arXiv subjects

Jin-Hui Wu

Publications and source records attributed to Jin-Hui Wu.

At least 37 records · Page 2Linked to original sources

arXiv2022

Light transfer transitions beyond higher-order exceptional points in parity-time and anti-parity-time symmetric waveguide arrays

We propose two non-Hermitian arrays consisting of $N=2l+1$ waveguides and exhibiting parity-time ($\mathcal{PT}$) or anti-$\mathcal{PT}$ symmetry for investigating light transfer dynamics based on $N$th-order exceptional points (EPs). The $\mathcal{PT}$-symmetric array supports two $N$th-order EPs separating an unbroken and a broken phase with real and imaginary eignvalues, respectively. Light transfer dynamics in this array exhibits radically different behaviors, i.e. a unidirectional oscillation behavior in the unbroken phase, an edge-towards localization behavior in the broken phase, and a center-towards localization behavior just at $N$th-order EPs. The anti-$\mathcal{PT}$-symmetric array supports also two $N$th-order EPs separating an unbroken and a broken phase, which refer however to imaginary and real eigenvalues, respectively. Accordingly, light transfer dynamics in this array exhibits a center-towards localization behavior in the unbroken phase and an origin-centered oscillation behavior in the broken phase. These nontrivial light transfer behaviors and their controlled transitions are not viable for otherwise split lower-order EPs and depend on the underlying $SU(2)$ symmetry of spin-$l$ matrices.

physics.optics↗

arXiv2022

Spatial Kramers-Kronig relation and unidirectional light reflection induced by Rydberg dipole-dipole interactions

Kramers-Kronig (KK) relation between the dispersion and absorption responses of a signal field can be mapped from the frequency domain into the space domain via the dipole-dipole interactions between a homogeneous sample of target atoms and a control atom. This is achieved by establishing an effective two-level configuration for the three-level target atoms in the single-photon far-detuned driving regime while maintaining a high Rydberg excitation for the three-level control atom in the single-photon resonant driving regime. We find in particular that it is viable to realize a dynamically tunable spatial KK relation supporting asymmetric and even unidirectional reflection for appropriate signal frequencies in a controlled range. Taking a periodic lattice of target atoms instead, multiple Bragg scattering can be further incorporated into spatial KK relation to largely enhance the nonzero reflectivity yet without breaking the asymmetric or unidirectional reflection.

physics.atom-ph↗

arXiv2021

Quantum transport in nonlinear Rudner-Levitov models

Quantum transport in a class of nonlinear extensions of the Rudner-Levitov model is numerically studied in this paper. We show that the quantization of the mean displacement, which embodies the quantum coherence and the topological characteristics of the model, is markedly modified by nonlinearities. Peculiar effects such as a "trivial-nontrivial" transition and unidirectional long-range quantum transport are observed. These phenomena can be understood on the basis of the dynamic behavior of the effective hopping terms, which are time and position dependent, containing contributions of both the linear and nonlinear couplings.d nonlinear couplings.

quant-ph↗

arXiv2021

Single-photon nonreciprocal excitation transfer with non-Markovian retarded effects

We study at the single-photon level the nonreciprocal excitation transfer between emitters coupled with a common waveguide. Non-Markovian retarded effects are taken into account due to the large separation distance between different emitter-waveguide coupling ports. It is shown that the excitation transfer between the emitters of a small-atom dimer can be obviously nonreciprocal by introducing between them a coherent coupling channel with nontrivial coupling phase. We prove that for dimer models the nonreciprocity cannot coexist with the decoherence-free giant-atom structure although the latter markedly lengthens the lifetime of the emitters. In view of this, we further propose a giant-atom trimer which supports both nonreciprocal transfer (directional circulation) of the excitation and greatly lengthened lifetime. Such a trimer model also exhibits incommensurate emitter-waveguide entanglement for different initial states in which case the excitation transfer is however reciprocal. We believe that the proposals in this paper are of potential applications in large-scale quantum networks and quantum information processing.

quant-ph↗

arXiv2021

Entanglement preparation and non-reciprocal excitation evolution in giant atoms by controllable dissipation and coupling

We investigate the dynamics of giant atom(s) in a waveguide QED scenario, where the atom couples to the coupled resonator waveguide via two sites. For a single giant atom setup, we find that the atomic dissipation rate can be adjusted by tuning its size. For the two giant atoms system, the waveguide will induce the controllable individual and collective dissipation as well as effective inter-atom coupling. As a result, we can theoretically realize the robust entangled state preparation and non-reciprocal excitation evolution. We hope our study can be applied in quantum information processing based on photonic and acoustic waveguide setup.

quant-ph↗

arXiv2020

Spatial Kramers-Kronig relation and controlled unidirectional reflection in cold atoms

We propose a model for realizing frequency-dependent spatial variations of the probe susceptibility in a cold atomic sample. It is found that the usual Kramers-Kronig (KK) relation between real and imaginary parts of the probe susceptibility in the frequency domain can be mapped into the space domain as a far detuned control field of intensity linearly varied in space is used. This non-Hermitian medium exhibits then a unidirectional reflectionless frequency band for probe photons incident from either the left or the right sample end. It is of special interest that we can tune the frequency band as well as choose the direction corresponding to the vanishing reflectivity by changing, respectively, the control field intensity and frequency. The nonzero reflectivity from the other direction is typically small for realistic atomic densities, but can be largely enhanced by incorporating the Bragg scattering into the spatial KK relation so as to achieve a high reflectivity contrast.

quant-ph↗

arXiv2019

Nonreciprocal quantum interference and coherent photon routing in a three-port optomechanical system

We study the quantum interference between different weak signals in a three-port optomechanical system, which is achieved by coupling three cavity modes to the same mechanical mode. If one cavity serves as a control port and is perturbed continually by a control signal, nonreciprocal quantum interference can be observed when another signal is injected upon different target ports. In particular, we exhibit frequency-independent perfect blockade induced by the completely destructive interference over the full frequency domain. Moreover, coherent photon routing can be realized by perturbing all ports simultaneously, with which the synthetic signal only outputs from the desired port. We also reveal that the routing scheme can be extended to more-port optomechanical systems. The results in this paper may have potential applications for controlling light transport and quantum information processing.

quant-ph↗

arXiv2019

Entanglement optimization of filtered output fields in cavity optomechanics

Output entanglement is a key element in quantum information processing. Here, we show how to obtain optimal entanglement between two filtered output fields in a three-mode optomechanical system. First, we obtain the key analytical expression of optimal time delay between the two filtered output fields, from which we can obtain the optimal coupling for output entanglement without time delay. In this case, our linearized analysis predicts that the entanglement saturates to an optimal value as the optomechanical coupling is increased. Furthermore, we obtain the optimal output entanglement with time delay. These results should be very helpful in conceiving new optomechanical schemes of quantum information processing with their efficiency depending critically on the degree of output entanglement.

quant-ph↗

arXiv2019

Discrete time crystal in a finite chain of Rydberg atoms without disorder

We study the collective dynamics of a clean Floquet system of cold atoms, numerically simulating two realistic set-ups based on a regular chain of interacting Rydberg atoms driven by laser fields. In both cases, the population evolution and its Fourier spectrum display clear signatures of a discrete time crystal (DTC), exhibiting the appearance of a robust subharmonic oscillation which persists on a time scale increasing with the chain size, within a certain range of control parameters. We also characterize how the DTC stability is affected by dissipative processes, typically present in this atomic system even though the Rydberg state is very long lived.

quant-ph↗

arXiv2018

Noise-induced distributed entanglement in atom-cavity-fiber system

The distributed quantum computation plays an important role in large-scale quantum information processing. In the atom-cavity-fiber system, we put forward two efficient proposals to prepare the steady entanglement of two distant atoms with dissipation. The atomic spontaneous emission and the loss of fiber are exploited actively as powerful resources, while the effect of cavity decay is inhibited by quantum Zeno dynamics and quantum-jump-based feedback control. These proposals do not require precisely tailored Rabi frequencies or coupling strength between cavity and fiber. Furthermore, we discuss the feasibility of extending the present schemes into the systems consisting of two atoms at the opposite ends of the $n$ cavities connected by $(n-1)$ fibers, and the corresponding numerical simulation reveals that a high fidelity remains achievable with current experimental parameters.

quant-ph↗

arXiv2018

Engineering steady Knill-Laflamme-Milburn state of Rydberg atoms by dissipation

The Knill-Laflamme-Milburn (KLM) states have been proved to be a useful resource for quantum information processing [Nature 409, 46 (2001)]. For atomic KLM states, several schemes have been put forward based on the time-dependent unitary dynamics, but the dissipative generation of these states has not been reported. This work discusses the possibility for creating different forms of bipartite KLM states in neutral atom system, where the spontaneous emission of excited Rydberg states, combined with the Rydberg antiblockade mechanism, is actively exploited to engineer a steady KLM state from an arbitrary initial state. The numerical simulation of the master equation signifies that a fidelity above 99\% is available with the current experimental parameters.

quant-ph↗

arXiv2018

Dissipation induced $W$ state in a Rydberg-atom-cavity system

A dissipative scheme is proposed to prepare tripartite $W$ state in a Rydberg-atom-cavity system. It is an organic combination of quantum Zeno dynamics, Rydberg antiblockade and atomic spontaneous emission to turn the tripartite $W$ state into the unique steady state of the whole system. The robustness against the loss of cavity and the feasibility of the scheme are demonstrated thoroughly by the current experimental parameters, which leads to a high fidelity above $98\%$.

quant-ph↗

arXiv2018

All-optical photon transmission switching in a passive-active optomechanical system

We propose a feasible scheme to realize all-optical photon transmission switching in a passiveactive optomechanical system, consisting of one ordinary passive cavity, one active cavity and one common movable membrane oscillator of perfect reflection, driven by two strong control fields and two weak probe fields symmetrically. By means of the gain effect of the active cavity, many novel and valuable phenomena arise, such as frequency-independent perfect reflection (FIPR) first proposed in this paper, adjustable photon bidirectional transmission, phase-dependent non-reciprocity and so on. The relevant parameters used for controlling the all-optical switching are precisely tunable by adjusting the strengths of control fields and the relative phase of probe fields. Furthermore, tunable fast and slow light can be realized in our system by accurately adjusting relevant parameters which is readily and feasible in experiments. These novel phenomena originate from the effective optomechanical coupling and the gain effect provide a promising platform for photonic devices, quantum network node fabrication and quantum information process (QIP).

quant-ph↗

arXiv2017

Phase sensitive photonic flash

We theoretically propose a photonic flash based on a linearly coupled cavity system. Via driving the two side cavities by external fields, it forms a cyclic energy-level diagram and therefore the phase difference between the driving fields acts as a controller of the steady state due to the quantum interference effect. In the optical trimer structure, we show that the perfect photonic flash can be realized in the situation of resonant driving. The perfect photonic flash scheme is furthermore generalized to multiple coupled cavity system, where the cavities with odd and even number turn bright and dark alternatively. {Our proposal may be applied in the designing of quantum neon and realizing a controllable photonic localization.

quant-ph↗

arXiv2017

All-optical transistor based on Rydberg atom-assisted opto-mechanical system

We study the optical response of double optomechanical cavity system assisted by Rydberg atomic ensembles. And atomic ensembles are only coupled with one side cavity by a single cavity mode. It has been realized that a long-range manipulation for optical properties of hybrid system, by controlling the Rydberg atomic ensembles decoupled with the optomechanical cavity. Switching on the coupling between atoms and cavity mode, the original time reversal symmetry of double cavity structure has been broken. Based on the controlled optical non-reciprocity, we put forward the theoretical schemes of all-optical controlled diode, rectifier and transistor.

physics.optics↗

arXiv2016

Interacting photon pulses in Rydberg medium

The understanding of dynamical evolutions of interacting photon pulses in Rydberg atomic ensemble is the prerequisite for realizing quantum devices with such system. We present an approach that efficiently simulates the dynamical processes, using a set of local functions we construct to reflect the profiles of narrowband pulses. For two counter-propagating photon pulses, our approach predicts the distinct phenomena from the widely concerned Rydberg blockade to the previously less noticed significant absorption in the anomalous dispersion regime, which can occur by respectively setting the pulse frequency to the appropriate values. Our numerical simulations also demonstrate how spatially extending photon pulses become deformed under realistic non-uniform interaction over their distributions.

quant-ph↗

arXiv2015

Storage and retrieval of photons under their mutual interaction in Rydberg medium

Stopping and regenerating a pair of single-photon pulses at adjacent locations in coherently prepared Rydberg atomic ensembles are significantly affected by their effective interaction mediated by Rydberg excitations, and the similar processes can differ notably from the one exhibiting the common Rydberg blockade as with the stationary propagation of multi-photon light beams in the same medium. Based on the complete dynamics, we reveal the detailed features in such processes by finding how the profiles of the involved quantum fields evolve in various situations. The findings help to determine the proper regimes for implementing photonic gates and transistors. In addition, we discuss the non-adiabatic corrections associated with quickly changing control fields, and illustrate a method that restores the photon pulses' original amplitude during their retrieval unless they are heavily damped before storage.

quant-ph↗

arXiv2015

Tunable multi-channel inverse optomechanically induced transparency

In contrast to the optomechanically induced transparency (OMIT) defined conventionally, the inverse OMIT behaves as coherent absorption of the input lights in the optomechanical systems. We characterize a feasible inverse OMIT in a multi-channel fashion with a double-sided optomechanical cavity system coupled to a nearby charged nanomechanical resonator via Coulomb interaction, where two counter-propagating probe lights can be absorbed via one of the channels or even via three channels simultaneously with the assistance of a strong pump light. Under realistic conditions, we demonstrate the experimental feasibility of our model using two slightly different nanomechanical resonators and the possibility of detecting the energy dissipation of the system. In particular, we find that our model turns to be an unilateral inverse OMIT once the two probe lights are different with a relative phase, and in this case we show the possibility to measure the relative phase precisely.

quant-ph↗