arXiv subjects

W. Z. Jia

Publications and source records attributed to W. Z. Jia.

18 recordsLinked to original sources

arXiv2025

Oscillating bound states in waveguide-QED system with two giant atoms

We study the bound states in the continuum (BIC) in a system of two identical two-level giant atoms coupled to a one-dimensional waveguide. By deriving general dark-state conditions, we clarify how coupling configurations and atomic parameters influence decay suppression. Through analysis of the long-time dynamical behaviors of atoms and bound photons, we carry out a detailed classification of bound states and explore the connections between these dynamical behaviors and the system's intrinsic light-matter interactions. The system supports static bound states with persistent atomic excitations, and oscillating bound states with periodic atom-photon or atom-atom excitation exchange. Under certain conditions, oscillating bound states can contain more harmonic components owing to the emergence of additional quasi-dark modes, rendering them promising platforms for high-capacity quantum information processing. These findings advance the understanding of BIC in waveguide quantum electrodynamics with multiple giant atoms and reveal their prospective applications in quantum technologies.

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arXiv2025

Simulating and probing many-body quantum states in waveguide-QED systems with giant atoms

Waveguide quantum electrodynamics (wQED) with giant atoms provides a distinctive opportunity to study one-dimensional (1D) coupled spin systems through its unique decoherence-free interactions. This study presents a theoretical framework for simulating the diagonal Aubry-André-Harper (AAH) model in the context of giant-atom wQED. The proposed scheme employs photonic modes in the waveguide to not only mediate interactions between atoms but also to detect the energy spectrum of the atom array. To illustrate the effectiveness of this approach, we present a simulation of the Hofstadter butterfly spectrum with high precision. Furthermore, for an incommensurate AAH atomic chain, we demonstrate that the photon transmission spectrum can accurately distinguish between the many-body localized phase and the extended phase. The method presented here is also applicable to the simulation of other types of 1D atomic chains based on giant-atom wQED.

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arXiv2024

Engineering photonic band gaps with a waveguide-QED structure containing an atom-polymer array

We investigate the generation and engineering of photonic band gaps in waveguide quantum electrodynamics systems containing periodically arranged atom-polymers. We first consider the configuration of a dimer array coupled to a waveguide. The results show that if the intra- and inter-cell phase delays are properly designed, the center and the width of the band gaps, as well as the dispersion relation of the passbands can be modified by adjusting the intra-cell coupling strength. These manipulations provide ways to control the propagating modes in the waveguide, leading to some interesting effects such as slowing or even stopping a single-photon pulse. Finally, we take the case of the tetramer chain as an example to show that, in the case of a larger number of atoms in each unit cell, tunable multi-gap structures and more sophisticated band-gap engineering can be realized. Our proposal provides efficient ways for photonic band-gap engineering in micro- and nano-quantum systems, which may facilitate the manipulation of photon transport in future quantum networks.

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arXiv2024

Single photon scattering from a chain of giant atoms coupled to a one-dimensional waveguide

We investigate coherent single-photon transport in a waveguide quantum electrodynamics structure containing multiple giant atoms. The single-photon scattering amplitudes are solved using a real-space method. The results give rise to a clear picture of the multi-channel scattering process. In the case of identical and equally-spaced giant atoms in a separate configuration, we also use the transfer-matrix method to express the scattering amplitudes in terms of compact analytical expressions, which allow us to conveniently analyze the properties of the scattering spectra. Based on these theoretical results, we find that the non-dipole effects of giant atoms, which are relevant to the design of the setup, can strongly manipulate several types of collective properties of the output fields, including the superradiant phenomenon, the multiple Fano interference, and the photonic band gap. This makes it possible to manipulate the photon transport in a more versatile way than with small atoms. We also make a proposal to probe the topological states of a chain of braided giant atoms by using photon scattering spectra, showing that waveguide quantum electrodynamics systems with giant atoms are ideal platforms to merge topological physics and on-chip quantum optics.

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arXiv2024

Atom-photon dressed states in a waveguide-QED system with multiple giant atoms

We study the properties of bound states in waveguide-QED systems consisting of multiple giant atoms coupled to a coupled-resonator waveguide. Based on the general analytical expressions for these states and the corresponding energy spectra, we analyze in detail the threshold conditions for the appearance of bound states and the photon-mediated interactions between dressed atoms for different configurations. In addition, when multiple giant atoms are coupled to the waveguide, different types of interacting atomic chain can be obtained by manipulating the coupling configurations. Accordingly, the energy spectra of the bound states form metaband structures in the photonic band gaps. This makes the system a useful platform for quantum simulation and quantum information processing.

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arXiv2022

Multiple electromagnetically induced transparency without a control field in an atomic array coupled to a waveguide

We investigate multiple electromagnetically induced transparency (EIT) in a waveguide quantum electrodynamics (wQED) system containing an atom array. By analyzing the effective Hamiltonian of the system, we find that in terms of the single-excitation collective states, a properly designed $N$-atom array can be mapped into a driven ($N+1$)-level system that can produce multiple EIT-type phenomenon. The corresponding scattering spectra of the atom-array wQED system are discussed both in the single-photon sector and beyond the single-photon limit. The most significant feather of this type of EIT scheme is control-field-free, which may provide an alternative way to produce EIT-like phenomenon in wQED system when external control fields are not available. The results given in our paper may provide good guidance for future experiments on multiple EIT without a control field in wQED system.

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arXiv2022

Spectrum of Single-Photon Scattering in a Strong-Coupling Hybrid Optomechanical System

We analyze theoretically the single-photon excitation and transmission spectra of a strong-coupling hybrid optomechanics, where a two-level system (TLS) is coupled to the mechanical resonator (MR), generating the Jaynes-Cummings-type polariton doublets. In our model, both the optomichanical coupling and the TLS-MR coupling are strong. In this parameter region, the polaron-assisted excitation and reemission processes can strongly affect the single-photon excitation and output spectra of the cavity. We find that the fine structure around each sideband can be used to characterize the TLS-MR and the effective TLS-photon couplings, even at single-quantum level. Thus, the spectrum structures may make it possible to sensitively probe the quantum nature of a macroscopic mechanical element. We further provide a possible approach for tomographic reconstruction of the state of a TLS, utilizing the single-photon transmission spectra.

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arXiv2022

Manipulating single-photon transport in a waveguide-QED structure containing two giant atoms

We investigate coherent single-photon transport in a waveguide-QED structure containing two giant atoms. The unified analytical expressions of the single-photon scattering amplitudes applicable for different topological configurations are derived. The spectroscopic characteristics in different parameter regimes, especially the asymmetric Fano line shapes and the electromagnetically induced transparency (EIT)-like spectra, are analyzed in detail. Specifically, we find that the appearance of Fano line shapes is influenced by not only the phase delays between coupling points but also the topologies of system. We also summarize the general conditions for appearance of EIT-like spectra by analyzing the master equation and verify these conditions by checking the corresponding analytical expressions of the scattering spectra. These phenomena may provide powerful tools for controlling and manipulating photon transport in future quantum networks.

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arXiv2022

Coherent single-photon scattering spectra for a giant-atom waveguide-QED system beyond dipole approximation

We investigate the single-photon scattering spectra of a giant atom coupled to a one dimensional waveguide via multiple connection points or a continuous coupling region. Using a full quantum mechanical method, we obtain the general analytic expressions for the single-photon scattering coefficients, which are valid in both the Markovian and the non-arkovian regimes. We summarize the influences of the non-dipole effects, mainly caused by the phases accumulated by photons traveling between coupling points, on the scattering spectra. We find that under the Markovian limit, the phase decay is detuning-independent, resulting in Lorentzian lineshapes characterized by the Lamb shifts and the effective decay rates. While in the non-Markovian regime, the accumulated phases become detuning-dependent, giving rise to non-Lorentzian lineshapes, characterized by multiple side peaks and total transmission points. Another interesting phenomenon in the non-Markovian regime is generation of broad photonic band gap by a single giant atom. We further generalize the case of discrete coupling points to the continuum limit with atom coupling to the waveguide via a continuous area, and analyze the scattering spectra for some typical distributions of coupling strength.

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arXiv2017

Efficient single-photon frequency conversion in the microwave domain using superconducting quantum circuits

We present an approach to achieve efficient single-photon frequency conversion in the microwave domain based on coherent control in superconducting quantum circuits, which consist of a driven artificial atom coupled to a semi-infinite transmission line. Using the full quantum-mechanical method, we analyze the single-photon scattering process in this system and find that single-photon frequency up- or down-conversion with efficiency close to unity can be achieved by adjusting the parameters of the control field applied to the artificial atom. We further show that our approach is experimentally feasible in currently available superconducting flux qubit circuits.

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arXiv2017

Phase-dependent optical response properties in an optomechanical system by coherently driving the mechanical resonator

We explore theoretically the optical response properties in an optomechanical system under electromagneti- cally induced transparency condition but with the mechanical resonator being driven by an additional coherent field. In this configuration, more complex quantum coherent and interference phenomena occur. In partic- ular, we find that the probe transmission spectra depend on the total phase of the applied fields. Our study also provides an efficient way to control propagation of amplification.

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arXiv2014

Optomechanically induced amplification and perfect transparency in double-cavity optomechanics

We study the optomechanically induced amplification and perfect transparency in a double-cavity optomechanical system. We find if two control lasers with appropriate amplitudes and detunings are applied to drive the system, the phenomenon of optomechanically induced amplification for a probe laser can occur. In addition, perfect optomechanically induced transparency phenomenon, which is robust to mechanical dissipation, can be realized by the same type of drive. These results are very important for signal amplification, light storage, fast light and slow light in the quantum information processes.

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arXiv2013

Single-photon transport in a one dimentional waveguide coupling to a hybrid atom-optomechanical system

We explore theoretically the single-photon transport in a single-mode waveguide that is coupled to a hybrid atom-optomechanical system in a strong optomechanical coupling regime. Using a full quantum real-space approach, transmission and reflection coefficients of the propagating single-photon in the waveguide are ob- tained. The influences of atom-cavity detuning and the dissipation of atom on the transport are also studied. Intriguingly, the obtained spectral features can reveal the strong light-matter interaction in this hybrid system.

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arXiv2011

Probing molecular chirality by coherent optical absorption spectra

We propose an approach to sensitively probe the chirality of molecules by measuring their coherent optical absorption spectra. It is shown that quantum dynamics of the cyclic three-level chiral molecules driven by appropriately-designed external fields is total-phase dependent. This will result in chirality-dependent absorption spectra for the probe field. As a consequence, these absorption spectra can be utilized to identify molecular chirality and determinate enantiomer excess. The feasibility of the proposal with chiral molecules confined in hollow-core photonic crystal fiber (HC-PCF) is also discussed.

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arXiv2010

Tunable one-dimensional microwave emissions from cyclic-transition three-level atoms

By strongly driving a cyclic-transition three-level artificial atom, demonstrated by such as a flux-based superconducting circuit, we show that coherent microwave signals can be excited along a coupled one-dimensional transmission line. Typically, the intensity of the generated microwave is tunable via properly adjusting the Rabi frequencies of the applied strong-driving fields or introducing a probe field with the same frequency. In practice, the system proposed here could work as an on-chip quantum device with controllable atom-photon interaction to implement a total-reflecting mirror or switch for the propagating probe field.

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arXiv2010

Vacuum induced Berry phases in single-mode Jaynes-Cummings models

Motivated by the work [Phys. Rev. Lett. 89, 220404 (2002)] for detecting the vacuum-induced Berry phases with two-mode Jaynes-Cummings models (JCMs), we show here that, for a parameter-dependent single-mode JCM, certain atom-field states also acquire the photon-number-dependent Berry phases after the parameter slowly changed and eventually returned to its initial value. This geometric effect related to the field quantization still exists, even the filed is kept in its vacuum state. Specifically, a feasible Ramsey interference experiment with cavity quantum electrodynamics (QED) system is designed to detect the vacuum-induced Berry phase.

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arXiv2010

Distinguishing left- and right-handed molecules by two-step coherent pulses

Chiral molecules with broken parity symmetries can be modeled as quantum systems with cyclic-transition structures. By using these novel properties, we design two-step laser pulses to distinguish left- and right-handed molecules from the enantiomers. After the applied pulse drivings, one kind chiral molecules are trapped in coherent population trapping state, while the other ones are pumped to the highest states for ionizations. Then, different chiral molecules can be separated.

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arXiv2010

Gain without inversion in quantum systems with broken parities

For a quantum system with broken parity symmetry, selection rules can not hold and cyclic transition structures are generated. With these loop-transitions we discuss how to achieve inversionless gain of the probe field by properly setting the control and auxiliary fields. Possible implementations of our generic proposal with specific physical objects with broken parities, e.g., superconducting circuits and chiral molecules, are also discussed.

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