Certifying the purity of quantum states with temporal correlations
Cornelia Spee · Physical Review A · 2020
Correlations obtained from sequences of measurements have been employed to distinguish among different physical theories or to witness the dimension of a system. In this work, we show that they can also be used to establish semi-device-independent lower bounds on the purity of the initial quantum state or even on one of the postmeasurement states. For single systems, this provides information on the quality of the preparation procedures of pure states or the implementation of measurements with anticipated pure postmeasurement states. For joint systems, one can combine our bound with results from entanglement theory to infer an upper bound on the concurrence based on the temporal correlations observed on a subsystem.