This letter presents the design of a compact, lossless, and programmable photonic state generator utilizing a closedloop architecture. The system strategically recirculates light until a steady-state condition is reached and the target is produced.
General-purpose programmable photonic processors offer a flexible foundation for integrating various functionalities within a single chip. A two-dimensional hexagonal waveguide mesh of Mach Zehnder interferometers has been shown to have great potential in the field of microwave photonics. Additionally, they are a promising platform for the creation of unitary linear transformations, which are key elements in photonic neural networks, In this article, we expand the portfolio of available applications for recirculating bricks mesh architecture to quantum technologies. We will show that a single programmable optical system is capable of performing various functions depending on the requirements. In particular, we will focus in this work on boson sampling, a task that best demonstrates quantum advantage, as well as on tasks that enable the determination of photon indistinguishability, which plays a key role in photonic quantum technologies. We will also show that, in addition to spatial modes, the same optical system can be equally well-suited for work on temporal modes through the implementation of an appropriate number of loops.
Recent efforts have demonstrated the first prototypes for compact and programmable photonic quantum computers (PQCs). Utilization of time-bin encoding in loop-like architectures enabled programmable generation of quantum states and execution of different (programmable) logic gates on a single circuit. Actually, there is still space for better compactness and complexity of available quantum states and gate operations: a photonic circuit (PC) can operate at multiple frequencies. Here, we propose an electrically-programmable frequency comb that generates continuously tunable entanglement among different frequencies. The device is not directly integrated into fragile quantum processing components but is to be used as a fast (picoseconds) tunable auxiliary source provided into state-of-the-art measurement-induced loop-based photonic quantum computers employing programmable (50 MHz) beam-splitters (BSs) and phase-shifters. Multimode entanglement generation is controlled via Fano resonance in the nonlinear response. The generated entanglement can be tuned continuously via an applied voltage which can be delivered to the device via nm-thick wires. The proposed device is integrable, CMOS-compatible, and operates below ps but is limited with transistor clock speeds 5-100 GHz.
ABSTRACT Quantum evolution is crucial for the understanding of complex quantum systems. However, current implementations of time evolution on quantum photonic platforms are limited by both low photon generation efficiency and high propagation loss, making photon detection difficult. Furthermore, the single‐layer complexity of most implementations cannot support multi‐step quantum simulations. In this work, we present a loop quantum photonic chip (Loop‐QPC) designed to efficiently simulate quantum dynamics over multiple time steps in a single chip. Our approach employs a recirculating loop structure to reuse computational resources and eliminate the need for multiple quantum tomography steps or chip reconfigurations. A cycle‐or‐measure circuit at the input and output stages allows dynamic routing of photons between evolution and measurement, enabling efficient control over the simulation loop and minimizing loss. We experimentally demonstrate the dynamics of the spin‐boson model on a low‐loss Silicon Nitride integrated photonic chip. The Loop‐QPC achieves a three‐step unitary evolution closely matching the theoretical predictions. These results establish the Loop‐QPC as a promising method for efficient and scalable quantum simulation, advancing the development of quantum simulation on programmable photonic circuits.