Nondemolition measurement of the vacuum state or its complement
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Updated: May 10, 2026

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions
Published on: March 29, 2016
Daniel K L Oi1, Václav Potoček, John Jeffers
1SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG, United Kingdom. daniel.oi@strath.ac.uk
Abstract:
Measurement is integral to quantum information processing and communication; it is how information encoded in the state of a system is transformed into classical signals for further use. In quantum optics, measurements are typically destructive, so that the state is not available afterwards for further steps. Here we show how to measure the presence or absence of the vacuum in a quantum optical field without destroying the state, implementing the ideal projections onto the respective subspaces. This not only enables sequential measurements, useful for quantum communication, but it can also be adapted to create novel states of light via bare raising and lowering operators.
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