Abstract
The quantum phase noise in a pulsed semiconductor laser is studied thoroughly in the context of its utilization as a quantum entropy source in a quantum random number generator (QRNG) device. We performed a numerical analysis of the phase diffusion process for a semiconductor laser in the continuous-wave operation mode and gain-switched (GS) mode. The result demonstrates the amplification of randomness in the GS mode, which is gauged physically by the variance VarΔϕ. The variance value, which is mathematically related to the temporal distance between the laser pulses used in the experimental setup, also determines the stability of the setup. Furthermore, we show how the QRNG probability distribution is influenced by several experimental factors such as the quality of the interference process and the noise in the detection system.
Highlights
A quantum random number generator (QRNG) is a special case of a hardware-based random number generator
The experimental parameters in the phase diffusion process influencing the probability distribution have been explained from the perspective of physicists who develop the hardware for the QRNG
The QRNG probability distribution has been found to be influenced by several factors such as the quality of the interference process and the noise in the detection system
Summary
A quantum random number generator (QRNG) is a special case of a hardware-based random number generator. The output of a semiconductor laser contains fluctuations in intensity and phase due to the spontaneous emission events that take place in the active medium. Phase measurement is not a feasible procedure for optical signals, so the phase fluctuation needs to be converted to an observable macroscopic parameter such as the optical intensity. This can be done by using an interferometer setup.. QRNG devices, the assessments will have to include a comprehensive understanding of the quantum physical process involved in the randomness generation and, the implication of its interaction with the various experimental factors during the operational execution. There are two reasons for the fluctuation in the phase; the first cause is the carrier-induced change in the refractive index, and the second cause is the fluctuation from spontaneous emission
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