Physicists on the University of Oxford have set a brand new global benchmark for the accuracy of controlling a single quantum bit, achieving the lowest-ever error rate for a quantum logic operation — just 0.000015%, or one error in 6.7 million operations. This record-breaking result represents nearly an order of magnitude improvement over the previous benchmark, set by the identical research group a decade ago.
To place the end in perspective: an individual is more prone to be struck by lightning in a given yr (1 in 1.2 million) than for considered one of Oxford’s quantum logic gates to make a mistake.
The findings, published in Physical Review Letters, are a significant advance towards having robust and useful quantum computers.
“So far as we’re aware, that is probably the most accurate qubit operation ever recorded anywhere on the planet,” said Professor David Lucas, co-author on the paper, from the University of Oxford’s Department of Physics. “It’s a vital step toward constructing practical quantum computers that may tackle real-world problems.”
To perform useful calculations on a quantum computer, thousands and thousands of operations will have to be run across many qubits. Which means that if the error rate is just too high, the outcome of the calculation will likely be meaningless. Although error correction may be used to repair mistakes, this comes at the associated fee of requiring many more qubits. By reducing the error, the brand new method reduces the variety of qubits required and consequently the associated fee and size of the quantum computer itself.
Co-lead creator Molly Smith (Graduate Student, Department of Physics, University of Oxford), said: “By drastically reducing the prospect of error, this work significantly reduces the infrastructure required for error correction, opening the way in which for future quantum computers to be smaller, faster, and more efficient. Precise control of qubits may also be useful for other quantum technologies equivalent to clocks and quantum sensors.”
This unprecedented level of precision was achieved using a trapped calcium ion because the qubit (quantum bit). These are a natural selection to store quantum information because of their long lifetime and their robustness. Unlike the standard approach, which uses lasers, the Oxford team controlled the quantum state of the calcium ions using electronic (microwave) signals.
This method offers greater stability than laser control and likewise has other advantages for constructing a practical quantum computer. For example, electronic control is less expensive and more robust than lasers, and easier to integrate in ion trapping chips. Moreover, the experiment was conducted at room temperature and without magnetic shielding, thus simplifying the technical requirements for a working quantum computer.
The previous best single-qubit error rate, also achieved by the Oxford team, in 2014, was 1 in 1 million. The group’s expertise led to the launch of the spinout company Oxford Ionics in 2019, which has turn into a longtime leader in high-performance trapped-ion qubit platforms.
Whilst this record-breaking result marks a significant milestone, the research team caution that it is an element of a bigger challenge. Quantum computing requires each single- and two-qubit gates to operate together. Currently, two-qubit gates still have significantly higher error rates — around 1 in 2000 in the very best demonstrations to this point — so reducing these will likely be crucial to constructing fully fault-tolerant quantum machines.
The experiments were carried out on the University of Oxford’s Department of Physics by Molly Smith, Aaron Leu, Dr Mario Gely and Professor David Lucas, along with a visiting researcher, Dr Koichiro Miyanishi, from the University of Osaka’s Centre for Quantum Information and Quantum Biology.
The Oxford scientists are a part of the UK Quantum Computing and Simulation (QCS) Hub, which was a component of the continued UK National Quantum Technologies Programme.
