Abstract
The generation of random bits is of enormous importance in modern information science. Cryptographic security is based on random numbers which require a physical process for their generation. This is commonly performed by hardware random-number generators. These often exhibit a number of problems, namely experimental bias, memory in the system, and other technical subtleties, which reduce the reliability in the entropy estimation. Further, the generated outcome has to be postprocessed to “iron out” such spurious effects. Here, we present a purely optical randomness generator, based on the bistable output of an optical parametric oscillator. Detector noise plays no role and postprocessing is reduced to a minimum. Upon entering the bistable regime, initially the resulting output phase depends on vacuum fluctuations. Later, the phase is rigidly locked and can be well determined versus a pulse train, which is derived from the pump laser. This delivers an ambiguity-free output, which is reliably detected and associated with a binary outcome. The resulting random bit stream resembles a perfect coin toss and passes all relevant randomness measures. The random nature of the generated binary outcome is furthermore confirmed by an analysis of resulting conditional entropies.
- Received 13 June 2017
DOI:https://doi.org/10.1103/PhysRevX.7.041050
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
The generation of random numbers is of enormous importance in modern information science. Securing personal information, financial transactions, and private communication depends on authentication and encryption protocols that rely on random numbers. To be certain that an alleged random number is truly random, one must consider the process of generating the number and not the value of the number itself. To create numbers that are sufficiently random, engineers have created a variety of hardware devices that leverage the intrinsic randomness of a physical system. One remaining problem, however, is that the desired randomness is often inseparably mixed with technical noise of the measurement process. Therefore, we have developed a laser-based randomness generator that cleanly separates the number generation from the measurement process.
The generator is based on an optical parametric oscillator, which emits optical pulses. Depending on the underlying quantum process of vacuum fluctuations, the optical phase of the pulses is either in or out of phase with an external clock of the pump laser. This bistability leads to a random phase relation among the two signals and can be interpreted as ones and zeros in a random bit stream. The generator resembles a perfect coin toss, does not require any postprocessing, and passes all relevant randomness measures.
Future development of all-optical randomness generators will play an important role for secure optical communication and quantum information protocols. One of the next goals is to implement a compact and miniaturized version of the generator.