UC Irvine physicists discover method to reverse ‘quantum scrambling'

• A problem in quantum computing called "quantum scrambling" hampers the technology's development.
• Scrambling results in the loss of data in a quantum computing system, an issue previously thought to be irreversible.
• A UC Irvine team has discovered a way to reverse the scrambling process.

Irvine, Calif., April 13, 2026 - Quantum computers stand to revolutionize research by helping investigators solve certain problems exponentially faster than with conventional computers. Current quantum computers encounter a challenge where they lose stored information in a process known as 'quantum scrambling.' However, scientists at the University of California, Irvine discovered a method to enable computers to preserve the data that would otherwise be lost during the scrambling process.

"My work is on understanding how this scrambling of quantum information works and in understanding how it emerges," said Thomas Scaffidi, assistant professor of physics & astronomy and lead author of the new Physical Review Letters study. "We're trying to figure out if the information is still there in some form and if we can reverse the scrambling process completely."

The fundamental unit of information in quantum computing is the qubit. Conventional computers use bits, which store information as either a 0 or a 1, while a qubit stores information as either a 0, a 1 or both at the same time.

Quantum scrambling happens when information encoded into qubits spreads within a quantum computing chip and then keeps spreading before disappearing entirely.

"Let's say you have many qubits that are all talking to each other and exchanging information," said Scaffidi. "If you try to locally encode some information in the qubits, after a while, there's going to be the scrambling effect - the encoded information is going to spread out over many qubits and will be effectively lost, and you won't be able to recover it. That's an issue if you want to retrieve that information or do calculations with it."

Scaffidi and his graduate student, Rishik Perugu, approached the problem by studying a subtle feature of quantum physics: Although scrambled quantum information can appear effectively lost, the underlying microscopic laws are in principle often reversible. That means the information may not be destroyed but dispersed in an extremely complex way across many interacting particles.

"At the microscopic level, our universe seems to be reversible in time, so if you think of two particles colliding, if you watch a movie of two particles colliding, the movie would look sensible if you played it forward or backwards," said Scaffidi.

Perugu discovered that this reversible behavior appears in many quantum systems, including quantum computers. That opens the door to counteracting quantum scrambling with a precisely tuned intervention that effectively drives the system backward, allowing previously dispersed information to refocus near where it started.

"It happens to be a very universal property," Scaffidi said. "The conclusion is that it is possible to reverse it, but it requires an extremely fine-tuned and very fine level of control on your system."

The breakthrough came after Perugu, soon after joining Scaffidi's research group, was able to perform the calculations revealing how quantum scrambling might be reversed.

"The project had stalled for a while before Rishik joined," said Scaffidi. "His work gave it new momentum, and he played a central role in making the new paper happen."

Scaffidi is funded by a U.S. Department of Energy Early Career Research Program Award, and key collaborators include Michael Flynn at BlocQ and Bryce Kobrin at Google.

About the University of California, Irvine: Founded in 1965, UC Irvine is a member of the prestigious Association of American Universities and is ranked among the nation's top 10 public universities by U.S. News & World Report. The campus has produced five Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UC Irvine has more than 36,000 students and offers 224 degree programs. It's located in one of the world's safest and most economically vibrant communities and is Orange County's second-largest employer, contributing $7 billion annually to the local economy and $8 billion statewide. For more on UC Irvine, visit www.uci.edu.

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