Measuring Nothing

TL;DR

This paper introduces a method for non-destructive measurement of the vacuum state in quantum optical fields, enabling sequential measurements and the creation of new light states, advancing quantum information processing capabilities.

Contribution

It presents a practical approach for non-destructive vacuum state measurement, allowing for sequential measurements and state engineering in quantum optics.

Findings

Achieved measurement of vacuum without destroying the quantum state

Enabled sequential measurement schemes in quantum optics

Demonstrated potential for creating novel light states

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 - crucial for sequential measurement schemes. The development of practical methods for non-destructive measurements on optical fields is therefore an important topic for future practical quantum information processing systems. 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.