We show that any spatially separated multi-part quantum device demonstrating nonlocality can be used in an untrusted-device protocol for randomness expansion with unconditional quantum security. A consequence is that the noise tolerance for secure randomness expansion only needs to be small enough that it rules out deterministic behavior of the device. This greatly reduces the requirement on im...

One of the fundamental results in quantum foundations is the Kochen-Specker no-go theorem. For the quantum theory, the no-go theorem excludes the possibility of a class of hidden variable models where value attribution is context independent. Recently, the notion of contextuality has been generalized for different operational procedures and it has been shown that preparation contextuality of mi...

Contextuality is a key feature of quantum mechanics, as was first brought to light by Bohr [ Albert Einstein: Philosopher-Scientist, Library Living Philosophers Vol. VII, edited P. A. Schilpp (Open Court, 1998), pp. 199–241] and later realized more technically Kochen Specker [J. Math. Mech. 17, 59 (1967)]. Isham Butterfield put contextuality at the heart their topos-based formalism gave reformu...