Wave function collapse as a nonlocal quantum effect

K. Lewin

Dipankar Home, Guruprasad Kar

Minggui Liang, Qiuying Li, Yichang Shou +5 more

Photonic spin Hall effect (SHE) is a fundamental and important optical phenomenon, which originates from the spin–orbit interactions (SOI) of light, forming the cornerstone for a wide range of optical precision measurements. However, the wave function collapse in the single-photon SHE is unpredictable as spin collapse has inherent randomness governed by the Born rule. Here, nonlocal spin bunching and anti-bunching of polarization-entangled photon pairs called two-photon SHE is realized to predict and manipulate the wave function collapse, which is fundamentally different from the single-photon SHE. The two-photon SHE is sensitive to the relative phase among entangled photon pairs, enabling continuous control from nonlocal spin bunching to anti-bunching. Owing to the phase sensitivity of the two-photon SHE, an accurate and simple quantitative phase imaging scheme is realized. The two-photon SHE may pave the way for unveiling the wave function evolution in the SOI of light and manipulating spin-dependent photonic quantum effects.

Edward J. Gillis

The assumption that wave function collapse is a real occurrence has very interesting consequences - both experimental and theoretical. Besides predicting observable deviations from linear evolution, it implies that these deviations must originate in nondeterministic effects at the elementary level in order to prevent superluminal signaling, as demonstrated by Gisin. This lack of determinism implies that information cannot be instantiated in a reproducible form in isolated microsystems (as illustrated by the No-cloning theorem). By stipulating that information is a reproducible and referential property of physical systems, one can formulate the no-signaling principle in strictly physical terms as a prohibition of the acquisition of information about spacelike-separated occurrences. This formulation provides a new perspective on the relationship between relativity and spacetime structure, and it imposes tight constraints on the way in which collapse effects are induced. These constraints indicate that wave function collapse results from (presumably small) nondeterministic deviations from linear evolution associated with nonlocally entangling interactions. This hypothesis can be formalized in a stochastic collapse equation and used to assess the feasibility of testing for collapse effects.

Ronald F. Peierls

Roland L. Omnes