of the relative momentum of the mechanical mirrors, which is transferred from the squeezed reservoir through the cavity. Numerical verification indicates that our scheme is within the present experimental state of the art of optomechanics.Comment: 9 pages, 6 figure

Canonical versus noncanonical equilibration dynamics of open quantum systems

In statistical mechanics, any quantum system in equilibrium with its weakly coupled reservoir is described by a canonical state at the same temperature as the reservoir. Here, by studying the equilibration dynamics of a harmonic oscillator interacting with a reservoir, we evaluate microscopically the condition under which the equilibration to a canonical state is valid. It is revealed that the non-Markovian effect and the availability of a stationary state of the total system play a profound role in the equilibration. In the Markovian limit, the conventional canonical state can be recovered. In the non-Markovian regime, when the stationary state is absent, the system equilibrates to a generalized canonical state at an effective temperature; whenever the stationary state is present, the equilibrium state of the system cannot be described by any canonical state anymore. Our finding of the physical condition on such noncanonical equilibration might have significant impact on statistical physics. A physical scheme based on circuit QED is proposed to test our results

Viscosity modeling for ionic liquid solutions by Eyring-Wilson equation

A semi-theoretical model based on the classical Eyring’s mixture viscosity equation and the Wilson activity coefficient equation is presented for correlating the viscosity of ionic liquids with solvent systems. The accuracy of the proposed model was verified by comparing calculated and experimental viscosity values from literatures for 49mixtures with total 1560 data points. The results show that the equation similar to the Wilson activity coefficient equation can be well applied to describe the non-ideal term in the Eyring’s mixture viscosity equation. The model has a relatively simple mathematical form and can be easily incorporated into process simulation software

Scheme for suppressing atom expansion induced contrast loss in atom interferometers

The loss of contrast due to atom expansion induced non-perfect Raman pulse area in atom interferometers is investigated systematically. Based on the theoretical simulation, we find that the expansion of the atomic cloud results in a decrease of the {\pi} pulse fidelity and a change of the {\pi} pulse duration, which lead to a significant reduction in fringe contrast. We propose a mitigation strategy of increasing the intensities of the second and third Raman pulses. Simulation results show that the fringe contrast can be improved by 13.6% in a typical atom interferometer gravimeter using this intensity compensation strategy. We also evaluate the effects of this mitigation strategy in the case of a lower atomic cloud temperature and a larger Raman beam size under different Raman pulse time interval conditions. This mitigation strategy has potential applications in increasing the sensitivity of atom interferometer-based precision measuring, including precision measuring of the gravity, gravity gradient, rotation, and magnetic field gradient, as well as testing of the Einstein equivalence principle.Comment: 14 pages, 8 figure