Image Courtesy: University of Oxford
Researchers at the University of Oxford have developed a new class of quantum superpositions, including an unconventional version of the famous Schrödinger’s cat state, by combining quantum states that are themselves highly nonclassical. The breakthrough could help advance future quantum computers and provide new ways to explore the foundations of quantum mechanics.
Quantum superpositions allow particles and systems to exist in multiple states at once, a phenomenon famously illustrated by Schrödinger’s cat, a thought experiment in which a cat is simultaneously alive and dead until observed. While scientists have created laboratory versions of such states before, the Oxford team took a different approach by building them from complex quantum states rather than from components that closely resemble classical behavior.
Traditional quantum “cat states” are typically formed using coherent states, which behave as closely to classical motion as quantum mechanics allows. In contrast, the Oxford researchers constructed superpositions from strongly nonclassical states, including squeezed states where quantum uncertainty is redistributed in unusual ways.
The experiment used a single trapped ion, a platform widely studied in quantum computing research. Trapped ions are particularly useful because they combine two different quantum systems: internal states that function like conventional qubits and motional states that behave as quantum harmonic oscillators capable of occupying many energy levels.
To create the new states, the researchers entangled the ion’s internal state with multiple possible motional states before performing a mid-circuit measurement. This process caused the ion’s motion to collapse into a carefully selected quantum superposition.
“This approach gave us a tool to sculpt the quantum superposition into almost any shape,” said lead author Dr. Sebastian Saner.
Measurements of the resulting states revealed interference patterns and regions of Wigner negativity, key indicators that the observed behavior could not be explained by classical physics. The results confirmed that the team had successfully generated genuine quantum superpositions composed of intrinsically nonclassical components.
Researchers believe the technique could support future quantum computing architectures that rely on quantum oscillators rather than traditional qubits alone. Such systems may offer improved error resistance and more efficient error correction. The states could also provide a valuable platform for investigating where the boundary between classical and quantum physics truly lies.