Direct Measurement of a Nonlocal Entangled Quantum State

• Published in: Physical review letters Vol. 123; no. 15; p. 150402
• Main Authors: Pan, Wei-Wei, Xu, Xiao-Ye, Kedem, Yaron, Wang, Qin-Qin, Chen, Zhe, Jan, Munsif, Sun, Kai, Xu, Jin-Shi, Han, Yong-Jian, Li, Chuan-Feng, Guo, Guang-Can
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 09-10-2019
• Subjects: Core making; Electrons; Entangled states; Helium; Modular systems; Quantum entanglement; Quantum mechanics; Wave functions
• ISSN: 0031-9007; 1079-7114; 1079-7114
• DOI: 10.1103/PhysRevLett.123.150402

Entanglement and the wave function description are two of the core concepts that make quantum mechanics such a unique theory. A method to directly measure the wave function, using weak values, was demonstrated by Lundeen et al. [Nature 474, 188 (2011)]. However, it is not applicable to a scenario of two disjoint systems, where nonlocal entanglement can be a crucial element, since that requires obtaining weak values of nonlocal observables. Here, for the first time, we propose a method to directly measure a nonlocal wave function of a bipartite system, using modular values. The method is experimentally implemented for a photon pair in a hyperentangled state, i.e., entangled both in polarization and momentum degrees of freedom.