Quantum Limits Enable Certified Randomness for Secure Communication.

The fundamental limits imposed by the laws of physics often define what is computationally possible, but recent research demonstrates these constraints can also be harnessed for practical applications. Specifically, limitations on how quickly a quantum system can evolve – dictated by the time-energy uncertainty principle – provide a means of generating verifiable randomness, a crucial resource for cryptography and secure communication. Caroline L. Jones, Albert Aloy, and Gerard Higgins, all from the Institute for Quantum Optics and Quantum Information at the Austrian Academy of Sciences, alongside Markus P. Müller from the Perimeter Institute for Theoretical Physics, detail this process in their article, “Certified randomness from quantum speed limits”. Their work establishes a framework for generating randomness even with limited knowledge of the underlying quantum device, relying solely on experimentally determined bounds on energy uncertainty and the ability to control the timing of quantum operations. This approach extends existing methods for device-independent security. It offers a pathway to demonstrating non-classical behaviour in relatively simple quantum systems, such as those based on the harmonic oscillator.

Quantum mechanics offers a pathway to generate certified random numbers by exploiting the inherent uncertainty in the timing and energy of quantum states. Researchers have recently detailed a protocol that leverages the time-energy uncertainty principle, a fundamental tenet of quantum theory stating that the more precisely one property is known, the less precisely the other can be.

The newly developed protocol distinguishes itself through its minimal reliance on assumptions about the quantum devices employed. Many existing quantum random number generators (QRNGs) require detailed characterisation of the apparatus, introducing potential vulnerabilities. This new approach necessitates only an experimentally determined, or theoretically promised, upper bound on the energy uncertainty of the initial quantum state and precise control over the timing of its preparation. This simplification enhances the practicality of implementing QRNGs in real-world scenarios.

Crucially, the framework demonstrates robustness against environmental interactions, a common challenge for quantum systems. Environmental noise typically introduces correlations that compromise the randomness of the output. However, the protocol is designed to mitigate these effects, ensuring the generated numbers remain demonstrably random even in imperfect conditions.

The research highlights that even relatively simple quantum states, such as coherent states – which resemble classical electromagnetic waves but retain quantum properties – are sufficient to generate high-quality randomness. This is significant because coherent states are readily produced in many quantum systems, lowering the technological barrier to implementation.

The development strengthens efforts to demonstrate non-classicality, a key goal in quantum information science. Demonstrating genuine randomness, provably originating from quantum mechanics rather than classical sources, provides compelling evidence for the non-classical nature of the underlying system. This has implications for secure communication, cryptography, and scientific simulations, all of which benefit from verifiable randomness.