Quantum computers should be much easier to build than previously thought, because they can still work with a large number of faulty or even missing components, according to a study published Nov. 9 in Physical Review Letters.

Dr. Sean Barrett, the lead author of the study, who is a Royal Society University Research Fellow in the Department of Physics at Imperial College London, and his colleague Dr. Thomas Stace, from the University of Queensland in Brisbane, Australia, have now found a way to correct for a particular sort of error, in which the qubits are lost from the computer altogether. They used a system of error-correcting code, which involved looking at the context provided by the remaining qubits to decipher the missing information.

“Just as you can often tell what a word says when there are a few missing letters, we used this idea in our design for a quantum computer,” said Dr Barrett. They discovered that the computers have a much higher threshold for error than previously thought — up to a quarter of the qubits can be lost — but the computer can still be made to work. “It’s surprising, because you wouldn’t expect that if you lost a quarter of the beads from an abacus that it would still be useful,” he added.

The findings indicate that quantum computers may be much easier to build than previously thought, but as the results are still based on theoretical calculations, the next step is to actually demonstrate these ideas in the lab. Scientists will need to devise a way for scaling the computers to a sufficiently large number of qubits to be viable, says Barrett. At the moment the biggest quantum computers scientists have built are limited to just two or three qubits.

Adapted from materials provided by Imperial College London