Google debuted Willow, its newest quantum chip, on Wednesday, and for those who’ve spent any time on-line since, you’ve undoubtedly run into some breathless reporting about it. Willow “crushes classical computers on a cosmic timescale,” proclaims one headline; Google “unveils ‘mind-boggling’ quantum computer chip,” reads one other. It’s all anchored by a declare that Willow can full a computation that will theoretically take a classical laptop considerably extra time than the 14 billion years the universe has existed. However, as you’ll be able to in all probability guess, what the chip represents shouldn’t be so easy.
First, with Willow, Google makes no declare of quantum supremacy, one thing the corporate did when it publicly debuted its earlier era quantum laptop, Sycamore, again in 2019. You could recall that, on the time, Google publicized the way it took Sycamore simply 200 seconds to carry out a calculation that will have theoretically taken the world’s then-fastest supercomputer 10,000 years to finish. That feat, the corporate stated, demonstrated that it had created a quantum laptop that would remedy issues one of the best classical computer systems couldn’t even try. In different phrases, Google had achieved quantum supremacy.
Nonetheless, that declare rapidly resulted in controversy, with one researcher calling the corporate’s announcement “indefensible” and “just plain wrong,” and Google has since averted speaking about quantum supremacy. As an alternative, it simply says it has achieved “beyond classical computation.” A part of the difficulty was that Sycamore was not a general-purpose quantum laptop; as an alternative, it was designed to surpass classical computer systems in a single process generally known as random circuit sampling or RCS. The factor about RCS is that, in Google’s personal phrases, it has “no known real-world applications.” But, right here once more, the corporate is touting RCS efficiency.
Google says Willow can full its newest RCS benchmark in underneath 5 minutes. Against this, the corporate estimates it might take Frontier, presently the world’s second strongest supercomputer, 10 septillion years to finish the identical process. That quantity, Google says, “lends credence to the notion that quantum computation occurs in many parallel universes, in line with the idea that we live in a multiverse.”
Extra virtually, Google tries to make the case that RCS efficiency ought to be the metric by which all quantum computer systems are judged. In accordance with Hartmut Neven, the founding father of Google Quantum AI, “it’s an entry point. If you can’t win on random circuit sampling, you can’t win on any other algorithm either.” He provides RCS is “now widely used as a standard in the field.“
However, other companies, including IBM and Honeywell, instead use a metric called quantum volume to tout their breakthroughs. They claim it points to a more holistic understanding of a machine’s capabilities by factoring in how its qubits interact with one another. Unfortunately, you won’t find any mention of quantum volume in the spec sheet Google shared for Willow, making comparisons difficult.
To that point, the far more impressive claim Google is making today is that Willow is “below the threshold.” To this point, the issue that has plagued each try to construct a helpful quantum laptop is that the quantum bits they’re based mostly on are troublesome to manage. They solely maintain their quantum state for fractions of a second, and the extra qubits are added to a system, the extra probably it’s to provide errors. Nonetheless, with Willow, Google says it has discovered a solution to cut back errors because it provides extra qubits to the system. In accordance with the corporate, Willow is the primary time this has been carried out.
“As the first system below threshold, this is the most convincing prototype for a scalable logical qubit built to date. It’s a strong sign that useful, very large quantum computers can indeed be built,” says Neven. “Willow brings us closer to running practical, commercially-relevant algorithms that can’t be replicated on conventional computers.”
That’s the actual breakthrough right here, and one which factors to a future the place quantum computer systems may remedy issues which have tangible results on individuals’s lives. That future, nonetheless, is not right here simply but, and even Google admits it has extra work to do earlier than it will get there.
