Towards a measurement theory in QFT: "Impossible" quantum measurements are possible but not ideal

• URL: http://arxiv.org/abs/2311.13644v2
• Date: Wed, 21 Feb 2024 16:17:09 GMT
• Title: Towards a measurement theory in QFT: "Impossible" quantum measurements are possible but not ideal
• Authors: Nicolas Gisin and Flavio Del Santo
• Abstract summary: We show that the same problem arises in non-relativistic quantum physics, where joint nonlocal measurements lead to signaling. We develop a non-relativistic quantum information approach developed independently of the impossible measurements in QFT. These considerations could help guide the development of a complete theory of measurement in QFT.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Naive attempts to put together relativity and quantum measurements lead to signaling between space-like separated regions. In QFT, these are known as impossible measurements. We show that the same problem arises in non-relativistic quantum physics, where joint nonlocal measurements (i.e., between systems kept spatially separated) in general lead to signaling, while one would expect no-signaling (based for instance on the principle of no-nonphysical communication). This raises the question: Which nonlocal quantum measurements are physically possible? We review and develop further a non-relativistic quantum information approach developed independently of the impossible measurements in QFT, and show that these two have been addressing virtually the same problem. The non-relativistic solution shows that all nonlocal measurements are localizable (i.e., they can be carried out at a distance without violating no-signaling) but they (i) may require arbitrarily large entangled resources and (ii) cannot in general be ideal, i.e., are not immediately reproducible. These considerations could help guide the development of a complete theory of measurement in QFT.

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