Highly integrated broadband entropy source for quantum random number generators based on vacuum fluctuations

In this work, we designed and experimentally verified a highly integrated broadband entropy source for a quantum random number generator (QRNG) based on vacuum fluctuations. The core of the entropy source is a hybrid laser-and-silicon-photonics chip, which is only 6.3 mm $~\times~$ 2.6 mm $~\times~$ 1.5 mm in size. A balanced homodyne detector based on cascaded radio-frequency amplifiers in the entropy source achieves a 3-dB bandwidth of 2.4 GHz and a common-mode rejection ratio above 25 dB. The quantum-to-classical-noise ratio is 9.51 dB at a photoelectron current of 1 mA. The noise equivalent power and equivalent transimpedance at 0.1 GHz arełinebreak 8.85 $\text{pW}/\sqrt{\text{Hz}}$, and 22.8 k$\Omega$, respectively. A trusted-device-dependent security framework that takes into account both classical and quantum side information is employed to calculate the minimum entropy. The equalization technology is used to extend the bandwidth and minimize the correlations between adjacent samples. The quantum random number generation rate reaches 58.24 Gbps. The developed hybrid chip enhances the integrability and speed of QRNG entropy sources based on vacuum fluctuations.