A new study has found that a single trapped atom can create a previously unseen form of quantum motion.
The result gives physicists a new way to control delicate quantum behavior, opening a path toward more capable quantum computers.
A trapped ion
Inside a single charged atom held nearly still by electric fields, a hidden effect appeared in measurable motion.
By steering that motion with lasers, Dr. Oana Băzăvan, a physicist at the University of Oxford, demonstrated quadsqueezing—a rare fourth-order form of quantum squeezing—alongside two simpler versions.
The newly created quantum state—built from four linked units of motion instead of the usual two—emerged more than 100 times faster than conventional laser-driving would have allowed.
That speed matters because fragile quantum motion can fade before slower techniques finish building the state.
Squeezing and quantum motion
Many quantum systems move in regular steps, and physicists describe that motion as a quantum harmonic oscillator—a tiny system with evenly spaced energy levels.
Ordinary squeezing—a way to redistribute quantum uncertainty—changes the tradeoff between position and momentum, making one clearer and the other less certain.
Similar squeezing has helped the Laser Interferometer Gravitational-Wave Observatory (LIGO)—a U.S. detector for gravitational waves—make cleaner measurements.
Oxford’s result moves beyond that familiar two-way tradeoff and starts shaping higher-order motion that quantum computers may need.
Forces that disagree
Instead of building a special device, the team combined two controlled laser forces that acted on the same ion.
Each force pushed the ion’s motion in a simple way, but their combined order changed the final outcome.
Physicists call this non-commutativity, which means doing A then B can differ from doing B then A.
“Here, we took the opposite approach and used that feature to generate stronger quantum interactions,” said Băzăvan.
Climbing higher orders
Changing laser frequencies let the same machine progress from ordinary quantum squeezing to a more complex three-part version of the effect.
A larger adjustment produced an even more complex state that linked four parts of the atom’s motion in a single controlled interaction.
Directly forcing such behavior usually weakens fast as the order rises, so noise can cover the signal.
Oxford’s method avoided much of that loss by using the ion’s spin, a quantum property with two controllable internal settings.
Seeing the shape
To confirm the states, the researchers rebuilt the ion’s quantum motion from many careful measurements.
The result was a Wigner function—a mathematical picture showing position and momentum information together.
Second-, third-, and fourth-order versions formed distinct patterns, matching simulations based on independently measured settings.
Those patterns gave the experiment more weight than a single number, because each state showed a different measurable shape.
Why shape matters
Higher-order states matter because they behave in ways that ordinary quantum states do not, creating patterns that standard calculations cannot easily reproduce.
That odd shape gives quantum machines operations that ordinary squeezing and basic movement cannot supply.
Continuous-variable quantum computing stores information in continuously changing quantum values rather than simple on-off states, and it depends on these unusual quantum effects to perform its full range of operations.
Without those tools, parts of the machine remain easy for classical computers to imitate.
Not a computer
One trapped ion cannot run a useful quantum computer, and the Oxford experiment did not claim that.
The ion served as a clean test bed where motion and spin could be controlled with unusually fine timing.
Background interference still weakened some of the clearest signatures of unusual quantum behavior in the weakest high-order states. For now, the result proves control, not a ready-made processor.
A flexible recipe
Years before the demonstration, a 2021 proposal mapped a route using spin-motion interactions. Such spin-motion interactions link an ion’s internal setting to its movement, giving physicists a way to steer richer effects.
By changing detuning—a small offset from a target frequency—the team selected which interaction appeared.
That adjustability makes the method appealing beyond one ion, provided extra motion does not add too much noise.
Importance of quantum motion
Scaling the method would mean controlling several motional modes, which are separate ways the trapped ion can move.
With several modes, researchers could build interactions useful for simulation, sensing, and error-resistant quantum information.
The same spin control could also help create specially prepared quantum states—carefully arranged patterns of quantum behavior—during a calculation instead of only before it begins.
“Fundamentally, we have demonstrated a new type of interaction that lets us explore quantum physics in uncharted territory, and we are genuinely excited for the discoveries to come,” said Dr. Raghavendra Srinivas, a physicist at Oxford’s Department of Physics and study supervisor.
A stronger handle
A single ion gave physicists a sharper handle on high-order quantum behavior by turning disagreeing forces into controlled motion.
That handle will matter only if future systems keep the speed advantage while adding more particles, modes, and checks.
The study is published in Nature Physics.
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