Środowiskowe Seminarium z Informacji i Technologii Kwantowych

We revisit the problem of detection of entanglement of an unknown two-qubit state using minimal resources. Using weak values and just two copies of an arbitrary two-qubit state, we present a protocol where a postselection measurement in the computational basis provides enough information to identify if the state is entangled or not. Our protocol enables complete state identification with a single-setting postselection measurement on two copies of the state. It follows that by restricting to pure states, the global interaction required for determining the weak values can be realized by local operations. We further show that our protocol is robust against errorsarising from inappropriate global interactions applied during weak valuedetermination. Reference: Phys. Rev. A 99, 012327 (2019).