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On the reality of the quantum state

Nature Physics volume 8, pages 475–478 (2012)Cite this article

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Abstract

Quantum states are the key mathematical objects in quantum theory. It is therefore surprising that physicists have been unable to agree on what a quantum state truly represents. One possibility is that a pure quantum state corresponds directly to reality. However, there is a long history of suggestions that a quantum state (even a pure state) represents only knowledge or information about some aspect of reality. Here we show that any model in which a quantum state represents mere information about an underlying physical state of the system, and in which systems that are prepared independently have independent physical states, must make predictions that contradict those of quantum theory.

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Figure 1: Physical properties.
Figure 2: The protocol.
Figure 3: The circuit.

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Acknowledgements

We thank K. Audenaert for code, and L. Hardy, M. Leifer and R. Spekkens for discussions. All authors are supported by the Engineering and Physical Sciences Research Council.

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Authors and Affiliations

  1. Department of Physics, Imperial College London, Prince Consort Road, London SW7 2AZ, UK

    Matthew F. Pusey & Terry Rudolph

  2. Department of Mathematics, Royal Holloway, University of London, Egham Hill, Egham TW20 0EX, UK

    Jonathan Barrett

Authors
  1. Matthew F. Pusey
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  2. Jonathan Barrett
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  3. Terry Rudolph
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M.F.P. devised the initial version of the result. All authors contributed to improvements in the result and the writing of the manuscript.

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Correspondence to Matthew F. Pusey.

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The authors declare no competing financial interests.

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Pusey, M., Barrett, J. & Rudolph, T. On the reality of the quantum state. Nature Phys 8, 475–478 (2012). https://doi.org/10.1038/nphys2309

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