Ping-Xing Chen

Ground state cooling of an optomechanical resonator assisted by a Lambda-type atom

We propose a ground state cooling scheme for an optomechanical resonator based on the system of one Λ-type three-level atom trapped in an optomechanical cavity. This cooling scheme works in a single-photon coupling, and strong atom-cavity coupling regimes. By investigating the cooling dynamics, we find that there is an EIT-like quantum coherent effect in this system which can suppress the undesired transitions for heating. Moreover, our study shows that the final average phonon number of the optomechanical resonator can be smaller than the one based on the sideband cooling. Furthermore, the ground state cooling of the resonator can still be achieved after thermal fluctuations included. In addition, in comparison with previous cooling methods, there are fewer limitations on the decay rates of both the cavity and the atom in this scheme. As a result, this scheme is very suitable to realize the ground cooling of an optomechanical resonator in the experiment.

Is ghost imaging intrinsically more powerful against scattering

We demonstrated experimental comparison between ghost imaging and traditional non-correlated imaging under disturbance of scattering. Ghost imaging appears more robust. The quality of ghost imaging does not change much when the scattering is getting stronger, while that of traditional imaging declines dramatically. A concise model is developed to explain the superiority of ghost imaging. Due to its robustness against scattering, ghost imaging will be useful in harsh environment.

Ground-state cooling of an optomechanical resonator assisted by an atomic ensemble

We investigate a ground-state cooling scheme for a mechanical resonator assisted by one two-level atomic ensemble. The atomic ensemble is confined in the optomechanical cavity and strongly couples to the cavity mode. Our scheme works in a strong excitation of the system. Thus, there are enough photons in the cavity to produce coupling between the mechanical and optical degrees of freedom. It is shown that our scheme can work well in the unresolved sideband regime and can accelerate the cooling process.

Scalable one-way quantum computer using on-chip resonator qubits

College of Science, National University of Defense Technology, Changsha 410073, People’s Republic of China(Dated: November 14, 2011)We propose a scalable and robust architecture for one-way quantum computation using couplednetworks of superconducting transmission line resonators. In our protocol, quantum information isencoded into the long-lived photon states of the resonators, which have a much longer coherencetime than the usual superconducting qubits. Each resonator contains a charge qubit used for thestate initialization and local projective measurement of the photonic qubit. Any pair of neighboringphotonic qubits are coupled via a mediator charge qubit, and large photonic cluster states can becreated by applying Stark-shifted Rabi pulses to these mediator qubits. The distinct advantage ofour architecture is that it combines both the excellent scalability of the solid-state systems and thelong coherence time of the photonic qubits. Furthermore, this architecture is very robust againstthe parameter variations.

Multi-scale Adaptive Computational Ghost Imaging

In some cases of imaging, wide spatial range and high spatial resolution are both required, which requests high performance of detection devices and huge resource consumption for data processing. We propose and demonstrate a multi-scale adaptive imaging method based on the idea of computational ghost imaging, which can obtain a rough outline of the whole scene with a wide range then accordingly find out the interested parts and achieve high-resolution details of those parts, by controlling the field of view and the transverse coherence width of the pseudo-thermal field illuminated on the scene with a spatial light modulator. Compared to typical ghost imaging, the resource consumption can be dramatically reduced using our scheme.

Sub-Rayleigh-diffraction imaging via modulating classical light.

The spatial resolution of a traditional imaging system is restricted by the Rayleigh diffraction limit. In this paper, two types of classical light sources are generated by modulating the amplitude distribution and wavefront of a laser beam randomly, and the generated light sources can exhibit the features of the superposition of two-photon Fock states and the incoherent mixture of two-photon Fock states, respectively. With the generated light sources, the two-fold coherent and incoherent imaging schemes can be achieved, which lead to spatial resolution enhancement, and exceed the Rayleigh diffraction limit in the imaging system.

Necessary and sufficient condition of separability of any system

The necessary and sufficient condition of separability of a mixed state of any systems is presented, which is practical in judging the separability of a mixed state. This paper also presents a method of finding the disentangled decomposition of a separable mixed state.

Quantum superposition of localized and delocalized phases of photons

Abstract Based on a variant of 2-site Jaynes–Cummings–Hubbard model constructed using superconducting circuits, we propose a method to coherently superpose the localized and delocalized phases of microwave photons, which makes it possible to engineer the collective features of multiple photons in the quantum way using an individual two-level system. Our proposed architecture is also a promising candidate for implementing distributed quantum computation since it is capable of coupling remote qubits in separate resonators in a controllable way.

Imaging through scattering layers exceeding memory effect range with spatial-correlation-achieved point-spread-function

We propose to measure intensity transmission matrices or point-spread-function (PSF) of diffusers via spatial-correlation, with no scanning or interferometric detection required. With the measured PSF, we report optical imaging based on the memory effect that allows tracking of moving objects through a scattering medium. Our technique enlarges the limited effective range of traditional imaging techniques based on the memory effect, and substitutes time-consuming iterative algorithms by a fast cross-correlation deconvolution method to greatly reduce time consumption for image reconstruction.

Enhancement of Electromagnetically Induced Transparency Cooling by an Optical Cavity

We theoretically investigate an enhanced electromagnetically induced transparency (EIT) cooling method by introducing a high finesse cavity. We find that the quantum destructive interference that is induced by the EIT effect and the cavity coupling can eliminate all of the heating effects in the cooling process by choosing appropriate parameters. Compared with the EIT cooling scheme, a lower final temperature can be obtained under the same conditions in our scheme.