One of the oldest rules in physics — that accelerating an electric charge always produces radiation — turns out to have an exception. A team of physicists has shown that in quantum mechanics, it is possible to accelerate a charged particle without it emitting any radiation at all.

The finding, published in the Proceedings of the National Academy of Sciences, comes from Yakir Aharonov of Chapman University and Tel Aviv University, Daniel Collins of the University of Bristol, and Sandu Popescu, also at Bristol.

A rule that seemed unbreakable

Since James Clerk Maxwell first described electromagnetic radiation in the 19th century, it has been understood that when a charged particle accelerates, it radiates energy. This principle underpins everything from radio transmitters to the glow of heated metals. The idea carried over into quantum electrodynamics largely unchallenged — acceleration means radiation, full stop.

But the researchers noticed something peculiar about how quantum mechanics handles acceleration. In classical physics, a particle can only change its momentum if a force acts on it. In quantum mechanics, that is not necessarily true. The Aharonov-Bohm effect, first described in 1959, demonstrated that particles can be physically affected by electromagnetic fields even in regions where no field is present — a phenomenon known as dynamical nonlocality.

The thought experiment

The team designed a scenario involving an electron split into a quantum superposition — two separate wavepackets passing on either side of a thin solenoid containing magnetic flux. Neither wavepacket enters the solenoid or encounters any electromagnetic field. Each, considered individually, behaves as a free particle and produces no radiation.

But because of the Aharonov-Bohm effect, the wavepacket passing on one side of the solenoid picks up a quantum phase relative to the other. This phase shift changes the momentum distribution of the electron. A change in momentum means acceleration — yet because neither wavepacket individually encountered any force or radiated, the superposition cannot radiate either. The mathematics is rigorous: radiation fields decay as 1/R with distance, while the Coulomb fields of the two wavepackets (and any interference between them) decay as 1/R², making it impossible for the superposition to produce radiation.

The same effect can be produced using a parallel-plate capacitor or Faraday cages instead of a solenoid, making it more than a mathematical curiosity tied to one specific configuration.

Two kinds of acceleration

The key insight is that in quantum mechanics, interactions have two distinct aspects: a local one and a nonlocal one. When part of a wavefunction enters a region with an electromagnetic field, it is accelerated by a force in the conventional sense, and it does radiate. But the nonlocal effect — the phase shift on the part of the wavefunction that never encounters the field — also produces acceleration, and this acceleration is radiation-free.

The researchers showed that by making the region containing the field arbitrarily small, the probability of the local (radiating) interaction can be driven as close to zero as desired, while the nonlocal (radiation-free) acceleration accounts for essentially all of the particle’s change in motion.

Beyond electromagnetism

The authors argue their result is not limited to electromagnetic radiation. Since the underlying mechanism relies on the Aharonov-Bohm effect — a general feature of quantum gauge theories — the same principle should apply to all types of radiation.

The paper concludes that the relationship between acceleration and radiation in quantum mechanics is “far more subtle than is usually appreciated” and that the classical way of thinking about radiation needs to be revised.

Source: Aharonov, Y., Collins, D. & Popescu, S. (2026). Charge acceleration without radiation. Proceedings of the National Academy of Sciences, 123(7), e2533033123.