A team of experts working on Google’s Sycamore processor claim in a paper published Wednesday that they have managed to demonstrate “quantum supremacy” by accomplishing in less than four minutes a task that would have taken a classical supercomputer 10,000 years to complete.
In a paper published in the science journal Nature titled “Quantum supremacy using a programmable superconducting processor,” Google’s team of experts say they have just demonstrated “an experimental realization of quantum supremacy.”
“The promise of quantum computers is that certain computational tasks might be executed exponentially faster on a quantum processor than on a classical processor. A fundamental challenge is to build a high-fidelity processor capable of running quantum algorithms in an exponentially large computational space,” the abstract of the report reads.
In their experiment, they constructed a quantum processer consisting of 54 qubits, fragments of data that can be both 1 and 0 at the same time, as opposed to binary bits. Google’s team then used the processor to carry out a task related to the generation of random numbers that they calculate would have taken a classical supercomputer 10,000 years. Their quantum processor did it in 200 seconds.
“Our Sycamore processor takes about 200 seconds to sample one instance of a quantum circuit a million times — our benchmarks currently indicate that the equivalent task for a state-of-the-art classical supercomputer would take approximately 10,000 years,” the abstract reads. “This dramatic increase in speed compared to all known classical algorithms is an experimental realization of quantum supremacy for this specific computational task, heralding a much-anticipated computing paradigm.”
Google CEO Sundar Pichai took to Twitter Wednesday to celebrate the “big breakthrough,” while Google released a video highlighting the significance of their team’s “research milestone.”
Quantum computers have the potential to solve problems that would be too difficult for classical computers. Today we’re marking a research milestone that opens up new possibilities for this technology. Learn more about this achievement → https://t.co/aAw6GPtweB pic.twitter.com/Jnyg3fFIvC
— Google (@Google) October 23, 2019
AFP notes that while Google is celebrating, a rival team of scientists working for IBM “has already expressed skepticism about their claim.” With the right traditional computers, the IBM said in a blogpost, the calculation could have been performed in just a few days rather than “10,000.” They also argue that declaring “quantum supremacy” is misleading.
“Recent advances in quantum computing have resulted in two 53-qubit processors: one from our group in IBM and a device described in the leaked preprint from Google,” they write. “In the preprint, it is argued that their device reached ‘quantum supremacy’ and that ‘a state-of-the-art supercomputer would require approximately 10,000 years to perform the equivalent task’. We argue that an ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity. This is in fact a conservative, worst-case estimate, and we expect that with additional refinements the classical cost of the simulation can be further reduced.”
“Because the original meaning of the term quantum supremacy, as proposed by John Preskill in 2012, was to describe the point where quantum computers can do things that classical computers can’t, this threshold has not been met,” they state.
Below is an excerpt from Google’s report providing some context for their potentially game-changing experiment (formatting adjusted, footnotes removed):
In the early 1980s, Richard Feynman proposed that a quantum computer would be an effective tool with which to solve problems in physics and chemistry, given that it is exponentially costly to simulate large quantum systems with classical computers. Realizing Feynman’s vision poses substantial experimental and theoretical challenges. First, can a quantum system be engineered to perform a computation in a large enough computational (Hilbert) space and with a low enough error rate to provide a quantum speedup? Second, can we formulate a problem that is hard for a classical computer but easy for a quantum computer? By computing such a benchmark task on our superconducting qubit processor, we tackle both questions. Our experiment achieves quantum supremacy, a milestone on the path to full-scale quantum computing.
In reaching this milestone, we show that quantum speedup is achievable in a real-world system and is not precluded by any hidden physical laws. Quantum supremacy also heralds the era of noisy intermediate-scale quantum (NISQ) technologies. The benchmark task we demonstrate has an immediate application in generating certifiable random numbers (S. Aaronson, manuscript in preparation); other initial uses for this new computational capability may include optimization, machine learning, materials science and chemistry. However, realizing the full promise of quantum computing (using Shor’s algorithm for factoring, for example) still requires technical leaps to engineer fault-tolerant logical qubits.
To achieve quantum supremacy, we made a number of technical advances which also pave the way towards error correction. We developed fast, high-fidelity gates that can be executed simultaneously across a two-dimensional qubit array. We calibrated and benchmarked the processor at both the component and system level using a powerful new tool: cross-entropy benchmarking. Finally, we used component-level fidelities to accurately predict the performance of the whole system, further showing that quantum information behaves as expected when scaling to large systems.