I M A G E C O U R T E S Y O F D - W A V E

more than 400 per year in 2016–2017. The U.S. leads with approximately 800 total patents, three to four times the numbers from Japan and China. The company with the largest portfolio is D-Wave, followed by IBM (which started research in 1990) and then Microsoft. IBM leads in annual patent filings. At universities, the leaders in patent applications are MIT, Harvard, Zhejiang (China), Yale, and Tsinghua (China). 2

What are some applications where quantum computers should excel? Experts list mathematical problems that require massive parallel computations such as in optimization and simulation, cryptography and secure communications, pattern matching and big-data analysis, and artificial intelligence and machine learning.

D-Wave computers seem to generate “good enough” solutions to complex combinatorial optimization problems with many potential solutions. For example, in 2012, Harvard researchers

How many different ways are there to
build quantum computers? There are
several competing technologies. D-
Wave was founded in 1999 to accumu-
late patent rights in exchange for re-
search grants. 17 It has been funded
mainly by venture capital, corporate
investors such as Goldman Sachs, and
more recently, Jeff Bezos and the CIA. 13
The company has focused on “adiabat-
ic quantum computing,” also known
as “quantum annealing.” D-Wave used
this approach to build a 28-qubit de-
vice in 2007 and has been marketing a
2,000-qubit device since 2017. Each
D-Wave qubit is a separate lattice con-
tained within a magnetic field of Jo-
sephson Junctions (logic circuits made
of superconductor materials that ex-
ploit quantum tunneling effects) and
couplers (which link the circuits and
pass information). You program the
device by loading mathematical equa-
tions into the lattices. The processor
then explores all possible solutions si-
multaneously, rather than one at a
time. The answer that requires the low-
est energy represents the optimal solu-
tion. 10 However, some critics note that
D-Wave qubits do not all seem to work
together or exhibit quantum entangle-
ment, and may not operate faster than
conventional computers. 4

Google and IBM, as well as startups such as Quantum Circuits and Righet-ti Computing, deploy a different logic-gate approach, using entangled electrons or nuclei. 19 Xanadu, a Toronto startup, uses photons.b Microsoft’s design relies on quasi-particles called anyons. Arranged into “topological qubits,” these resemble braided knots on a string, with (theoretically) high levels of stability and coherence. Microsoft plans to build a device within five years and make it commercially available via the cloud. 1, 16

Who leads in the patent race? Pat-ent-related publications have increased from a handful in the 1990s to b https://bit.ly/2B04tP1

The D-Wave 2000Q chip, designed to run quantum computing problems, increases from 1,000 qubits to 2,000 qubits, allowing larger problems to be run—increasing the number of qubits yields an exponential increase in the size of the feasible search space.