arXiv subjects

Shutian Liu

Publications and source records attributed to Shutian Liu.

30 records · Page 2Linked to original sources

arXiv2020

Enhanced photon blockade in an optomechanical system with parametric amplification

We propose a scheme to enhance the single- and two-photon blockade effect significantly in a standard optomechanical system (OMS) via optical parametric amplification (OPA). The scheme does not rely on the strong single-photon optomechanical coupling and can eliminate the disadvantages of suppressing multi-photon excitation incompletely. Through analyzing the single-photon blockade (1PB) mechanism and optimizing the system parameters, we obtain a perfect 1PB with a high occupancy probability of single-photon excitation, which means that a high quality and efficient single-photon source can be generated. Moreover, we find that not only the two-photon blockade (2PB) effect is significantly enhanced but also the region of 2PB occurring is widened when the OPA exists, where we also derive the optimal parameter condition to maximize the two-photon emission and the higher photon excitations are intensely suppressed at the same time.

quant-ph↗

arXiv2019

Topological phase induced by distinguishing parameter regimes in cavity optomechanical system with multiple mechanical resonators

We propose two kinds of distinguishing parameter regimes to induce topological Su-Schrieffer-Heeger (SSH) phase in a one dimensional (1D) multi-resonator cavity optomechanical system via modulating the frequencies of both cavity fields and resonators. The introduction of the frequency modulations allows us to eliminate the Stokes heating process for the mapping of the tight-binding Hamiltonian without usual rotating wave approximation, which is totally different from the traditional mapping of the topological tight-binding model. We find that the tight-binding Hamiltonian can be mapped into a topological SSH phase via modifying the Bessel function originating from the frequency modulations of cavity fields and resonators, and the induced SSH phase is independent on the effective optomechanical coupling strength. On the other hand, the insensitivity of the system to the effective optomechanical coupling provides us another new path to induce the topological SSH phase based on the present 1D cavity optomechanical system. And we show that the system can exhibit a topological SSH phase via varying the effective optomechanical coupling strength in an alternative way, which is much more easier to be achieved in experiment. Furthermore, we also construct an analogous bosonic Kitaev model with the trivial topology by keeping the Stokes heating processes. Our scheme provides a steerable platform to investigate the effects of next-nearest-neighboring interactions on the topology of the system.

quant-ph↗

arXiv2019

Controllable double quantum state transfers by one topological channel in a frequency-modulated optomechanical array

We propose a scheme to achieve the quantum state transfer via the topological protected edge channel based on a one dimensional frequency-modulated optomechanical array. We find that the optomechanical array can be mapped into a Su-Schrieffer-Heeger model after eliminating the counter rotating wave terms via frequency modulations. By dint of the edge channel of the Su-Schrieffer-Heeger model, we show that the quantum state transfer between the photonic left edge state and the photonic right edge state can be achieved with a high fidelity. Specially, our scheme can also achieve another phononic quantum state transfer based on the same channel via controlling the next-nearest-neighboring interactions between the cavity fields, which is different from the previous investigations only achieving one kind of quantum state transfer. Our scheme provides a novel path to switch two different kinds of quantum state transfers in a controllable way.

quant-ph↗

arXiv2019

Distinguishing photon blockade in a PT-symmetric optomechanical system

We study the effects of parity-time(PT)-symmetry on the photon blockade and distinguish the different blockade mechanisms in a double-cavity optomechanical system. By studying the light statistics of the system, we find the completely different photon blockade behaviors when the PT-symmetry is broken or unbroken, which is related to the PT phase transition. Furthermore, an interesting phenomenon that the two cavities are blocked at the same time is found with the appropriate system parameters. Those statistical phenomenons are all analyzed in detail and demonstrated by analytically solving the Schrodinger equation and numerically simulating the master equation, respectively. Finally, we also consider the non-PT symmetric situations which further reveal the physical essence of the photon blockade by comparing those results. Different from the usual photon blockade, our proposal is feasible even with weak parameter mechanism, i.e., the proposal neither requires the strong optomechanical coupling nor the large tunneling coupling between cavities.

quant-ph↗

arXiv2018

Amplitude-modulation-based atom-mirror entanglement and mechanical squeezing in a hybrid optomechanical system

We consider a hybrid optomechanical system which is composed of the atomic ensemble and a standard optomechanical cavity driven by the periodically modulated external laser field. We investigate the asymptotic behaviors of Heisenberg operator first moments and clearly show the approaching process between the exact numerical results and analytical solutions. Based on the specific modulation forms of external driving and effective optomechanical coupling, we discuss in detail the atom-mirror entanglement enhancement, respectively. Compared with the constant driving regime, the entanglement can be greatly enhanced with more loose cavity decay rate and is more resistant to the thermal fluctuations of the mechanical bath. The desired form of periodically modulated effective optomechanical coupling can be precisely engineered by the external driving modulation components which can be derived analytically via Laplace transform. Meanwhile, resorting to the quantum interference mechanism caused by atomic ensemble and modulating the external driving appropriately, the mechanical squeezing induced by the periodic modulation can be generated successfully in the unresolved regime.

quant-ph↗

arXiv2018

Manipulation of nanomechanical resonator via shaking optical frequency

In the usual optomechanical systems, the stability of the systems severely limits those researches of the macroscopic quantum effects. We study an usual cavity optomechanical system where the frequency of the optical mode is shaken periodically. We find that, when the optical shaking frequency is large enough, the shake of the optical mode can stabilize the system. That means we can study the macroscopic quantum effects of the mechanical resonator even in the strong coupling region where the standard optomechanical systems are always unstable. As examples, we study the ground-state cooling of the mechanical resonator and the entanglement between the optical and mechanical modes in the conventional unstable region, and the results indicate that the final mean phonon number and entanglement not only can be achieved but also can be modulated by the optical shaking parameters. Our proposal provides a method to study the macroscopic quantum effects even in conventional unstable region.

quant-ph↗

arXiv2018

Optomechanical cooling beyond the quantum backaction limit with frequency modulation

In the usual optomechanical cooling, even if the system has no thermal component, it still has a quantum limit-known as the quantum backaction limit (QBL)-on the minimum phonon number related to shot noise. By studying the side-band cooling regime in optomechanical system (OMS), we find that the cooling can be improved significantly when the frequency modulation (FM) that can suppress the Stokes heating processes is introduced into the system. We analyze and demonstrate the reasons of the phonon number below the QBL redefined in the whole stable region of the standard OMSs. The above analyses are further checked by numerically solving the differential equations of second order moments derived from the quantum master equation with broad system parameters, ranging from weak coupling (WC) to ultra-strong coupling (USC) and resolved side-band (RSB) to unresolved side-band (USB) regimes. Comparing with the cases of those without FM, the stable ground-state cooling can also be achieved even in the conventional unstable region.

quant-ph↗

arXiv2008

Repulsive and restoring Casimir forces with left-handed materials

We investigate repulsive Casimir force between slabs containing left-handed materials with controllable electromagnetic properties. The sign of Casimir force is determined by the electric and magnetic properties of the materials, and it is shown that the formation of the repulsive force is related to the wave impedances of two slabs. The sign change of the Casimir force as a function of the distance is studied. Special emphasis is put on the restoring Casimir force which may be found to exist between perfectly conducting material and metamaterial slabs. This restoring force is a natural power for the system oscillation in vacuum and also can be used for system stabilization.

quant-ph↗

arXiv2006

The discrete fractional random cosine and sine transforms

Based on the discrete fractional random transform (DFRNT), we present the discrete fractional random cosine and sine transforms (DFRNCT and DFRNST). We demonstrate that the DFRNCT and DFRNST can be regarded as special kinds of DFRNT and thus their mathematical properties are inherited from the DFRNT. Numeral results of DFRNCT and DFRNST for one and two dimensional functions have been given.

math-ph↗

arXiv2006

A discrete fractional random transform

We propose a discrete fractional random transform based on a generalization of the discrete fractional Fourier transform with an intrinsic randomness. Such discrete fractional random transform inheres excellent mathematical properties of the fractional Fourier transform along with some fantastic features of its own. As a primary application, the discrete fractional random transform has been used for image encryption and decryption.

math-ph↗

arXiv2005

Low crosstalk intersections of CCWs composed by mono-mode cavities

Low crosstalk intersections formed by two crossing coupled cavity waveguides (CCWs), which are formed by series of \textit{mono-mode} cavities in a two dimensional photonic crystal structure, are investigated. Although the individual cavities are \textit{mono-mode}, the modes of the properly designed CCWs (which are called \textit{supermodes} in this paper) may be dipole-like, and antisymmetry along the axis of the other perpendicular CCW, which ensures the low crosstalk of the intersections. According to the results of coupled mode analysis, we divide the intersections into two kinds based on the number of cavities of each CCW, and the transmission and crosstalk spectra of both kinds are numerically obtained using finite difference time domain (FDTD) method. The results show that crosstalk power is lower than -30dB. We also discuss the factors that affect the performance of the intersections.

physics.optics↗

arXiv2005

Supermodes of photonic crystal CCWs and multimode bistable switchings with uniform thresholds

Photonic crystal (PC) coupled cavity waveguides (CCWs) with \textit{completely separated eigenfrequencies} (or supermodes) are investigated. Using a coupled mode theory, the properties of the supermodes, such as the electric field profiles, the eigenfrequencies (including the central frequencies and corresponding linewidths), and the quality factors (Qs) are expressed in very simple formulas, and these results agree well with those of ``exact'' numerical method. We also discuss the great differences between the supermodes and \textit{continuous modes}, which are described by tight binding (TB) theory. Then, the properties of supermodes are used to investigate their potential applications in multichannel (covering the whole C-band) bistable switchings, and bistable loops are obtained numerically. We also predict and verify that all the thresholds are uniform inherently.

physics.optics↗