Researchers Break Quantum Computing Logic Gate Record

A team of Oxford University researchers has broken a record vital to the creation of a quantum computer, which could harness the quantum-mechanical phenomena of entanglement and superposition in order to perform superfast computational operations without electronic transistors.

The researchers, from the University of Oxford’s Engineering and Physical Sciences Research Council (EPSRC)-funded Networked Quantum Information Technologies Hub (NQIT), achieved a quantum logic gate with 99.9% precision, the threshold at which it is possible to run a quantum computer. The details of the research are outlined in the paper ‘High-Fidelity Quantum Logic Gates Using Trapped-Ion Hyperfine Qubits’, as published in Physical Review Letters, written by Prof. Lucas, plus C. J. Ballance, T. P. Harty, N. M. Linke, and M. A. Sepiol.

“A quantum logic gate is an operation which can take two independent atoms and put them into this special entangled state,” Professor David Lucas, of Oxford University’s Department of Physics and Balliol College, explained. “The precision of the gate is a measure of how well this works: in our case, 99.9% precision means that, on average, 999 times out of 1,000 we will have generated the entangled state correctly, and one time out of 1,000 something went wrong.”

“To put this in context, quantum theory says that – as far as anyone has found so far – you simply can’t build a quantum computer at all if the precision drops below about 99%,” he continued. “At the 99.9% level you can build a quantum computer in theory, but in practice it could very difficult and thus enormously expensive. If, in the future, a precision of 99.99% can be attained, the prospects look a lot more favourable.”

Theoretically, a quantum computer could process massive amounts of information at once, rather than the sequential manner in which conventional computers function. The logic gate – which places a pair of atoms into a state of quantum entanglement, a requirement to attain quantum computing – achieved by the researchers is the highest on record, but that alone does not mean that quantum computing is a reality, yet.

“Achieving a logic gate with 99.9% precision is another important milestone on the road to developing a quantum computer. A quantum logic gate on its own does not constitute a quantum computer, but you can’t build the computer without them,” Prof. Lucas added. “An analogy from conventional computing hardware would be that we have finally worked out how to build a transistor with good enough performance to make logic circuits, but the technology for wiring thousands of those transistors together to build an electronic computer is still in its infancy.”