Online optimal exact identification of a quantum change point
This solves the problem of exact quantum change point detection for quantum information processing, establishing that local protocols can match global ones in this task.
The paper tackled the problem of identifying a change point in a stream of quantum particles without error, achieving optimal performance as set by quantum mechanics through sequential local measurements.
We consider online detection strategies for identifying a change point in a stream of quantum particles allegedly prepared in identical states. We show that the identification of the change point can be done without error via sequential local measurements while attaining the optimal performance bound set by quantum mechanics. In this way, we establish the task of exactly identifying a quantum change point as an instance where local protocols are as powerful as global ones. The optimal online detection strategy requires only one bit of memory between subsequent measurements, and it is amenable to experimental realization with current technology.