Noise-rejecting photonic integrated circuit for robust quantum random number generation

Recent advancements in integrated photonics have shown great promise for the serial production of chip-scale quantum random number generators (QRNG). Considerable progress has been made towards developing fully on-chip QRNGs that exploit the interference of phase-randomized fields from two independent lasers. While a common alternative design, based on a single laser and interferometer, would further improve power consumption and ease of operation, monolithic integration of such a design has thus far faced challenges, including high losses and crosstalk. We solve these key challenges and report fast single-laser interferometric QRNGs integrated onto monolithic chips. By combining on-chip optical amplification with electronic common-mode rejection techniques, our photonic integrated circuits (PICs) stably convert the spontaneous emission phase noise of a diode laser into electronic pulses of high-contrast random intensity at GHz clock rates. Using real-time, hash-function-based randomness extraction, uniformly distributed, truly unpredictable random numbers are generated at a rate of 3 Gbps.