What’s All the Fuss About?
One small step for Google, one giant leap for computing
Quantum supremacy
What is it?
It’s the point at which quantum computers overtake traditional computers, ushering in a new age of almost unimaginably powerful machines. It may be upon us soon.
How exciting. What’s happened?
Google published a paper on Nasa’s website saying it has built a processor called Sycamore (pictured) that performed a calculation that can only be carried out on a quantum computer.
Surely it could be performed by a normal computer?
Technically yes, but it would take even the most powerful super-computers around 10,000 years, by which time most people would get bored of waiting. By contrast, it took Google a mere three minutes, 20 seconds.
What exactly are quantum computers?
They’re powered by the central theory of quantum physics, which is that an object can exist in two different states at the same time. Normal computers treat data in bits (zeroes and ones); quantum computers use qubits, in which data can be both zero and one simultaneously. They’re the computing equivalent of Schrödinger’s cat.
Schrödinger’s what?
His cat. In 1935 Austrian physicist Erwin Schrödinger (pictured below) devised a thought experiment to illustrate what he saw as the fundamental problem of quantum physics. Imagine, he said, placing a cat in a box, then putting something inside that could kill it, such as a radioactive atom. You wouldn’t know whether the cat was alive or dead until you opened the box, so in a sense it existed in both states at the same time.
Poor cat. But how does that translate into computing?
If qubits can be zeroes and ones at the same time, they can quickly process an infinite amount of information. Look at it this way: a pair of qubits can embody four possible states simultaneously, three qubits can be in eight different states, but three hundred qubits can be in more states than there are atoms in the universe.
Blimey. So why did Google’s test work so well?
It reduced the problem of ‘crosstalk’, which is when qubits interfere with each other, causing errors that reduce the accuracy of their results. This was an impressive achievement, but there’s a slight hitch.
Oh. What’s that?
Google’s claim of quantum supremacy may be complete tosh.
Really? Says who?
Rival companies. Dario Gil, director of research at IBM, was scathing, calling Google’s claim “indefensible – just plain wrong”. He said Google’s work had “no practical applications” and thinks we remain “very far” from quantum technology being used in a meaningful way. He said IBM had made more progress in quantum computers.
What’s Google’s view?
It admits that “realising the full promise of quantum computing still requires technical leaps”. And it soon removed the paper from Nasa’s site, suggesting it realised it had jumped the gun. Indeed, it’s been reported that some Google researchers thought using the term ‘supremacy’ would make them look arrogant. They considered coining a different phrase, but stuck with what most people already use.
So who’s right?
Perhaps they both are. Independent experts agree it’s a breakthrough, but doubt quantum computers will soon reign supreme. Jonathan Oppenheim, a physics professor at UCL, said: “While this is a milestone, it is very far from being a quantum computer that can compute anything useful”. Not quite a quantum leap then, more of a bunny hop.
Quantum PCS use qubits, in which data can be both zero and one simultaneously