Quantum supremacy: not a Jason Bourne movie

In a development at the edge of scientific advance and journalistic descriptive capabilities, a group of Google researchers say they have achieved the science fiction-sounding feat known as “quantum supremacy.” In a paper published in Nature, members of Google’s AI Quantum team describe their successful efforts to create a computer that capitalizes on the laws of physics most obviously in play at the subatomic realm. That quantum computer, named Sycamore, “performed the target computation in 200 seconds, and from measurements in our experiment we determined that it would take the world’s fastest supercomputer 10,000 years to produce a similar output,” two scientists involved in the experiment—John Martinis, chief scientist quantum hardware, and Sergio Boixo, chief scientist quantum computing theory—wrote on the Google AI Blog.

For those who know some physics and are up for the challenge, the Nature paper is an enticing forest of quantum concepts—from qubits to cross-entropy benchmarking and beyond—that explains precisely how the quantum supremacy experiment was carried out and why it is of inestimable import. If you go the Nature route, you will encounter fascinating sentences such as these:

In a superconducting circuit, conduction electrons condense into a macroscopic quantum state, such that currents and voltages behave quantum mechanically. Our processor uses transmon qubits, which can be thought of as nonlinear superconducting resonators at 5–7 GHz. The qubit is encoded as the two lowest quantum eigenstates of the resonant circuit.

For those who don’t know quantum eigenstates from The Eiger Sanction (and might, therefore, wonder whether quantum supremacy were a new Jason Bourne movie), both the Washington Post and New York Times offer engaging layman’s explanations of the import of the quantum supremacy achievement. I think the Post’s elevator pitch the most elegant of the descriptions I’ve seen:

The achievement has been compared to the Wright brothers’ 12-second first flight at Kitty Hawk—an early, aspirational glimpse at a revolution to come. By providing exponentially greater calculation power than the machines we use today, quantum computers could one day transform the way we communicate ideas, conceal data, and comprehend the universe. The result is also a feather in the cap for both Google and the United States, because quantum technology is expected to confer huge economic and national security advantages to whoever can master it first.

The national security implications of quantum computing are, indeed, hard to precisely specify but potentially enormous. As technology and national security researcher Elsa B. Kania carefully wrote in the Bulletin lasts year, “Today’s [quantum] revolution looks likely to create a range of disruptive quantum technologies that leverage paradoxical principles of quantum mechanics, such as superposition (that is, quantum systems can exist in all possible states at the same time) and entanglement (famously referred to by Einstein as “spooky action at a distance”). The harnessing of these unique properties will allow for unprecedented power, precision, security, and sensitivity in quantum applications across communications, computing, radar, timing, sensing, imaging, metrology, and navigation. These varied and disparate quantum technologies, as they develop, will likely produce a range of important commercial and defense applications that bring both lucrative market opportunities and disruptive military capabilities.”