Exploiting a common environment, we study the synchronization dynamics of three nonidentical and mechanically isolated microwave optomechanical resonators. The common environment induces indirect coupling between any two resonators, which can be described by an effective non-Hermitian interaction Hamiltonian. Combined with the Hermitian interaction regulated by the tunable coupler, we demonstrate that the common environment breaks the reciprocity of the interaction. We propose four microwave optomechanical circuits with nonreciprocal or even unidirectional interactions, and study the regulation of synchronization dynamics by the common environment. By utilizing the excellent tunability of superconducting circuits, we show that different synchronization states can be switched in a controllable way. This work may open up a new perspective for synchronization research and have potential applications in synchronization networks.

Waveguide cavity quantum electrodynamics (QED) with atomic mirrors is a growing research area of quantum optics and can be applied to quantum information processing. We here study the photon statistics of output fields from a waveguide cavity QED system, in which the waveguide is coupled to quantized mirror atoms and one driven medium atom. Our results show that the photon blockade can occur even for a bad atom cavity with large dissipation and small coupling between the medium atom and the cavity, in contrast to the small dissipation and the strong coupling of the medium atom to the cavity field for the conventional photon blockade or the quantum interference for the unconventional photon blockade in the cavity QED system. Utilizing both the master equation and scattering theories, we derive the condition under which the photon blockade occurs in weakly driven systems. We find that such photon anomalous blockade is due to the quantum Zeno effect and is robust against variations of the medium atom's position within the cavity. Our study paves a way to exploit the photon blockade and single-photon devices via the waveguide cavity QED.

Fast and low-cost monitoring of coherent transmitter is achieved using a 3-GHz photodetector and an alternating iterative algorithm. It enables accurate estimation of IQ skew (0.16 ps) and frequency response within only 10 iterations.

Single-photon sources are crucial for quantum information technologies. Here, we demonstrate a microwave single-photon source based on tantalum thin films, whose favorable material properties enable high-quality, stable photon emission. The antibunching behavior of the emitted radiation is revealed by second-order correlation measurements. Furthermore, traveling-wave parametric amplifiers are used as low-noise pre-amplifiers in the detection chains, substantially improving the signal-to-noise ratio and thereby greatly reducing the acquisition time required for second-order correlation measurements. These results demonstrate the viability of tantalum-based superconducting devices as reliable platforms for microwave quantum photonics.

Non-Hermitian physics has recently transformed our understanding of topology by uncovering a range of effects that are unique to systems with gain and loss. The realization of non-Hermitian topology in strongly coupled light-matter systems not only offers degrees of freedom for the enhanced manipulation of topological phenomena, but is also promising for developing on-chip active photonic devices. Exciton-polaritons-strongly coupled quasiparticles from excitons and photons-emerge as a promising candidate with intrinsic non-Hermitian features. However, limited by the challenges in achieving non-reciprocity, the experimental observation of non-Hermitian topology and its associated transport features has remained elusive. Here we experimentally demonstrate the non-Hermitian topology of exciton-polaritons induced by a twist degree of freedom in a liquid-crystal-filled CsPbBr3 perovskite microcavity at room temperature. The geometric twist between birefringent perovskites and liquid crystals acts as a degree of freedom to tailor the polaritonic complex spectra, leading to non-Hermitian bands with spectral winding topology and non-reciprocity. Furthermore, the induced non-Hermitian topology gives rise to the non-Hermitian exciton-polariton skin effect in real space, manifesting as polariton accumulation at open boundaries. Our findings open new perspectives on tunable non-Hermitian phenomena and the development of on-chip polaritonic devices with enhanced functionalities.

Decoherence-free subspace (DFS) provides a crucial mechanism for passive error mitigation in quantum computation by encoding information within symmetry-protected subspaces of the Hilbert space, which are immune from collective decoherence. Constructing a complete set of orthogonal basis states for the DFS is essential to realize fault-tolerant quantum computation by using the DFS codes. However, existing methods for preparing these basis states are often non-scalable, platform-specific, or yield mixed states. Here, we propose a deterministic approach to prepare pure, orthogonal and complete DFS basis states for systems of arbitrary size composed of qubits. Our method employs projective measurements and quantum circuits with single-qubit, two-qubit and Toffoli gates. We provide a rigorous resource cost analysis both mathematically and numerically. Meanwhile, we demonstrate the realizability of our method on NISQ devices by discussing how to implement our method on a superconducting chip. The proposed method offers a universal solution for preparing the DFS basis states across diverse quantum computing platforms and system sizes, which is realizable in the NISQ era.

We study an adiabatic topological passage of two Su-Schrieffer-Heeger (SSH) chains mediated by a giant atom. When two finite SSH chains are in the topological phase and the frequency of the giant atom is equal to the center frequency of the SSH chains, the system is reduced to a subsystem that describes the coupling of a giant atom to the edge states of two SSH chains. In this case, we can find dark states that act as adiabatic topological passages. This allows us to adiabatically transfer excitations of the giant atom to either one end of two SSH chains in a fully controllable way. In addition, we show good robustness of the adiabatic topological passages to both giant atom frequency mismatch and the coupling disorders in two SSH chains. Our study provides a method to realize quantum information processing and fabricate quantum optical devices based on the coupling of the giant atom to topological matter.

Topological active materials have emerged as a powerful paradigm bridging the discovery of exotic topological phases of matter with the development of functional topological devices. The recent extension of these material systems into dynamic regime, where topological properties can be actively manipulated at ultrafast timescales, promises unprecedented control over topological states and their functionalities. However, translating the static topological lasing signals into high-performance logic functions remain highly challenging, which imposes a far more stringent set of materials attributes. Here, leveraging the strong nonlinearity and pronounced spectral isolation of perovskite exciton-polaritons embedded in a Dirac vortex microcavity, we experimentally demonstrate the dynamic topological Majorana-like state polariton condensation with its ultrafast logic operations at room temperature, achieving record extinction ratio (∼20 dB), extremely low control fluence (∼0.2 nJ/cm 2 ) and sub-picosecond response time (∼500 fs). Our results expand the frontier of dynamic topology and establish an innovative pathway towards robust, ultrafast, and reconfigurable on-chip polaritonic logic circuits.

Surface acoustic wave (SAW) devices are key components of classical communication systems and recently studied for quantum information processing. We here propose and study a hybrid quantum system composed of skyrmion qubit and a SAW cavity, which supports a number of long-lived phononic modes. The results show that the system allows for strong coupling between skyrmion qubit and single phonon of different modes. By manipulating the qubit(s) through a static magnetic field and a time-dependent modulation magnetic field, we further study the interaction between skyrmion qubit and individual phononic modes, phonon-phonon interaction, and qubit-qubit interaction, which operates in strong-coupling regime. The controllability of nanoscale skyrmion qubit and the dense phononic modes of single SAW cavity would make our system have promising applications in large-scale quantum communication and computing.

The most widely used approach for simulating the dynamics of time-dependent Hamiltonians via quantum computation depends on the quantum-classical hybrid variational quantum time evolution algorithm, in which ordinary differential equations of the variational coefficients for determining time evolution are solved via classical simulations with a time discretization method. We here present a full-quantum approach, in which ordinary differential equations of the variational coefficients are transformed into static linear equations via the Chebyshev spectral discretization method and then solved via the quantum singular value transformation algorithm. Our full quantum algorithm avoids classical feedback, achieves exponential convergence for smooth Hamiltonians, and yields a quantum circuit depth that is independent of the number of time steps. We demonstrate two implementation strategies, with a global formulation designed for fault-tolerant architectures and a sequential formulation tailored to near-term devices, and validate the approach through numerical simulations of proton-hydrogen charge-transfer dynamics, a prototypical time-dependent quantum chemistry problem. This work establishes a systematic pathway from quantum-classical hybrid variational quantum algorithms to full-quantum solvers for general time-dependent Hamiltonians, particularly those whose dynamics admit compact variational descriptions, opening a route toward full quantum computational advantages in time-dependent simulations.

Frequency-tunable superconducting transmon qubits are a cornerstone of scalable quantum processors, yet their performance is often degraded by sensitivity to low-frequency flux noise. Here we present a doubly-connected gradiometric transmon (the ``8-mon") that incorporates a nano-airbridge to link its two loops. This design preserves full electrical tunability and remains fully compatible with standard X-mon control and readout, requiring no additional measurement overhead. The airbridge interconnect eliminates dielectric loss, which enables the 8-mon to achieve both energy relaxation times $T_{\rm 1}$ comparable to reference X-mons and, in the small flux-bias regime, a nearly threefold enhancement in Ramsey coherence time $T_{\rm 2}^*$. This improved $T_{\rm 2}^*$ reaches the same order as $T_{\rm 1}$ without employing echo decoupling. The device also exhibits superior long-term frequency stability even without any magnetic field shielding. We develop a spatially correlated flux-noise model whose simulations quantitatively reproduce the experimental coherence trends, revealing the coexistence of short- and long-correlation-length magnetic noise in the superconducting chip environment. By unifying high tunability with intrinsic flux-noise suppression through a robust geometric design, the 8-mon provides a practical pathway toward more coherent and stable superconducting quantum processors.

High-fidelity quantum state transfer over lossy and thermally populated channels is a major challenge for quantum information processing in quantum networks. Here, we propose a dark-mode-based protocol for high-fidelity quantum state transfer between two distant microwave cavities coupled via a thermal waveguide. By dynamically shaping the microwave cavity-waveguide couplings, the transmission path of quantum information is confined to a decoherence-free subspace, enabling robust transfer even in the presence of thermal photons and waveguide loss. The core mechanism of the protocol is that the dynamical modulation induces an additional effective dissipation channel, which destructively interferes with the waveguide-mediated coupling, thereby realizing genuine dark-mode immunity. Numerical simulations confirm the protocol's robustness and identify key parameters governing fidelity. We also discuss the feasibility of noise-immune quantum communication over experimentally relevant distances. Our work provides a pathway for long-distance quantum network construction and practical applications of future quantum computing systems.

We study two-photon scattering by a two-level giant atom in a waveguide. We first study the case that the giant atom is coupled to the waveguide via two coupling points, and obtain Bethe ansatz eigenstates and eigenvalues in the Hilbert space of two-excitation. Then we derive bound states by subtracting the states corresponding to Bethe ansatz solutions from the entire two-excitation Hilbert space, and construct the two-photon scattering matrix (S-matrix) by using Bethe ansatz eigenstates and bound states. We further study the properties of output states, which include both the scattering and bound states, for arbitrarily incident two-photon states by using a concrete example. We find that the oscillation period of the scattering states and decay rates of the bound states strongly depend on the distance between two coupling points. Moreover, we find that the two-photon correlation in the bound states can be enhanced by changing such distance when the total energy of two incident photons equals to two times of single photon resonance energy. We also generalize our study to the case that the giant atom is coupled to the waveguide via N coupling points. We obtain all the eigenstates and eigenvalues of the scattering matrix and construct the S-matrix. Comparing with the case of the two coupling points, we find the photon correlation can be further enhanced by increasing the number of the coupling points for the same incident states when the distance of any two nearest neighbor coupling points is half of the wavelength.

Accurate electromagnetic (EM) feature extraction, including element characterization, eigenmodes, and field distributions, is essential for superconducting quantum circuit design. To streamline this process, we present a workflow built around Palace, an open-source, high-performance finite element method solver tailored for quantum applications. Starting from circuit layouts, the workflow automates mesh generation, multiple EM solver processing, and EM-to-Hamiltonian post-processing. We benchmark the workflow on a chip with bare resonators and qubits coupled with readout resonators, achieving resonator frequencies prediction within 0.3

Chaos is a fundamental phenomenon in nonlinear dynamics, manifesting as irregular and unpredictable behavior across various physical systems. Among the diverse routes to chaos, intermittent chaos is a distinct transition pathway, characterized by the temporal or spatial alternation between periodic and chaotic motions. Here, we experimentally demonstrate, for the first time, optomechanically induced intermittent chaos in an optical whispering-gallery-mode microresonator. Specifically, the system evolves from stable periodic oscillation through an intermittent-chaos regime before fully developing into chaotic motion. As system parameters vary, the proportion of chaotic motion in the time-domain increases asymptotically until chaotic dynamics dominates entirely. Moreover, it is counterintuitive that, intermittent chaos can act as noise of a favorable intensity compared with purely periodic or fully chaotic states, and enhance rather than reduce system's responses in nonlinear ultrasonic detection. These findings not only deepen the comprehensive understanding of chaos formation but also broaden its potential applications in high-precision sensing and information processing.

The noise-biased Kerr-cat qubit is an attractive candidate for fault-tolerant quantum computation; however, its initialization faces challenges due to the squeezing pump-induced frequency shift. Here we propose and demonstrate a dynamic compensation method to mitigate the effect of pump-induced frequency shift during the Kerr-cat qubit initialization. Using a nonlinearity-engineered multiloop superconducting quantum interference device, we realize a stabilized Kerr-cat qubit and validate the advantages of the dynamic compensation method by increasing the initialization fidelity from 57% to 78%, with a projected fidelity of 91% after exclusion of state preparation and measurement errors. Our results not only advance the practical implementation of Kerr-cat qubits, but also provide valuable insights into the fundamental adiabatic dynamics of these systems. This work is valuable for scalable quantum processors that leverage the noise-biased properties of Kerr-cat qubits.

Nonlocal interactions between photonic resonator array and giant atoms have attracted extensive attentions. Optimization and control of quantum states via giant atoms have been shown. We here study the dynamical scattering of a single-photon wave packet by a giant atom coupled to a two-dimensional photonic resonator array via multiple spatial points. Using several iterations of time evolutions, we can prepare an expected wave packet with a stable size and use it as the incident state for the scattering process. We show that spatially symmetric or asymmetric target scattering states of single-photon wave packet can be generated by adjusting the coupling strengths between the giant atom and different lattice sites of the resonator array. Furthermore, the dynamical scattering of the wave packets enables us to study the atomic excitation and propagating properties of the scattering states. We find that the atomic excitation has negligibly small probability during the scattering process. Our study may provide a new way to generate an expected photon state via photon scattering by a giant atom in two-dimensional photonic array.

Vector set orthogonal normalization and matrix QR decomposition are fundamental problems in matrix analysis with important applications in many fields. We know that the Gram-Schmidt process is a widely used method to solve these two problems. However, existing methods, including the Gram-Schmidt process, have problems of high complexity, scaling O(N3) in the system dimension N, which leads to difficulties when calculating large-scale or ill-conditioned problems. With the development of quantum information processing, a series of quantum algorithms have been proposed, providing advantages and speedups over classical algorithms in many fields. In this paper we propose quantum algorithms to solve these two problems based on the idea of the Gram-Schmidt process and quantum phase estimation. The complexity of proposed quantum algorithms is theoretically and numerically analyzed. We find that our algorithms provide polynomial acceleration over the best-known quantum algorithms and a potential polynomial acceleration over the best-known classical algorithms on these two problems, scaling O(N2poly(logN)) in the dimension N of the system when ignoring the complexity of state readout or O(N2poly(logN)) when considering the complexity of state readout.

Errors in superconducting quantum chips are inevitable for developing robust logical qubits and implementing complex quantum algorithms. These errors arise from various physical mechanisms, each with unique dependence on qubit frequencies. Here, we propose an algorithm for optimizing qubit frequencies to effectively mitigate multiple types of frequency-dependent errors. We employ multichannel message-passing neural networks, with each channel tailored to address a specific error type. Our neural-network model is trained to minimize the weighted sum of different errors, based on frequency-dependent error models, e.g., two-level-system defects that affect individual qubits, quantum crosstalk that depends on the graph structure formed by qubit couplings, and microwave crosstalk that relies on the spatial arrangement of qubits. The trained neural-network model is adaptable to chips with varying qubit arrangements and scales. Recognizing the diverse experimental conditions of different chips, we compare our algorithm with the snake algorithm across various scales and error weights, providing valuable guidance for experimenters in algorithm selection. Our results show that, in most scenarios, our algorithm achieves lower overall errors than the snake algorithm.

Hybrid mechanical-superconducting systems for quantum information processing have attracted significant attention due to their potential applications. In such systems, the weak coupling regime, dominated by dissipation, has been extensively studied. The strong coupling regime, where coherent energy exchange exceeds losses, has also been widely explored. However, the transition-coupling regime, which lies between the above two and exhibits rich, unique physics, remains underexplored. In this study, we fabricate a tunable coupling device to investigate the coupling of a superconducting transmon qubit to a seven-mode surface acoustic wave resonator (SAWR), with a particular focus on the transition-coupling regime. Through a series of phonon oscillation experiments and studies in the dispersive regime, we systematically characterize the performance of the SAWR. We then explore the complex dynamics of energy exchange between the qubit and the mechanical modes, highlighting the interplay between dissipation and coherence. Finally, we propose a protocol for qubit readout and fast reset with a multimode mechanical cavity using one mode for readout and another mode for reset. We have demonstrated in simulation that the qubit achieves both fast reset and high coherence performance when the qubit is coupled to the reset mode in the transition-coupling regime.