How long does it take to implement a projective measurement?

Philipp Strasberg, Kavan Modi, Michalis Skotiniotis

Research output: Contribution to journalArticleResearchpeer-review

5 Citations (Scopus)

Abstract

According to the Schrödinger equation, a closed quantum system evolves continuously in time. If it is subject to a measurement however, its state changes randomly and discontinuously, which is mathematically described by the projection postulate. But how long does it take for this discontinuous change to occur? Based on simple estimates, whose validity rests solely on the fact that all fundamental forces in nature are finite-ranged, we show that the implementation of a quantum measurement requires a minimum time. This time scales proportionally with the diameter of the quantum mechanical object, on which the measured observable acts non-trivially, with the proportionality constant being around 10-5 s m-1. We confirm our bound by comparison with experimentally reported measurement times for different platforms. We give a pedagogical exposition of our argumentation introducing along the way modern concepts such as ancilla-based measurements, the quantum speed limit, and Lieb-Robinson velocity bounds.

Original languageEnglish
Article number035404
Number of pages16
JournalEuropean Journal of Physics
Volume43
Issue number3
DOIs
Publication statusPublished - May 2022

Keywords

  • Lieb-Robinson bounds
  • macroscopicity
  • quantum measurement
  • quantum physics
  • quantum speed limit

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