Quantum computers are one of the most challenging research of our century due to their ability to execute exponentially faster processing respect to classical computers. The qubit (or quantum bit) is the basic unit of information in a quantum processor, replacing the bit in a classical computer. It exploits the laws of quantum mechanics to process information. A traditional bit encodes either a zero or a one while a qubit, thanks to quantum mechanics, will have the advantage of using ones, zeros and “superpositions” of ones and zeros. Certain quite impossible tasks for classical computers will be achieved quickly and efficiently by a quantum computer.

On 23rd October, in Nature [1], Google seems have won the challenge with their 53-qubit quantum computer, named Sycamore; they claimed that they have achieved the milestone of quantum computers, the so called “quantum supremacy”: “Our Sycamore processor takes about 200 seconds to sample one instance of a quantum circuit a million times—our benchmarks currently indicate that the equivalent task for a state-of-the-art classical supercomputer would take approximately 10,000 years. This dramatic increase in speed compared to all known classical algorithms is an experimental realization of quantum supremacy  for this specific computational task the milestone in quantum computing.”

Google has given us the first experimental proof that a quantum speed-up is possible; although the calculation performed by the Sycamore system—checking the outputs from a quantum random-number generator— seems not so useful in the real word, the achievement itself is powerful, creating the impression that quantum computers are closer to practical applications.

[1] https://www.nature.com/articles/s41586-019-1666-5