Nonlocal operation enhanced entanglement detection and classification

Abstract

Based on the nature that nonlocal operation will change the fixed quantum statistical speed limited by the local operation, we study the performance of Ising-type nonlocal operation in multipartite entanglement detection and classification. We first present the formula of quantum statistical speed for general quantum state under the two-body nonlocal operation, and then investigate several important and experimentally relevant states, including N-qubit W state, Twin-Fock state, Q state and N-qubit GHZ state. The results show that the optimal nonlocal operation can be used to address some intractable problems encountered under the local operation, such as the classification of N-qubit W state and entanglement detection of Q state at the edges. Meanwhile, some defects are presented and discussed. Interestingly, the N-qubit GHZ state is found to be stable when it is probed by weaker nonlocal operation (γ≤N−1) and it maybe helpful to the experimental research. Our work provides an alternative route to investigate entanglement detection and classification, especially for the novel and complex quantum system.