Device-Independent Randomness Amplification*

Successful realization of loophole-free Bell tests has settled an 80-year-long debate and manifested that non-locality is an innate property of quantum physics and could be a useful resource for quantum information processing. Applications envisaged more than three decades ago, non-locality forms a basis for device-independent algorithms, especially suited for quantum key distribution, generating certified randomness or self-verification of untrusted devices. With the body of proof-of-principle experiments and applications growing, one crucial flaw of non-locality-based algorithms remains uncontested to date: the requirement for perfect input randomness to either distribute a secret key or generate new certified random bits. To tackle this problem, a concept of randomness amplification has been put forward, allowing generating stronger randomness out of weak input randomness resource -- a task impossible in classical physics. We implement it under a device-independent framework -- again, not attainable without a quantum system possessing the resource of non-locality. In this work, we combine two recent developments -- a theoretical protocol implementing the concept of randomness amplification with realistic devices and only a two-node system; and the experimental progress enabling executing a loophole-free Bell test with superconducting circuits providing a unique combination of degree of non-locality and bit-rate.