We study distributed inner product estimation for n-qubit states using local randomized measurements, for which rigorous worst-case guarantees are less understood. We first reduce the minimax kernel optimization to Hamming-distance kernels. Within this class, unbiasedness fixes a unique kernel. For this kernel under local Clifford sampling, we prove a sharp fourth-moment bound using the single-qubit Clifford commutant. This yields worst-case sample complexity 𝒪(√(4.5^n)), attained by identical pure product stabilizer states. For the same kernel under local Haar sampling, we prove a local twirling identity that compares its fourth moment with the Clifford fourth moment. This gives the same rigorous upper bound as in the Clifford case, but the comparison is lossy. This motivates the conjectured sharper Haar scaling 𝒪(√(3.6^n)) attained by product states, and verify it for several important classes of states. We also show that independent single-qubit Pauli shadows have worst-case scaling 𝒪(√(7.5^n)) for large n.

The quantum Zeno effect, which inhibits quantum state evolution via repeated weak measurements, significantly enhances the efficiency of interaction-free measurement (IFM). This fundamental mechanism facilitates high-efficiency counterfactual quantum communication, enabling information delivery without particle transmission through the channel. However, the transmission time of the counterfactual communication requires minutes for bit and suffers the bit error when transmitting an image. Applying the quantum Zeno effect, we experimentally demonstrate high-efficiency weak-trace-free counterfactual communication on a quantum photonic chip, achieving a transmission probability of 74.2 1.6% for bit 0 and 85.1 1.3% for bit 1. Furthermore, we successfully transmit our group's logo - Quanta - through counterfactual communication, and reduce the time cost from minutes to seconds for bit, with zero bit errors after information processing. Our study provides a promising approach for secure and efficient communication using integrated silicon quantum photonics.

State-of-the-art ultra-stable lasers have achieved a fractional frequency stability at the 10 −17 level. Further advancement to the 10 −18 level requires frequency stabilization servo controllers with stronger noise suppression capabilities over a broader frequency band. For external-cavity semiconductor lasers, the prevailing stabilization approach utilizes a combination of current frequency modulation and PZT frequency modulation. In this study, we employed a dedicated loop analyzer and an IQ demodulation frequency measurement method to perform detailed measurements of the transfer functions of individual stages and the closed-loop system of this dual feedback loop, with particular focus on its performance limitations in the frequency range within 10 kHz. By optimizing the feedback path, we improved the laser noise suppression at 1 kHz by three orders of magnitude, thereby reducing the contribution of residual laser frequency noise below 10 kHz to the fractional frequency stability at one second to 4.4×10 −19 . The proposed method not only provides significant value for achieving ultra-stable lasers at the 10 −18 level but is also applicable to newer types of semiconductor lasers that rely solely on current frequency modulation.

Distributed inner product estimation (DIPE) is a fundamental task in quantum information, aiming to estimate the inner product between two unknown quantum states prepared on distributed quantum platforms. Existing rigorous sample complexity analyses are limited to unitary 4-designs, which pose significant practical challenges for near-term quantum devices. This work addresses this challenge by exploring DIPE with structured random circuits. We first establish that DIPE with an arbitrary unitary 2-design ensemble achieves an average sample complexity of $${\mathcal{O}}(\sqrt{{2}^{n}})$$, where n is the number of qubits. We then analyze ensembles below unitary 2-designs—specifically, the brickwork and local unitary 2-design ensembles—demonstrating average sample complexities of $${\mathcal{O}}(\sqrt{2.1{8}^{n}})$$ and $${\mathcal{O}}(\sqrt{2.{5}^{n}})$$, respectively. Furthermore, we analyze the state-dependent sample complexity. For brickwork ensembles, we develop a tensor network approach to compute the asymptotic state-dependent sample complexity, showing that it converges to $${\mathcal{O}}(\sqrt{2.1{8}^{n}})$$ as the circuit depth increases. Remarkably, we find that DIPE with the global Clifford ensemble requires $$\Theta (\sqrt{{2}^{n}})$$ copies, matching the performance of unitary 4-designs. For both local and global Clifford ensembles, we find that the efficiency can be further enhanced by the nonstabilizerness of states. Additionally, for approximate unitary 4-designs, the performance exponentially approaches that of exact unitary 4-designs as the circuit depth increases. Our results provide theoretically guaranteed methods for implementing DIPE with experimentally feasible unitary ensembles.

We address the task of verifying whether a quantum computer, designed to be protected by a specific stabilizer code, correctly encodes the corresponding logical qubits. To achieve this, we develop a general framework for subspace verification and explore several stabilizer code subspaces of practical significance. First, we present two efficient verification strategies for general stabilizer code subspaces, utilizing measurements of their stabilizer generators and stabilizer groups, respectively. Then, building on the observation that certain tests can be conducted in parallel when the subspace exhibits specific structural properties, we propose a coloring strategy tailored to graph code subspaces and an XZ strategy tailored to Calderbank-Shor-Steane (CSS) code subspaces. Compared to stabilizer-based strategies, these new strategies require significantly fewer measurement settings and consume fewer state copies, approaching near-global optimality. Notably, all the strategies employ a limited number of Pauli measurements, are non-adaptive, and work on mixed states, enabling efficient experimental certification of both logical qubits and logical operations in noisy quantum computers. This work contributes to the first systematic study of efficient verification of stabilizer code subspaces with local measurements.

The quantum photonic chip is a powerful platform to prepare multi-functional quantum light sources and actualize complex quantum information processing for its advantages of integration, stability, mass production, and reconfigurability. In this work, we design and fabricate a lithium niobate quantum photonic chip, consisting of tandem multi-poling structures, Mach-Zehnder interferometers, and electro-optic modulators. By programming these components, we produce multiple wavelength-tunable high-fidelity quantum light sources, including anti-bunching, path, and frequency entangled photon pairs. The anti-bunching photon pairs exhibit off-chip Hong-Ou-Mandel interference visibilities above 99%. The fidelities of both frequency and path entanglement exceed 0.99. Meanwhile, all the quantum states maintain high coupling efficiency from the chip. Our work paves the way for the development of programmable multi-functional quantum light sources and fiber-based quantum sensing and quantum communication networks that are sensitive to the useful brightness and quality of quantum light sources.

We report a systematic uncertainty of 9.2 & times;10-19 for the Sr1 optical lattice clock at the University of Science and Technology of China (USTC), achieving accuracy at the level required for the roadmap of the redefinition of the SI second. A finite-element model with in situ-validated, spatially-resolved chamber emissivity reduced blackbody radiation (BBR) shift uncertainty to 6.3 & times;10-19. Concurrently, the externally mounted lattice cavity, by providing a larger beam waist, reduced the atomic density and thereby suppressed the density shift. Enhanced lattice depth modulation consolidated lattice light shift uncertainty to 6.3 & times;10-19 by enabling simultaneous determination of key polarizabilities and magic wavelength. Magnetic shifts were resolved below 10-18 via precision characterization of the second-order Zeeman coefficient. Supported by a clock laser stabilized on an ultralow-expansion glass cavity with crystalline-coated mirrors and refined temperature control suppressing BBR fluctuations, the clock also achieves a frequency stability better than 1 & times;10-18 at 30 000 s averaging time. These developments collectively establish a new benchmark in USTC Sr1 clock performance and pave the way for high-accuracy applications in metrology and fundamental physics.

Low-loss and high-efficiency optical phase shifters, as essential components in optical communication, have attracted significant attention in the field of photonic integrated circuits. However, phase shifters based on silicon microring (Si-MRR) often face challenges such as fabrication complexity, high loss, low efficiency, and high power consumption. In this work, we propose a high-efficiency nonvolatile phase shifter by integrating two-dimensional (2D) ferroelectric NbOI2 into a Si-MRR waveguide. Our results reveal an effective refractive index modulation of -22.95 x 10(-3) RIU (refractive index unit) while preserving nearly constant extinction ratio and resonant line width. Significantly, these devices exhibit an exceptional modulation efficiency of 0.0265 Vcm with low optical loss, which surpasses the performance of earlier research results on 2D material-based phase shifters. Moreover, this work validates the nonvolatile stability of the devices and their advantages in multilevel switching and trimming initial phase errors in the symmetric Mach-Zehnder interferometer (MZI). These advantages make the proposed phase shifter highly promising for applications in the field of silicon photonics, such as optical communication and optical neural networks.

Bipartite Gaussian boson sampling (BipartiteGBS) produces output probabilities governed by squared permanents of submatrices of arbitrary complex matrices, matching the nonsymmetric structure of directed graphs. Most GBS-based graph algorithms, however, rely on symmetric hafnian structure and are formulated for undirected problems. Here we propose a BipartiteGBS-based framework for directed-graph heuristic optimization. We introduce Max-Perm as a canonical optimization task for BipartiteGBS and derive a closed-form sampling enhancement factor relative to uniform classical sampling in this idealized setting. We then use permanent-biased BipartiteGBS samples to guide a genetic algorithm for the celebrated directed Hamiltonian cycle problem. Numerical experiments on Erdős–Rényi random directed graphs show that the resulting BipartiteGBS-enhanced algorithms improve success rates over a standard genetic algorithm and yield longer valid paths when no Hamiltonian cycle is found, while ablation tests indicate that BipartiteGBS-guided initialization is the dominant contributor. These results show how permanent-based photonic sampling can provide useful algorithmic guidance for asymmetric combinatorial search.

Due to the unique phase wavefront structure modulated by orbital angular momentum (OAM), vortex electromagnetic wave (VEMW) radar offers enhanced capabilities for imaging performance improvement. However, the beam inconsistency is intensified with increasing OAM mode numbers, which is further accompanied by worse sidelobe level (SLL). In this paper, a hybrid differential evolution-particle swarm optimization (DE-PSO) method is proposed for radiation pattern synthesis with uniform concentric circle arrays (UCCAs). A multi-objective optimization framework for simultaneous main-lobe alignment and sidelobe suppression is established, which is beneficial for target imagingSimulation results show that the main-lobe of the OAM beam generated by the proposed method is almost accurately pointing to 11°, and the sidelobe level is lower than -22 dB, which verifies its effectiveness in improving the beam quality in OAM-based radar imaging applications.

The ultra-stable laser is a key component of the optical frequency standard system, where one of the primary limitations on its secondary stability index arises from thermal noise. This makes it essential to maintain the laser cavity within an extremely stable thermal environment. We develop and validate experimentally a thermal model for a typical Fabry-P & eacute;rot cavity for accuracy. To improve the thermal stability of the design, a machine learning-assisted optimization design method is proposed, which includes a deep neural network surrogate model, sensitivity analysis, and multi-objective optimization based on the Pareto front. The primary optimization targets are minimizing temperature fluctuations and system weight. A case study demonstrates the efficacy of this approach, showing that the thermal response time constant increased from 97 h before optimization to 190 h after optimization, with only a minimal weight cost. Furthermore, under an external temperature fluctuation of 1 mK, the silicon crystal's temperature fluctuation is reduced to 0.46 mu K-an improvement over the 6 mu K fluctuation reported in previous studies. We provide crucial guidance for the thermal design of ultra-stable laser cavities, enhancing their accuracy and performance in optical systems. (c) 2025 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI:

Upconversion efficiency in heterostructure hosts is critical for multicolor emission in biomedical applications, where cellular uptake is dependent on particle size. In chemo-photodynamic therapy (chemo-PDT), reducing cellular glutathione (GSH) levels through reactive nitrogen species (RNS) generation, combined with reactive oxygen species (ROS), offers a dual strategy to halt cancer cell proliferation. Herein, We optimized NaYbF4:Er3+ upconversion nanoparticles (UCNPs) with size control (final nanocapsule size: 60.5 nm) and applied heterogeneous NaGdF4:Yb3+,Er3+ and inert NaGdF4 shelling, achieving a 30-fold enhancement in fluorescence intensity at 520 nm and 545 nm, alongside improved magnetic resonance imaging (MRI) efficacy. These core@shell@shell UCNPs were nano-precipitated with O2-(2,4-dinitrophenyl)-1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate a class of diazeniumdiolate prodrug and AIEgen molecule to form nanocapsules that generate reactive oxygen and nitrogen species (RONS). Under 980 nm NIR laser (0.25 W/cm²) and white light (0.5 W/cm²) irradiation, these nanocapsules deplete GSH to produce nitric oxide (NO), while AIEgen generates superoxide (∙O2-) and hydroxyl (•OH) radicals via type-I PDT, with NO and ∙O2- forming peroxynitrite (OONO-). In LNCaP prostate cancer cells, 99.7 % nanocapsule internalization occurred within 1 h, and a low dose of 0.625 µg/mL achieved near-complete cell death under dual irradiation, demonstrating synergistic chemo-PDT efficacy. This dual drug delivery system, combining enhanced fluorescence, MRI, and RONS generation, holds promise for precise bioimaging and effective prostate cancer therapy.

Optical atomic clocks play a crucial role in fundamental physics, relativistic geodesy, and the future redefinition of the Systeme International second. Standard operation relies on cyclic interrogation sequences, which alternate between atomic interrogation and dead time used for state preparation and readout. This approach introduces the Dick effect, where laser frequency noise aliases onto the atomic transition frequency. Although reducing laser noise improves clock stability, the Dick effect remains a key limitation. In this Letter, we demonstrate a zero-dead-time optical clock based on two interleaved ensembles of cold ^{87}Sr atoms. Our system significantly suppresses this noise and achieves a fractional frequency instability at the 10^{-19} level between 10 000 and 20 000 s over repeated measurements, with a best value of 2.9×10^{-19} at τ=20000  s. The estimated long-term stability based on the combined data of these measurements reaches 2.5×10^{-19} at 1 day. These results represent a more than ninefold improvement over a conventional single-ensemble clock, highlighting its potential for next-generation timekeeping applications.

We demonstrate a laser emission scheme based on a 2-μm-thick Er3+-doped lithium niobate on insulator (Er:LNOI), using a Fabry-Pérot (FP) cavity with Sagnac loop reflectors (SLRs). The experimental results show a multimode laser output at a central wavelength of 1531.5 nm, with a measured on-chip power of 0.36 mW, and slope efficiency of 0.57%. We enhance the laser power of Er:LNOI lasers via a 2-μm-thick lithium niobate on insulator (LNOI) with an enlarged mode area. Additionally, it offers high coupling efficiency with the taper-lensed fiber, making it suitable for light sources in lithium niobate based photonic integrated circuits (PICs) and optical communication systems.

Quantum walks (QWs) can be used as an arena to study the transition between the quantum and classical behaviors in general. We report that the quantum control makes QWs be in a coherent superposition of wave state and particle state with a relative phase between them, which is named as coherent wave-particle (W-P) QWs. Therefore, the continuous transition between the quantum and classical behaviors in both coherent and mixed ways can be achieved, and it is demonstrated by using the position distribution and variance. Further the coherent W-P QWs are implemented and the conceptual findings are confirmed with the IBM quantum computer.

Optical isolators, the photonic analogs of electronic diodes, are essential for ensuring the unidirectional flow of light in optical systems, thereby mitigating the destabilizing effects of back reflections. Thin-film lithium niobate (TFLN), hailed as "the silicon of photonics," has emerged as a pivotal material in the realm of chip-scale nonlinear optics, propelling the demand for compact optical isolators. We report a breakthrough in the development of a fully passive, integrated optical isolator on the TFLN platform, leveraging the Kerr effect to achieve an impressive 10.3 dB of isolation with a minimal insertion loss of 1.87 dB. Further theoretical simulations have demonstrated that our design, when applied to a microring resonator with a Q factor of 5 x 106, can achieve 20 dB of isolation with an input power of merely 8 mW. This advancement underscores the immense potential of lithium niobate-based Kerr-effect isolators in propelling the integration and application of high-performance on-chip lasers, heralding a new era in integrated photonics.

This work proposes an all-optical on-chip nonlinear activation function unit for multi-wavelength computing applications. Our proposed unit utilizes the unique properties of silicon, specifically the two-photon absorption and thermo-optic effects, to achieve nonlinearity essential for optical neural networks. We designed the parameters of the corresponding unit structure through simulation, fabricated and tested the actual structure experimentally, and obtained a CELU-like response curve. In practical classification tasks, we evaluated its performance in various classification tasks through numerical simulation and achieved a recognition accuracy of 98.84% on the MNIST dataset. This work addresses a critical gap in multi-wavelength systems and contributes to the development of more powerful and efficient optical computing platforms.

Computing the number of perfect matchings of a graph is a famous #P-complete problem. In this work, taking the advantages of the frequency dimension of photon, we propose and implement a photonic perfect matching solver, by combining two key techniques, frequency grouping and multi-photon counting. Based on a broadband photon-pair source from a silicon quantum chip and a wavelength-selective switch, we configure graphs up to sixteen vertices and estimate the perfect matchings of subgraphs up to six vertices. The experimental fidelities are more than 90% for all the graphs. Moreover, we demonstrate that the developed photonic system can enhance classical stochastic algorithms for solving nondeterministic-polynomial-time(NP) problems, such as the Boolean satisfiability problem and the densest subgraph. Our work contributes a promising method for solving the perfect matchings problem, which is simple in experiment setup and convenient to transform or scale up the object graph by regulating the frequency-correlated photon pairs.

We propose an algorithm for directed graph centrality ranking, called the ancilla-assisted pseudo-Hermitian continuous-time quantum walk algorithm (AA-PHCTQW). AA-PHCTQW overcomes a common limitation for existing CTQW-based centrality ranking algorithms, both for undirected and directed graphs, which is the requirement of an initial state in a uniform superposition over all vertices. Leveraging an ancilla vertex, we enable the use of a single-vertex basis state as the initial system state, thereby significantly improving the algorithm's experimental feasibility and robustness against noise. We prove the correctness of AA-PHCTQW and analyze centrality measures from PHCTQW and AA-PHCTQW on random graphs. Furthermore, we experimentally validate the algorithm on a silicon-based reconfigurable photonic chip with heralded single-photon source and multiphoton sources, complete the AA-PHCTQW of three-node and nine-node directed graphs. Here we provide an on-chip experimental demonstration of a quantum walk algorithm for directed graph centrality ranking.

Microring resonators (MRRs) are extensively utilized in photonic chips for generating quantum light sources and enabling high-efficiency nonlinear frequency conversion. However, conventional microrings are typically optimized for a single specific function, limiting their versatility in multifunctional applications. In this work, we propose a reconfigurable microring resonator architecture designed to accommodate diverse application requirements. By integrating a cascaded Mach-Zehnder interferometer (MZI) as the microring coupler, the design enables independent control of the quality factors for pump, signal and idler photons through two tunable phase shifters. This capability allows for dynamic tuning and optimization of critical performance parameters, including photon-pair generation rate (PGR), spectral purity and single photon heralding efficiency (HE). The proposed structure is implemented on a silicon photonic chip, and experimental results exhibit a wide range of tunability for these parameters, with excellent agreement with theoretical predictions. This flexible and multi-functional design offers a promising pathway for high-performance, highly integrated on-chip quantum information processing systems.