Scientists report 'quadsqueezing' quantum advance

University of Oxford physicists said on May 1 that they had demonstrated “quadsqueezing,” a fourth-order quantum interaction, in a single trapped ion, a result described in a paper published in *Nature Physics*. The work was led by O. Băzăvan, S. Saner, D. J. Webb, E. M. Ainley, P. Drmota, D. P. Nadlinger, G. (physics.ox.ac.uk) Araneda, D. M. Lucas, C. J. Ballance and R. Srinivas, according to the paper. The researchers said they combined two spin-dependent linear bosonic interactions to generate higher-order nonlinear interactions, including squeezing, trisqueezing and quadsqueezing. (nature.com) The paper says the team achieved quadsqueezing more than 100 times faster than conventional methods. ### What exactly did the Oxford team say it built? The *Nature Physics* paper describes quadsqueezing as a fourth-order generalized squeezing interaction in a hybrid oscillator-spin system. The experiment used a single trapped ion, with the ion’s motion acting as the oscillator and its internal state acting as the spin, according to the paper and Oxford’s summary. Oxford said the team demonstrated not just ordinary squeezing but also “trisqueezing” and “quadsqueezing,” extending the interaction order beyond the second-order processes commonly used in quantum control. The paper says the method works by combining two non-commuting spin-dependent linear interactions to synthesize stronger nonlinear effects. (nature.com) ### Why is “quadsqueezing” different from ordinary squeezing? The paper says ordinary squeezing comes from second-order bosonic processes and is already used in precision measurements, including gravitational-wave detection. Higher-order interactions such as trisqueezing and quadsqueezing are different because they generate non-Gaussian states, which the authors say are useful for continuous-variable quantum computation and for simulating interacting boson models. (nature.com) The authors wrote that these higher-order interactions have been difficult to engineer because they are usually weak or require specialized hardware. Their approach, they said, offers an alternative route in platforms that support spin-dependent linear interactions. (nature.com) ### Where does the “100 times faster” claim come from? The “over 100 times faster” figure appears in the *Nature Physics* paper’s abstract and in Oxford’s May 1 research summary. Oxford’s publication pages also describe the result as the first implementation of fourth-order generalized squeezing on any platform, while saying the achieved quadsqueezing was over 100 times stronger than what conventional methods allow. (nature.com) Balliol College, which highlighted three Oxford-affiliated physicists involved in the work, repeated that the trapped-ion system demonstrated quadsqueezing at speeds more than 100 times faster than existing methods. (nature.com) ### Who are the researchers behind the paper? The paper lists O. Băzăvan as first author and R. Srinivas as the final listed author, alongside eight other Oxford-linked co-authors. Balliol College named Raghavendra Srinivas, David Lucas and David Nadlinger in its account of the work. Raghavendra Srinivas said in Balliol’s May 8 item: “Fundamentally, we have demonstrated a new type of interaction that lets us explore quantum physics in uncharted territory.” Oxford’s researcher profile for Srinivas separately says the work amounted to the first realization of a fourth-order quadsqueezing interaction on any platform. (nature.com) (balliol.ox.ac.uk) ### What did the team actually measure in the lab? The paper says the researchers demonstrated and characterized squeezing, trisqueezing and quadsqueezing, and reconstructed Wigner functions of the resulting states. Those measurements are standard ways to characterize quantum states in oscillator systems and are cited by the authors as evidence that the engineered interactions produced the targeted states. (nature.com) The Oxford summary says the method provides a way to engineer interactions that could be used in quantum simulation, sensing and computing. That language comes from the university’s description of the work, not from an independent commercial benchmark. (balliol.ox.ac.uk) ### What comes next, based on the paper? The paper says the approach has “no fundamental limit on the interaction order” and can be applied to platforms that support spin-dependent linear interactions. That is the clearest next-step statement in the published research: extending the same method to higher-order interactions or to other hardware systems. (nature.com) As of May 18, 2026, the published record available through Oxford and *Nature Physics* is the May 1 paper, “Squeezing, trisqueezing and quadsqueezing in a hybrid oscillator–spin system,” by Băzăvan and colleagues. (nature.com) (physics.ox.ac.uk)