[Paper Review] High-speed Source-Device-Independent Quantum Random Number Generator on a Chip

Tommaso Bertapelle, Marco Avesani+12 more|arXiv (Cornell University)|May 21, 2023

Chaos-based Image/Signal Encryption4 citations

TL;DR

This paper presents the first chip-integrated, source-device-independent quantum random number generator (QRNG) achieving a secure generation rate exceeding 20 Gbps. By leveraging an integrated heterodyne receiver on a 4×4 MMI interferometer photonic chip and a Toeplitz hashing extractor, the system ensures high security, compactness, low power consumption, and resilience—making it ideal for high-speed quantum key distribution in space and portable applications.

ABSTRACT

A wide range of applications require, by hypothesis, to have access to a high-speed, private, and genuine random source. Quantum Random Number Generators (QRNGs) are currently the sole technology capable of producing true randomness. However, the bulkiness of current implementations significantly limits their adoption. In this work, we present a high-performance source-device independent QRNG leveraging a custom made integrated photonic chip. The proposed scheme exploits the properties of a heterodyne receiver to enhance security and integration to promote spatial footprint reduction while simplifying its implementation. This characteristics could represents a significant advancement toward the development of generators better suited to meet the demands of portable and space applications. The system can deliver secure random numbers at a rate greater than 20 Gbps with a reduced spatial and power footprint.

Motivation & Objective

• To develop a high-speed, compact, and energy-efficient quantum random number generator (QRNG) suitable for real-world deployment.
• To overcome limitations of trusted-device QRNGs by implementing a source-device-independent (SDI) protocol that reduces trust assumptions on both source and detector.
• To integrate the entire QRNG system on a single photonic integrated circuit (PIC) to minimize size, power consumption, and environmental sensitivity.
• To achieve a secure random number generation rate exceeding 20 Gbps while maintaining robustness for space and portable applications.
• To demonstrate the feasibility of a fully passive, stable, and scalable QRNG architecture without active phase control or feedback loops.

Proposed method

• Utilizes a heterodyne detection scheme with a 4×4 multimode interference (MMI) coupler to measure quadrature amplitudes of a weak coherent light source.
• Employs a high-speed, low-noise balanced receiver and fast analog-to-digital converters (ADCs) to digitize the quadrature signals at high bandwidth.
• Applies a 2-universal Toeplitz matrix-vector multiplication as a randomness extractor to distill uniform, secure random bits from the raw data.
• Sets the security parameter to ε ~ 10⁻¹⁷ by choosing matrix dimensions (n = 11008, m = 17600) based on the min-entropy and ADC bit width.
• Operates the local oscillator (LO) at 21.1496 mW to maximize signal-to-noise ratio and purity (0.883 ± 0.003), ensuring high-quality quantum randomness.
• Eliminates active phase stabilization by relying on the intrinsic stability of the passive MMI-based interferometer, reducing power and complexity.

Experimental results

Research questions

• RQ1 Can a fully integrated, chip-scale QRNG achieve high-speed, secure random number generation with minimal trust in device components?
• RQ2 How does the performance of a source-device-independent QRNG compare to trusted or device-independent schemes in terms of speed, footprint, and power efficiency?
• RQ3 To what extent can passive photonic integration (e.g., using an MMI coupler) replace active phase stabilization in high-speed heterodyne QRNGs?
• RQ4 What is the maximum secure generation rate achievable with a compact, low-power, and robust integrated QRNG architecture?
• RQ5 Can such a system maintain high randomness quality and pass rigorous statistical tests (e.g., NIST) under real-world operating conditions?

Key findings

• The QRNG achieves a secure random number generation rate of 20.015 Gbps, the highest reported for a semi-device-independent QRNG to date.
• The system delivers a purity of 0.883 ± 0.003 at maximum local oscillator power (21.1496 mW), indicating high-quality quantum state preparation.
• The device operates stably with a local oscillator power below 1 mW, demonstrating exceptional energy efficiency and low power consumption.
• All 16 NIST statistical tests passed with p-values ranging from 0.091 to 0.963, confirming the high quality and uniformity of the extracted random bits.
• The QRNG is fully passive, with no active feedback or phase control, enhancing reliability, scalability, and resilience to harsh environments.
• The chip-based design enables compactness, low power, and robustness, making it suitable for satellite-based quantum key distribution with repetition rates above 5 GHz.