Maximum violations of the quantum-witness equality

Schild, Greg; Emary, Clive

Abstract

We consider the quantum-witness test of macroscopic realism and derive an upper bound for possible violations of this equality due to quantum mechanics. The bound depends only on the number of possible outcomes for the blind measurement at the heart of the witness protocol. Mirroring recent results for the related Leggett-Garg inequality, we show that quantum mechanics can saturate the algebraic bound for large systems. We also establish a connection between the quantum witness and the trace distance between density matrices and discuss how the quantum witness can be used to obtain a bound on the Hilbert-space dimension of the system under study.

Citation

Schild, G., & Emary, C. (2015). Maximum violations of the quantum-witness equality. Physical review. A, 92(3), 1-6. https://doi.org/10.1103/PhysRevA.92.032101

• Acceptance Date: Jul 19, 2015
• Online Publication Date: Sep 3, 2015
• Publication Date: Sep 3, 2015
• Deposit Date: Oct 15, 2015
• Publicly Available Date: Nov 23, 2017
• Journal: Physical review A
• Print ISSN: 1050-2947
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 92
• Issue: 3
• Article Number: ARTN 032101
• Pages: 1-6
• DOI: https://doi.org/10.1103/PhysRevA.92.032101
• Keywords: Quantum-witness equality
• Public URL: https://hull-repository.worktribe.com/output/379765
• Publisher URL: http://journals.aps.org/pra/abstract/10.1103/PhysRevA.92.032101
• Additional Information: Authors' accepted manuscript of article published in: Physical review A, v.92, issue 3
• Contract Date: Nov 23, 2017