Skip to main content
SpringerLink
Log in

Addressing the Clumsiness Loophole in a Leggett-Garg Test of Macrorealism

  • Published:
Foundations of Physics Aims and scope Submit manuscript

Abstract

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.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  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 

  3. Aspect, A., Dalibard, J., Roger, G.: Experimental test of Bell’s inequalities using time-varying analyzers. Phys. Rev. Lett. 49(25), 1804–1807 (1982)

    Article  MathSciNet  ADS  Google Scholar 

  4. Leggett, A.J., Garg, A.: Quantum mechanics versus macroscopic realism: is the flux there when nobody looks? Phys. Rev. Lett. 54(9), 857–860 (1985)

    Article  MathSciNet  ADS  Google Scholar 

  5. Home, D., Sengupta, S.: Bell’s inequality and non-contextual dispersion-free states. Phys. Lett. A 102(4), 159–162 (1984)

    Article  MathSciNet  ADS  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

  8. Palacios-Laloy, A., Mallet, F., Nguyen, F., Bertet, P., Vion, D, Esteve, D, Korotkov, A.N.: Experimental violation of a bell’s inequality in time with weak measurement. Nat. Phys. 6, 442–447 (2010)

    Article  Google Scholar 

  9. Kofler, J., Brukner, C.: Conditions for quantum violation of macroscopic realism. Phys. Rev. Lett. 101(9), 090403 (2008)

    Article  ADS  Google Scholar 

  10. Kofler, J., Brukner, C.: Classical world arising out of quantum physics under the restriction of coarse-grained measurements. Phys. Rev. Lett. 99(18), 180403 (2007)

    Article  ADS  Google Scholar 

  11. Ruskov, R., Korotkov, A.N., Mizel, A.: Signatures of quantum behavior in single-qubit weak measurements. Phys. Rev. Lett. 96(20), 200404 (2006)

    Article  ADS  Google Scholar 

  12. Jordan, A.N., Korotkov, A.N., Büttiker, M.: Leggett-garg inequality with a kicked quantum pump. Phys. Rev. Lett. 97(2), 026805 (2006)

    Article  ADS  Google Scholar 

  13. Williams, N.S., Jordan, A.N.: Weak values and the leggett-garg inequality in solid-state qubits. Phys. Rev. Lett. 100(2), 026804 (2008)

    Article  ADS  Google Scholar 

  14. Lindblad, G.: On the generators of quantum dynamical semigroups. Commun. Math. Phys. 48(2), 119–130 (1976)

    Article  MathSciNet  ADS  MATH  Google Scholar 

  15. Leggett, A.J., Chakravarty, S., Dorsey, A.T., Fisher, M.P.A., Garg, A., Zwerger, W.: Dynamics of the dissipative two-state system. Rev. Mod. Phys. 59(1), 1–85 (1987)

    Article  ADS  Google Scholar 

  16. Nielsen, M.A., Chuang, I.L.: Quantum Computation and Quantum Information. Cambridge University Press, Cambridge (2000)

    MATH  Google Scholar 

  17. Abbott, D., Davies, P.C.W., Pati, A.K. (eds.): Quantum Aspects of Life. Imperial College Press, London (2008)

    Google Scholar 

  18. Wilde, M.M., McCracken, J.M., Mizel, A.: Could light harvesting complexes exhibit non-classical effects at room temperature? Proc. R. Soc. A 466(2117), 1347–1363 (2010)

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. School of Computer Science, McGill University, Montreal, Quebec, Canada

    Mark M. Wilde

  2. Laboratory for Physical Sciences, 8050 Greenmead Drive, College Park, MD, USA, 20740

    Ari Mizel

Authors
  1. Mark M. Wilde
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Ari Mizel
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Mark M. Wilde.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Wilde, M.M., Mizel, A. Addressing the Clumsiness Loophole in a Leggett-Garg Test of Macrorealism. Found Phys 42, 256–265 (2012). https://doi.org/10.1007/s10701-011-9598-4

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s10701-011-9598-4

Keywords

Search

Navigation