Addressing the Clumsiness Loophole in a Leggett-Garg Test of Macrorealism
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The rise of quantum information theory has lent new relevance to experimental tests for non-classicality, particularly in controversial cases such as adiabatic quantum computing superconducting circuits. The Leggett-Garg inequality is a “Bell inequality in time” designed to indicate whether a single quantum system behaves in a macrorealistic fashion. Unfortunately, a violation of the inequality can only show that the system is either (i) non-macrorealistic or (ii) macrorealistic but subjected to a measurement technique that happens to disturb the system. The “clumsiness” loophole (ii) provides reliable refuge for the stubborn macrorealist, who can invoke it to brand recent experimental and theoretical work on the Leggett-Garg test inconclusive. Here, we present a revised Leggett-Garg protocol that permits one to conclude that a system is either (i) non-macrorealistic or (ii) macrorealistic but with the property that two seemingly non-invasive measurements can somehow collude and strongly disturb the system. By providing an explicit check of the invasiveness of the measurements, the protocol replaces the clumsiness loophole with a significantly smaller “collusion” loophole.
KeywordsLeggett-Garg inequality Macrorealism Non-invasive measurability Clumsiness loophole
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- 1.Bell, J.S.: On the Einstein-Podolsky-Rosen paradox. Physics 1, 195 (1964) Google Scholar
- 2.Bell, J.S.: Speakable and Unspeakable in Quantum Mechanics. Cambridge University Press, Cambridge (1987) Google Scholar
- 6.Xu, J.-S., Li, C.-F., Zou, X.-B., Guo, G.-C.: Experimentally identifying the transition from quantum to classical with leggett-garg inequalities, July 2009. arXiv:0907.0176
- 7.Goggin, M.E., Almeida, M.P., Barbieri, M., Lanyon, B.P., O’Brien, J.L., White, A.G., Pryde, G.J.: Violation of the Leggett-Garg inequality with weak measurements of photons (2009). arXiv:0907.1679
- 17.Abbott, D., Davies, P.C.W., Pati, A.K. (eds.): Quantum Aspects of Life. Imperial College Press, London (2008) Google Scholar