arXiv subjects

Peng-Bo Li

Publications and source records attributed to Peng-Bo Li.

At least 19 recordsLinked to original sources

arXiv2026

Quantum Magnonics: Quantum States Generation and Applications

Hybrid systems based on magnons in ferromagnetic materials, such as yttrium iron garnet, have achieved remarkable development in the last decade. These include the coupling of magnons to microwave and optical photons, superconducting qubits, phonons, spins, the center-of-mass motion of a ferromagnet, etc. Here, we review both the experimental and theoretical progress in this field, focusing on the generation of magnonic quantum states and their applications in a broad range of fields. Since the strong coupling is a prerequisite for achieving coherent quantum control of magnons and preparing magnonic quantum states, we start by introducing representative strong-coupling experiments in cavity magnonics, then review a series of protocols for creating various magnonic quantum states, such as Fock, cat, squeezed, and entangled states, and discuss their potential applications in macroscopic quantum studies, quantum information science, quantum sensing, magnonic quantum devices, dark matter detection, and so on. Finally, we summarize the review and give an outlook for the future study of quantum magnonics.

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arXiv2026

Nonreciprocal quantum rotation sensing via virtual-excitation enhancement in a spinning cavity

Quantum sensing with high precision and sensitivity plays an important role in quantum technologies and quantum information processing. Here, we propose a nonreciprocal quantum metrological scheme for estimating rotational angular velocity in a hybrid light-matter platform, where the setup consists of a spinning ring cavity coupled to a two-level system and an auxiliary bosonic mode. Through the Sagnac effect, the angular velocity is converted into a direction-dependent detuning, which modifies the effective light-matter dressing of the hybrid system. As a result, the angular velocity is encoded not only into the renormalized hybrid-mode spectrum, but also into the virtual excitations generated by ultrastrong coupling. These virtual excitations modify the polaritonic frequency response to rotation and enhance the quantum Fisher information (QFI) associated with angular velocity estimation, without requiring direct extraction of virtual excitations. Moreover, since the Sagnac-Fizeau shift enters the virtual-transition energy denominators, the metrological response becomes intrinsically different for opposite driving directions, leading to a tunable nonreciprocal sensitivity contrast. In addition, we also discuss a readout scheme and show that bundle emission coincidence counting can serve as an auxiliary direction-dependent readout channel. Our results provide a route toward exploiting nonreciprocal light-matter dressing and virtual excitations as resources for quantum rotation sensing.

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arXiv2026

Photon blockade via three-body interactions: toward high-purity and bright single-photon sources

Photon blockade is vital for single-photon generation, but current schemes with conventional and unconventional photon blockade face critical limitations like the purity-brightness trade-off, hindering the generation of high-performance single-photons. To overcome these limitations, we introduce a fundamentally new photon blockade mechanism by utilizing three-body interactions between a single photonic mode and two qubits. This kind of interaction intrinsically cuts off the excitation path to the two-photon state, resulting in a perfect photon blockade effect. The mechanism operates across a broad parameter range, free from the constraints of strong coupling or weak driving. Remarkably, it breaks the purity-brightness trade-off, enabling the simultaneous achievement of extreme purity and high brightness, both significantly outperforming previous mechanisms. Furthermore, this approach demonstrates robustness against thermal noise and avoids unwanted oscillations in the time-delayed correlation function. This work provides a path for generating high-purity, high-brightness, and robust single-photon sources, a key resource for quantum technologies.

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arXiv2026

Loss-induced quantum nonreciprocity and entanglement in superconducting qubits

Losses are ubiquitous in physics and are usually regarded as harmful in quantum information processing. Here, we propose a loss-induced scheme to achieve nonreciprocity and nonreciprocal entanglement in a superconducting platform, where two remote superconducting transmon qubits are connected via two lossy auxiliary cavities. The nonreciprocity in our scheme originates from interference between multiple lossy coupling paths. The coherent phases associated with the qubit-resonator couplings reverse sign under propagation reversal, while the loss-induced phases remain direction independent. Their combined effect leads to different interference conditions in the opposite directions, resulting in unequal effective couplings. We show that this loss-induced scheme can generate nonreciprocal quantum entanglement, indicating that loss can be utilized as a resource. Moreover, the tunability of nonreciprocity and nonreciprocal entanglement in our scheme can be manipulated by the relative phase induced by loss, allowing to tailor both reciprocal and nonreciprocal behaviors. Our results establish a direct link between engineered loss and nonreciprocal entanglement in quantum information processing and offer potential applications in scalable quantum networks.

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arXiv2026

Quantum gravimetry with mechanical qubits

Levitated mesoscopic particles hold the promise of revolutionizing gravity sensing by using quantum effects. However, conventional quantum gravimeters based on such systems fail to harness the intrinsic large-mass advantage of the particles, because their commonly utilized auxiliary quantum systems counteract the role of mass as a resource. To overcome this limitation, we propose a quantum gravimetry by directly using the mechanical qubit (QM) formed by a levitated particle as the gravity sensor. Without resorting to the auxiliary quantum system, our scheme enables a straightforward readout of the particle's motion under gravitational influence. The obtained sensitivity behaves as a $m^{-1/2}$-scaling with the mass $m$. We also generalize our scheme to the \textit{mechanical cat qubit} as the gravity sensor. The sensitivity further scales as $N^{-1/2}$ with the mean phonon number $N$. In the experimentally realizable parameter regime, a sensitivity on the order of $0.1~ \text{\textmu}\text{Gal}/\sqrt{\text{Hz}}$ can be achieved, which outperforms the traditional schemes by two orders of magnitude. Reaching the \textit{double standard quantum limits} with $m$ and $N$ simultaneously, our scheme provides a feasible route toward compact high-sensitivity quantum gravimetry.

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arXiv2026

Surpassing Quantum Noise Limits with Nonlinear Amplification

Linear quantum amplifiers are indispensable tools for quantum technologies, yet their performance is fundamentally limited by quantum noise, precluding any signal-to-noise ratio (SNR) enhancement unless supplemented by post-selection or non-classical resources. To surpass this limitation, we propose a nonlinear quantum amplification strategy that exploits the interplay between a gain-stabilized bright eigenmode of a coupled two-mode bosonic system and Kerr nonlinearity. We demonstrate that this interplay enables the signal gain to surpass the noise gain in a selected quadrature, leading to a net increase in the SNR beyond the quantum limits of conventional linear amplifiers. Our work thus establishes a novel nonlinear amplification paradigm capable of enhancing the SNR, with promising applications across quantum information processing, quantum communications, and quantum metrology.

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arXiv2025

Three-body interaction in a magnon-Andreev-superconducting qubit system: collapse-revival phenomena and entanglement redistribution

Three-body interactions are fundamental for realizing novel quantum phenomena beyond pairwise physics, yet their implementation -- particularly among distinct quantum systems -- remains challenging. Here, we propose a hybrid quantum architecture comprising a magnonic mode (in a YIG sphere), an Andreev spin qubit (ASQ), and a superconducting qubit (SCQ), to realize a strong three-body interaction at the single-quantum level. Leveraging the spin-dependent supercurrent and circuit-integration flexibility of the ASQ, it is possible to engineer a strong tripartite coupling that jointly excites both qubits upon magnon annihilation (or excites magnons and SCQs upon ASQ deexcitation). Through analytical and numerical studies, we demonstrate that this interaction induces synchronized collapse and revival in qubit populations when the magnon is initially prepared in a coherent state. Notably, during the collapse region -- where populations remain static -- the entanglement structure undergoes a dramatic and continuous reorganization. We show that the genuine tripartite entanglement is redistributed into bipartite entanglement between the two qubits, and vice versa, with the total entanglement conserved. These phenomena, unattainable via two-body couplings, underscore the potential of three-body interactions for exploring intrinsically new quantum effects and advancing hybrid quantum information platforms.

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arXiv2025

Exotic quantum light-matter interactions in bilayer square lattices

We investigate quantum emitters (QEs) interacting with a photonic structured bath made of bilayer square lattices, where the resonance anti-crossing between the energy bands opens a symmetric middle energy gap. Due to the intrinsic chiral symmetry of the bath and interactions with the square-like band-edges, the QE-photon dressed states generated in this inner bandgap are odd-neighbor, robust, and anisotropic, when the emitters' transition frequencies lie in the middle of the bandgap. We also use giant artificial atoms to engineer and modify the dressed states' patterns. Exotic bound states can lead to spin models with symmetry protection, resulting in fascinating many-body phases. As an example, we show that this proposal can be used to generate both edge states and corner states in the generalized 2D Su-Schrieffer-Heeger (SSH) model. This work opens up new avenues for research into innovative quantum many-body physics and quantum simulations with photonic or phononic multilayer structures.

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arXiv2025

Mechanical Squeezed-Fock Qubit: Towards Quantum Weak-Force Sensing

Mechanical qubits offer unique advantages over other qubit platforms, primarily in terms of coherence time and possibilities for enhanced sensing applications, but their potential is constrained by the inherently weak nonlinearities and small anharmonicity of nanomechanical resonators. We propose to overcome this shortcoming by using squeezed Fock states of phonons in a parametrically driven nonlinear mechanical oscillator. We find that, under two-phonon driving, squeezed Fock states become eigenstates of a Kerr-nonlinear mechanical oscillator, featuring an energy spectrum with exponentially enhanced and tunable anharmonicity, such that the transitions to higher energy states are exponentially suppressed. This enables us to encode the mechanical qubit within the ground and first excited squeezed Fock states of the driven mechanical oscillator. This kind of mechanical qubit is termed mechanical squeezed-Fock qubit. We also show that our mechanical qubit can serve as a quantum sensor for weak forces, with its resulting sensitivity increased by at least one order of magnitude over that of traditional mechanical qubits. The proposed mechanical squeezed-Fock qubit provides a powerful quantum phonon platform for quantum sensing and information processing.

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arXiv2025

Photon-mediated interactions by Floquet photonic lattices

We investigate the interactions between two-level emitters mediated by time-dependent, one-dimensional, structured photonic baths, focusing on Floquet topological lattices. Building on the framework of periodically driven photonic lattices, we demonstrate and characterize the emergence of tunable-range emitter's interactions mediated by bound states absent in static photonic lattices. In particular, we show that one can not only obtain different spatial interaction dependencies with respect to the static bath scenarios, but also in qualitatively different regimes due to the time-dependent nature of the bath, for example, when the emitters have different frequencies. This work sheds light on the interplay between non-equilibrium photonics and quantum optics and can serve as the basis for analyzing Floquet photonic lattices in higher dimensions.

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arXiv2025

Magnon blockade in spin-magnon systems with frequency detuning

Magnon blockade is a physical mechanism for the preparation of a single-magnon source, which has important applications in quantum information processing. Here we propose a scheme for generating an optimal magnon blockade in the spin-magnon quantum system. By introducing frequency detuning between the magnon and the spin qubit of the NV center, the conventional magnon blockade and the unconventional magnon blockade can be obtained under both strong and weak coupling, relaxing the requirements for coupling strength. Moreover, the conventional and unconventional magnon blockade can occur simultaneously when both the magnon and the spin qubit are driven. This allows the equal-time second-order correlation function to reach $10^{-8}$, about five orders of magnitude lower than that in previous works. Additionally, the time-delayed second-order correlation function avoids oscillation. Our study demonstrates the impact of frequency detuning on the magnon blockade and proposes methods to enhance the magnon blockade and relax the requirements for coupling strength through frequency detuning.

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arXiv2025

Tripartite hybrid quantum systems: Skyrmion-mediated quantum interactions between single NV centers and superconducting qubits

Nitrogen-vacancy (NV) centers in diamond and superconducting qubits are two promising solid-state quantum systems for quantum science and technology, but the realization of controlled interfaces between individual solid-state spins and superconducting qubits remains fundamentally challenging. Here, we propose and analyze a hybrid quantum system consisting of a magnetic skyrmion, an NV center, and a superconducting qubit, where the solid-state qubits are both positioned in proximity to the skyrmion structure in a thin magnetic disk. We show that it is experimentally feasible to achieve strong magnetic (coherent or dissipative) coupling between the NV center and the superconducting qubit by using the \textit{quantized gyration mode of the skyrmion} as an intermediary. This allows coherent information transfer and nonreciprocal responses between the NV center and the superconducting qubit at the single quantum level with high controllability. The proposed platform provides a scalable pathway for implementing quantum protocols that synergistically exploit the complementary advantages of spin-based quantum memories, microwave-frequency superconducting circuits, and topologically protected magnetic excitations.

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arXiv2025

Single photon isolation and nonreciprocal frequency conversion in atom-waveguide systems

In this work, we utilize a two-level atom and a ${\Lambda}$-type atom to link two identical waveguides, subsequently extending the model to a giant-atom configuration. Our analytical solutions and numerical simulations demonstrate that this setup can achieve single-photon isolation and nonreciprocal frequency conversion by tuning the atom-waveguide coupling strengths $g_i$, respectively. We also examine single-photon scattering in the giant-atom model within both the Markovian and non-Markovian regimes. The results reveal that ultranarrow scattering windows are induced by the phases ${\phi}_1$ and ${\phi}_2$ under specific conditions, making them well-suited for precise frequency conversion and sensing. Additionally, in the non-Markovian regime, the spectra exhibit irregular polygonal shapes, offering enhanced opportunities for exploring nonreciprocal frequency conversion in the off-resonant regime. Our work provides a new perspective on achieving optical nonreciprocity at the single-photon level in atom-waveguide systems.

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arXiv2025

Non-Markovian dynamics with ${\Lambda}$-type atomic systems in a single end photonic waveguide

In this work, we investigate the non-Markovian dynamical evolution of a ${\Lambda}$-type atom interacting with a semi-infinite one-dimensional photonic waveguide via two atomic transitions. The waveguide terminates at a perfect mirror, which reflects the light and introduces boundary effects. We derive exact analytical expressions and show that, under suitable conditions, the instantaneous and retarded decay rates reach equilibrium, leading to the formation of an atom-photon bound state that suppresses dissipation. Consequently, the atom retains a long-lived population in the asymptotic time limit. Furthermore, we analyze the output field intensity and demonstrate that blocking one of the coupling channels forces the atomic system to emit photons of a single frequency. Finally, we extend the model to a two-atom system and examine the disentanglement dynamics of the two spatially separated atoms. These findings elucidate the dynamic process of spontaneous emission involving multi-frequency photons from multi-level atoms and provide insights into the complex interference between different decay pathways.

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arXiv2025

Optical nonreciprocity induced by quantum squeezing in temperature sensitive optomechanical systems

We investigate single photon transmission and the statistical properties of photon correlations in $\chi^{(2)}$ microring optomechanical systems, where optical nonreciprocity is induced by directional quantum squeezing. Due to the presence of thermal phonons in the mechanical resonator, the system is highly sensitive to temperature changes. Our numerical simulations show that as the thermal phonons vary from 0 to 10, the isolation ratio of single-photon transmission decreases from 22.2 dB to 1.1 dB (or from -23 dB to -3.3 dB). Additionally, the statistical properties of photon correlations transition from exhibiting a strong bunching effect to a weak bunching effect. Moreover, the parametric amplification component enhances the device's temperature response, distinguishing it from other similar nonreciprocal devices. Our protocol suggests a potential application for nonreciprocal setups in precise temperature measurement at ultralow temperatures, thereby enriching quantum networks and quantum information processing.

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arXiv2025

Waveguide QED with dissipative light-matter couplings

Dissipative light-matter coupling plays a vital role in non-Hermitian physics, but it remains largely unexplored in waveguide QED systems. In this work, we find that by employing pseudo-Hermitian symmetry rather than anti-PT symmetry, the concept of dissipative coupling could be generalized and applied to the field of waveguide QED. This leads to a series of intriguing results, such as spontaneous breaking of pseudo-Hermitian symmetry across the exceptional points (EPs), level attraction between the bound states, and critical transition across the EPs for the population of quantum emitters in the bound state. Thanks to the tunability of photonic bands in crystal waveguides, we also demonstrate that dissipative light-matter coupling leads to the emergence of nonstandard third-order exceptional points with chiral spatial profiles in a topological waveguide QED system. This work provides a promising paradigm for studying non-Hermitian quantum phenomena in waveguide QED systems.

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arXiv2025

Nonlinear Tripartite Coupling of Trapped Electrons with Magnons in a Hybrid Quantum System

Coherent nonlinear tripartite interactions are critical for advancing quantum simulation and information processing in hybrid quantum systems, yet they remain experimentally challenging and still evade comprehensive exploration. Here, we predict a nonlinear tripartite coupling mechanism in a hybrid setup comprising a single trapped electron and a nearby micromagnet. The tripartite coupling here leverages the electron's intrinsic charge (motional) and spin degrees of freedom interacting with the magnon modes of the micromagnet. Thanks to the large spatial extent of the electron zero-point motion, we show that it is possible to obtain a tunable and strong spin-magnon-motion coupling at the single quantum level, with two phonons simultaneously interacting with a single spin and magnon excitation. This enables, for example, magnons to mediate coupling among distinct degrees of freedom of two electrons, which can be used for the rapid preparation of few-body entangled states. This protocol can be readily implemented with the well-developed techniques in electron traps and quantum magnonics, and may open new avenues for quantum simulations and hybrid quantum information processing by introducing a versatile platform for exploring multipartite interactions and nonclassical state generation.

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arXiv2024

Nonreciprocal interaction and entanglement between two superconducting qubits

Nonreciprocal interaction between two spatially separated subsystems plays a crucial role in signal processing and quantum networks. Here, we propose an efficient scheme to achieve nonreciprocal interaction and entanglement between two qubits by combining coherent and dissipative couplings in a superconducting platform, where two coherently coupled transmon qubits simultaneously interact with a transmission line waveguide. The coherent interaction between the transmon qubits can be achieved via capacitive coupling or via an intermediary cavity mode, while the dissipative interaction is induced by the transmission line via reservoir engineering. With high tunability of superconducting qubits, their positions along the transmission line can be adjusted to tune the dissipative coupling, enabling to tailor reciprocal and nonreciprocal interactions between the qubits. A fully nonreciprocal interaction can be achieved when the separation between the two qubits is $(4n+3)\lambda_{0} /4$, where $n$ is an integer and $\lambda_{0}$ is the photon wavelength. This nonreciprocal interaction enables the generation of nonreciprocal entanglement between the two transmon qubits. Furthermore, applying a drive field to one of the qubit can stabilize the system into a nonreciprocal steady-state entangled state. Remarkably, the nonreciprocal interaction in this work does not rely on the presence of nonlinearity or complex configurations, which has more potential applications in designing nonreciprocal quantum devices, processing quantum information, and building quantum networks.

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