Lei Zhang

We demonstrate a continuous-variable quantum key distribution system with an integrated silicon photonic receiver, achieving a 1.89 Mbps asymptotic secret key rate over 60 km, enabling metropolitan-area chip-based quantum secure communications.

Random thermal states of many-body Hamiltonians underpin studies of thermalization, chaos, and quantum phase transitions, yet their generation remains costly when each Hamiltonian must be prepared individually. We introduce the thermal-drift channel, a measurement-based operation that implements a tunable nonunitary drift along a chosen Pauli term. Based on this channel, we present a measurement-controlled sampling algorithm that generates thermal states together with their Hamiltonian ``labels'' for general physical models. We prove that the total gate count of our algorithm scales cubically with system size, quadratically with inverse temperature, and as the inverse error tolerance to the two-thirds power, with logarithmic dependence on the allowed failure probability. We also show that the induced label distribution approaches a normal distribution reweighted by the thermal partition function, which makes an explicit trade-off between accuracy and effective range. Numerical simulations for a 2D Heisenberg model validate the predicted scaling and distribution. As an application, we compute unfolding-free level-spacing ratio statistics from sampled thermal states of a 2D transverse-field Ising model and observe a crossover toward the Wigner-Dyson prediction, demonstrating a practical and scalable route to chaos diagnostics and random matrix universality studies on near-term quantum hardware.

We develop a chip-based continuous-variable quantum key distribution system using an integrated optical switch for real-time shot noise calibration. Experimental results demonstrate a secure key rate of 12.30 Mbps over 25.3 km, establishing foundational capabilities for practical applications.