In a world where the word “supremacy” has negative political connotations (does “white supremacy” ring a bell?), John Preskill, a professor of theoretical physics at the California Institute of Technology, couldn’t find a more accurate term to describe the advantages of Quantum Physics over its classical counterpart, which is why he coined the term “quantum supremacy” in his paper back in 2012.

“Supremacy” amplifies the already overhyped advancements in quantum technology, but Google’s AI Quantum team embraced the term when they conducted a successful experiment to show how quantum computers can outperform the world’s best classical supercomputers. The groundbreaking experiment involved performing calculations on a quantum computer in just three minutes and twenty seconds; calculations that would have taken “Summit” (currently the world’s most advanced supercomputer) around 10,000 years.

Quantum computers harness their power from “qubits” – quantum bits. While classical bits exist as 0’s or 1’s, qubits can exist in both states simultaneously. Thanks to this and other quantum phenomena, quantum computers can process multiple data sets at the same time, which conventional machines can only manage sequentially.

Even though the performance of quantum computers sounds extremely promising, the Google team admits that the problem their machine solved with astounding speed was carefully chosen just for the purpose of demonstrating the quantum computer’s superiority. It is not otherwise a problem of much practical interest. Dario Gil of IBM (also working on quantum computers), says the experiment doesn’t mean the machines will be superior. “In fact, quantum computers will never reign ‘supreme’ over classical ones,” says Gil, “but will work in concert with them, since each have their specific strengths.” For many problems, classical computers will remain the best tool to use – at least for now.

Phenomena such as Heisenberg’s uncertainty principle imply that merely looking at a quantum system could disturb it. We’d want the qubits to interact with one another so we can process the information; we also need to control the system from the outside and eventually measure the qubits to learn the results of our computations, but small errors caused by observing the system would eventually lead to incorrect results.

Despite that we still have decades of work to do before we can claim expertise in quantum technology, Google hopes to find practical applications for their quantum devices. A much larger quantum computer might help researchers design new materials and chemical compounds or build better tools for machine learning, but a noisy quantum computer with a few hundred qubits might not be capable of anything useful. Then again, Google’s experiment proves that quantum computation isn’t as far-fetched as one might think.

References

https://www.quantamagazine.org/john-preskill-explains-quantum-supremacy-20191002/
https://www.technologyreview.com/2019/09/20/132923/google-researchers-have-reportedly-achieved-quantum-supremacy/
https://www.technologyreview.com/2019/10/23/102523/google-ceo-quantum-supremacy-interview-with-sundar-pichai/

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