Researchers at the University of Oxford have achieved a breakthrough in quantum physics, demonstrating a new type of interaction, “quadsqueezing,” for the first time
Quadsqueezing opens new avenues for exploring previously inaccessible quantum effects and could improve technologies such as quantum computing, sensing, and simulation.
Rethinking how quantum systems are controlled
Many physical systems can be described as quantum harmonic oscillators, which behave like tiny springs or pendulums.
Controlling these systems is key to modern quantum technology. One established technique is “squeezing,” which redistributes uncertainty between paired properties, such as position and momentum. By tightening precision in one property, the other becomes less certain, a trade-off governed by quantum mechanics.
Squeezing is already used in real-world applications, such as improving the sensitivity of gravitational-wave detectors.
More complex forms, such as trisqueezing and quadsqueezing, have remained largely theoretical because they are extremely weak and difficult to observe experimentally.
A new method to amplify subtle effects
The Oxford team overcame this challenge by combining two carefully tuned forces applied to a single trapped ion.
While each force alone produces a simple effect, together they create a much stronger and more complex interaction. This happens due to a quantum phenomenon called non-commutativity, where the order and combination of actions influence the final outcome in a non-trivial way.
By exploiting this effect, the researchers were able to generate higher-order squeezing interactions far more efficiently than traditional approaches would allow. The quadsqueezing interaction, in particular, was produced over 100 times faster than expected, making it practical to observe and study.
New quantum states
Using a highly controlled experimental setup involving lasers and electromagnetic fields, the team manipulated the motion of a single ion and reconstructed its quantum state. This allowed them to directly observe distinct patterns associated with different levels of squeezing, including second-order (standard squeezing), third-order (trisqueezing), and fourth-order (quadsqueezing).
These observations provide clear experimental evidence of interactions that were previously out of reach, marking an important step forward in quantum control techniques.
The ability to engineer complex quantum interactions has wide-ranging implications. The method demonstrated in this study can be adapted to more complex systems, including those involving multiple particles or modes of motion. This flexibility makes it a promising tool for advancing quantum simulation, where researchers model complex physical systems, and for improving precision measurements in sensing technologies.
In quantum computing, the technique could help create new types of quantum states and operations, potentially leading to more powerful and efficient systems. Early demonstrations have already shown its compatibility with advanced methods such as mid-circuit measurements, enabling the creation of tailored quantum states and the simulation of theoretical models.
This breakthrough represents more than just the observation of a new quantum effect. It introduces a general strategy for accessing and controlling interactions that were once considered too weak to be useful. By turning a traditionally problematic feature of quantum systems into a powerful tool, the researchers have opened up new possibilities for exploring the quantum world.
