QUAntum SAfe Randomness
Semi-Device-Independent Heterodyne-based Quantum Random Number Generator
Journal publication available on: Phys. Rev. App. 15, 034034 (2021)
Preprint available on: [arXiv:2004.08344]
Randomness is a fundamental feature of quantum mechanics, which is an invaluable resource for both classical and quantum technologies. For critical applications, such as cryptography, it is fundamental that the generated random numbers are private and known only to the end-user. However, all commercial QRNG are trusted, meaning that the user needs to trust the manufacturer and all the internal components of the device. A new type of protocols, called Semi-Device-Independent, has been recently proposed to drastically reduce the required trust o the manufacturer, with a minimal impact on the performance.
In this work, we present a new robust implementation of a Semi-Device-Independent QRNG that guarantees both security and fast generation rates. The system works in a prepare and measure scenario where measurement and source are untrusted, but a bound on the energy of the prepared states is assumed. In our new implementation, we exploit heterodyne detection, which offers increased generation rate and improved long-term stability compared to alternative measurement strategies. In particular, since heterodyne detection can sample the entire phase space, we can track the unavoidable phase fluctuations of the system and compensate them via post-processing. In this way, we avoid complex and expensive active phase stabilization systems.
As a result, our scheme combines high security and speed with a simple setup featuring only commercial-off-the-shelf components, making it an attractive solution in many practical scenarios.