Feeding quantum “cats” to boost calculations

Brave ? Reckless? Unconscious? How to qualify the founders of a French start-up which intends to compete with Amazon? Admittedly, Alice & Bob, created in 2020 and installed in the 15and district of Paris, does not want to compete with the American giant on online sales. She aims to achieve what her rival does not yet know how to do. Or anyone else: a quantum computer.

This type of machine is supposed to accelerate certain calculations, or even make possible certain others, deemed unfeasible even with current supercomputers. Finance, the chemical and pharmaceutical industry, the energy and transport sectors expect wonders from it. The major computer companies, Google, IBM, Microsoft, and the main countries (China and the United States in the lead) are investing billions in it. Laboratories, start-ups, large companies compete to achieve this first.

Qubits, for quantum bits, replace computer bits

Alice & Bob, one of the latest in the race, raised 27 million euros in March, provided by the Elaia, BPI France and Supernova Invest funds. Supported by the CNRS, from which it originated, and by the Atomic Energy Commission, which participates in the production of its electronic chips, it is distinguished by its original way, taken over by Amazon a few months after the creation of the start-up. up, to achieve his goal. “I am passionate about physics and electronics and therefore very motivated to invent and try new rules of the game”, testifies Théau Peronnin, polytechnician, co-founder of the start-up of 40 people with Raphaël Lescanne, normalien, whom he knew during his thesis. His ambition is to domesticate a… quantum cat.

“Domesticate the Cat”

The expression is to be taken literally. It is a metaphor to popularize the property of an object to be simultaneously in two states at once, 0 and 1 in computer language, or dead and alive, according to the words of Erwin Schrödinger, one of the fathers of mechanics quantum and author of the image of the cat. This capacity is the key to the promised acceleration, because, by authorizing several simultaneous states, it allows a kind of parallelization of calculations. Qubits, for quantum bits, replace computer bits.

Creating such a cat is not so difficult. Take a microwave oven (with niobium walls), then miniaturize it by a few millimeters. Inside, the microwave photons are like seesaws going back and forth between the walls. Two of these oscillators are selected so that when one swing is at its peak forward, the other is at its peak backward. A few more efforts, and the engineers mix these two states to form a Schrödinger cat: it is then impossible to know on which swing the photons play. It’s a cat qubit.

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