A universal quantum state, long the subject of theoretical predictions, has been achieved for the first time in simulated quantum matter, according to researchers.

As materials reach tipping points, like the boiling of water or the loss of magnetic attraction, they begin to act universally. For the first time, scientists now say they have observed such an effect at the quantum level.

An international team of researchers from Caltech, the Université Paris-Saclay, and the Technical University of Munich revealed their quantum breakthrough in a recent paper published in the journal Nature. The work experimentally explores decades-old theories for the first time, providing new insight into quantum behaviors.

Universal Behavior

Tipping points are the liminal spaces of physics. In them, behavior can become universal, following the same rules, until differentiation occurs as a new state is entered. It could be compared to the orderly behavior usually seen in hotel hallways, while anything can happen behind closed doors.

To explore this concept, physicists use a theoretical framework known as conformal field theory.

“Physicists call this trait universality—the messy, microscopic details wash out, and only a few essential features survive,” explained co-author Jason Alicea, a Professor of Theoretical Physics at Caltech.

Simulating the Quantum World

Using simplified quantum computers called quantum simulators, the researchers tested two varieties of conformal field theories, Ising and tricritical Ising, both named for physicist Ernst Ising. The theories attempt to describe the emerging universal behavior of a quantum system at a tipping point into an exotic state like superposition or entanglement.

In conventional physics, these tipping points are driven by heat, but in this new work, the team is investigating exotic quantum effects that occur in the same temperature range, close to absolute zero. Like climbing the rungs of a ladder, laser manipulation can push the material through different quantum states once it reaches the tipping point.

Conformal field theory has allowed physicists to theoretically calculate the distance between these rungs for decades, but this is the first time they have been experimentally observed. 

In these quantum simulators, specialized lasers called optical tweezers trap arrays of neutral atoms. This experiment focused on strontium atoms, which the optical tweezers first trapped before other lasers excited them into high-energy Rydberg states. In this high-energy state, the atoms interact so strongly that they behave as a single entity. Finally, lasers were then also used to push the strontium atoms to the tipping point.

Viewing Quantum States

Many-body modulation spectroscopy is a new technique that researchers developed to measure the energy ladder. The technique uses lasers set to varying frequencies to shake the chain of strontium atoms and then measure the response. When a certain frequency caused a spike in the response measurement, the team identified a rung in the ladder. Notably, various settings produced results consistent with tricritical Ising theory.

“Even though we believed these theories to be true, it’s important to have an experimental realization, something you can poke and prod,” Alicea says. “To see those predictions borne out is a beautiful thing.”

Next, the researchers hope to scale up their work to study the effect on atoms in a two-dimensional grid, instead of in a single-file line. These theories are far less well understood in two dimensions, which intrigues the team.

“What excites me is that the technique doesn’t require knowing the answer in advance. Here we could check our measurements against exact predictions,” co-author Manuel Endres of Caltech concluded. “The next step is to point this at systems where nobody knows the response of the system quantitatively—including regimes that classical computers can’t reach.”

The paper, “Observation of Conformal Field Theory Spectra in a Quantum Simulator,” appeared in Nature on August 19, 2026.

Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org.

An unusual new type of quantum state has been revealed by theoretical physicists, which they say demonstrates a critical new phase of matter that arises from pushing particles to their limits.

Known as “fractional Fermi seas,” this class of quantum states can be created on demand by exciting quantum particles beyond their typical equilibrium states, as detailed in new research published in Physical Review Letters, based on findings by theoretical physicist Alvise Bastianello of CNRS and Université Paris-Dauphine, working in collaboration with the Nägerl group.

To achieve this, the team relied on ultracold cesium atoms, which they were able to successfully confine to a single dimension. Then, by manipulating the strength of the interactions between these particles, the unusual quantum state they induced produced characteristics the team says are far beyond predicted models.

Going Beyond What Models Predict

Specifically, the findings reveal characteristics that extend well beyond what physicists call the Tomonaga-Luttinger liquid theory, a well-characterized model that describes the way electrons or other fermions operate within a one-dimensional conductor, such as carbon nanotubes that restrict their movement to a single dimension.

“Fermions, for instance, stack neatly into the available energy states to form the so-called ‘Fermi sea’,” according to researcher Alvise Bastianello, who notes that quantum particles generally behave predictably at low temperatures and follow very specific rules in terms of their self-arrangement.

“But what happens if one forces interacting atoms to continuously cycle through extreme conditions, smoothly shifting them from strongly repelling each other to strongly attracting each other?” he asks.

To address this, the team implemented experiments where they created conditions that repeated this interaction cycle, intentionally forcing atoms from their typical ground state into more highly excited ones. Despite their excited state, the atoms still maintained a surprising degree of organization as the so-called “fractional Fermi sea” was induced.

“Instead of simply heating the system, the interaction cycle reorganizes the atoms into a new many-body state,” according to lead author Yi Zeng, who added that the team’s observations provided “a controlled way to explore quantum matter beyond the usual equilibrium paradigms.”

Rise of the “Super-Fermions”

One of the team’s key findings had been the odd conditions they observed within the newly created state, which include what are characterized as Friedel oscillations, a term for the ripples the team observed as anticipated based on mathematical correlations between particles. Additionally, the team says they observed decay behavior that was present across all levels of the repulsive interactions between particles.

“This state is highly excited, but it is not random,” according to team leader Hanns-Christoph Nägerl. This is significant, he says, since the state the research team achieved is markedly different from what Tomonaga-Luttinger liquid theory predicts.

“It has a hidden order that becomes visible in its correlations,” Nägerl said of the team’s unique discovery, adding that they have not yet determined the name they plan to give these newly characterized quasiparticles, although ‘super-Fermions’ is a possible contender.

Evidence of Exotic States

Also of key importance, the team believes these specific signatures could point to the presence of a new and exotic type of critical phase which has never been previously recognized, and which could point to promising new approaches to studying quantum mysteries with the help of cold atom simulation technologies.

Presently, the team says a companion paper is in the works, which elaborates on the team’s experiments and the creation of fractional Fermi seas through quantum simulations.

“The discovery of fractional Fermi seas shows how far we can push quantum simulation: not only reproducing known models, but creating and probing states that go beyond established paradigms,” Nägerl concluded.

Presently, the team’s work, detailed in the papers “Exotic critical states as fractional Fermi seas in the one-dimensional Bose gas,” and “Realization of fractional Fermi seas” is available on the preprint arXiv.org server.

Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.