Researchers at the University of Oxford have developed a groundbreaking class of “cat states”—quantum superpositions created from unique, non-classical elements instead of traditional wave packets. This advancement paves the way for more robust quantum computers.
Quantum mechanics challenges classical intuitions, most famously showcased in Schrödinger’s cat, where systems exist in a superposition of states. Superpositions are critical for advancing quantum technology. Quantum “cat” states have been previously realized in harmonic oscillators, predominantly limited to Fock, displacement, or Gottsman-Kitaev-Preskill states. A different type of macroscopic superposition, where the oscillator is squeezed along orthogonal axes, had been suggested but never achieved. Zahner et al. introduced a trapped ion hybrid spin oscillator system that enables the experimental realization of these ‘brothers’ to Schrödinger’s cat. Image credit: Saner et al., doi: 10.1103/k1xk-yt42.
“Unlike classical physics, quantum mechanics permits objects to exist in multiple states simultaneously,” stated Dr. Sebastian Zahner of the University of Oxford and his research team.
“This concept is famously embodied in Schrödinger’s cat, which is imagined to be both alive and dead until observation occurs.”
“In experimental settings, physicists can create a less dramatic but highly realistic version of this phenomenon by placing atoms, light, or motion in two different quantum states simultaneously.”
“Manipulating these superpositions is vital for applications ranging from quantum computing to precise timekeeping.”
“A quintessential example is a quantum bit, or qubit, which represents a superposition of both 0 and 1. However, quantum systems can exhibit more than merely two states.”
“Quantum harmonic oscillators, which can occupy several distinct energy levels, provide even richer possibilities.”
“These quantum harmonic oscillators describe a variety of physical systems, such as light, vibrations, and confined particle motion, while creating diverse quantum superpositions.”
“A notable instance is the cat state, where an oscillator exists in a superposition of two wave packets positioned in opposite directions.”
“These wave packets, termed coherent states, closely resemble classical motion constrained by quantum mechanics.”
In their latest study, Dr. Zaner and colleagues presented a novel family of quantum superpositions.
Rather than constructing cat-like states from traditional wave packets, they devised a method to create superpositions using a broad array of components that are inherently non-classical.
For instance, in superposition of squeezed states, the quantum uncertainty is distributed differently within each component of the state.
“The experiment leveraged the motion of a single trapped ion,” the physicists reported.
“A trapped ion integrates two distinct types of quantum systems: its internal state functions like a qubit, while its motion acts as a quantum harmonic oscillator capable of inhabiting various motion states.”
“This provides a powerful platform for engineering quantum states beyond conventional qubits.”
To create these innovative states, researchers initially employed engineered interactions to entangle the ions’ internal states with different possible motion states.
Subsequent intermediate-circuit quantum measurements of internal states then projected the ion’s motion onto a particular superposition of non-classical components.
“This method equips us with the instruments to fabricate quantum superpositions in nearly any configuration,” Dr. Sanner mentioned.
This technique allows researchers to precisely control the generated states.
By modifying the experimental arrangement, they could adjust the relative sizes, rotations, and separations of the components, enabling a diverse range of exotic motion superpositions within the same trapped ion system.
The scientists also directly reconstructed the quantum states they produced.
This reconstruction revealed interference patterns and regions demonstrating Wigner negativity, confirming that the state transcends a typical classical mixture.
These characteristics affirm that the experiment achieved a genuine quantum superposition of authentically non-classical states of motion.
The authors are now collaborating with theorists to determine the precise “quantum” nature of these states.
Dr. Raghavendra Srinivas, also from the University of Oxford, expressed, “I was genuinely heartened by my colleagues’ reactions when I presented our findings.”
“We believe we are merely scratching the surface of the potential applications and the deeper understanding of these conditions.”
The team’s research paper was published in this month’s edition of Physical Review X.
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S. Zaner et al. 2026. Generation of arbitrary superpositions of non-classical quantum harmonic oscillator states. Physical Review X 16, 021049; doi: 10.1103/k1xk-yt42
Source: www.sci.news
