Balliol physicists report another achievement in quantum technology research

Friday 2 March

Vera Schafer and Dr Chris Ballance (photo: David Fisher / NQIT)Professor David Lucas (Fellow and Tutor in Physics) and DPhil student Vera Schäfer, with others, have published a paper in Nature in which they report on an achievement that brings the realisation of a quantum computer one step closer.

Ion trap for quantum computing (photo: Lucas Lab, Oxford)The researchers are from the Networked Quantum Information Technologies Hub (NQIT), which is led by Oxford University. They are using a trapped-ion technique to develop a quantum computer, in which logic gates place two charged atoms – containing information in the form of quantum bits, or qubits – in a state of quantum entanglement.;

Building on previous research in which they made the logic gates more precise, the team implemented a method for a two-qubit gate that is more than ten times faster than previously reported trapped-ion gates, without comprising accuracy. Vera, who is one of the lead authors of the paper (with Dr Chris Ballance), explains: ‘Trapped ions move like a pendulum during the gate operation, but when this process is sped up they become sensitive to a number of factors that cause errors. By making use of a technique that precisely shapes the force on the ions such that the gate performance becomes robust to these factors, we were able to increase the speed by a factor of 20 to 60 compared with the previous best gates – 1.6 microseconds long, with 99.8% precision.

‘We have now produced the highest fidelity and the fastest gate, reaching a point where our gates are in principle good enough for quantum computing. The next step is to think about it in practical terms and work towards scaling up our system to create a viable quantum computer.’

There is a fuller explanation of the technique, and a link to the published paper, in this article in Nature.

The experiments were performed in the same trap photographed by Balliol student David Nadlinger, who won the EPSRC photography competition.