arXiv subjects

Guan-Qiang Li

Publications and source records attributed to Guan-Qiang Li.

7 recordsLinked to original sources

arXiv2026

Multiple mobility rings in non-Hermitian Su-Schrieffer-Heeger chain with quasiperiodic potentials

The localization property of a non-Hermitian Su-Schrieffer-Heeger (SSH) chain with quasi-periodic on-site potential is investigated. In contrast to the preceding investigations, the quantum phase transition between localized state and extended one is achieved by adjusting the strength of intracellular or intercellular hopping. The energy spectra and eigenstate distributions of the system's Hamiltonian near the boundary of the phase transition exhibit different behaviors when the Hermiticity, non-Hermiticity and mosaic modulation of the quasi-periodic potential are considered, respectively. The existence of the mobility ring is revealed in the non-Hermitian SSH chain by studying of the critical behaviors near the boundary. More interestingly, the multiple mobility rings emerge when the period number of the mosaic modulation is increased. The result is helpful for the investigation of the localization-delocalization transition in the SSH-type system under the combined action of the non-Hermiticity and quasi-periodicity.

quant-ph↗

arXiv2025

Optimal control of population transfer in multi-level systems by dynamical quantum geometric tensor

The optimal control of population transfer for multi-level systems is investigated from the perspective of quantum geometry. Firstly, the general theoretical framework of optimizing the stimulated Raman adiabatic passage (STIRAP) scheme based on the dynamical quantum geometric tensor is given, and then the dynamical quantum geometric tensor and the nonadiabatic transition rate are calculated by taking the detuned $Λ$-type three-level system and tripod-type four-level system for example. Secondly, the transfer dynamics of the particle population of the system are investigated in detail. For a three-level system, the optimal STIRAP scheme has an efficiency of over 98\% in transferring the population to the final state, while the transfer efficiency of traditional STIRAP is about 72\%. The superposition states with arbitrary proportions can be efficiently prepared for a four-level system due to the decoupling of the degenerate dark states. Finally, the influences of system parameters, such as the operation time of the Rabi pulses, the amplitude fluctuation and the single-photon detuning, on the transfer process are discussed. Especially, the phenomenon of the adiabatic resonance transfer is revealed. Choosing the pulse parameters in the resonance window can reduce the infidelity of the population transfer to below $10^{-3}$. It is found that the optimal STIRAP scheme by the dynamical quantum geometric tensor provides faster and more efficient transfer than the traditional STIRAP scheme.

quant-ph↗

arXiv2025

A continuous variable quantum battery with wireless and remote charging

Quantum battery has become one of the hot issues at the research frontiers of quantum physics recently. Charging power, extractable work and wireless charging over long-distance are three important aspects of interest. Non-contact electromagnetic interaction provides an important avenue for wireless charging. In this paper, we design a wireless and remote charging scheme based on the quantized Hamiltonian of two coupled LC circuits, and focus on the charging dynamics of a continuous variable quantum battery. It is found that the quantum entanglement, which is regarded as a significant quantum resource, is not a prerequisite for charging the battery and extracting useful work. On the contrary, all of the energy in the battery could be converted into useful work in the absence of the entanglement for our model. The often overlooked counter-rotating wave coupling in the interacting Hamiltonian is helpful for extracting more useful work from the charger. If the coupling between the battery and the charger is designed to contain both the rotating and counter-rotating wave couplings, the extractable work can be obtained even if the charger is prepared in thermal states, while such effect cannot be achieved in the presence of a rotating or counter-rotating wave coupling alone. Finally, the effect of the system's parameters on the extractable work is discussed, which will provide a reference for full use of the thermal state energy.

quant-ph↗

arXiv2025

Dicke-Ising quantum battery of an ion chain driven by a mechanical oscillator

A scheme for implementing quantum batteries in a realizable and controllable platform based on a trapped ion chain driven by a mechanical oscillator is proposed. The effects of the hopping interaction between the two-level ions and the coupling interaction between the ions and the external mechanical oscillator on the charging process of the battery are investigated. The importance of the counter-rotating wave terms in the system's Hamiltonian, which are often ignored, is analyzed, and it is found that the charging energy and the ergotropy of the battery are dramatically affected by the counter-rotating wave terms. The quantum phase transition of the two-level system is restrained by the counter-rotating wave terms due to the destruction of the quantum coherence. Lastly, the power-law dependence of the charging process on the distance between the ions is discussed. Our theoretical analysis provides a solid foundation for the development of a practical quantum battery.

quant-ph↗

arXiv2025

Fast and robust production of quantum superposition states by the fractional shortcut to adiabaticity

The fractional shortcut to adiabaticity (f-STA) for production of quantum superposition states is proposed firstly via a three-level system with $Λ$-type linkage pattern and a four-level system with tripod structure. \textcolor[rgb]{1,0,0}{\sout{The fast, robust and efficient}} \textcolor[rgb]{0,0,1}{\uwave{The fast and robust}} production of the coherent superposition states is studied by comparing the populations for the f-STA and the fractional stimulated Raman adiabatic passage (f-STIRAP). The \textcolor[rgb]{1,0,0}{\sout{superposition}} states with equal proportion can be produced by fixing the controllable parameters of the driving pulses at the final moment of the whole process. The effects of the pulse intensity and the time delay of the pulses on the production process are discussed by monitoring the populations on all of the quantum states. In particular, the spontaneous emission arising from the intermediate state is investigated by the quantum master equation. The result reveals that the f-STA exhibits superior advantages over the f-STIRAP in producing the superposition states.

quant-ph↗

arXiv2021

Pseudo-Goldstone Excitations in a Striped Bose-Einstein Condensate

Significant experimental progress has been made recently for observing long-sought supersolid-like states in Bose-Einstein condensates, where spatial translational symmetry is spontaneously broken by anisotropic interactions to form a stripe order. Meanwhile, the superfluid stripe ground state was also observed by applying a weak optical lattice that forces the symmetry breaking. Despite of the similarity of the ground states, here we show that these two symmetry breaking mechanisms can be distinguished by their collective excitation spectra. In contrast to gapless Goldstone modes of the \textit{spontaneous} stripe state, we propose that the excitation spectra of the \textit{forced} stripe phase can provide direct experimental evidence for the long-sought gapped pseudo-Goldstone modes. We characterize the pseudo-Goldstone mode of such lattice-induced stripe phase through its excitation spectrum and static structure factor. Our work may pave the way for exploring spontaneous and forced/approximate symmetry breaking mechanisms in different physical systems.

cond-mat.quant-gas↗

arXiv2006

Collective excitations of a Bose-Einstein condensate in an anharmonic trap

We investigate the collective excitations of a one-dimensional Bose-Einstein condensate (BEC) with repulsive interaction between atoms in a quadratic plus quartic trap. By using the variational approach, the coupled equations of motion for the center-of-mass coordinate of the condensate and its width are derived. Then, two low-energy excitation modes are obtained analytically. The frequency shift induced by the anharmonic distortion, and the collapse and revival of the collective excitations, which originate from the nonlinear coupling between the two modes, are discussed.

cond-mat.mes-hall↗