Chaotic oscillation and random-number generation based on nanoscale optical-energy transfer

Abstract

By using nanoscale energy-transfer dynamics and density matrix formalism, we demonstrate theoretically and numerically that chaotic oscillation and random-number generation occur in a nanoscale system. The physical system consists of a pair of quantum dots (QDs), with one QD smaller than the other, between which energy transfers via optical near-field interactions. When the system is pumped by continuous-wave radiation and incorporates a timing delay between two energy transfers within the system, it emits optical pulses. We refer to such QD pairs as nano-optical pulsers (NOPs). Irradiating an NOP with external periodic optical pulses causes the oscillating frequency of the NOP to synchronize with the external stimulus. We find that chaotic oscillation occurs in the NOP population when they are connected by an external time delay. Moreover, by evaluating the time-domain signals by statistical-test suites, we confirm that the signals are sufficiently random to qualify the system as a random-number generator (RNG). This study reveals that even relatively simple nanodevices that interact locally with each other through optical energy transfer at scales far below the wavelength of irradiating light can exhibit complex oscillatory dynamics. These findings are significant for applications such as ultrasmall RNGs.

Random walk with chaotically driven bias

“…To characterise the ‘chaotic probability’ observed in the nanoscale optical energy transfer between quantum dots (QDs)6, we investigated one-dimensional random walks with fluctuating biases generated by fixed, periodic, quasi-periodic, and chaotic time series. In this study, we demonstrated that the ETVAR clearly characterises the diffusive nature in random walks with fluctuating biases in the time-quenched framework, while the ETMSD does not estimate the diffusivity.…”

“…Thus, the mean of p(t ) is exactly 0.5, which implies that the net bias is zero. Figure 5 shows four different time series of p(t ) obtained from a data set of nanophotonic oscillations6: e.g. (a) fixed, (b) periodic (No.…”

“…Previously, some of the authors theoretically and numerically demonstrated that chaotic oscillation occurs in a nanoscale system consisting of a pair of quantum dots (QDs), between which energy transfers via optical near-field interactions6. The chaotic oscillation occurs at the values of the existence probability of an exciton in one of the QDs when the QDs are connected with an external time delay.…”

“…The chaotic oscillation occurs at the values of the existence probability of an exciton in one of the QDs when the QDs are connected with an external time delay. It is scientifically and technologically important to elucidate the exact nature of this new oscillatory phenomenon, which we call ‘nanochaos’, since it implies that ultrafast random number generators6, problem solvers78, and decision makers91011 can be constructed by the nanoscale elements. These results also inspire us to study the random walk with a temporally fluctuating bias, which is an annealed version of Sinai’s model.…”

Quantum random number generator based on silicon nanocrystals LED

“…Quantum dots [5,6], single photon avalanche photodiode (SPAD) [7], light emitting devices (LEDs) [8,9], laser [10,11], chaotic laser [12] , and atmospheric turbulence [13] have been employed as sources of entropy to produce random numbers. In this paper we present a quantum RNG (QRNG) based on silicon nanocrystals (SiNCs) LEDs, able to produce statistically good bit sequences using a simple experimental setup for data extraction.…”