Efficient measurement-device-independent detection of multipartite entanglement structure

Witnessing entanglement is crucial in quantum information processing. With properly preparing ancillary states, it has been shown previously that genuine entanglement can be witnessed without trusting measurement devices. In this work we generalize the scenario and show that generic multipartite entanglement structures, including entanglement of subsystems and entanglement depth, can be witnessed via measurement-device-independent means. As the original measurement-device-independent entanglement witness scheme exploits only one out of four Bell measurement outcomes for each party, a direct generalization to multipartite quantum states will inevitably cause inefficiency in entanglement detection after taking account of statistical fluctuations. To resolve this problem, we also present a way to utilize all the measurement outcomes. The scheme is efficient for multipartite entanglement detection and can be realized with state-of-the-art technologies.

Figure 1

Measurement device-independent entanglement witness. Two users, Alice and Bob, are asked to witness the entanglement of a bipartite state ${\rho }_{AB}$. In the MDIEW scheme, Alice and Bob randomly prepare ancillary states and perform a Bell state measurement jointly on the to-be-witnessed state and the ancillary state.