Insider Brief
- Researchers at the University of Chicago proposed a simple cavity QED method that can generate and control a wide range of highly entangled quantum states using standard laboratory tools and adjustable laser-driven energy offsets.
- The approach breaks the symmetry of conventional cavity QED systems by assigning paired atoms opposite energy shifts, enabling the creation of new entangled states without changing the underlying hardware.
- The team showed the method could support highly sensitive and noise-resistant quantum sensing applications and produce complex many-body states, including AKLT states that are of interest for quantum computing and condensed matter physics.
- Image courtesy of Clerk Group
PRESS RELEASE — Building useful quantum technologies—from sensors to computers—requires generating highly complex entangled states, in which the properties of particles are deeply intertwined. Producing such states has traditionally required complex tools and carefully engineered setups with many parts.
Now, researchers at the University of Chicago Pritzker School of Molecular Engineering (UChicago PME) have found a surprisingly simple method to create and control a broad variety of entangled quantum states. Their theoretical approach, described in the journal Physical Review X, begins with experimental tools already common in quantum physics laboratories and has immediate applications for ultraprecise sensing technologies and fundamental physics.
“We wanted to take simple ingredients that you find in a lot of physical platforms and put these together in a minimal way to get something interesting, complex and powerful,” said Aashish Clerk, professor of molecular engineering at UChicago PME and senior author of the new study.
The study is supported by Q-NEXT, a U.S. Department of Energy (DOE) National Quantum Information Science Research Center led by DOE’s Argonne National Laboratory.
An optical cavity with a twist
The starting point for the new entangled states is a well-established experimental platform called cavity quantum electrodynamics, or cavity QED. In these systems, atoms or other particles are placed inside an optical cavity — a chamber formed by two mirrors. The particles interact with light that is confined in the optical cavity.
In most cavity QED systems, all atoms interact with the confined light identically, making them indistinguishable from one other. This symmetry limits the range of quantum states the system can produce.
“The challenge has always been that these systems have too much symmetry. All the atoms are talking to light in the same way,” Clerk said. “That really restricts what kind of entangled states you get.”
Each atom in a cavity QED setup has a ground and excited state, separated by an energy difference.
Clerk’s group had an idea for a simple way to break that symmetry: While all atoms are driven with a common laser, scientists use an additional magnetic field or additional lasers to tune the excited-state energy of different groups of atoms relative to one another. The researchers arranged the system so that each atom is paired with another whose energy offset is equal and opposite. This gives the particles distinct identities while allowing enough structure for the system to behave predictably. By changing which atoms get different energy assignments, the researchers can tune the whole system to produce a range of different states, all without changing any physical components.
“You turn these lasers on and wait, and at some point the system stabilizes into an interesting, highly entangled quantum state,” said Anjun Chu, a postdoctoral researcher in the Clerk group and first author of the new work. “By simply adjusting the lasers, we can access kinds of entangled states that no one had thought about before.”
Sensing differences
One of the most important applications for the new system is quantum sensing, Clerk said. Entangled states can, in principle, detect tiny differences in magnetic or gravitational fields between two locations. But generating entangled states that are highly sensitive, robust to noise and easy to measure has been a major open challenge in the field.
Clerk, Chu and colleagues showed how one version of their new proposed cavity QED system — involving two ensembles of atoms — could be used to measure a gradient in magnetic or gravitational fields. Placed in two locations, the systems’ final quantum states would reflect the differences between the local fields while remaining insensitive to background noise that affects both locations equally.
“You’re able to do two things that are normally not compatible with one another: Use entanglement to build an exquisitely sensitive sensor but also have robustness to arbitrarily large amounts of noise,” Clerk said. “Normally, entanglement is very fragile. This approach has some amazing resilience.”
Importantly, extracting information from these states doesn’t require exotic measurements. Standard techniques known as Ramsey measurements are sufficient to read the quantum states.
Next steps
Beyond sensing, the researchers showed that the same platform can produce exotic quantum states of broad interest to physicists. One example is the AKLT state — a famous many-body entangled state, first described in the 1980s as a way to describe exotic magnetic materials. The team showed their simple setup can stabilize this state, which in addition to its relevance to complex magnetic material, is potentially useful in quantum computing.
The work is currently theoretical, and the researchers are in discussions with experimental groups about implementing and testing the ideas. They are also exploring more complex ways of arranging the atoms within the system and working to more fully map out the quantum states the method can generate.
“The fact that such simple ingredients can generate such complex and useful quantum states gives us hope that even before we reach the dream of a general all-purpose quantum computer, we can already generate quantum states that let us do things we couldn’t do in a purely classical world,” Clerk said.
Citation: “Reconfigurable dissipative entanglement between many spin ensembles: from robust quantum sensing to many-body state engineering,” Chu et al, Physical Review X, June 1, 2026. DOI: 10.1103/qdh9-2pc7
This material is based upon work supported by the U.S. Department of Energy Office of Science National Quantum Information Science Research Centers as part of the Q-NEXT center.
