arXiv subjects

Yuangang Deng

Publications and source records attributed to Yuangang Deng.

At least 19 recordsLinked to original sources

arXiv2026

Quantum Interference Amplifies Weak Chirality into Giant Quantum Nonreciprocity

Quantum nonreciprocity at few-photon level typically requires strong symmetry breaking, posing significant experimental challenges. Here we demonstrate that phase-controlled quantum interference can amplify weak chirality into giant quantum nonreciprocity. We consider two phase-programmable atoms coupled to a spinning whispering-gallery-mode resonator, where interference dramatically amplifies the effect of weak Fizeau splitting. This mechanism generates pronounced directional asymmetry in photon statistics, featuring bright antibunched emission in one direction and strongly bunched emission in the opposite direction. Remarkably, both correlation and brightness isolations obey phase-controlled power-law scaling with Fizeau splitting, reaching up to 65~dB and 17.3~dB, respectively. Our results establish interference-enhanced weak chirality as a powerful route toward directional nonclassical light sources.

quant-ph↗

arXiv2026

Many-Body Amplified Nonclassical Photon Emission in Cavity-Coupled Atomic Arrays

The generation of high-performance nonclassical light remains a cornerstone of quantum technologies, yet faces a fundamental trade-off between emission purity and brightness. Here, we demonstrate that cavity-mediated many-body spin-exchange interactions provide a route to overcome this constraint by collectively amplifying spectral anharmonicity. In a cavity-coupled atomic array with a programmable relative phase $ϕ$, the resulting interference-interaction mechanism reshapes the dressed-state manifold and enables deterministic switching between distinct quantum emission regimes. For $ϕ=0$, constructive interference yields high-purity single-photon emission with antibunching improved by four orders of magnitude while preserving strong photon flux. Conversely, for $ϕ=π$, destructive interference creates a dark single-photon manifold, resonantly activating two-photon processes to produce bright and pure photon-pair bundles. Our work establishes interference-engineered many-body interactions as a scalable mechanism for on-demand quantum light generation and open a new avenue for harnessing collective many-body physics in quantum photonics.

quant-ph↗

arXiv2026

Deterministic multiphoton bundle emission via interference-interaction control

The controlled generation of nonclassical light beyond single photons remains a central challenge in quantum optics, due to the difficulty of enhancing multiphoton processes while suppressing lower-order excitations. Here we propose an interference-interaction-engineered scheme for programmable few-photon emission in a cavity-QED system of three atoms coupled to orthogonal cavity modes. By adiabatically eliminating an auxiliary Fabry-Pérot cavity, we generate a tunable cavity-mediated spin-exchange interaction $χ$, which, combined with a controllable geometric phase $ϕ$, reshapes the many-body dressed-state spectrum. This interplay enables selective addressing of excitation manifolds ($N=1,2,3$), establishing a direct mapping between excitation structure and photon-emission channels. For $ϕ=0$, constructive interference enhances the spectral anharmonicity of low-excitation manifolds, yielding tunable single- and two-photon emission associated with the $N=1$ and $N=2$ manifolds. In contrast, for $ϕ=2π/3$, destructive interference suppresses lower-order excitation pathways and activates a resonant three-photon channel originating from the $N=3$ manifold. Importantly, the cavity-mediated interaction $χ$ further enhances spectral separation between manifolds, enabling a substantial improvement in multiphoton purity while maintaining a sizable photon population. We demonstrate a three-order-of-magnitude enhancement in two-photon purity and more than two orders of magnitude improvement in three-photon emission. Our results establish a unified interference-interaction framework in which effective optical nonlinearities can be programmably engineered through phase and interaction, providing a scalable route toward high-purity multiphoton sources and programmable quantum photonic devices.

quant-ph↗

arXiv2026

Dual-mode ground-state cooling in quadratic optomechanical systems: from multistability to general dark-mode suppression

We theoretically investigate a quadratic optomechanical system comprising a single-mode optical cavity linearly coupled to one mechanical resonator and quadratically coupled to a second resonator. By tuning the cavity detuning and optomechanical coupling strengths, we demonstrate the transition from optical bistability to multistability with up to seven steady-state solutions. Notably, simultaneous ground-state cooling of both mechanical resonators occurs on the dynamically stable branch of the nonlinear steady-state solutions, offering new opportunities for combined nonlinear optical and quantum cooling functionalities. Beyond the multistable regime, we systematically study dual-mode ground-state cooling and find that robust simultaneous cooling can be achieved over a broad parameter range, except when the linear and quadratic couplings become comparable, where a dark-mode effect arises. In this case, tuning the second-order optomechanical-induced frequency shifts effectively suppresses dark-mode interference, enabling controllable and simultaneous ground-state cooling. Our results provide a versatile framework for engineering multimode quantum states in optomechanical systems and open new avenues for the development of multifunctional quantum devices, including ultra-sensitive sensors, scalable quantum memories, and integrated quantum networks.

quant-ph↗

arXiv2025

Tunable Single- and Multiphoton Bundles in Cavity-Coupled Atomic Arrays

We propose an experimentally accessible scheme for realizing tunable nonclassical light in cavity-coupled reconfigurable atomic arrays. By coherently controlling the collective interference phase, the system switches from single-photon blockade to high-purity multiphoton bundle emission, unveiling a hierarchical structure of photon correlations dictated by atom-number parity and cavity detuning. The scaling of photon population identifies the transition between superradiant and subradiant regimes, while parity- and phase-dependent spin correlations elucidate the microscopic interference processes enabling coherent multiphoton generation. This work establishes a unified framework connecting cooperative atomic interactions to controllable nonclassical photon statistics and introduces a distinct interference-enabled mechanism that provides a practical route toward high-fidelity multiphoton sources in scalable cavity QEDs.

quant-ph↗

arXiv2025

Dark Superradiance in Cavity-Coupled Polar Molecular Bose-Einstein Condensates

We propose an experimental scheme to realize phase transition from {\it dark superradiance} to conventional superradiance in a microwave cavity coupled to polar molecules. The competition between cavity-mediated infinite-range repulsions and finite-range attractive dipolar interactions stabilizes a variety of exotic quantum phases, including vortex, vortex anti-vortex pairs, and superradiant phase, all emerging without external driving fields. In vortex phase associated with {\it dark superradiance}, cavity remains in vacuum state while profoundly reshaping the condensate's ground-state wave functions. In particular, the spin configuration locally parallel but globally anti-parallel is a direct consequence of competing for two nonlocal interactions. Beyond Dicke paradigm, dipolar dressing of condensate enables access to an unexplored regime of repulsion-dominated superradiance. A Bogoliubov analysis of low-energy excitation spectrum confirms that the condensate remains stable, avoiding roton-maxon induced collapse even in strongly dipolar regime.

cond-mat.quant-gas↗

arXiv2025

Topological Dynamics and Correspondences in Composite Exceptional Rings

The study of unconventional phases and elucidation of correspondences between topological invariants and their intriguing properties are pivotal in topological physics. Here, we investigate a complex exceptional ring (CER), composed of a third-order exceptional ring and multiple Weyl exceptional rings, and establish a direct correspondence between Chern numbers and the distinctive behaviors of these structures. We show that band braiding during quasistatic encircling processes correlates with nontrivial Chern numbers, resulting in triple (double) periodic spectra for topologically nontrivial (trivial) middle bands. Moreover, Chern numbers predict mode transfer during dynamical encircling. Experimental schemes for realizing CER in cold atoms are proposed, emphasizing the crucial role of Chern numbers as both measurable quantity and descriptor of exceptional physics in dissipative systems. This discovery broadens topological classifications in non-Hermitian systems, with promising applications in quantum computing and metrology.

cond-mat.quant-gas↗

arXiv2025

Atom-Molecule Superradiance and Entanglement with Cavity-Mediated Three-Body Interactions

Ultracold atoms coupled to optical cavities offer a powerful platform for studying strongly correlated many-body physics. Here, we propose an experimental scheme for creating biatomic molecules via cavity-enhanced photoassociation from an atomic condensate. This setup realizes long-range three-body interactions mediated by tripartite cavity-atom-molecule coupling. Beyond a critical pump strength, a self-organized square lattice phase for molecular condensate emerges, resulting in hybrid atom-molecule superradiance with spontaneous $U(1)$ symmetry breaking. Distinct from previously observed ultracold bosonic (fermionic) atomic superradiance, our findings demonstrate bosonic enhancement characterized by a cubic scaling of steady-state photon number with total atom number. Additionally, strong photon-matter entanglement is shown to effectively characterize superradiant quantum phase transition. Our findings deepen the understanding of quantum superchemistry and exotic many-body nonequilibrium dynamics in cavity-coupled quantum gases.

cond-mat.quant-gas↗

arXiv2024

$N$-photon bundles emission in high-spin Jaynes-Cummings model

High-spin quantum systems, endowed with rich internal degrees of freedom, constitute a promising platform for manipulating high-quality $n$-photon states. In this study, we explore $n$-photon bundles emission by constructing a high-spin Jaynes-Cummings model (JCM) within a single-mode cavity interacting with a single spin-$3/2$ atom. Our analysis reveals that the $n$-photon dressed state splittings can be significantly enhanced by adjusting the linear Zeeman shift inherent to the internal degrees of freedom in high-spin systems, thereby yielding well-resolved $n$-photon resonance. The markedly enhanced energy-spectrum anharmonicity, stemming from strong nonlinearities, enables the realization of high-quality $n$-photon bundles emission with large steady-state photon numbers, in contrast to conventional spin-1/2 JCM setups. Of particular interest is the realization of an optical multimode transducer capable of transitioning among single-photon blockade, two- to four-photon bundles emission, and photon-induced tunneling by tuning the light-cavity detuning in the presence of both cavity and atomic pump fields. This work unveils significant opportunities for diverse applications in nonclassical all-optical switching and high-quality multiphoton sources, deepening our understanding of creating specialized nonclassical states and fundamental physics in high-spin atom-cavity systems.

cond-mat.quant-gas↗

arXiv2024

Tunable multiphoton bundles emission in a Kerr-type two-photon Jaynes-Cummings model

We present a study on manipulation and enhancement of multiphoton bundles emission under a moderate atom-cavity coupling, by constructing a two-photon Jaynes-Cummings model integrated with Kerr nonlinearity in a single atom-cavity system. We show that the vacuum-Rabi splittings for the $n$th dressed states can be significantly enhanced by Kerr interaction. This remarkable enhancement in energy-spectrum anharmonicity with the well-resolved multiphoton resonance facilitates the generation of special nonclassical states beyond the strong-coupling limit in the experiment. In particular, both two- and three-photon blockades are observed with adjusting the amplitude of the cavity-driving or atom-pump fields. Moreover, we discover that transitions between two- and three-photon bundles can be achieved through tuning the atom-cavity detuning or Kerr nonlinearity. It further showcases the three-photon blockade is substantially strengthened when both the cavity and atomic fields are jointly driven. Our proposal unveils a pathway for realizing highly controllable nonclassical states and quantum devices with combining two-photon Jaynes-Cummings interactions and Kerr nonlinearity, which may pave the way for versatile applications in quantum information science, e.g., all-optical switches and transistors.

quant-ph↗

arXiv2024

The synthetic gauge field and exotic vortex phase with spin-orbital-angular-momentum coupling

Ultracold atoms endowed with tunable spin-orbital-angular-momentum coupling (SOAMC) represent a promising avenue for delving into exotic quantum phenomena. Building on recent experimental advancements, we propose the generation of synthetic gauge fields ,and by including exotic vortex phases within spinor Bose-Einstein condensates, employing a combination of a running wave and Laguerre-Gaussian laser fields. We investigate the ground-state characteristics of the SOAMC condensate, revealing the emergence of exotic vortex states with controllable orbital angular momenta. It is shown that the interplay of the SOAMC and conventional spin-linear-momentum coupling induced by the running wave beam leads to the formation of a vortex state exhibiting a phase stripe hosting single multiply quantized singularity. The phase of the ground state will undergo the phase transition corresponding to the breaking of rotational symmetry while preserving the mirror symmetry. Importantly, the observed density distribution of the ground-state wavefunction, exhibiting broken rotational symmetry, can be well characterized by the synthetic magnetic field generated through light interaction with the dressed spin state. Our findings pave the way for further exploration into the rotational properties of stable exotic vortices with higher orbital angular momenta against splitting in the presence of synthetic gauge fields in ultracold quantum gases.

cond-mat.quant-gas↗

arXiv2024

Self-Ordered Supersolid in Spinor Condensates with Cavity-Mediated Spin-Momentum-Mixing Interactions

Ultracold atoms with cavity-mediated long-range interactions offer a promising platform for investing novel quantum phenomena. Exploiting recent experimental advancements, we propose an experimental scheme to create self-ordered supersolid in spin-$1/2$ condensates confined within an optical cavity. The interplay of cavity and pump fields gives rise to supersolid square and plane wave phases, comprehensively described by the two-component Tavis-Cummings model. We show that the self-ordered supersolid phase exhibits an undamped gapless Goldstone mode over a wide parameter range. This proposal, achievable with current experimental setups utilizing identical laser configurations, is in contrast to the realization of checkerboard supersolidity, which hinges on constructing a $U(1)$ symmetry by utilizing two ${\cal Z}_2$ symmetries with precisely matched atom-cavity coupling in multimode resonators. By employing the superradiant photon-exchange process, we realize for the first time cavity-mediated spin-momentum-mixing interactions between highly correlated spin and momentum modes, analogous to that observed spin-mixing in spin-1 condensates. Our scheme provides a unique platform for realizing spin-momentum squeezing and spatially distributed multipartite entanglement.

cond-mat.quant-gas↗

arXiv2023

Unveiling Vacuum Fluctuations and Nonclassical States with Cavity-Enhanced Tripartite Interactions

Enhancing and tailoring light-matter interactions offer remarkable nonlinear resources with wide-ranging applications in various scientific disciplines. In this study, we investigate the construction of strong and deterministic tripartite `beamsplitter' (`squeeze') interactions by utilizing cavity-enhanced nonlinear anti-Stokes (Stokes) scattering within the spin-photon-phonon degrees of freedom. We explore the exotic dynamical and steady-state properties associated with the confined motion of a single atom within a high-finesse optical cavity. Notably, we demonstrate the direct extraction of vacuum fluctuations of photons and phonons, which are inherent in Heisenberg's uncertainty principle, without requiring any free parameters. Moreover, our approach enables the realization of high-quality single-quanta sources with large average photon (phonon) occupancies. The underlying physical mechanisms responsible for generating nonclassical quantum emitters are attributed to decay-enhanced single-quanta blockade and the utilization of long-lived motional phonons, resulting in strong nonlinearity. This work unveils significant opportunities for studying hitherto unexplored physical phenomena and provides novel perspectives on fundamental physics dominated by strong tripartite interactions.

quant-ph↗

arXiv2023

Self-ordered supersolid phase beyond Dicke superradiance in a ring cavity

The supersolid phase characterized by the superfluid and long-range spatial periodicity of crystalline order is central to many branches of science ranging from condensed matter physics to ultracold atomic physics. Here we study a self-ordered checkerboard supersolid phase originating from dynamical spin-orbit coupling for a transversely pumped atomic Bose-Einstein condensate trapped in a ring cavity, corresponding to a superradiant anti-Tavis-Cummings phase transition. In particular, an undamped gapless Goldstone mode is observed in contrast to the experimentally realized lattice supersolid with a gapped roton mode for Dicke superradiance. This zero energy mode reveals the rigidity of the self-ordered superradiant phase, which spontaneously breaks a continuous translational symmetry. Our work will highlight the significant opportunities for exploring long-lived supersolid matter by utilizing dynamical spin-orbit coupling in controllable optical cavities.

cond-mat.quant-gas↗

arXiv2022

Topological classification of Higher-order topological phases with nested band inversion surfaces

Higher-order topological phases (HOTPs) hold gapped bulk bands and topological boundary states localized in boundaries with codimension higher than one. In this paper, we provide a unified construction and topological characterization of HOTPs for the full Altland-Zirnbauer tenfold symmetry classes, based on a method known as nested band inversion surfaces (BISs). Specifically, HOTPs built on this method are decomposed into a series of subsystems, and higher-order topological boundary states emerges from the interplay of their first-order topology. Our analysis begins with a general discussion of HOTPs in continuous Hamiltonians for each symmetry class, then moves on to several lattice examples illustrating the topological characterization based on the nested-BIS method. Despite the example minimal models possessing several spatial symmetries, our method does not rely on any spatial symmetry, and can be easily extended into arbitrary orders of topology in dimensions. Furthermore, we extend our discussion to systems with asymmetric boundary states induced by two different mechanisms, namely, crossed BISs that break a $\mathcal{C}_4$ rotation symmetry, and non-Clifford operators that break certain chiral-mirror symmetries of the minimal models.

cond-mat.mes-hall↗

arXiv2022

Nonclassical correlated optical multistability at low photon level for cavity electromagnetically induced transparency

We study the nonequilibrium dynamic behaviors in a driven-dissipative single-atom cavity electromagnetically induced transparency. The optical bistability and multistability beyond a Kerr nonlinearity are observed utilizing the optical Stark shift induced strong nonlinearity. We show that the nonequilibrium dynamical phase transition between bistability and multistability is highly tunable by the system parameters in a large parameter region. The first-order dissipative optical bistability (multistability) always corresponds to the photon-bunching quantum statistics, which indicates that the quantum fluctuations and correlations play important roles in nonequilibrium dynamics.Interestingly, bistability and multistability with photon-bunching quantum statistics occurring at extremely low steady-state cavity photon number are observed, even under a very strong cavity driven field. Furthermore, we demonstrate that the unique cavity steady-state solution of the full quantum calculation is excellently consistent with the lowest solution based on the semiclassical mean-field approach in bistability and multistability regimes when the cavity photon number is much less than unity, albeit these nonclassical quantum states should possess strong quantum fluctuations in this parameter regime. Our results pave the way to exploring nonclassical correlated optical multistability in quantum regime, which may bring exciting opportunities for potential applications from quantum information processing to quantum metrology.

quant-ph↗

arXiv2022

Tunable symmetry-protected higher-order topological states with fermionic atoms in bilayer optical lattices

Higher-order topological states that possess gapped bulk energy bands and exotic topologically protected boundary states with at least two dimension lower than the bulk have significantly opened a new perspective for understanding of topological quantum matters. Here, we propose to generate two-dimensional topological boundary states for implementing synthetic magnetic flux of ultracold atoms trapped in bilayer optical lattices, which includes Chern insulator, Dirac semimetals, and second-order topological phase (SOTP) by the interplay of the two-photon detuning and effective Zeeman shift. These observed topological phases can be well characterized by the energy gap of bulk, Wilson loop spectra, and the spin textures at the higher symmetric points of system. We show that the SOTP exhibits a pair of $0$D boundary states. While the phases of Dirac semimetals and Chern insulator support the conventional $1$D boundary states due to the principle of bulk-boundary correspondence. Strikingly, the emerged boundary states for Dirac semimetals and SOTP are topologically protected by $\cal P T$-symmetry and chiral-mirror symmetry ($\mathcal{\widetilde{M}}_α$), respectively. In particular, the location of $0$D corner states for SOTP which are associated with existing $\mathcal{\widetilde{M}}_α$-symmetry can be highly manipulated by tuning magnetic flux. Our scheme herein provides a platform for emerging exotic topological boundary states, which may facilitate the study of higher-order topological phases in ultracold atomic gases.

cond-mat.quant-gas↗

arXiv2022

Strong single-photon to two-photon bundles emission in spin-1 Jaynes-Cummings model

The realization of high-quality special nonclassical states beyond strong single atom-cavity coupling regime is a fundamental element in quantum information science. Here, we study the nonclassical photon emission in a single spin-1 atom coupled to an optical cavity with constructing a spin-1 Jaynes-Cummings model. By tuning quadratic Zeeman shift, the energy-spectrum anharmonicity can be significantly enhanced with respect to the dressed-state splitting of well-resolved n-photon resonance largely increased. The photon emission exhibit high-quality single photon and two-photon bundles properties with large photon numbers in the cavity and atom driven cases, respectively. More interestingly, nonclassical optical switching from strong single-photon blockade to two-photon bundles and super-Poissonian photon emission is achieved and highly controllable by light-cavity detuning in the presence of both atom and cavity driven fields. Our proposal not only open up a new avenue for generating high-quality n-photon sources but also provide versatile applications in quantum networks and quantum metrology.

quant-ph↗