Perspective: Quantum computingA Quantum Computing Future Is Unlikely, Due to Random Hardware Errors
Earlier this fall Google announced that it had demonstrated “quantum supremacy” – that is, that it performed a specific quantum computation far faster than the best classical computers could achieve. IBM promptly criticized the claim, saying that its own classical supercomputer could perform the computation at nearly the same speed with far greater fidelity. “So how can you make sense of what is going on?” Subhash Kak, a professor of Electrical and Computer Engineering, asks. “As someone who has worked on quantum computing for many years, I believe that due to the inevitability of random errors in the hardware, useful quantum computers are unlikely to ever be built.”
Earlier this fall Google announced that it had demonstrated “quantum supremacy” – that is, that it performed a specific quantum computation far faster than the best classical computers could achieve.
IBM promptly criticized the claim, saying that its own classical supercomputer could perform the computation at nearly the same speed with far greater fidelity and, therefore, the Google announcement should be taken “with a large dose of skepticism.”
Subhash Kak, a professor of Electrical and Computer Engineering, writes in The Conversation that this wasn’t the first time someone cast doubt on quantum computing. Last year, Michel Dyakonov, a theoretical physicist at the University of Montpellier in France, in an article in IEEE Spectrum, the flagship journal of electrical and computer engineering. offered a long list of technical reasons why practical quantum supercomputers will never be built
“So how can you make sense of what is going on?” Kak asks. “As someone who has worked on quantum computing for many years, I believe that due to the inevitability of random errors in the hardware, useful quantum computers are unlikely to ever be built.”
He notes that A classical computer uses 0s and 1s to store data. These numbers could be voltages on different points in a circuit. quantum bits, also known as qubits, have special properties: They can exist in superposition, where they are both 0 and 1 at the same time, and they may be entangled so they share physical properties even though they may be separated by large distances.
“Due to superposition, a quantum computer with 100 qubits can represent 2100 solutions simultaneously,” Kak writes.
The mathematics that underpin quantum algorithms is well established, but there are daunting engineering challenges that remain.
For computers to function properly, they must correct all small random errors. In a quantum computer, such errors arise from the non-ideal circuit elements and the interaction of the qubits with the environment around them. For these reasons the qubits can lose coherency in a fraction of a second and, therefore, the computation must be completed in even less time. If random errors – which are inevitable in any physical system – are not corrected, the computer’s results will be worthless.
He concludes:
While quantum cryptography holds some promise if the problems of quantum transmission can be solved, I doubt the same holds true for generalized quantum computing. Error-correction, which is fundamental to a multi-purpose computer, is such a significant challenge in quantum computers that I don’t believe they’ll ever be built at a commercial scale.
