Researchers at the University of Oxford have achieved the first-ever demonstration of quadsqueezing, a fourth-order quantum effect, using a single trapped ion. The breakthrough, published on May 1 in Nature Physics, introduces a novel method to engineer complex quantum interactions. This advance could enhance quantum simulation, sensing, and computing.
Scientists at the University of Oxford developed a technique combining two precisely controlled forces on a single trapped ion to generate advanced forms of squeezing. These include standard squeezing, trisqueezing, and quadsqueezing—a fourth-order interaction previously out of reach. The method leverages non-commutativity, where the order of forces alters outcomes, amplifying effects more than 100 times faster than conventional approaches, according to lead author Dr. Oana Băzăvan from Oxford's Department of Physics. Dr. Băzăvan explained, “In the lab, non-commuting interactions are often seen as a nuisance because they introduce unwanted dynamics. Here, we took the opposite approach and used that feature to generate stronger quantum interactions.” By adjusting frequencies, phases, and strengths, the team switched between squeezing levels while minimizing noise. Measurements of the ion's quantum motion confirmed distinct patterns for each order of squeezing. The work builds on a 2021 theory by Dr. Raghavendra Srinivas and Robert Tyler Sutherland. Study co-author Dr. Srinivas said, “Fundamentally, we have demonstrated a new type of interaction that lets us explore quantum physics in uncharted territory, and we are genuinely excited for the discoveries to come.” Researchers are extending the technique to multi-mode systems and combining it with spin measurements to simulate lattice gauge theories. The approach uses existing quantum platform tools, potentially broadening its applications in precise measurements and quantum computers.