Physicists at the University of Oxford have created a new class of quantum superposition states in a single trapped ion, advancing beyond the traditional Schrödinger’s cat concept. Instead of relying on simple two-state systems, the team used a trapped strontium ion’s motion to generate complex superpositions from nonclassical components like squeezed, trisqueezed, and quadsqueezed states. These states exhibit strong quantum features such as Wigner negativity and interference patterns, which are essential for surpassing classical computing limits.

The experiment used a Paul trap to isolate the ion and entangled its internal spin state with its motional state, acting as a quantum harmonic oscillator. By applying mid-circuit measurements and engineered spin-dependent forces, the researchers projected the ion’s motion into tailored superpositions. They demonstrated control over the phase, strength, and spacing of these states, even combining different types of squeezed states in a single superposition.

This work opens new possibilities for quantum computing and sensing. The structured spacing of Fock states and rotational symmetries in the Wigner function suggest improved error resilience compared to conventional cat states. The approach may also enhance displacement sensing in trapped ions, useful for detecting weak electric fields. While challenges remain in quantifying the 'quantumness' of such states, the platform offers a rich testbed for exploring the quantum-classical boundary.