Finally, we are discovering what quantum computers will be useful

During the last decade, quantum computing has become an industry of one billion dollars. Everyone seems to be investing in it, from technological giants, such as IBM and Google, to the US army.

But Ignacio Cirac At the Max Planck Institute of Quantum Optics in Germany, a pioneer of technology has a more sober evaluation. “A quantum computer is something that does not exist at this time,” he says. This is because building one that really works, and is practical to use, is incredibly difficult.

Instead of the “bits” of conventional machines, these computers use quantum bits or qubits, to encode information. These can be made in several ways, from small superconductor circuits to extremely cold atoms, but all are complex to build.

The advantage is that their quantum properties can be used to make certain types of calculation faster than standard computers.

Such accelerations are attractive to a variety of problems that normal computers fight, from the simulation of exotic physics systems to efficiently program passenger flights or deliveries of groceries to supermarkets. Five years ago, it seemed that quantum computers would improve these and many other computational challenges.

Today, the situation is much more nuanced. Progress in the construction of increasingly large quantum computers has been, without a doubt, impressive, and several companies develop machines with more than 1000 qubits. But this has also revealed difficulties impossible to ignore.

An important problem is that, as these computers become bigger, they tend to make more mistakes, and find ways to prevent or solve them has proven more difficult than expected. Last year, Google researchers made the most notable aboller in this problem so far, but even so, useful and totally intense quantum computers are not yet here, as Cirac points out.

Because of this, the list of realistic applications for these machines can be shorter than we expected. Despite the cost of building one against the smallest savings than those imagined that I could deliver and, for many cases of use, it may not have economic sense. “The biggest error is that a quantum computer can accelerate any problem,” says Cirac.

So what problems could still benefit from the quantum calculation? Quantum computers could break the cryptography systems that we currently use for safe communication, and this makes technology interesting for governments and other institutions whose security could be in danger for it, he says. Scott Aaronson at the University of Texas in Austin.

Another place where quantum computers must still be useful is in the modeling of chemical materials and reactions. This is because quantum computers, in themselves a system of quantum objects, are perfectly suitable for simulating other quantum systems, such as electrons, atoms and molecules.

“These will be simplified models; they will not represent real materials. But if you design the system appropriately, they will have enough properties of real materials that can learn something about your physics,” he says Daniel Gottesman At Maryland University.

Quantum chemistry simulations may sound more niche than programming flights, but some of the possible results, finding an ambient temperature superconductor, for example, would be transformer.

The extent to which all this can really be done significantly depends on quantum algorithms, the instructions that tell quantum computers how to execute and help correct those annoying errors. This is a new challenging field that They see Dunjko At the University of Leiden in the Netherlands, he says he is forcing researchers like him to face fundamental questions about what information and computer science they are.

“This provides surprising motivation to study the hardness of the problems and power of computer devices,” says Dunjko. “For me, this would be a sufficient reason to dedicate a significant fraction of my life to these questions.”