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Opening up three quantum boxes causes classically undetectable wavefunction collapse

Research output: Contribution to journalJournal article


  • Richard George
  • Lucio Robledo
  • Owen Maroney
  • Machiel Blok
  • Hannes Bernien
  • Matthew Markham
  • Daniel Twitchen
  • John Morton
  • Andrew Briggs
  • Ronald Hanson
Journal publication date5/03/2013
JournalProceedings of the National Academy of Sciences
Number of pages5
Early online date14/02/13
Original languageEnglish


One of the most striking features of quantum mechanics is the profound effect exerted by measurements alone. Sophisticated quantum control is now available in several experimental systems, exposing discrepancies between quantum and classical mechanics whenever measurement induces disturbance of the interrogated system. In practice, such discrepancies may frequently be explained as the back-action required by quantum mechanics adding quantum noise to a classical signal. Here, we implement the “three-box” quantum game [Aharonov Y, et al. (1991) J Phys A Math Gen 24(10):2315–2328] by using state-of-the-art control and measurement of the nitrogen vacancy center in diamond. In this protocol, the back-action of quantum measurements adds no detectable disturbance to the classical description of the game. Quantum and classical mechanics then make contradictory predictions for the same experimental procedure; however, classical observers are unable to invoke measurement-induced disturbance to explain the discrepancy. We quantify the residual disturbance of our measurements and obtain data that rule out any classical model by ≳7.8 standard deviations, allowing us to exclude the property of macroscopic state definiteness from our system. Our experiment is then equivalent to the test of quantum noncontextuality [Kochen S, Specker E (1967) J Math Mech 17(1):59–87] that successfully addresses the measurement detectability loophole.

Bibliographic note

Freely available online through the PNAS open access option