33 Gbit/s source-device-independent quantum random number generator based on heterodyne detection with real-time FPGA-integrated extraction

TL;DR

This paper addresses the need for high-rate, secure quantum random numbers by implementing a source-device-independent continuous-variable QRNG based on heterodyne detection of vacuum fluctuations. The authors integrate real-time Toeplitz hashing on an FPGA to extract randomness from both quadratures of the vacuum, achieving a net rate of 33.92 Gbit/s while maintaining SDI security that relies only on a trusted measurement device and discretization. Key contributions include a detailed experimental setup with a 1550 nm LO, a 90° optical hybrid, balanced photodiodes, and a 3.2 GS/s, 12-bit ADC, all processed on FPGA with 20 parallel Toeplitz extractors, plus extensive calibration, QCNR measurements, and statistical validation (NIST and Dieharder). The results demonstrate a practical, compact, FPGA-based implementation suitable for high-rate quantum communications and secure key distribution, with clear pathways for further rate improvements via higher ENOB ADCs and improved calibrations.

Abstract

We present a high-speed continuous-variable quantum random number generator (QRNG) based on heterodyne detection of vacuum fluctuations. The scheme follows a source-device-independent (SDI) security model in which the entropy originates from quantum measurement uncertainty and no model of the source is required; security depends only on the trusted measurement device and the calibrated discretization, and thus remains valid even under adversarial state preparation. The optical field is split by a 90$^\circ$ optical hybrid and measured by two balanced photodiodes to obtain both quadratures of the vacuum state simultaneously. The analog outputs are digitized using a dual-channel 12-bit analog-to-digital converter operating at a sampling rate of 3.2 GS/s per channel, and processed in real time by an FPGA implementing Toeplitz hashing for randomness extraction. The quantum-to-classical noise ratio was verified through calibrated power spectral density measurements and cross-checked in the time domain, confirming vacuum-noise dominance within the 1.6 GHz detection bandwidth. After extraction, the system achieves a sustained generation rate of $R_{\rm net}= 33.92~\mathrm{Gbit/s}$ of uniformly distributed random bits, which pass all NIST and Dieharder statistical tests. The demonstrated platform provides a compact, FPGA-based realization of a practical heterodyne continuous-variable source-independent QRNG suitable for high-rate quantum communication and secure key distribution systems.

Figures (8)

• Figure 1: Schematic diagram of the vacuum fluctuation-based quantum random number generator using heterodyne detection. The setup consists of a laser source followed by a variable optical attenuator (VOA) for power control and stabilization. The laser output is mixed with vacuum fluctuations in a 90$^\circ$ optical hybrid, which simultaneously measures both X and P quadratures of the electromagnetic field. Each of the four hybrid outputs are individually controlled by electronically variable optical attenuators (EVOAs) with electrical control inputs before being detected by balanced photodiode detectors (BPD1 and BPD2). The analog electrical signals from both detectors are first filtered by a low-pass and high-pass filters to filter out as much classical electrical noise as possible and then digitized by a 2-channel analog-to-digital converter (ADC) and processed in real-time by a field-programmable gate array (FPGA) connected via an FMC (FPGA Mezzanine Card) interface.
• Figure 2: The pipelined Toeplitz extraction scheme. The scheme consists of separate pipeline stages. The dashed arrows indicate binary signals, the normal lines indicate the flow of the program and the bold, larger lines indicate flow of data. The square blocks represent operations and the diamond blocks represent conditionals.
• Figure 3: The overall schematic of the FPGA design. All parallel blocks contain the same functions and I/O, only the first block is fully drawn to make the diagram more compact. The dashed arrows indicate binary signals, the normal lines indicate the flow of the program and the bold, larger lines indicate flow of data.
• Figure 4: PSD of both ADC channels that are connected to the balanced diodes. The blue curve corresponds to no laser power and the orange curve to a local-oscillator power of $8.4\,\mathrm{mW}$. The gray colored area shows over which range the PSD is integrated for QCNR.
• Figure 5: The dependence of both quadrature measured signal variance on the local oscillator laser power.

Theorems & Definitions (2)

• Lemma 1
• proof