Physicists Learned to Reshape the Quantum Arrow of Time - and Turn Measurement Itself Into a Source of Energy

The universe has a direction. Coffee cools, glass shatters, and we remember the past but never the future - a one-way flow physicists call the “arrow of time.” Yet down at the level of individual quantum particles, the fundamental equations barely notice which way the clock is running. Now a team led by Los Alamos National Laboratory has shown how to take hold of that arrow inside a quantum system - bending it, blunting it, and even making a system trace a path that looks, statistically, like time running backward. And along the way, they found a way to turn the simple act of measuring a quantum system into a source of usable energy.

The work, titled “Reshaping the Quantum Arrow of Time,” was published on July 3, 2026 in the journal Physical Review X by Luis Pedro García-Pintos, Yi-Kai Liu, and Alexey V. Gorshkov. It is a theoretical result with a very practical payoff: a new lever for controlling quantum machines, and a fresh way of thinking about measurement not as a cost, but as a resource.

1. Why time points one way (except when it does not)

Almost every basic law of physics - Newton’s mechanics, Maxwell’s electromagnetism, the Schrödinger equation - works just as well run forward as backward. Play a film of two billiard balls colliding in reverse and nothing looks wrong. So where does the everyday one-way flow of time come from? From statistics: there are overwhelmingly more disordered arrangements of the world than orderly ones, so systems drift toward disorder, and that drift - the rise of entropy described by the second law of thermodynamics - is what we experience as the arrow of time.

Quantum systems add a second source of directionality: measurement. Observing a quantum system disturbs it - the famous “backaction” - and that disturbance is random and, crucially, time-asymmetric. As García-Pintos put it: “Unlike phenomena we observe around us, at the microscopic level most fundamental laws of physics see forward and backward movement in time as physically possible.” The question the team asked was simple and audacious: if the underlying laws are symmetric, can we engineer the arrow that measurement imposes?

2. Taking the wheel: measurement plus feedback

When you monitor a quantum system continuously and weakly, it does not jump to a single answer. Instead it follows a jittery, random path known as a quantum trajectory - a sequence of tiny, measurement-induced nudges. Normally those nudges push the system in a way that carries a clear direction in time.

García-Pintos, Liu, and Gorshkov added a second ingredient: feedback. After each measurement, a tailored control Hamiltonian - a carefully designed sequence of fields and pulses, chosen based on the measurement outcome - acts on the system. By tuning that control, the team showed you can cancel, strengthen, or even overcorrect the disturbance the measurement introduced.

3. Measurement as fuel: the quantum “measurement engine”

Then comes the payoff that may prove most useful. The same measurement-and-feedback machinery, the authors show, can be operated as an engine - one that extracts usable energy directly from the act of measurement itself. Measurement, long treated as an unavoidable tax on quantum information, is recast as a genuine thermodynamic resource.

The idea has a distinguished ancestor. In 1867 James Clerk Maxwell imagined a tiny “demon” that could sort fast and slow molecules and seemingly conjure order from chaos - a thought experiment that took a century to fully resolve and taught physicists that information and energy are deeply linked. The new result is a concrete, quantum-mechanical recipe in that lineage: turn the information you gain by measuring into work you can use.

4. What this is - and is not

5. Why it matters, and what comes next

This is not just a philosophical curiosity. Quantum computers live and die by how well engineers can control measurement and tame decoherence - the leakage of quantum information into the environment. A principled way to reshape measurement backaction is exactly the kind of tool that could sharpen quantum error correction and real-time feedback control.

The measurement engine, meanwhile, points toward quantum batteries and information-powered thermal machines - devices that treat measurement as fuel. And because the effects are rooted in standard quantum mechanics, they are testable. The team plans an experimental demonstration on superconducting qubits, the same technology inside many of today’s leading quantum processors, which allow the rapid feedback and efficient detection the scheme needs.

What we still do not know

• Whether it survives real hardware. The result is theoretical; noise and imperfection in actual devices could blunt the effect at useful scales.
• How much energy a measurement engine can deliver. The principle is established; the practical power output is an open question.
• Whether it beats existing tools. Reshaping the arrow of time is elegant, but it will have to prove a concrete advantage over today’s error-correction and control methods.

Sources

• L. P. García-Pintos, Y.-K. Liu, A. V. Gorshkov, “Reshaping the Quantum Arrow of Time,” Physical Review X 16, 011 (2026) (DOI 10.1103/l18s-9vmh)
• Scientific American: The quantum arrow of time can be reshaped, physicists show
• ScienceDaily / Los Alamos National Laboratory: reshaping the quantum arrow of time
• The Quantum Insider: controls developed to reshape the quantum arrow of time

Curated by Jerry Cards - jerrycards.com. We research the most fascinating developments in science and technology so you do not have to. More at jerrycards.com/news.