Google has officially announced that it’s achieved quantum supremacy in a new article published in the scientific journal Nature. The announcement comes exactly one month after it initially leaked, when Google’s paper was accidentally published early. Now, however, it’s official, meaning the full details of the research are public, and the broader scientific community can fully scrutinize what Google says it’s achieved.

In classical computers, the unit of information is called a "bit" and can have a value of either 1 or 0. But its equivalent in a quantum system - the qubit (quantum bit) - can be both 1 and 0 at the same time.

This phenomenon opens the door for multiple calculations to be performed simultaneously. But the qubits need to be synchronised using a quantum effect known as entanglement, which Albert Einstein termed "spooky action at a distance".

However, scientists have struggled to build working devices with enough qubits to make them competitive with conventional types of computer.

Some researchers say the demonstration isn’t so much a computation as an effort to cook up a quantum state that’s hard to simulate. “Quantum computers are not ‘supreme’ against classical computers because of a laboratory experiment designed to essentially … implement one very specific quantum sampling procedure with no practical applications,” says Dario Gil, director of IBM Research in Yorktown Heights, New York, which is also developing machines with superconducting qubits.

Source: theverge.com, sciencemag.org, bbc.com