A leaked paper suggests that
Google has achieved a milestone known as quantum supremacy, using a quantum computer to perform a calculation
that couldn’t be achieved even with the world’s most powerful supercomputers.
It’s a hotly anticipated goal,
and one intended to mark the beginning of a new
era of quantum computation (SN:
6/29/17). But it’s also largely symbolic: The calculation in question serves
no practical purpose and is designed to be difficult for classical computers,
standard computers that are not rooted in quantum physics.
On September 20, the Financial Times reported
that a scientific paper, briefly published on a NASA website before being
removed, claims that Google has built a quantum computer that achieved quantum
supremacy. It’s a benchmark that the company’s quantum researchers, led by
physicist John Martinis of the University of California, Santa Barbara, have set
their sights on for years (SN:
3/5/18). An apparent plain-text version of the paper,
posted anonymously on the site Pastebin, has since been circulating among
scientists and on Twitter. A spokesperson for Google declined to comment to Science News.
According to the Pastebin version
of the paper, Google created a quantum computer named Sycamore with 54 quantum
bits called qubits, 53 of which were functional. The researchers used it to
perform a series of operations in 200 seconds that would take a supercomputer about
10,000 years to complete.
The calculation consists of
performing random operations on the qubits and reading out the result. After
doing this many times, the researchers are left with a nearly random assortment
of numbers, one that is extremely difficult to reproduce with a classical
Despite its lack of
applications, quantum supremacy has been billed as a major breakthrough in the
quest for a quantum computer that could eventually perform useful calculations
that are not possible with classical computers. “This dramatic speedup relative
to all known classical algorithms provides an experimental realization of
quantum supremacy on a computational task and heralds the advent of a much-anticipated
computing paradigm,” the text of the Pastebin paper reads.
The machines might
eventually be capable of defeating encryption techniques used to secure certain
transmissions, such as financial transactions made by computers. But that
advance will require many more qubits and a method to correct the errors that
inevitably creep into quantum calculations. “While this is a milestone, it is
*very* far from being a quantum computer that can compute anything useful,”
physicist Jonathan Oppenheim of University College London wrote on Twitter.
Not everyone agrees that
quantum supremacy is a useful benchmark. “Quantum computers are not ‘supreme’
against classical computers because of a laboratory experiment designed to
essentially (and almost certainly exclusively) implement one very specific
quantum sampling procedure with no practical applications,” IBM’s director of
research Dario Gil wrote in a statement sent to Science News.
IBM is developing
their own line of quantum computers (SN: 11/10/17), and researchers there prefer to talk about “quantum
advantage,” which they define as “the point at which quantum
applications deliver a significant, practical benefit beyond what classical
computers alone are capable.” The new result falls short of that standard.
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