Xiao-Wen Shang

The spontaneous breaking of the time translation symmetry has led to the emergence of quantum time crystals as a novel phase of matter, which is a phenomenon sustained by quantum coherence over long periods. Among them, discrete time crystals are recognized by the spontaneous generation of robust subharmonic oscillations. So far, most time crystals are restricted to exhibit a “period‐doubled” behavior. However, a fertile ground in time crystalline with period‐‐tupling has been suggested. Here we experimentally realize scalable period‐2‐tupling and period‐‐tupling in the one‐ (1D) and two‐dimensional (2D) photonic lattices, respectively. In this non‐interacting system, no spontaneous symmetry breaking occurs; instead, the period‐‐tupling arises from the preparation of specific superpositions of eigenmodes with quasienergy gaps of . All levels of the 2D spectrum are paired with different gaps, so that different response periods can be achieved by exciting different sites of the same lattice. The period ‐tupling is robust against perturbations over an extraordinarily long time evolution. The results may promote further research into arbitrary higher‐order time crystals in interacting photonic systems and into non‐equilibrium physics adopting Floquet driving. Next‐generation quantum devices, such as topologically protected quantum state registers, quantum sensors, and simulators, can also be inspired by this approach.

In-memory computing, which enables computation directly within memory, represents an efficient approach to processing massively parallel computation tasks that are intractable for conventional computers. However, implementations of in-memory computing have been primarily limited to the classical regime, with its nonclassical counterpart yet to be fully explored. Quantum memory, with its unique capability to generate, preserve, and nontrivially operate on quantum states, offers spectacular quantum-enhanced advantages and is thus a promising candidate for in-memory computing. Here, leveraging a room-temperature quantum memory, we demonstrate a quantum-enhanced and reconfigurable in-memory stochastic computing system, where correlated photons, randomly produced in the quantum memory, serve as the computing resources. We show that addition and multiplication operations can be straightforwardly achieved by accumulating photon counts, and multiple computing tasks can be accelerated by mapping them into parallel accumulations of photon counts. Furthermore, the calculation results are obtained through stochastic processes, ensuring security in remote computation since no efficient information can be distinguished by eavesdropping on a small portion of the computation data. This in-memory computing system is enhanced by nonclassical correlations, which accelerate computing process and may stimulate future research and applications in the emerging field of quantum-enhanced computing architectures.

Quantum effects in photosynthetic energy transport in nature, especially for the typical Fenna-Matthews-Olson (FMO) complexes, are extensively studied in quantum biology. Such energy transport processes can be investigated as open quantum systems that blend the quantum coherence and environmental noise, and have been experimentally simulated on a few quantum devices. However, the existing experiments always lack a solid quantum simulation for the FMO energy transport due to their constraints to map a variety of issues in actual FMO complexes that have rich biological meanings. Here we successfully map the full coupling profile of the seven-site FMO structure by comprehensive characterisation and precise control of the evanescent coupling of the three-dimensional waveguide array. By applying a stochastic dynamical modulation on each waveguide, we introduce the base site energy and the dephasing term in coloured noise to faithfully simulate the power spectral density of the FMO complexes. We show our photonic model well interprets the phenomena including reorganisation energy, vibrational assistance, exciton transfer and energy localisation. We further experimentally demonstrate the existence of an optimal transport efficiency at certain dephasing strength, providing a window to closely investigate environment-assisted quantum transport.

Dynamic localization, which originates from the phenomena of particle evolution suppression under an externally applied AC electric field, has been simulated by suppressed light evolution in periodically curved photonic arrays. However, experimental studies on their quantitative dynamic transport properties and application for quantum information processing are rare. Here we fabricate one-dimensional and hexagonal two-dimensional arrays both with sinusoidal curvatures. We successfully observe the suppressed single-photon evolution patterns, and for the first time, to the best of our knowledge, measure the variances to study their transport properties. For one-dimensional arrays, the measured variances match both the analytical electric-field calculation and the quantum walk Hamiltonian engineering approach. For hexagonal arrays as anisotropic effective couplings in four directions are mutually dependent, the analytical approach suffers, whereas quantum walk conveniently incorporates all anisotropic coupling coefficients in the Hamiltonian and solves its exponential as a whole, yielding consistent variances with our experimental results. Furthermore, we implement a nearly complete localization to show that it can preserve both the initial injection and the wave packet after some evolution, acting as a memory of a flexible time scale in integrated photonics. We demonstrate a useful quantum simulation of dynamic localization for studying their anisotropic transport properties and a promising application of dynamic localization as a building block for quantum information processing in integrated photonics.