The quantum supremacy

Alarge team of researchers drawn from from Google, Nasa’s Ames Research Centre, the University of California, The Oak Ridge National Laboratory in the US and the Forschungszentrum Research Centre in Germany claims to have achieved “quantum supremacy.” According to the paper published in Nature, the team conceptualised and completed a computational task, which the most powerful conventional supercomputer (the IBM-designed Summit at Oak Ridge) would take about 10,000 years to solve. This took 200 seconds on Google’s Sycamore quantum chip. The results, generated by Sycamore, were being tested simultaneously by Summit, which was tackling the same problems until the complexity became too much for Summit.

This claim is being disputed by IBM, which says that the programmers did not program Summit efficiently. IBM has released a paper estimating that Summit could solve this within about 60 hours. However, as even IBM’s rebuttal concedes, there is a vast difference between 200 seconds and 60 hours.

The problem itself was esoteric, consisting of the generation of random numbers, and testing to see if these are random. The team used the architecture of the 54-Qubit Sycamore to generate those random sequences, translated into random binary numbers. The solution has no apparent practical application beyond being complex enough to benchmark versus the fastest conventional super-computer. 

This is the first demonstration that can indeed perform tasks beyond the capacity of conventional machines. It is understandable that it has led to hyperbolic comparisons with the first powered flight. After all, the Wright brothers’ Flyer stayed aloft only for 12 seconds on December 17, 1903, at Kittyhawk, North Carolina. The premise backing research in quantum computers is simple. A conventional bit is binary. It can be set to one, or zero, depending on whether there is a current flowing through or not. A quantum bit uses the phenomenon of superposition to be in both states, zero and one, at the same time. When you create a quantum machine with many qubits, it has the ability, in theory, to process exponentially greater information. Moreover, using entanglement, a property so strange that Einstein called it “spooky”, a qubit influences the state of another qubit at a distance. That has other applications, including communication and cryptography.

The engineering and mathematical challenges in handling Q-chips are formidable. Q-chips have to be cooled to near absolute zero and kept in that state to function. They generate huge errors, which have to be catered for, and eliminated, to generate meaningful results, when the superpositions are collapsed. This means entirely new algorithms and error-correction codes must be written to handle quantum computing. The research team admits that this is a narrow result and Google is nowhere near solving these major problems yet. 

But these are known unknowns. This result indicates that there are no unknown barriers to prevent quantum computing from scaling beyond conventional machines. That gives cause for optimism that quantum computers will be capable of tackling real-world problems, which conventional machines cannot. 

Some obvious applications would include biological problems of genetic mapping, drug development, and protein folding. Google also cites the possibility that Q-machines could be used to design better batteries, or more efficient processes for manufacturing fertiliser (which contributes about 2 per cent of global carbon emission). The utility would also include cryptography. Quantum machines could conceivably break all current high-end encryption very quickly. They could also generate unbreakable codes that make it impossible to intercept, or tamper with messages, or to read a message without the key. This result is bound to lead to an acceleration of investment into research. Google has shared its data set and promised to offer time to independent programmers who can think up creative applications. It might take years but this could be the dawn of a new era.

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