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.