Now the quantum computer is something real. A new Google computing experiment published in Nature has ushered in a new era of computing. The publication is an experiment in theoretical computer science. Google scientists would demonstrate the ability of a quantum processor to solve a calculation that a traditional computer would perform in years and years. To date, no one has managed to maintain quantum coherence for so long.

Quantum computers work in a substantially different way from classical machines: a classic bit is a 1 or a 0, but a quantum bit, or qubit, can exist simultaneously in more states. A team led by John Martinis, an experimental physicist at the University of California, Santa Barbara, and Google in Mountain View, California, said his quantum computer performed a specific calculation that goes beyond the practical capabilities of "classical" computers. The same calculation would also require the best classical supercomputer 10,000-years to complete.

A fundamental property that characterizes the qubit concerns the so-called interference; a third important property is related to the possibility of the qubit to be entangled, which is to say intertwined, leading to a deep correlation. It means, to simplify, to be able to calculate at speed never seen before.

Physicists and engineers have long been studying how to manage qubit. To exploit its characteristics and therefore maintain quantum coherence, efficient thermal management systems are needed. Moreover, they must be isolated in particular laboratory conditions; otherwise, they collapse. So far superconductors have been used, metals capable of working at temperatures well below zero. Both IBM and Google work on Josephson junctions composed of two strips of superconductors separated by an insulator. There are other techniques, such as the topological quantum computing that Microsoft is betting on.

The example computation implemented in Google's experiment was the control of the outputs of a quantum random number generator. Although a limited example, it represents a huge scientific result. The news was also leaked from the NASA website, which collaborates with Google on quantum computing.

With this goal, Google has reached the quantum supremacy that has been a military stone for a long time. “It looks like Google has given us the first experimental evidence that quantum speed-up is achievable in a real-world system,” says Michelle Simmons, a quantum physicist at the University of New South Wales in Sydney, Australia.

Google's algorithm was run on a 54-qubit quantum chip, each consisting of superconducting loops. In general, this number is a small fraction of the million qubits that might be needed for a machine for computational purposes (Figure 1).

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Figure 1: Google's quantum computer [Source: Google]

The solution test essentially consisted of a comparison of data with different computational models performed by various classical computers, including the supercomputer Summit at the Oak Ridge National Laboratory in Tennessee. The Google team has estimated that simulating the entire circuit would take 10,000 years, even on a computer with a million processing units. The quantum computer, on the other hand, would only take 3 minutes and 20 seconds.

This is a further step towards a complete optimization of quantum computers to solve more sophisticated tasks. Physicists think this will be essential to make large-scale quantum computers work. Google is working towards this, seeking to make further improvements to further demonstrate quantum super charity even in a forthcoming commercial market.

The availability of a universal quantum computer can have a fundamental impact on a vast number of research fields and on our society. Quantum computing and artificial intelligence could reserve things we have never seen before.