Biggish Blue Boffins say they have devised a method to manage the unreliability of quantum computers in a way that would lead to reliable, valuable answers which do not require computers the size of a bus.

Dorit Aharonov, a professor of computer science at the Hebrew University of Jerusalem who was not involved with the research said that IBM has showed an important step in that direction of making progress towards serious quantum algorithmic design.

While researchers at Google in 2019 claimed that they had achieved "quantum supremacy" -- a task performed much more quickly on a quantum computer than a conventional one -- IBM's researchers say they have achieved something new and more practical, if more modestly named.

IBM Quantum VP Jay Gambetta said "We're entering this phase of quantum computing that I call utility. A team of IBM boffins who work for Dr. Gambetta described their results in a paper published on Wednesday in Nature.

The IBM researchers in the new study performed a different task that interests physicists. They used a quantum processor with 127 qubits to simulate the behaviour of 127 atom-scale bar magnets in a magnetic field that is tiny enough to be governed by quantum mechanics.

A simple system uses the Ising model, which is used to study magnetism. This problem is too complex for a precise answer to be calculated even on the largest, fastest supercomputers. The calculation took less than a thousandth of a second on the quantum computer. Each quantum calculation was unreliable -- fluctuations of quantum noise inevitably intrude and induce errors -- but each calculation was so quick so that it could be checked repeatedly.