There is more to quantum interferometry than entanglement

Bromley, Thomas R.; Silva, Isabela A.; Oncebay-Segura, Charlie O.; Soares-Pinto, Diogo O.; deAzevedo, Eduardo R.; Tufarelli, Tommaso; Adesso, Gerardo

Abstract

Entanglement has long stood as one of the characteristic features of quantum mechanics, yet recent developments have emphasized the importance of quantumness beyond entanglement for quantum foundations and technologies. We demonstrate that entanglement cannot entirely capture the worst-case sensitivity in quantum interferometry when quantum probes are used to estimate the phase imprinted by a Hamiltonian, with fixed energy levels but variable eigenbasis, acting on one arm of an interferometer. This is shown by defining a bipartite entanglement monotone tailored to this interferometric setting and proving that it never exceeds the so-called interferometric power, a quantity which relies on more general quantum correlations beyond entanglement and captures the relevant resource. We then prove that the interferometric power can never increase when local commutativity-preserving operations are applied to qubit probes, an important step to validate such a quantity as a genuine quantum correlations monotone. These findings are accompanied by a room-temperature nuclear magnetic resonance experimental investigation, in which two-qubit states with extremal (maximal and minimal) interferometric power at fixed entanglement are produced and characterized.

Citation

Bromley, T. R., Silva, I. A., Oncebay-Segura, C. O., Soares-Pinto, D. O., deAzevedo, E. R., Tufarelli, T., & Adesso, G. (2017). There is more to quantum interferometry than entanglement. Physical Review A, 95(5), Article 052313. https://doi.org/10.1103/PhysRevA.95.052313

• Journal Article Type: Article
• Acceptance Date: Apr 13, 2017
• Publication Date: May 8, 2017
• Deposit Date: May 10, 2017
• Publicly Available Date: May 10, 2017
• Journal: Physical Review A
• Print ISSN: 2469-9926
• Electronic ISSN: 2469-9934
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 95
• Issue: 5
• Article Number: 052313
• DOI: https://doi.org/10.1103/PhysRevA.95.052313
• Public URL: https://nottingham-repository.worktribe.com/output/859567
• Publisher URL: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.95.052313
• Additional Information: ©2017 American Physical Society