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Related Experiment Video

Updated: Feb 16, 2026

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

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Published on: May 30, 2014

Arrow of Time for Continuous Quantum Measurement.

Justin Dressel^1,2, Areeya Chantasri^3,4,5, Andrew N Jordan^1,3,4

¹Institute for Quantum Studies, Chapman University, Orange, California 92866, USA.

Physical Review Letters

|December 30, 2017

Summary

We show that quantum systems monitored by measurements can be time-reversed if the measurement record is also reversed. A statistical arrow of time emerges and can be quantified, revealing universal reversibility in nonprojective quantum measurements.

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Area of Science:

Quantum mechanics
Statistical physics
Information theory

Background:

The arrow of time in thermodynamics is linked to irreversibility.
Quantum measurements can introduce irreversibility.
Understanding time's direction in quantum systems is crucial.

Purpose of the Study:

To investigate the statistical arrow of time in monitored quantum systems.
To determine if time-reversed evolution is possible under continuous measurement.
To quantify the emergent arrow of time and explore its universality.

Main Methods:

Analyzing a continuous qubit measurement model.
Developing time-reversed evolution protocols with negated measurement records.
Quantifying the statistical arrow of time using log-likelihood differences.
Generalizing findings to nonprojective quantum measurements.

Main Results:

Time-reversed evolution is physically possible for monitored quantum systems when measurement records are negated.
A quantifiable statistical arrow of time emerges even with restored dynamical reversibility.
This reversibility is a universal characteristic of nonprojective measurements.
Janus measurement sequences demonstrate time-reversed inverse relationships.

Conclusions:

Dynamical reversibility can be restored in monitored quantum systems.
A statistical arrow of time is a fundamental emergent property of quantum measurement.
Nonprojective measurements exhibit universal time-reversal properties.