A few weeks ago, rumors that Google was about to claim the achievement of “quantum supremacy” started to spread like wildfire. “Google claims to have built the first quantum computer that can carry out calculations beyond the ability of today’s most powerful supercomputers,” reported Financial Times.
Google’s draft paper was quickly pulled from the NASA website, where it had been posted, but (of course) not before copies had been made and reposted.
While the term “quantum supremacy” can suggest unpleasant impressions, it was first introduced by physicist John Preskill “to describe the point where quantum computers can do things that classical computers can’t.”
A commentary by quantum computing expert Scott Aaronson was widely praised and discussed. Aaronson, who was in the know, confirmed (sort of) the rumors and the importance of Google’s achievement. However, he advised the public and the press to wait for Google’s official announcement and the publication of Google’s paper in a peer-reviewed journal.
Now the paper, titled “Quantum supremacy using a programmable superconducting processor,” has been published in Nature. And Google has posted an official announcement. NASA and other research institutions have contributed to the achievement.
According to New York Times, quantum supremacy “could allow new kinds of computers to do calculations at speeds that are inconceivable with today’s technology.” In a new commentary, titled “Quantum supremacy: the gloves are off,” Aaronson describes Google’s research results as “a historic milestone for our whole field.”
Google’s new 54-qubit processor, dubbed “Sycamore,” solved in about 3 minutes a computational problem that, according to Google’s analysis, would take the world’s fastest supercomputer 10,000 years. That the problem is uninteresting in itself, and designed to prove the desired result, doesn’t reduce the importance of the proof that real-world quantum computers are able to dramatically outperform conventional computers.
It seems likely that interesting and important applications of quantum supremacy will follow. The Nature paper concludes:
“As a result of these developments, quantum computing is transitioning from a research topic to a technology that unlocks new computational capabilities. We are only one creative algorithm away from valuable near-term applications.”
Days before the publication of Google’s Nature paper, IBM (one of the tech giants competing with Google in the race to build the first operational and scalable quantum computers) posted a commentary and a draft research paper on arXiv. According to IBM, the 10,000 years that Google estimates for the equivalent classical computation are really 2.5 days. According to Aaronson, IBM’s proposed method is sound, but would require huge (and expensive) computational resources to achieve, in days, what Google achieved in minutes.
Because quantum physics is fundamental, any physical system, including classical computers, is a quantum system. However, “a classical computer does not take advantage of the specific properties and states that quantum mechanics affords us in doing its calculations,” explains an introduction to quantum computing recent enough to mention quantum supremacy.
Classical computing is based on bits, physical systems that can be in one of two states (zero and one). Quantum computing is based on qubits that can be in a quantum superposition of zero and one states, and exhibit “entangled” correlations with each other, thus “dancing in synchronicity,” explains a NASA press release. “Quantum computers can use these correlations to store, transfer and compute information in ways impossible on traditional computers.”
Of course, the devil is in the details: How can we maintain delicate quantum states in the messy real world? Or, how can we work around that? It turns out that there are error correction methods that mitigate the problem.
Two well-known algorithms for quantum computers are Shor’s method to find prime factors of large numbers, and Grover’s method to sort unordered input. Both methods are theoretically faster than classical counterparts, with speed-ups increasing with input size. Shor’s algorithm has one evident application: code breaking, which is certainly “real-world” enough. Grover’s algorithm has plenty of real-world applications, including applications to optimization and Big Data.
Efficient quantum computing methods have been developed for simulating physics and chemistry, materials science, and machine learning applications.
These are, I think, the first applications of quantum computing that will make an impact on health science and human enhancement. Drug discovery makes use of complex computer simulations, and engineered biomaterials are used in biomedical research and preliminary clinical applications. Machine learning, a subset of Artificial Intelligence (AI), is used all over the field, from the research lab to the hospital.
It can be expected that these first applications will begin to materialize once the first operational and scalable quantum computers are available, perhaps in a few years.
But the real quantum computing killer app for radical human enhancement could be, I think, producing and reproducing consciousness.
While most neuroscientists are persuaded that consciousness is a byproduct of essentially classical physics and chemistry in the brain (in other words, that the brain is a classical computer that does not take advantage of quantum physics), a growing minority of top-level scientists, including Roger Penrose, consider quantum phenomena as essential to consciousness.
If so, classical computers could not “run” conscious AIs and human uploads (that is, human minds “copied” from biological brains to computers). But perhaps some quantum computers could.
Can delicate quantum states survive in the messy, wet, and warm brain? Are quantum phenomena essential to consciousness? The jury is on. But I suspect that quantum physics is, indeed, central to the mystery of consciousness.
How could deterministic classical physics give rise to free will? And please don’t tell me that free will is an illusion. I know that I am a free agent, and so do you. I tend to think of free will and basic awareness, upon which human consciousness is built, as part of the quantum fabric of reality.
If so, conscious AIs and human uploads could not run on classical computers, but we could build quantum computers able to exploit the same quantum phenomena that give rise to human consciousness.