What Google’s quantum supremacy claim means for you

Google announced yesterday that it had made something of a breakthrough in the field of quantum computing by achieving a much-coveted state of computing called ‘quantum supremacy’. IBM, which is also an active participant in the race to make powerful quantum computing systems, refuted Google’s claim in a blog post earlier today. With giants such as Google and IBM warring to achieve meta-supercomputer performance, let’s try and understand what quantum computing is, and what Google’s latest claim means for us all.

What is quantum computing?

Quantum computing is a type of computing that works on the principles of quantum theory, which talks about the nature and behaviour of energy and matter on an atomic and subatomic level. This type of computing is by no means new. Scientists have been trying to build quantum computers since the early 1980s. Because it involves atoms in different states, quantum computing is not the same as classical computing, what we find in our PCs, smartphones, tablets, etc.

Classical computing involves carrying out logical operations using just two states: 0 and 1—or—on and off (aka binary number). The basic unit of classical computing is bit, and it can be represented either as 0 or 1 at any given time. With quantum computing though, the basic unit is qubit (quantum bit). Instead of using just two states, it uses four. That means a qubit can be 0 and 1 at the same time. An increase in qubits can increase the computational power of the system that uses it exponentially.

If you’re still not getting the picture, imagine the whistle your PE teacher used to use in school. If blowing the whistle is 1, and not blowing it is 0 in classical computing, then the entire whistle becomes a flute in quantum computing. Instead of the single air hole at the top of a whistle, you end up with numerous finger holes, each of which can be covered or opened individually at the same time to create a tune. And more such flutes playing together means higher computational power.

Google’s quantum supremacy claim

Publishing a paper in the scientific journal Nature, Google announced yesterday that its new 54-qubit quantum processor called Sycamore had succeeded in completing Google’s target computation in 200 seconds. The maker of the popular Pixel smartphones went on to say that the same target computation would take “the world’s fastest supercomputer 10,000 years to produce a similar output.” Just so we’re clear, the fastest supercomputer as of today is Summit (OLCF-4), which is developed by IBM.

In its recently published paper, Google claimed that this specific experiment allowed its Sycamore quantum processor to achieve quantum supremacy, a term proposed by American theoretical physicist John Preskill of Caltech back in 2012 to refer to the point at which quantum computers can do things that classical computers can’t. “This moment represents a distinct milestone in our effort to harness the principles of quantum mechanics to solve computational problems,” wrote Google CEO Sundar Pichai in his blog post.

IBM’s response

IBM responded to this claim earlier this morning in a blog post, saying that Google had not used the right parameters on its classical computing simulation to arrive at that pessimistic figure of 10,000 years. “We argue that an ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity. This is in fact a conservative, worst-case estimate, and we expect that with additional refinements the classical cost of the simulation can be further reduced,” wrote Edwin Pednault, John Gunnels, and Jay Gambetta from IBM Research.

Citing Preskill from a recent article in Quanta Magazine to explain how the term quantum supremacy is overhyped in reporting, the three IBMers wrote, “A headline that includes some variation of “Quantum Supremacy Achieved” is almost irresistible to print, but it will inevitably mislead the general public. First because, as we argue above, by its strictest definition the goal has not been met. But more fundamentally, because quantum computers will never reign “supreme” over classical computers, but will rather work in concert with them, since each have their unique strengths.”

What this means for you

During the closed-door media presentation that we at Digit.in were invited to earlier this morning, Google explained that its new Sycamore processor could find a variety of valuable applications in the near future, including the design of new materials. According to Google, its high computational power could help speed up the design of more eco-friendly plastics for water bottles, lightweight batteries for electric cars, and catalysts that can produce agricultural fertiliser more efficiently, including Haber’s process for the industrial production of ammonia.

While it’s hard to buy Google’s claim of having achieved quantum supremacy through its recent experiment at face value, especially after reading IBM’s thought-provoking rebuttal, it’s easy to see that Google has invested an immense amount of effort and money in making quantum computing work towards solving large problems. Though you obviously won’t see Google plonking a Sycamore quantum processor in its next Pixel device, you can expect to see the Californian giant taking on bigger experiments with its 54-qubit chip.

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Vignesh Giridharan

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