Can quantum “eternity” survive real-world disorder?

For nearly 70 years, physicists have hunted a way for quantum states to remain frozen indefinitely. The concept, many-body localisation, promises an “eternal” hold—yet thermodynamics predicts it should eventually dissolve. Now, experiments using ultracold atom

On a quantum timescale, the promise sounds almost mischievous: build an arrangement of atoms so the quantum state between them never, ever settles—like light bouncing in a never-ending hall of mirrors.

That idea has been pursued for nigh on 70 years. Physicists talk about “quantum eternity” as an arrangement of atoms positioned so that quantum states between them are frozen forever. It isn’t only a philosophical flex. If quantum states could truly last forever—or even just for a very long time—it could unlock completely new states of matter. with some of those states potentially serving as foundations for powerful new quantum computers. “It would open up a whole new class of phases that are otherwise impossible. ” mathematical physicist Wojciech De Roeck at KU Leuven in Belgium says.

But there’s a reason eternity has always felt like a dare. Thermodynamics—one of the pillars of modern theoretical physics—says fine details don’t keep their crispness. Over time, quantum systems should thermalise, with different parts mixing into averages. The fine print of reality smudges, unless energy is expended to intervene. The theory even comes with everyday analogies: pour milk into coffee and you get a creamy, uniform beige without stirring.

The hope for a loophole dates back to 1958, when physicist Philip Anderson suggested that some materials might resist this fate. Anderson imagined a crystalline material with a clean. repeating atomic pattern—then deliberately introduced disorder: impurities. or atoms knocked slightly out of place. In his scenario, an electron moving as a quantum wave would scatter off the disorder again and again. The scattered ripples would cancel out so completely that the electron couldn’t get anywhere. In effect. the particle would be trapped—a quantum state frozen in time—at least until the material itself ceased to exist.

Anderson theoretically showed that this could happen, earning a share of a Nobel prize in physics in 1977. Later experiments backed the idea, though in simplified setups where particles didn’t tug, shove, and exchange energy the way they would in real materials.

That left a thorny question. Would Anderson’s freeze hold in the messy world of real materials, where many-body interactions constantly jostle particles?. The name for this possibility became many-body localisation, or MBL. “Chaos should be everywhere. It should be more or less inescapable,” De Roeck says. “However, these many-body-localised systems do not exhibit chaos.”.

The longer physicists chased MBL, the clearer it became that “eternity” might be conditional, not guaranteed.

The field’s first major constraint comes from scale. Thermodynamics allows for disorder and thermalisation to play out in small regions. But for MBL to defy thermodynamics, it would need to survive throughout a large piece of material. Whether that can happen is deeply uncertain.

Then there’s time itself. Even if localisation seems to persist—watch it for 10 minutes, an hour, a day—can anyone promise it won’t vanish if you look for longer?

Both objections intensified in the past decade. In 2018, De Roeck and Huveneers made a discovery aimed directly at the scale issue. Disorder has to permeate a material for MBL to emerge. Yet real materials would inevitably contain small. unusually neat patches where particles don’t freeze and remain free to move and share energy. De Roeck and Huveneers mathematically proved that those neat patches could feed energy into the frozen regions, disrupting the MBL. They named the mechanism a thermal avalanche. And the effect, they showed, would rapidly spread until no frozen quantum states were left.

A separate 2024 challenge targets the time issue. Nicolas LaFlorencie. Fabien Alet. and Jeanne Colbois at the University of Toulouse. France. identified a phenomenon known as resonances that could undermine MBL over long enough durations. In an MBL material, atoms usually remain locked in a specific set of quantum properties. But the lock is rarely perfect: those properties vary ever so slightly over time. In some cases. the material can stumble on a different arrangement that happens to have exactly the same energy as its starting point. When that happens, the two states can resonate or meld together, undermining the pristine MBL regions.

At this point, it would be easy to read the story as a collapse of the eternity dream. But experiments from the past few years are starting to tilt the narrative. The bottleneck has been simple: most knowledge of MBL comes from computer models. and simulations can only get so big before complexity becomes unmanageable. Testing MBL properly requires delicate quantum states, precisely controlled disorder, and observation that doesn’t wash out the effect.

That’s only recently become realistic thanks to experiments with ultracold atoms, trapped ions, and superconducting qubits—systems that are now precise enough for the job.

The shift is visible in a 2025 study led by Junhyeok Hur at the Korea Advanced Institute of Science and Technology. Hur and his team probed MBL in real arrays of ultracold atoms as large as a 24-by-24 grid. “This is an experiment on a system that has a size and timescale larger than what we can achieve in simulations. ” Alet says. Alet and LaFlorencie both work at the cutting edge of computer simulations. and they note that simulations begin to struggle at around two dozen particles.

The experiment compared two kinds of disorder in the atomic array.

In one approach, each atom was assigned a completely random energy. That produced a mottled landscape: regions of strong disorder interspersed with unusually clean stretches—rare patches thought to act as seeds of thermalisation.

In the other, the disorder followed a quasi-random pattern. It was completely free of ordered patches.

As Hur’s team tested successively larger arrays, the contrast between these disorder types became sharp. With random disorder. larger systems needed ever-stronger disorder to remain localised. signaling that MBL would inevitably be washed out as systems grew. But with quasi-periodic disorder, the threshold barely shifted even as simulations and system sizes increased. The implication is that structuring a material’s disorder could help stabilise MBLs as scales get larger.

Amos Chan at the University of Warwick. UK—who worked with Hur on the study—puts the emphasis on uncertainty where it still matters. “It isn’t yet clear what drives thermalisation in the randomly disordered case. whether avalanches. resonances or something else. ” Chan says. But he adds that newer data measured since the paper only builds confidence that localisation can persist in two-dimensional arrays when disorder is carefully controlled. Though it isn’t definitive proof of MBL, the result helps answer a question that may destroy it: scale.

A second experiment landed soon after Hur’s work, this time involving up to 70 superconducting qubits. It found that at moderate disorder, the system settled into a strange in-between state—“not quite MBL, but something that resisted thermalisation nonetheless,” known as a quantum glass.

The field’s hope now rests not just on seeing localisation linger, but on defining what it means in a way experiments can measure.

In a quantum materials sense, phases aren’t confirmed by tracking every atom forever. Iron becomes a magnet because of a property of atoms called quantum mechanical spin: when enough spins align. the material changes phase. Largely analogously, Alet, LaFlorencie, and others have tried to find an MBL fingerprint.

Their approach looks at abstract quantum states. They consider every quantum property of each atom in a material and map those properties over a multidimensional landscape. At a given moment, the material sits at one point on this map; as time passes, it explores the terrain. But in a 2019 finding, a material exhibiting MBL wouldn’t roam. Instead it would be confined to patches of the map—frozen in little islands with no way to explore beyond them. This behaviour is called multifractality. If a material shows it, the multifractal pattern would indicate an MBL state.

Since 2019, theorists have worked to turn that fingerprint into something measurable. In 2025. a paper by David Logan at the Tata Institute of Fundamental Research in Mumbai and Sthitadhi Roy at the University of Oxford set out a possible test in a system of quantum spins. The idea: prepare the spins in a simple pattern—alternating up and down. Let the system evolve, then measure how much of that pattern remains visible later. In an ordinary thermalising system, the pattern should wash away. If MBL is present, some of the pattern should stubbornly survive.

“Multifractality is appealing in that it’s rather directly connected to what experiments would be able to look at. ” theorist David Huse at Princeton University says. LaFlorencie adds that his group is beginning to search for this fingerprint this year using ultracold atoms. “The idea is to begin probing experimentally this multifractal dimension,” he says. “It’s very exciting.”.

Even so, Huse still doubts that multifractality alone will settle everything. “We’re probably still waiting on big mathematical physics theorems that finally resolve all these disagreements,” he says. The idea of quantum eternity may not be short on grand goals—but no one promised it would be a quick road.

For De Roeck. the central tension is hard to miss: thermodynamics says systems should smear into averages. yet experiments are now beginning to test whether localisation can resist the forces that scramble it. Whether the “forever” of quantum eternity is truly achievable may still depend on how disorder is engineered. how large the systems get. and what long time reveals.

If MBL can be made to hold, it would ripple outward into other exotic states of matter.

Frank Wilczek’s time crystal—envisioned in 2012—imagines a material whose structure varies in time rather than space. in theory forever. Nicolàs Lorente at Donostia International Physics Center in Spain and his colleagues have since built what’s known as a discrete time crystal. a real material fitting Wilczek’s vision except that it lasts mere seconds at most. A fully fledged time crystal that goes on and on would depend on learning how to construct many-body localisation. It would mean time crystals could exist without consuming any energy. making them a genuinely new phase of matter and. potentially. an exquisitely stable way to store quantum information or keep time.

The same logic applies to at least two other exotic states. Topological insulators conduct current only around their edges and do so robustly against impurities—an attractive trait for low-loss electronics and quantum computers—but they must be kept extremely cold to function. If MBL can be conjured, it could help make topological insulators work at temperatures much closer to everyday ones.

Then there are Kitaev chains. a one-dimensional quantum wire state of matter also viewed as useful for quantum computers. yet similarly constrained by the lowest temperatures. Stabilising MBL could help sustain quantum-computing components as systems warm, making them less prone to heat-induced errors.

For now, quantum eternity still sounds like something you’d put in a physicist’s imagination. But the field is no longer stuck at the level of diagrams and elegant proofs. Experiments with ultracold atoms and superconducting qubits are starting to push on the exact weaknesses that thermodynamics targets—scale and time. And in that pressure. the dream of states that last forever is finally moving from hypothesis toward something that can be tested.

quantum eternity many-body localisation MBL thermodynamics ultracold atoms superconducting qubits quantum glass time crystal topological insulators Kitaev chains multifractality