If processor speed seems to have reached its upper limit, don't worry! The expected performance of the quantum computer leads us in a whole new dimension. Where our current computers will have all of the antediluvian "escarGo" [snail] characteristics.

To get a fair idea of what we are talking about, we must imagine that for a given operation, 10,000 years would be necessary for a classic supercomputer, whereas three minutes will suffice for a quantum computer. Reading this information, one might think of a hoax, had it not been published in the journal Nature. Behind this announcement, we find Google and its Sycamore 54-qubit processor. So, is quantum supremacy, to use the term coined by John Preskill, a physicist at the California Institute of Technology, launched?

Son of a cat!

But back to the first question, how does a quantum computer work? Of course, this goes back to atomic and sub-atomic physics. This strange world of the infinitely small is governed by a very particular type of physics, quantum mechanics. Here, a particle can have different natures simultaneously within the framework of a superposition of possible states. To be here and elsewhere at the same time, to present two states simultaneously or alternately, excited or not. To illustrate, nothing like the good old Schrödinger cat, this thought experiment set out in 1935. We imagine a cat, locked in a box equipped with a nuclear and deadly device. According to the principles of quantum physics, as long as the box is closed, the cat would be both dead and alive.

By opening the box, we will have the answer. The sighting will take us back to our "physical" world where the feline will be dead or alive. So to put it simply, a quantum superposition is only valid in a quantum universe. But then what about the computer of the same name, inscribed in our reality?

Quantum tactics

The memory of a typical computer is based on bits. Each bit carries 1 or 0. Then the machine calculates by arranging these bits. For its part, a quantum computing circuit is organized from quantum bits (qubits or qbits). They can record data of 1 or 0 but in a simultaneous way. The qbit can therefore carry data of 1, 0 or the superposition of a 1 and a 0. And in the logic of quantum physics, the latter can also be combined, this is called entanglement. The computer calculates by manipulating these different distributions for spectacular computing power. An example: in a library, you choose a book in which you draw a cross on a page taken at random. Once the book is put back in place, you then ask the computer to find it. The modern computer will proceed by successively opening all the pages of each book in the library until it finds the cross in question. If you gave the same query to a quantum computer, it would be able to go through all the pages of all the books at the same time, and find the page almost instantly!

When is quantum coming?

Not tomorrow. Already, it is necessary to be able to produce qbits in sufficient quantity to arrive at operational applications. Faced with the resulting security and therefore sovereignty issues, States are encouraging large companies and research centers. The Americans and the Chinese are investing en masse on the subject. Big tech giants regularly publish the status of their progress in the race for quantum supremacy. Google, like IBM, Honeywell, Microsoft or Intel are competing with thunderous announcements on breakthroughs that lead to imagination-defying performance. The strategic issue has not escaped Europe's notice. In 2017, the EU committed one billion euros over ten years to the Quantum Technology Flagship program.

When China, through one of its BATXs, Alibaba, invests $ 15 billion in AI, fintech and quantum research...

Whether in telecommunications, intelligence, energy infrastructure, the pharmaceutical industry, supercomputers could play a decisive role. This technology would also support artificial intelligence by leveraging machine-learning capabilities. Along with the United Kingdom and Germany, France appears to be one of the leaders in quantum research. But while it is involved in many projects, France does not lead any. Nevertheless, it is very involved in the QuQube quantum processor project in Grenoble, funded by the European Research Council. Elsewhere, initiatives are developing.

Labs, start-ups, investment funds... France and Europe have at their disposal certain advantages so as not to be left behind. The Pulsalys incubator has enabled the young Alice & Bob start-up, created by two young physicists from the Lyon ENS [National Science School], with people talking about it with work that could well revolutionize the approach to quantum computing. The idea: to correct errors that occur naturally with these supercomputers. At the physics laboratory of the ENS in Lyon, Théau Peronnin, co-founder, explains: "our work shows that it is possible to protect quantum information in the long term". A breakthrough that, if confirmed, would open up a market estimated at between 400 and 800 billion euros. Together with Raphaël Lescanne, they now wish to bring together university energies and knowledge around their project. They have raised three million euros and are giving themselves between two and three years to make it happen. "We realized that in France, there was unique know-how in the design of quantum machines", gladly note the two founders. As if by echo, Cédric O, French Secretary of State for Digital Matters, confirms that there is in our country an exclusive porosity between research and young‘uns which must be able to bring France to be among the best players in the sector.

The hare and the turtle

Where are we today? "The first five kilometers of a marathon and an adventure of ten to twenty years", said Romain Alléaume, researcher in quantum cryptography at Télécom Paris. Google has invested hundreds of millions of dollars over the years, he says, but may have gone down an uncertain path. This would allow Europe and France to catch up. So much the better in view of the major security issues and national sovereignty. Florence Parly, French Defense Minister, underlines: "one cannot be surprised by a potential quantum computer which would come to break the encryption of our military data."

As for Mr. Everybody, it’s not tomorrow morning he’ll be walking around with a quantum smartphone. Already, to reduce particle instabilities, quantum devices must be maintained at temperatures close to absolute zero (-273°C) and occupy an entire room. Rather, the future of quantum computing is likely to be in the cloud, where companies will lease uptime.

Whatever it may be, for Honeywell boss Darius Adamczyk, thanks to quantum computing, materials specialists will discover new molecular structures, transportation companies will optimize their logistics. Financial institutions will have faster and more accurate applications. And pharmaceutical groups will be accelerating the discovery of new drugs.°

Sources : site web radio Canada, Agence France Presse, Le Monde, Lyon Entreprises, Financial Times, New York Times, Le Parisien, The Verge, Washington Post