فيزيائيو أكسفورد يفتحون بابين جديدين للتحكم الكمومي بأيون واحد محتجز

The University of Oxford’s trapped-ion physics group has long pushed the boundaries of quantum control, but two breakthroughs reported in the spring and early summer of 2026 stand apart. Within weeks of each other, the team published results in Nature Physics and Physical Review X that expand what a single atomic ion can do—from generating a previously elusive fourth-order quantum effect to building entirely new kinds of superposition states. Though both experiments revolve around the same platform, they solve different problems and open distinct technological doors.

Quadsqueezing: Bringing a fourth-order ghost into the light

Standard quantum squeezing is a second-order technique that reshapes uncertainty to improve measurement precision—think of it as compressing noise in one direction at the expense of expanding it in another. For decades, squeezing has boosted gravitational-wave detectors and atomic clocks. Going beyond this, to fourth-order squeezing, was theoretically straightforward but experimentally inaccessible because noise that could be ignored at lower orders became overwhelming .

In May 2026, an Oxford-led team that included Dr. Oana Băzăvan, Professor David Lucas, and Dr. David Nadlinger changed that by applying a sequence of controlled forces to a single calcium ion suspended in an electric field trap. By combining those forces in a specific order, they generated quadsqueezing—a fourth-order quantum correlation that manifests as entanglement among four distinct motional states—at unprecedented speed. The method produced these effects 100 times faster than conventional approaches and rendered them visible for the first time .

The key methodological insight was simplicity: rather than layering exotic hardware, the team used existing trapped-ion tools in a sequence that isolated the fourth-order signal from the noise that had previously buried it . The result, published in Nature Physics, marks the first experimental observation of fourth-order quantum entanglement effects .

Why it matters. Quadsqueezing provides a more sensitive knob for quantum metrology because higher-order correlations can beat the standard quantum limit by wider margins. It also opens a pathway toward engineering complex quantum states that serve as building blocks for fault-tolerant quantum computing and next-generation sensors .

Schrödinger cats built from the strange, not the simple

The second breakthrough landed in June 2026 in Physical Review X. Quantum superposition states—often called Schrödinger cat states—are typically assembled from ordinary coherent-state wave packets, the closest quantum analog to a classical orbit. The Oxford team, however, asked a different question: what if each part of the superposition was itself intrinsically nonclassical?

Using the motion of a single trapped ion, the researchers built superpositions in which the two overlapping components were squeezed states—quantum configurations where uncertainty is already redistributed in a counterintuitive way. By programming the ion’s state with high precision, they sculpted complex, asymmetric superpositions that had not been achievable before .

The method gives physicists programmable control over the shape and properties of the cat state. In conventional cat states, the quantum uncertainty looks identical in both branches; here, it differs, creating a richer interference structure that could be harnessed for error correction and fundamental tests of quantum mechanics .

Why it matters. Quantum error correction relies on encoding information across states that are robust against noise. Generating superpositions from nonclassical components, such as squeezed states, could produce logical qubits that are inherently more resilient. The work also sharpens the testbed for foundational questions about decoherence and the quantum-to-classical transition .

Why a single trapped ion?

Both breakthroughs share a common stage: a single trapped ion—likely a calcium or strontium isotope—held near motionless by radiofrequency electric fields. A trapped ion combines two different quantum systems: a well-isolated internal electronic state that acts as a qubit, and motional modes that can be laser-cooled to the quantum ground state. This dual nature makes ions an ideal platform for generating and analyzing complex quantum states .

Critically, the Oxford Ion Trap Group has been refining this platform for years. In June 2025, the same group set a world record for single-qubit gate fidelity, achieving an error rate of just 0.000015%, or one mistake in 6.7 million operations . That extreme control over individual qubits is the foundation that made the 2026 quadsqueezing and cat-state results possible.

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Neither quadsqueezing nor programmable cat states will appear in a commercial quantum computer tomorrow. But together they fill two different gaps in the quantum toolbox: one provides a faster, cleaner path to high-order entanglement for sensing and metrology, while the other delivers a new way to shape information for error correction. Both show that a single well-controlled ion remains one of the most versatile platforms for exploring—and exploiting—the deepest rules of quantum physics.