Computer scientists set benchmarks to optimize quantum computer
performance

Date:
August 14, 2020
Source:
University of California - Los Angeles
Summary:
Computer scientists have shown that existing compilers, which
tell quantum computers how to use their circuits to execute
quantum programs, inhibit the computers' ability to achieve
optimal performance.

Specifically, their research has revealed that improving quantum
compilation design could help achieve computation speeds up to 45
times faster than currently demonstrated.



FULL STORY ==========================================================================
Two UCLA computer scientists have shown that existing compilers,
which tell quantum computers how to use their circuits to execute
quantum programs, inhibit the computers' ability to achieve optimal performance. Specifically, their research has revealed that improving
quantum compilation design could help achieve computation speeds up to
45 times faster than currently demonstrated.


==========================================================================
The computer scientists created a family of benchmark quantum circuits
with known optimal depths or sizes. In computer design, the smaller
the circuit depth, the faster a computation can be completed. Smaller
circuits also imply more computation can be packed into the existing
quantum computer. Quantum computer designers could use these benchmarks
to improve design tools that could then find the best circuit design.

"We believe in the 'measure, then improve' methodology," said lead
researcher Jason Cong, a Distinguished Chancellor's Professor of Computer Science at UCLA Samueli School of Engineering. "Now that we have revealed
the large optimality gap, we are on the way to develop better quantum compilation tools, and we hope the entire quantum research community
will as well." Cong and graduate student Daniel (Bochen) Tan tested
their benchmarks in four of the most used quantum compilation tools. A
study detailing their research was published in IEEE Transactions on
Computers, a peer-reviewed journal.

Tan and Cong have made the benchmarks, named QUEKO, open source and
available on the software repository GitHub.

Quantum computers utilize quantum mechanics to perform a great
deal of computations simultaneously, which has the potential to
make them exponentially faster and more powerful than today's best supercomputers. But many issues need to be addressed before these devices
can move out of the research lab.

For example, due to the sensitive nature of how quantum circuits work,
tiny environmental changes, such as small temperature fluctuations,
can interfere with quantum computation. When that happens, the quantum
circuits are called decoherent -- which is to say they have lost the information once encoded in them.

"If we can consistently halve the circuit depth by better layout
synthesis, we effectively double the time it takes for a quantum device
to become decoherent," Cong said.

"This compilation research could effectively extend that time, and
it would be the equivalent to a huge advancement in experimental
physics and electrical engineering," Cong added. "So we expect these
benchmarks to motivate both academia and the industry to develop
better layout synthesis tools, which in turn will help drive advances
in quantum computing." Cong and his colleagues led a similar effort
in the early 2000s to optimize integrated circuit design in classical computers. That research effectively pushed two generations of advances
in computer processing speeds, using only optimized layout design,
which shortened the distance between the transistors that comprise the
circuit. This cost-efficient improvement was achieved without any other
major investments in technological advances, such as physically shrinking
the circuits themselves.

"Quantum processors in existence today are extremely limited by
environmental interference, which puts severe restrictions on the length
of computations that can be performed," said Mark Gyure, executive
director of the UCLA Center for Quantum Science and Engineering,
who was not involved in this study. "That's why the recent research
results from Professor Cong's group are so important because they have
shown that most implementations of quantum circuits to date are likely extremely inefficient and more optimally compiled circuits could enable
much longer algorithms to be executed. This could result in today's
processors solving much more interesting problems than previously thought.

That's an extremely important advance for the field and incredibly
exciting."

========================================================================== Story Source: Materials provided by
University_of_California_-_Los_Angeles. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Bochen Tan, Jason Cong. Optimality Study of Existing Quantum
Computing
Layout Synthesis Tools. IEEE Transactions on Computers, 2020;
1 DOI: 10.1109/TC.2020.3009140 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200814163311.htm

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