The power of a quantum computer tested online


They were the first to test a quantum computer available remotely, a unique machine in Europe. About sixty young international students and researchers had this opportunity on the Sorbonne University campus in Paris, from November 7 to 9. This technology promises to perform certain calculations faster than the most powerful supercomputers, and even to solve problems inaccessible today.

Several companies, IBM, Microsoft, Google, Amazon, Rigetti, D-Wave… already offer prototypes of such machines, but whose performance remains very far from promises. To this list, we must now add the French start-up Quandela. Born in 2017, it launched its quantum processor online on November 15, the first in Europe outside the UK.

Quandela's single photon source with a piece of optical fiber to route light to a quantum computing chip.

“The weekend before this hackathon at the Sorbonne, I was sitting on my sofa, and from my laptop, I was able to launch a calculation that would have taken three months to develop in my laboratory. I couldn’t believe it! », says Pascale Sénellart, research director at the CNRS, and co-founder of Quandela. The day before, on Friday evening, her husband Jean, the company’s software engineering director, was still working on fine-tuning with his team. And on Monday, apprentice quantum computer scientists from Spain, Portugal, Germany, the Netherlands and France could program and launch the machine.

Massive parallelization of operations

This one, called Ascella, is installed 15 kilometers away, in Massy (Essonne), in the premises of the start-up. It fits in a black metal cabinet, as big as a fridge, which evokes the installations of data center. A regular noise punctuates the seconds and betrays the operation of a pump which circulates helium in order to cool down to –260°C an essential part of the computer: the source from which the so-called “qubits” will flow. This portmanteau, a contraction of quantum and bits, is the key to the power of these machines. In a typical computer, information is stored with 0s or 1s, bits. In it, and in its counterparts, it is possible to be 0 and 1 at the same time, and even any combination of the two. This allows for a kind of massive parallelization of operations, exploring a set of possibilities all at once, rather than piecemeal.

These qubits can be trapped individual atoms, or superconducting electronic mini-circuits, or even, as here, photons, the particles that make up light. The Quandela source thus sends 80 million single photons per second, after excitation by a laser beam of a nanoscopic sandwich of semiconductor layers. It is already sold to research laboratories and even to competitors.

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