Scientists at the University of Chicago have cracked a surprisingly elegant recipe for creating some of the most complex quantum states known to physics—and they're doing it with tools that already sit on laboratory shelves. The discovery, reported in Physical Review X, challenges the assumption that building useful quantum technologies requires elaborate, custom-engineered setups. Instead, researchers led by Aashish Clerk at the Pritzker School of Molecular Engineering show that a few simple tweaks to an existing platform can unlock a whole universe of entangled quantum possibilities.
Entanglement is the quantum property that makes particles' fates intertwined—measure one, and you instantly know something about the other, even across vast distances. Building quantum computers, sensors, and other technologies depends on creating highly entangled states, but traditionally this has meant assembling complex apparatus with many moving parts. What Clerk and his team recognized is that physicists were already working with much of what they needed.
The starting point is cavity quantum electrodynamics—cavity QED for short—an established experimental platform where atoms or particles sit inside an optical cavity formed by two mirrors and interact with light trapped inside. The problem, as Clerk explains it, is that these systems have "too much symmetry." All atoms interact with the confined light identically, which severely limits the variety of quantum states the system can produce.
The breakthrough comes from a deceptively simple idea: break the symmetry. While all atoms are still driven with a common laser, the researchers add either a magnetic field or additional lasers to tune the energy levels of different groups of atoms relative to one another. Specifically, they pair each atom with another whose energy offset is equal and opposite—giving the particles distinct identities while maintaining enough structure for the system to remain predictable and controllable. "By simply adjusting the lasers, we can access kinds of entangled states that no one had thought about before," says Anjun Chu, a postdoctoral researcher and first author of the study.
What makes this genuinely powerful is the flexibility. By changing which atoms get different energy assignments, researchers can tune the entire system to produce a range of different entangled states—all without changing any physical hardware. It's like discovering that by rearranging the same ingredients on your kitchen counter, you can create entirely different dishes.
The practical applications are immediate. Clerk and his colleagues showed that two versions of their system could serve as quantum sensors capable of measuring tiny gradients in magnetic or gravitational fields. When placed in two locations, the systems' final quantum states would reflect the differences between local fields while remaining immune to background noise affecting 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 says. Remarkably, reading information from these states requires only standard measurement techniques—no exotic equipment needed.
Beyond sensing, the platform can generate exotic quantum states of fundamental interest to physicists. One example is the AKLT state, a famous many-body entangled state first described in the 1980s to explain exotic magnetic materials and potentially useful in quantum computing. The team demonstrated their setup can stabilize this state reliably.
While the work remains theoretical, researchers are already in discussions with experimental groups to bring these ideas to the laboratory. What they've shown is that complexity in quantum systems doesn't always require complexity in the tools—sometimes the most powerful breakthroughs come from seeing new possibilities in what you already have.