  Quantum random number generator (QRNG) can produce true randomness by
utilizing the inherent probabilistic nature of quantum mechanics. Recently, the
spontaneous-emission quantum phase noise of the laser has been widely deployed
for QRNG, due to its high rate, low cost and the feasibility of chip-scale
integration. Here, we perform a comprehensive experimental study of phase-noise
based QRNG with two independent lasers, each of which operates in either
continuous-wave (CW) or pulsed mode. We implement QRNGs by operating the two
lasers in three configurations, namely CW+CW, CW+pulsed and pulsed+pulsed, and
demonstrate their tradeoffs, strengths and weaknesses.
