Quantum Chips: Computing Like A Soap Bubble?
Google Quantum AI has made a breakthrough with its Willow quantum chip, demonstrating exponential quantum error correction, suggesting real progress toward reliable quantum computing. However, comparing Willow's performance to conventional computers in the benchmark test used may be misleading.
This is not financial advice and is for entertainment purposes only. Do your own due diligence. The author does not hold a beneficial long or short position in any of the publicly traded companies mentioned.
Since Google Quantum AI reported in Nature on December 9 that its Willow quantum chip is capable of "quantum error correction below the surface code threshold," Wall Street has been on a quantum computing hype, with shares of Alphabet, Rigetti Computing, and D-Wave Quantum, among others, soaring.
There is no question that Google Quantum AI has made a breakthrough: With Willow, it has now been shown that an exponential decrease in the error rate can be achieved with an increasing number of qubits. This first convincing demonstration that exponential quantum error correction is possible supports the feasibility of reliable quantum computers.
In particular, however, the public seems to have picked up on the statement from Google's research blog that "Willow performed a standard benchmark computation in under five minutes that would take one of today’s fastest supercomputers 10 septillion (that is, 1025) years". That "standard benchmark" was Random Current Sampling (RCS). Willow's performance in RCS was not actually mentioned in the December 9 Nature article, but another Nature article published on October 9 reported that quantum chips can vastly outperform conventional supercomputers in RCS. By the way, it's worth noting that RCS is a rather artificial task and "has no known real-world applications", according to the Google Research blog post.
But does it even make sense to compare the performance of quantum computers in RCS to that of conventional binary computers? RCS involves running random quantum circuits on a set of qubits to create complex, entangled quantum states - in other words, quantum states have been created in a quantum system.
If we simply define a computer as a system that can solve at least one problem, then there are many such systems that are superior to conventional supercomputers. For example, a soap bubble is the most powerful system we know for many surface optimization problems as it simply minimizes surfaces through the laws of physics. Similarly, a quantum chip directly "experiences" the exponentially growing Hilbert space during RCS, while a classical computer has to simulate it computationally. Therefore, in my opinion, the comparison with conventional (super)computers can be misleading. What would be the best system to model the fermentation of milk by lactobacilli down to the molecular level? - Cheese. However, I very much doubt that future AI will run on a wheel of Gouda.
Quantum computers are still far from being as versatile as our binary computers, if they ever are. Also, today's quantum chips only run near absolute zero, which is extremely energy-intensive. In any case, I have no doubt that quantum computers could be enormously disruptive: A reliable and functioning quantum computer could make all current encryption standards obsolete, and would indeed be the "atomic bomb of the information age," as it is often called. There could be numerous applications that require some form of computation for which a quantum computer is as inherently perfect as a soap bubble for surface optimization. But I think we are a long way from that, or as it says at the end of the Google AI research paper of December 9th: "With below-threshold surface codes, we have demonstrated processor performance that can scale in principle, but which we must now scale in practice."
