Wednesday, May 18

Quantum computing silences criticism: we are already close to error correction, one of its greatest challenges, with the tips of our fingers


Gil Kalai has fewer and fewer arguments to cling to. This Israeli mathematician and professor at Yale has predicted that quantum computers will never be able to make amends for your mistakes. And it is necessary that they do so if we want to use them to solve a wide range of problems that are really significant.

Fortunately, the rapid development that quantum computing is undergoing is gradually dismantling the opinions that cast doubt on the potential of this discipline. One of the biggest challenges it faces consists precisely in the need for quantum computers to be able to correct their own errors, and three different studies defend how close we are to achieving it.

An Australian, a Dutch and a third Japanese quantum computing research group have published in Nature many other scientific articles in which they explain in detail the procedure they have used to fine-tune superconducting qubits that have an accuracy greater than 99%. But best of all, when errors are so infrequent it is much easier to correct them.

We are closer to fully functional quantum computers

During the conversation we had a few months ago with Ignacio Cirac, the director of the Theoretical Division of the Max Planck Institute for Quantum Optics Hosted in Garching (Germany), this Spanish scientist explained to us how important it is for quantum computers to be able to correct the errors they make, and also what are the two paths that we can follow to ensure that these machines are capable of solving really significant problems:

There are two paths. Developing a quantum computer that does not have errors is very complicated. I have no doubt that it will happen (in this area I do not agree with what Gil Kalai says), but I think it will take a long time. The other way is to take the prototypes we already have, which are very small and don’t work very well because they have bugs, and do something meaningful with them.

The first option is the most important because I think it will have a huge impact on society, but we will have to wait. The second, however, is something that is open. There may be some big applications that can be addressed with the quantum computer prototypes we have, or they may not. We still don’t know for sure, but I think it’s worth betting on it because if one of them arises, it could have a big impact on society.

Ignacio Cirac is a rigorous and extremely prudent scientist, two qualities that honor him, and for this reason during our conversation he preferred not to fantasize about the possibility that the long-awaited correction of errors will arrive soon. but i could do it.

Each of these three research teams has carried out its analysis independently

And it is that the researchers that I have spoken of a few lines above have managed to perfect superconducting qubits with extremely high precision, and that, in addition, they can be manufactured using the silicon-based semiconductor production technology that is currently used to produce high-integration chips.

That these qubits can be produced using robust and well-known technology is very important. But it is that, in addition, each of these three research teams has carried out its analysis in an independent way. And two of them, the Australian and the Dutch, have certified their measurements using a tomographic method very accurate and widely accepted by the scientific community. As you can see, it sounds very good.

quantum computer 2

Let’s take a look at your results. The Australian team led by Andrea Morello has obtained an accuracy of 99.95% using one qubit, and 99.37% using two superconducting qubits. The Dutch research group led by Lieven Vandersypen has achieved an accuracy of 99.87% using one qubit, and 99.65% using two qubits. And finally, the Japanese team led by Seigo Tarucha has shown an accuracy of 99.84% with one qubit, and 99.51% using two qubits.

As we can guess, these high figures indicate that the operations carried out with these qubits rarely introduce any error because they are capable of preserving quantum coherence for a long time. According to Andrea Morello, in fact, for no less than 35 seconds. It may seem like an instant, and for us it is, but for a quantum processor it is an eternity because during this time it is capable of carrying out many calculations.

The reason why it is important that the incidence of errors be so low is that when you are below 1% quantum error-correcting protocols find it much easier to do their job. A one- or two-qubit quantum processor is too simple to solve significant problems, but these research groups they have established an extraordinary starting point from which it should be possible to scale this number and develop reliable quantum processors with many more qubits. That will be the biggest challenge from now on.

Pictures | IBM

More information | Nature | SciTechDaily



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