built, would be 100 times faster, largely
due to increased parallelism in measuring the error syndromes. Overall,
coordinated changes of physical technology, error correction mechanism,
and architecture may gain 3–4 orders
of magnitude in performance, demonstrating the impact of the field of quantum computer architecture.
A principal lesson learned so far in research on quantum computer architectures is that systems capable of solving classically intractable problems
will be large, although the search for
the smallest commercially attractive
machine continues. Device sizes will
limit integration levels, affecting architecture, and determining logical clock
speed requires making many design
decisions but dramatically affects what
can and cannot be effectively computed (as shown in Figure 1). Architectural
problems cover a broad range, but have
received only modest amounts of attention compared to near-term experimental hurdles, leaving much room
for high-impact research that can help
guide the focus of experimental work.
To sharpen the community focus on
building systems, it seems to be time
to begin demanding Moore’s Law-like
improvements in system capacity. Reviewers of papers and funding proposals should look for realistic estimates
of logical Toffoli gate time, incorporating error correction, for some target
logical fidelity. Even more ambitiously,
we recommend requiring realistic estimates of application performance.
Developing a sense of community is
critical. Creating a shared understanding including vocabulary, concepts, and
important problems among the physics
and CS theory, algorithm design, physics experiment, engineering, and architecture communities has proven to
be difficult, and few journals or conferences currently provide good venues for
such interdisciplinary endeavors, but
we expect the number will grow.
Let us close with a question that pro-
vokes answers ranging from, “Already
has,” (in reference to direct quantum
simulation of a specific quantum sys-
tem20) to “Twenty years,” to “Never,”—
and all these from people actually
working in the field:
When will the first paper appear in
Science or Nature in which the point is
the results of a quantum computation,
rather than the machine itself? That is,
when will a quantum computer do science, rather than be science?
This research is supported by the Cabinet Office, Government of Japan, and
the Japan Society for the Promotion
of Science (JSPS) through the Funding
Program for World-Leading Innovative R&D on Science and Technology
(FIRST Program). We thank Simon Devitt, Dave Farber, Joe Touch, Michio
Honda, Hajime Tazaki, Shigeya Suzuki, the referees and editors for careful
reading of the manuscript.
additional information and references for this article are
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Rodney Van Meter ( firstname.lastname@example.org) is an associate
professor in the Faculty of environment and Information
studies at keio university’s shonan Fujisawa Campus,
kanagawa Prefecture, Japan.
Clare horsman ( email@example.com) was a
project assistant professor at keio university’s sFC. she is
currently a research assistant at the university of oxford’s
Department of Cs, oxford, u.k.
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