23-Oct-2019: Google achieves quantum supremacy

Researchers at Google claim their quantum computer has solved a problem that would take even the very best conventional machine thousands of years to crack.

The milestone, known as quantum supremacy, represents a long-sought stride towards realising the immense promise of quantum computers, devices that exploit the properties of quantum physics to speed up certain calculations.

A quantum processor consisting of 54 superconducting quantum bits, or qubits, was able to perform a random sampling calculation – essentially verifying that a set of numbers is randomly distributed – exponentially faster than any standard computer.

Google’s Sycamore device did it in just 3 minutes and 20 seconds, although one of the qubits had to be turned off as it wasn’t working properly.

IBM has already pushed back on that claim, insisting that with some clever classical programming, its machine can solve the problem in 2.5 days. Indeed, IBM, which has its own 53-qubit quantum computer, prefers a higher threshold for quantum supremacy, which explains its argument that Google has not yet reached the milestone. Even if we accept IBM’s claims at face value, Google’s quantum computer is still a big step forward.

It doesn’t mean quantum computers are ready to tackle real-world problems though – that remains decades away. Instead, it is a proof of concept. Researchers are looking forward to the next milestone: proof that we have sufficient control over the qubits that we can overcome the small errors they accumulate during calculations.

We are now in a phase we call noisy intermediate-scale quantum computing, or NISQ. To get beyond that, we need to start doing error correction. The nice thing is that we can see from this paper that the architecture of the Google chip is already optimised for that.