Entanglement signatures for quantum synchronization with single-ion phonon laser.

The entanglement properties of quantum synchronization, based on a single-ion phonon laser subjected to an external drive, have been studied. It is found that the maximum value of steady-state entanglement between the ion's internal and external states occurs near the noiseless boundary from synchronization to unsynchronization, accompanied by noticeable oscillatory behaviors during the corresponding time evolution of entanglement. In addition, the later time dynamics of entanglement also indicates the occurrence of frequency entrainment, as evidenced by the strong consistency between the bending of the observed frequency and the emergence of Liouvillian exceptional points (LEPs) in the first two eigenvalues of the Liouvillian eigenspectrum. Moreover, the emergence of LEPs, which is intimately associated with frequency entrainment, should be widely observed in quantum synchronization and can be explored in LEPs-based applications.

All oxide based flexible multi-folded invisible synapse as vision photo-receptor.

All oxide-based transparent flexible memristor is prioritized for the potential application in artificially simulated biological optoelectronic synaptic devices. SnOx memristor with HfOx layer is found to enable a significant effect on synaptic properties. The memristor exhibits good reliability with long retention, 104 s, and high endurance, 104 cycles. The optimized 6 nm thick HfOx layer in SnOx-based memristor possesses the excellent synaptic properties of stable 350 epochs training, multi-level conductance (MLC) behaviour, and the nonlinearity of 1.53 and 1.46 for long-term potentiation and depression, respectively, and faster image recognition accuracy of 100% after 23 iterations. The maximum weight changes of -73.12 and 79.91% for the potentiation and depression of the synaptic device, respectively, are observed from the spike-timing-dependent plasticity (STDP) characteristics making it suitable for biological applications. The flexibility of the device on the PEN substrate is confirmed by the acceptable change of nonlinearities up to 4 mm bending. Such a synaptic device is expected to be used as a vision photo-receptor.

Entropy Exchange and Thermodynamic Properties of the Single Ion Cooling Process.

A complete quantum cooling cycle may be a useful platform for studying quantum thermodynamics just as the quantum heat engine does. Entropy change is an important feature which can help us to investigate the thermodynamic properties of the single ion cooling process. Here, we analyze the entropy change of the ion and laser field in the single ion cooling cycle by generalizing the idea in Reference (Phys. Rev. Lett. 2015, 114, 043002) to a single ion system. Thermodynamic properties of the single ion cooling process are discussed and it is shown that the Second and Third Laws of Thermodynamics are still strictly held in the quantum cooling process. Our results suggest that quantum cooling cycles are also candidates for the investigation on quantum thermodynamics besides quantum heat engines.

Ghost imaging normalized by second-order coherence.

Towards improvements in the quality of reconstructed images, the errors in the point spread function of a ghost imaging system caused by a limited number of samplings and imperfect illumination are discussed. We propose an algorithm by normalizing with the second-order coherence of the illumination field, with which the errors caused by imperfect illumination can be reduced, such as non-uniform spatial distribution of the average intensity, spatially varying profile of the second-order degree of coherence, or power fluctuation.

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.

Detecting fast signals beyond bandwidth of detectors based on computational temporal ghost imaging.

Measurement of fast signal is getting more and more important in many fields. In this paper, we propose to detect a temporal signal based on the idea of computational ghost imaging (GI), which can greatly reduce requirements on bandwidth of detectors. In experiments, we implement retrieving of a temporal signal with time scale of 50ns using a detector of 1kHz bandwidth, which is much lower than the requirement on bandwidth of detector according to information theory. The performance of our technique are also investigated under different detection bandwidths.

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.

High-resolution interference with programmable classical incoherent light.

A scheme of high-resolution interference with classical incoherent light is proposed. In this scheme, the classical incoherent light is programmable in the amplitude distribution and wavefront, and with the programmable classical incoherent light we improve the resolution of the interference pattern by a factor of 2 compared with the scheme by Erkmen [J. Opt. Soc. Am. A29, 782 (2012)JOAOD60740-323210.1364/JOSAA.29.000782]. Compared with other schemes for observing interference patterns, only single-pixel detection is needed in our proposal. Moreover, the high-resolution interference pattern can be inverted to obtain an image with better resolution compared with that of the scheme proposed by Erkmen. Furthermore, this scheme of high-resolution interference is verified in detail by theoretical analysis and numerical simulations.

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 a Λ-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.

Experimental quantum state tomography via compressed sampling.

A fundamental difficulty in demonstrating quantum state tomography is that the required resources grow exponentially with the system size. For pure states and nearly pure states, the task of tomography can be more efficient. We proposed two methods for state reconstruction, by (1) minimizing entropy and (2) maximizing likelihood. The algorithm of compressed sampling is employed to solve the optimization problem. Experiments are demonstrated considering 4-qubit photonic states. The results show that (1) much fewer measurements than the standard tomography are sufficient to obtain high fidelity, and (2) the method of maximizing likelihood is more accurate and noise robust than the original reconstruction method of compressed sampling. Furthermore, the physical meaning of the methods of minimizing entropy and maximizing likelihood is clear.