TY - JOUR T1 - Tomography is necessary for universal entanglement detection with single-copy observables JF - Physical Review Letters Y1 - 2016 A1 - Dawei Lu A1 - Tao Xin A1 - Nengkun Yu A1 - Zhengfeng Ji A1 - Jianxin Chen A1 - Guilu Long A1 - Jonathan Baugh A1 - Xinhua Peng A1 - Bei Zeng A1 - Raymond Laflamme AB - Entanglement, one of the central mysteries of quantum mechanics, plays an essential role in numerous applications of quantum information theory. A natural question of both theoretical and experimental importance is whether universal entanglement detection is possible without full state tomography. In this work, we prove a no-go theorem that rules out this possibility for any non-adaptive schemes that employ single-copy measurements only. We also examine in detail a previously implemented experiment, which claimed to detect entanglement of two-qubit states via adaptive single-copy measurements without full state tomography. By performing the experiment and analyzing the data, we demonstrate that the information gathered is indeed sufficient to reconstruct the state. These results reveal a fundamental limit for single-copy measurements in entanglement detection, and provides a general framework to study the detection of other interesting properties of quantum states, such as the positivity of partial transpose and the k-symmetric extendibility. VL - 116 U4 - 230501 UR - http://arxiv.org/abs/1511.00581 CP - 23 U5 - 10.1103/PhysRevLett.116.230501 ER -