IBM announced today at the 2019 American Physical Society March Meeting that they had reached a significant new level of performance for their 20-qubit integrated quantum computing system, the IBM Q System One.
Defining IBM Q System One's Performance Using Quantum Volume
IBM Q System One has doubled the 20-qubit performance over IBM’s earlier IBM Q Network 20-qubit system, using a measure that IBM proposed last November [PDF] as a means of measuring disparate quantum computing systems, which they call Quantum Volume (QV).
“A variety of factors determine Quantum Volume,” IBM says, “including the number of qubits, connectivity, and coherence time, plus accounting for gate and measurement errors, device cross talk, and circuit software compiler efficiency.”
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By this specific measure, IBM Q System One scored a QV of 16, whereas IBM Q Network scores a QV of 8. According to IBM, “the higher the Quantum Volume, the more real-world, complex problems quantum computers can potentially solve, such as simulating chemistry, modeling financial risk, and supply chain optimization.”
IBM’s newest quantum computer achieved this QV in part due to “some of the lowest error rates IBM has ever measured, with an average 2-qubit gate error less than 2 percent, and its best gate achieving less than 1 percent error rate,” the company reports.
Qubits are fragile things and they can be knocked out of their superposition at the slightest disturbance, something known as decoherence. Since you cannot look at the qubit itself, identifying these errors and correcting them is a challenge.
Creating a quantum computer with extremely low error rates is essential to making a quantum computer that is practical and reliable enough to trust with important data.
Pursuing Quantum Advantage Through Moore's Law
IBM intends QV to be a performance metric that the industry can use as they attempt to reach what IBM calls Quantum Advantage, that threshold where quantum computing applications can perform significant, useful tasks that classical computing applications cannot.
IBM hopes to achieve quantum advantage within the next decade and it believes that they have found a new application for Moore’s Law, now that Moore’s Law is dead as far as silicon transistors go.
Gordon Moore, the co-founder of Intel, proposed in 1965 that the number of transistors on a silicon chip would double every year, later revising it to every two years.
This is exactly what happened since 1965, but now computer chip manufacturers have announced that it is physically impossible to make transistors any smaller than they currently are—which is only a few atoms wide.
IBM says that it’s seeing the same kind of doubling of performance every year in their quantum computers and they propose that their QV will more or less follow Moore’s Law as well.
This remains to be seen, but IBM is banking on this being the case and is using it as a “roadmap” to achieving quantum advantage sometime in the 2020s.