Quantum walks on photonic platforms represent a physics-rich framework for quantum measurements, simulations and universal computing. Dynamic reconfigurability of photonic circuitry is key to controlling the walk and retrieving its full operation potential. Universal quantum processing schemes based on time-bin encoding in gated fibre loops have been proposed but not demonstrated yet, mainly due to gate inefficiencies. Here we present a scalable quantum processor based on the discrete-time quantum walk of time-bin-entangled photon pairs on synthetic temporal photonic lattices implemented on a coupled fibre-loop system. We utilize this scheme to path-optimize quantum state operations, including the generation of two- and four-level time-bin entanglement and the respective two-photon interference. The design of the programmable temporal photonic lattice enabled us to control the dynamic of the walk, leading to an increase in the coincidence counts and quantum interference measurements without recurring to post-selection. Our results show how temporal synthetic dimensions can pave the way towards efficient quantum information processing, including quantum phase estimation, Boson sampling and the realization of topological phases of matter for high-dimensional quantum systems in a cost-effective, scalable and robust fibre-based setup.

光子平台上的量子行走代表了量子测量、模拟和通用计算的丰富物理框架。光子电路的动态可重构性是控制行走和恢复其全部运行潜力的关键。基于门控光纤环路中时间仓编码的通用量子处理方案已经提出，但尚未得到验证，主要是由于门效率低下。在这里，我们提出了一个可扩展的量子处理器，该处理器基于在耦合光纤环系统上实现的合成时间光子晶格上时间仓纠缠光子对的离散时间量子游走。我们利用此方案对量子态操作进行路径优化，包括生成两级和四级时间仓纠缠以及相应的双光子干涉。可编程时间光子晶格的设计使我们能够控制游走的动态，从而增加符合计数和量子干涉测量，而无需重复进行后选择。我们的结果显示了时间合成维度如何为高效的量子信息处理铺平道路，包括量子相位估计、玻色子采样和在经济高效、可扩展和强大的基于光纤的设置中实现高维量子系统的物质拓扑相位。