Quantum computing enters the era of utility, says IBM – 06/27/2023 – Marcelo Viana

Quantum computers use tiny units, called qubits, which take advantage of the bizarre behavior of subatomic matter, described by quantum mechanics, to perform calculations at extraordinary speed, beyond the reach of any conventional computer.

In an article published in the journal Nature on June 14, an IBM team used quantum computing to solve a physics problem that is called the Ising model, in honor of the German physicist Ernst Ising (1900-1998).

It is a system formed by tiny magnets that interact according to the laws of electromagnetism. In theory, it is possible to calculate how magnets evolve over time under the effect of these interactions. But if the number of magnets is relatively large, on the order of a hundred, say, the calculation is too complex for even the fastest conventional supercomputers out there.

IBM researchers used a quantum computer with just 127 qubits to find the solution to the Ising model in a millisecond! This, by itself, is not very useful. The problem is that qubits are unstable, because they are easily affected by their interactions with the environment. For this reason, the result is not reliable: each time we repeat the same calculation, the answer may be different.

The big news is that the IBM team would have found a method to mitigate the effects of this “noise” caused by the interactions of the qubits with the surrounding environment. Interestingly, the way they did this was by introducing additional noise, which makes the calculation results even less reliable!

The point is that by varying the size and type of noise appropriately, they can identify its effects on the calculation and “subtract” them from the result. In practice, they ran the program 600,000 times, which took about ten minutes: although each of the answers obtained is unreliable in itself, from the set of them a correct solution for the Ising model is obtained.

For simple particular cases, in which classical computers manage to solve the problem, and we can compare, the quantum solutions proved to be equal or better than the conventional ones. But it is not clear that this is true in all cases, that is, we do not know if we are facing a case of “quantum supremacy”. But the folks at IBM are confident enough to herald a new phase in quantum computing, the “age of utility.”

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