Artist's impression of the entangled logic gate built by University of Sydney quantum scientists. Quantum researchers at the University ...
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| Artist's impression of the entangled logic gate built by University of Sydney quantum scientists. |
Quantum Computing
For years, GKP codes have been theorized as a way to shrink the massive overhead required to correct quantum errors. Instead of needing thousands of fragile physical qubits to stabilize one logical qubit, GKP encoding translates continuous quantum oscillations into digital-like states, making errors easier to spot and fix. The Sydney team demonstrated this in practice, earning the code its nickname as the "Rosetta stone" of quantum computing.
“Our experiments have shown the first realization of a universal logical gate set for GKP qubits,” said Dr. Tingrei Tan, Sydney Horizon Fellow. “By precisely controlling the natural vibrations of a trapped ion, we can manipulate individual GKP qubits or entangle them as a pair.”
The team used a single ytterbium ion held in a Paul trap, where lasers control its quantum oscillations. By entangling two vibrational modes of the ion, they created a compact logic gate — the building block of quantum computing. This marks the first time a universal gate has been demonstrated using GKP-encoded qubits.
PhD student Vassili Matsos, first author of the study, explained: “We effectively stored two error-correctable logical qubits in one atom and demonstrated entanglement between them. That’s a huge reduction in the hardware needed to run reliable quantum operations.”
Software Meets Physics
The breakthrough was powered by advanced quantum control software developed by Q-CTRL, a startup spun out of the University of Sydney. The software minimized distortions in GKP states, ensuring that delicate error-correcting structures were preserved while the qubits performed computations.
One of the biggest obstacles to quantum computing is the physical-to-logical qubit ratio. Current architectures often require thousands of physical qubits to protect a single logical qubit from errors caused by noise, instability, and decoherence. This overhead has made scaling to useful, fault-tolerant machines daunting. The Sydney team’s approach reduces this burden by encoding logical information directly into the motion of a single ion, opening the door to smaller and more efficient machines.
A Global Race for Quantum
Efforts to shrink qubit overhead are underway worldwide. IBM, Google, and Rigetti have focused on superconducting qubits, while others like PSI in Switzerland and IonQ in the US explore trapped-ion systems. The Sydney team’s work stands out because it demonstrates universal gates with GKP qubits — something long considered possible in theory but elusive in practice.
If error correction can be achieved with far fewer physical qubits, quantum computers will become vastly more practical for solving problems in chemistry, drug discovery, cryptography, and finance. Instead of waiting for machines with millions of qubits, industry may soon benefit from mid-scale systems that can run useful algorithms with just thousands.
Future Outlook
Looking ahead, the team plans to expand beyond single atoms to multi-ion systems, scaling the architecture while retaining efficiency. The work also lays a foundation for hybrid quantum platforms where GKP-encoded ions could interface with superconducting or photonic qubits, creating flexible, fault-tolerant networks. As Dr. Tan put it: “This is a foundation to work towards large-scale quantum-information processing in a highly hardware-efficient fashion.”
The research was published in Nature Physics and supported by the Australian Research Council, the US Department of Defense, and industry partners including Lockheed Martin. It underscores a simple but powerful truth: the road to quantum advantage may not require more qubits — just smarter ones.
