Scientists at Oxford University have for the first time discovered a fourth‑order quantum interaction, opening new horizons for exploring the nature of the Universe

Quantum breakthrough: the first creation of “quadrature squeezing”

*Oxford scientists have discovered a new type of quantum interaction that could improve the precision of sensors and simulators.*

What is squeezing in quantum mechanics?
In classical physics one can measure both the position and velocity of an object precisely. In the quantum world this is impossible – Heisenberg’s uncertainty principle limits simultaneous knowledge of an electron’s coordinate and its speed.

When we “squeeze” one of the quantities (for example, reduce the error in measuring position), the probability distribution changes: instead of a circle it becomes an ellipse. This is already a more subtle state than in the classical case.

What new did the researchers propose?
The Oxford team has for the first time demonstrated quadrature squeezing – a fourth‑order quantum interaction.

- Unlike “ordinary” squeezing (second order), which is already used in gravitational‑wave detectors, quadrature squeezing creates probability distributions of a more complex shape: not an ellipse, but “petals and spikes”.

- Such states allow detection of even weaker signals, opening the way to ultra‑sensitive sensors.

How was it done?
1. Experimental system – a single trapped ion.

2. Two controllable laser forces (with different frequencies, phases, and amplitudes) are applied to the ion.

- Each force alone produces only a linear effect.

- Their non‑commuting interaction generates a strong nonlinear fourth‑order quantum action.

3. The parameters of the forces can be tuned so as to “turn off” unwanted effects and activate the desired type of squeezing.

Result: quadrature squeezing was generated more than 100 times faster than with traditional methods.

Confirmation and prospects
- Quantum motional states of the ion were reconstructed, confirming the characteristic shapes for different orders of interaction.

- Researchers are now extending the approach to multimode systems and applying it to other quantum platforms: superconducting circuits, cold atoms, etc.

- The method is already used to generate superposition squeezed states and to model lattice‑calibration theories.

What does this mean?
- Quantum simulation gains a new tool for creating complex quantum states.

- Ultra‑precise sensors could become more sensitive, which is important for gravitational‑wave observations and other high‑precision measurements.

- The ability to control fourth‑order interactions opens new horizons in quantum computing.

Thus, quadrature squeezing is the first step toward using “heavy” quantum interaction for practical tasks that were previously thought unattainable.