Anomalous weak values and contextuality: Robustness, tightness, and imaginary parts
| Autor: | Matthew F. Pusey, Matteo Lostaglio, Ravi Kunjwal |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Physics
Quantum Physics Operator (physics) FOS: Physical sciences 01 natural sciences 010305 fluids & plasmas Kochen–Specker theorem Theoretical physics Postselection Qubit 0103 physical sciences Weak measurement Anomaly (physics) Quantum Physics (quant-ph) 010306 general physics Quantum Eigenvalues and eigenvectors |
| Zdroj: | Physical Review A |
| ISSN: | 2469-9934 2469-9926 1094-1622 |
| DOI: | 10.1103/physreva.100.042116 |
| Popis: | Weak values are quantities accessed through quantum experiments involving weak measurements and post-selection. It has been shown that 'anomalous' weak values (those lying beyond the eigenvalue range of the corresponding operator) defy classical explanation in the sense of requiring contextuality [M. F. Pusey, Phys. Rev. Lett. 113, 200401, arXiv:1409.1535]. Here we elaborate on and extend that result in several directions. Firstly, the original theorem requires certain perfect correlations that can never be realised in any actual experiment. Hence, we provide new theorems that allow for a noise-robust experimental verification of contextuality from anomalous weak values, and compare with a recent experiment. Secondly, the original theorem connects the anomaly to contextuality only in the presence of a whole set of extra operational constraints. Here we clarify the debate surrounding anomalous weak values by showing that these conditions are tight -- if any one of them is dropped, the anomaly can be reproduced classically. Thirdly, whereas the original result required the real part of the weak value to be anomalous, we also give a version for any weak value with nonzero imaginary part. Finally, we show that similar results hold if the weak measurement is performed through qubit pointers, rather than the traditional continuous system. In summary, we provide inequalities for witnessing nonclassicality using experimentally realistic measurements of any anomalous weak value, and clarify what ingredients of the quantum experiment must be missing in any classical model that can reproduce the anomaly. 13+12 pages, 4+1 figures, revised abstract, improved presentation |
| Databáze: | OpenAIRE |
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