arXiv subjects

Chun-Jie Yang

Publications and source records attributed to Chun-Jie Yang.

10 recordsLinked to original sources

arXiv2026

Floquet engineering in hybrid magnetic quantum systems

The advancement of magnonics has facilitated the utilization of hybrid magnetic systems in quantum technologies. A hybrid magnetic lattice formed by an array of superconducting loops and magnetic particles has been devised as a quantum bus to disseminate quantum resources among magnetic quantum entities serving as nodes of a quantum network. However, the lattice also exerts a decoherence effect on the quantum entities, which impairs its practical performance. By studying the non-Markovian dynamics of nitrogen-vacancy centers and magnon modes coupled to two independent hybrid magnetic lattices, we propose a Floquet-engineering scheme via periodic driving on the quantum entities to suppress decoherence. We find that significant steady-state entanglement is preserved when a Floquet bound state exists in the quasienergy spectrum of the system consisting of each driven quantum entity and its lattice. This result enables a precise manipulation of hybrid magnetic systems and benefits their applications in quantum networks.

quant-ph↗

arXiv2025

Quantum surface effects on quantum emitters coupled to surface plasmon polariton

As an ideal platform for exploring strong quantized light-matter interactions, surface plasmon polariton (SPP) has inspired many applications in quantum technologies. Recent experiments discovered that quantum surface effects (QSEs) of the metal, including nonlocal optical response, electron spill-out, and Landau damping, invalidate the classical electromagnetic theory and contribute additional loss sources to the SPP in the nanoscale. This hinders its applications. Going beyond the widely used classical local response approximation, we use the Feibelman $d$-parameter method to investigate the QSE-modified non-Markovian dynamics of quantum emitters (QEs) coupled to a SPP in a planar metal-dielectric nanostructure. A mechanism to overcome the dissipation of the QEs caused by the lossy SPP with the QSEs is discovered. We find that, as long as the QE-SPP bound states are formed, a dissipationless entanglement among the far-separated QEs is created. Compared with the local-response approximate results, the QSEs play a constructive role in establishing such a coherent correlation. The result lays a foundation for understanding the light-matter interactions in absorptive media and paves the way for the application of SPP in quantum network.

quant-ph↗

arXiv2024

Non-Markovian quantum interconnect formed by a surface plasmon polariton waveguide

Allowing the generation of effective interactions between distant quantum emitters (QEs) via flying photons, quantum interconnect (QI) is essentially a light-matter interface and acts as a building block in quantum technologies. A surface plasmon polariton (SPP) supported by a metallic waveguide provides an ideal interface to explore strong light-matter couplings and to realize QI. However, the loss of SPP in metal makes the mediated entanglement of the QEs damp with the increase of the distance and time, which hinders its applications. We propose a scheme of non-Markovian QI formed by the SPP of a metallic nanowire. A mechanism to make the generated entanglement of the QEs persistent is discovered. We find that, as long as bound states are formed in the energy spectrum of total QE-SPP system, the damping of the SPP-mediated entanglement is overcome even in the presence of the metal absorption to the SPP. Our finding enriches our understanding of light-matter couplings in absorptive medium and paves the way for using the SPP in designing QI.

quant-ph↗

arXiv2024

Quantum-state engineering in cavity magnomechanics formed by two-dimensional magnetic materials

Cavity magnomechanics has become an ideal platform to explore macroscopic quantum effects. Bringing together magnons, phonons, and photons in a system, it opens many opportunities for quantum technologies. It was conventionally realized by an yttrium iron garnet, which exhibits a parametric magnon-phonon coupling $\hat{m}^†\hat{m}(\hat{b}^†+\hat{b})$, with $\hat{m}$ and $\hat{b}$ being the magnon and phonon modes. Inspired by the recent realization of two-dimensional (2D) magnets, we propose a cavity magnomechanical system using a 2D magnetic material with both optical and magnetic drivings. It features the coexisting photon-phonon radiation-pressure coupling and quadratic magnon-phonon coupling $\hat{m}^†\hat{m}(\hat{b}^†+\hat{b})^2$ induced by the magnetostrictive interaction. A stable squeezing of the phonon and bi- and tri-partite entanglements among the three modes are generated in the regimes with a suppressed phonon number. Compared with previous schemes, ours does not require any extra nonlinear interaction and reservoir engineering and is robust against the thermal fluctuation. Enriching the realization of cavity magnomechanics, our system exhibits its superiority in quantum-state engineering due to the versatile interactions enabled by its 2D feature.

quant-ph↗

arXiv2019

Signatures of quantized coupling between quantum emitters and localized surface plasmons

Confining light to scales beyond the diffraction limit, quantum plasmonics supplies an ideal platform to explore strong light-matter couplings. The light-induced localized surface plasmons (LSPs) on the metal-dielectric interface acting as a quantum bus have wide potential in quantum information processing; however, the loss nature of light in the metal hinders their application. Here we propose a mechanism to make the reversible energy exchange and the multipartite quantum correlation of a collective of quantum emitters (QEs) mediated by the LSPs persistent. Via investigating the quantized interaction between the QEs and the LSPs supported by a spherical metal nanoparticle, we find that the diverse signatures of the quantized QE-LSP coupling in the steady state, including the complete decay, population trapping, and persistent oscillation, are essentially determined by the different number of bound states formed in the energy spectrum of the QE-LSP system. Enriching our understanding on the light-matter interactions in a lossy medium, our result is instructive in the design of quantum devices using plasmonic nanostructures.

quant-ph↗

arXiv2017

Suppressed dissipation of a quantum emitter coupled to surface plasmon polaritons

Enabling the confinement of light to a scale far below the one of conventional optics, surface plasmon polaritons (SPPs) induced by an electromagnetic field in a metal-dielectric interface supply an ideal system to explore strong quantized light-matter coupling. The fast matter-SPP population exchange reported in previous works makes it a candidate for spin manipulation, but such reversible dynamics asymptotically vanishes accompanying the quantum matter relaxing completely to its ground state. Here, we study the exact dissipative dynamics of a quantum emitter (QE) coupled to SPPs. It is interesting to find that, qualitatively different from conventional findings, the QE can be partially stabilized in its excited state even in the presence of the lossy metal. Our analysis reveals that it is the formation of a QE-SPP bound state which results in such suppressed dissipation. Enriching the decoherence dynamics of the QE in the lossy medium, our result is helpful to understand QE-SPP interactions and apply plasmonic nanostructures in quantum devices.

quant-ph↗

arXiv2016

Exact decoherence-free state of two distant quantum systems in a non-Markovian environment

Decoherence-free state (DFS) encoding supplies a useful way to avoid the detrimental influence of the environment on quantum information processing. The DFS was previously well established in either the two subsystems locating at the same spatial position or the dynamics under the Born--Markovian approximation. Here, we investigate the exact DFS of two spatially separated quantum systems consisting of two-level systems or harmonic oscillators coupled to a common non-Markovian zero-temperature bosonic environment. The exact distance-dependent DFS and the explicit criterion for forming the DFS are obtained analytically, which reveals that the DFS can arise only in one-dimensional environment. It is remarkable to further find that the DFS is just the system-reduced state of the famous bound state in the continuum (BIC) of the total system predicted by Wigner and von Neumann. On the one hand our result gives insight into the physical nature of the DFS, and on the other hand it supplies an experimentally accessible scheme to realize the mathematically curious BIC in the standard quantum optical systems.

quant-ph↗

arXiv2016

Resonance fluorescence beyond the dipole approximation of a quantum dot in a plasmonic nanostructure

The mesoscopic characteristics of a quantum dot (QD), which make the dipole approximation (DA) break down, provide a new dimension to manipulate light-matter interaction [M. L. Andersen et al., Nat. Phys. 7, 215 (2011)]. Here we investigate the power spectrum and the second-order correlation property of the fluorescence from a resonantly driven QD placed on a planar metal. It is revealed that due to the pronounced QD spatial extension and the dramatic variation of the triggered surface plasmon near the metal, the fluorescence has a notable contribution from the quadrupole moment. The π-rotation symmetry of the fluorescence to the QD orientation under the DA is broken. By manipulating the QD orientation and quadrupole moment, the spectrum can be switched between the Mollow triplet and a single peak, and the fluorescence characterized by the antibunching in the second-order correlation function can be changed from the weak to the strong radiation regime. Our result is instructive for utilizing the unique mesoscopic effects to develop nanophotonic devices.

cond-mat.mes-hall↗

arXiv2015

Generation of stable entanglement between two cavity mirrors by squeezed-reservoir engineering

The generation of quantum entanglement of macroscopic or mesoscopic bodies in mechanical motion is generally bounded by the thermal fluctuation exerted by their environments. Here we propose a scheme to establish stationary entanglement between two mechanically oscillating mirrors of a cavity. It is revealed that, by applying a broadband squeezed laser acting as a squeezed-vacuum reservoir to the cavity, a stable entanglement between the mechanical mirrors can be generated. Using the adiabatic elimination and master equation methods, we analytically find that the generated entanglement is essentially determined by the squeezing of the relative momentum of the mechanical mirrors, which is transferred from the squeezed reservoir through the cavity. Numerical verification indicates that our scheme is within the present experimental state of the art of optomechanics.

quant-ph↗

arXiv2014

Canonical versus noncanonical equilibration dynamics of open quantum systems

In statistical mechanics, any quantum system in equilibrium with its weakly coupled reservoir is described by a canonical state at the same temperature as the reservoir. Here, by studying the equilibration dynamics of a harmonic oscillator interacting with a reservoir, we evaluate microscopically the condition under which the equilibration to a canonical state is valid. It is revealed that the non-Markovian effect and the availability of a stationary state of the total system play a profound role in the equilibration. In the Markovian limit, the conventional canonical state can be recovered. In the non-Markovian regime, when the stationary state is absent, the system equilibrates to a generalized canonical state at an effective temperature; whenever the stationary state is present, the equilibrium state of the system cannot be described by any canonical state anymore. Our finding of the physical condition on such noncanonical equilibration might have significant impact on statistical physics. A physical scheme based on circuit QED is proposed to test our results.

quant-ph↗