Self-testing of a single quantum device under computational assumptions

Self-testing is a method to characterise an arbitrary quantum system based only on its classical input-output correlations, and plays important role in device-independent information processing as well complexity theory. Prior works self-testing require the assumption that system's state shared among multiple parties perform local measurements cannot communicate. Here, we replace setting of non-communicating parties, which difficult enforce practice, by single computationally bounded party. Specifically, construct protocol allows verifier robustly certify device must have prepared Bell pair performed single-qubit it, up change basis applied both device's measurements. This means under computational assumptions, able presence entanglement, property usually closely associated with two separated subsystems, inside device. To achieve this, build techniques first introduced Brakerski et al. (2018) Mahadev allow constrain actions assuming does not break post-quantum cryptography.