PIRSA:12110073 Scientific Series Quantum Foundations

DOI10.48660/12110073

Series: Quantum Foundations

Zaopo, M. (2012). Principle of relativity for quantum theory. Perimeter Institute. https://pirsa.org/12110073

Zaopo, Marco. Principle of relativity for quantum theory. Perimeter Institute, Nov. 20, 2012, https://pirsa.org/12110073 

@misc{ pirsa_PIRSA:12110073,
  doi = {10.48660/12110073},
  url = {https://pirsa.org/12110073},
  author = {Zaopo, Marco},
  keywords = {Quantum Foundations},
  language = {en},
  title = {Principle of relativity for quantum theory},
  publisher = {Perimeter Institute},
  year = {2012},
  month = {nov},
  note = {PIRSA:12110073 see, \url{https://pirsa.org}}
}

Abstract

In a generic quantum experiment we have a given set of devices analyzing some physical property of a system. To each device involved in the experiment we associate a set of random outcomes corresponding to the possible values of the variable analyzed by the device. Devices have apertures that permit physical systems to pass through them. Each aperture is labelled as "input" or "output" depending on whether it is assumed that the aperture lets the system go inside or outside the device. Assuming a particular input/output structure for the devices involved in a generic experiment is equivalent to assume a particular causal structure for the space-time events constituted by the outcomes happening on devices. The joint probability distribution of these outcomes is usually predicted assuming an absolutely defined input/output structure of devices. This means that all observers of the experiment agree on whether an aperture is labelled as "input" or "output". In this talk we show that the mathematical formalism of quantum theory permits to predict the joint probability distribution of outcomes in a generic experiment in such a way that the input/output structure is indeed relative to an observer. This means that two observers of the same experiment can predict the joint probability distribution of outcomes assuming different input/output labels for the apertures. Since input/output structure is the causal structure of the space-time events constituting the outcomes involved in the experiment we conclude that in quantum theory, the causal structure of events may not be regarded as absolute but rather as relative to the observer. We finally point out that properly extending this concept to the cosmological domain could shed light on the problem of dark energy.

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