Google says that its 54-qubit Sycamore processor was able to perform a calculation in 200 seconds that would have taken the world’s most powerful supercomputer 10,000 years. That would mean the calculation, which involved generated random numbers, is essentially impossible on a traditional, non-quantum computer.
Standard computers and quantum computers are radically different. While standard computers perform calculations with “bits”, which must be either 0 or 1, quantum computers have “qubits” that can take any value between 0 and 1. Another quirk of quantum physics allows qubits to be “entangled” such that the value of one is tied to the values of those around it. Make a quantum computer that is stable enough – a tough enough feat in itself – and it can, in principle, explore multiple solutions to a problem at once.
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.