The study aiming to reduce the physical-to-logical qubit overhead by building logic gates inside a single trapped ion.
Physicists at the University of Sydney have reported a universal set of logic gates for Gottesman–Kitaev–Preskill (GKP) qubits built inside a single trapped ion. The work is published in Nature Physics.
The result targets a core scaling problem. Today, one useful “logical” qubit often needs many “physical” qubits for error correction. Encoding logic in an oscillator can cut that overhead. That is the role of the GKP code.
In the experiment, the team used one ytterbium ion held in a Paul trap. A Paul trap confines a charged atom with radio-frequency and direct-current electric fields inside a vacuum chamber. The ion’s motion then acts like a tiny spring–mass oscillator.
Two of these oscillators, called radial vibrational modes as they are perpendicular to the trap’s axis and stored two logical qubits. Running logic inside one atom avoids wiring two separate ions for this step. The group performed single-qubit operations and an entangling two-qubit gate between the two modes.
GKP encoding maps the oscillator’s continuous variables (position and momentum) onto a grid of discrete states. Small shifts become measurable errors that can be corrected. Logic then runs on these encoded states rather than on raw hardware states.
Control came from lasers that couple the ion’s internal state to its motion. By driving motional “sidebands”, the team prepared, manipulated and entangled the modes. The authors describe an optimal-control strategy to keep the encoded states from distorting during gates.
Gate design and calibration were supported by quantum-control software from Q-CTRL, a University of Sydney spin-out. This links the lab protocol to tools used across trapped-ion platforms.
The result shows that two error-correctable logical qubits can be stored and entangled within one atom. It also shows that a universal gate set can run on GKP qubits in a standard trapped-ion setup at room temperature. The paper outlines next steps in extending the gate library and connecting to multi-ion systems.
