On-chip tunable SOI interferometer for quantum random number generation based on phase diffusion in lasers

Long term experimental verification of a single chip quantum random number generator fabricated on the InP platform

“…Figure 6(a) shows the distribution of the peak power of the first 125 μs data file, recorded at the output of the PIC for the conditions described above. The bin frequency profiles of the other 25 files exhibited almost identical profiles with a single peak of max value in the 6(a) though comes in contrast to the expected arcsine shape with the two peaks reported in other similar phase diffusion QRNG layouts [22,23,29]. To identify the reason for this discrepancy, the next step was the formation of a simplified model following the well-known interference equation:…”

“…The usual arcsine profile that appears in other QRNG demonstrators based on the random phase of independent pulses appears when the Gaussian phase is wide enough to be, for all practical purposes, a uniform random variable between 0 and 2π [22,23,29]. For continuous wave lasers, the Gaussian phase drift depends on the delay between the interfering signals, but usually has a smaller variance [26,31].…”

“…This method measures the accelerated phase noise because the laser is below the threshold or even reversed bias for a long period of the pulse [23]. This type of QRNG's were originally shown with polarization-maintaining fiber based delayed interferometers [22,23], but with the progress of photonic integration technology, the latest results are coming from Silicon photonics [28], and silicon on insulator (SOI) [29], platforms. A gain-switch (GS) mode laser is employed as a phase-diffusion quantum entropy source and coupled to a Si photonic chip that comprises the uMZI and the detection components [28], and achieves full entropy capacity around 820 Mbps.…”

“…A gain-switch (GS) mode laser is employed as a phase-diffusion quantum entropy source and coupled to a Si photonic chip that comprises the uMZI and the detection components [28], and achieves full entropy capacity around 820 Mbps. Recently, a 10 Gbps QRNG has been demonstrated [29], using a packaged on-chip tunable SOI critical interferometry structure for QRNGs based on phase diffusion laser operating in GS mode. A major problem though with Si photonics based devices is that the laser sources should be external, although hybrid integration of directly modulated lasers has been recently demonstrated [30].…”

Advanced Laser Technology for Quantum Communications (Tutorial Review)

“…However, this scheme turns out to be more advantageous than the single laser one, when realized with integrated photonic chips [113,114]. In fact, the integrated delay line introduces high losses with respect to the short arm of the interferometer creating in this way an unbalance between the two arms, which needs to be compensated either by adding additional losses in the short arm [115] or by splitting light with uneven ratio at the input of the interferometer [116]. As explained in Section 3.1, DFB lasers can be modulated at very high rates such that, if the laser is matched with a high bandwidth PD and a fast ADC, bit generation rates in the range of hundreds of Mbit/s and tens of Gbit/s can be achieved [117,118].…”