True Random Number Generators based on Amplified Spontaneous Emission
Low-cost, high-speed quantum random number generators (QRNGs) are imperative to develop in order to have a widespread application in areas ranging from cryptography and stochastic simulations to banking and internet. Amplified spontaneous emission (ASE) based QRNGs offer a great advantage in this pursuit. However, most ASE-based QRNGs use costlier and more complex components compared to their speed. In this work, we discuss two QRNG schemes where we alleviate this problem. We also develop a comprehensive theoretical study to understand then in detail. In our ASE-ASE beating based QRNG, random numbers are generated by performing balanced detection of two independent ASE signals. Our second QRNG scheme is based on mixing a laser and an ASE of similar power and measuring the beat noise using a balanced detector. Our theoretical analysis shows that introducing the laser improves the standard deviation of the raw data, which can result a higher minimum entropy in the later QRNG. This fact is corroborated by the experiments as well. Our first experimental implementation of ASE based QRNGs use a balanced detector of 1.6GHz bandwidth and clock in bit generation rates of 7.44Gbps (ASE-ASE) and 7.9898Gbps (ASE-Laser) using an 8-bit ADC. Then we reduce the bandwidth of the detector to 100MHz since most available ADCs with higher bit resolution have bandwidths of few hundreds of MHz. In this case also, we achieve half a Gbps speeds for our QRNGs using the aforementioned 8-bit ADC - 546.03Mbps (ASE-ASE), 507.94Mbps (ASE-Laser). Furthermore, we develop two multiplexed QRNG schemes to double the speed of the QRNGs. Our experimental implementations of them show that multiplexing can achieve 1Gbps speed with a very slow detector (bandwidth of 100MHz). All the random numbers are verified using industry-standard statistical tests - NIST and DIEHARD - and obtain satisfactory results. Moreover, they can be easily integrated on a chip for commercial use.