Experimental Detection of Initial System–Environment Entanglement in Open Systems

We experimentally investigate how initial entanglement between the system and environment can be detected in an open by using some prior knowledge of joint evolutions. The protocol we employed requires classical optimization on results after performing measurements state. Such approach does not require a full 2-qubit QST, works scenarios where one has access to only. demonstrate both pure entangled states mixed states. obtained show experimental accessibility validity protocol. Compared with previous methods, which also assume only system, this is less demanding terms measurement state preparation. that, interaction, fine-tune protocol, thus showing potential for developing feasible practical detection methods.