Bristol team chase down advantage in quantum race
Claimed speedups from optical quantum computers take a big hit

Date:
January 26, 2022
Source:
University of Bristol
Summary:
Quantum researchers have dramatically reduced the time to simulate
an optical quantum computer, with a speedup of around one billion
over previous approaches.



FULL STORY ========================================================================== Quantum researchers at the University of Bristol have dramatically
reduced the time to simulate an optical quantum computer, with a speedup
of around one billion over previous approaches.


========================================================================== Quantum computers promise exponential speedups for certain problems,
with potential applications in areas from drug discovery to new materials
for batteries. But quantum computing is still in its early stages, so
these are long-term goals. Nevertheless, there are exciting intermediate milestones on the journey to building a useful device. One currently
receiving a lot of attention is "quantum advantage," where a quantum
computer performs a task beyond the capabilities of even the world's
most powerful supercomputers.

Experimental work from the University of Science and Technology of China
(USTC) was the first to claim quantum advantage using photons -- particles
of light, in a protocol called "Gaussian Boson Sampling" (GBS). Their
paper claimed that the experiment, performed in 200 seconds, would take
600 million years to simulate on the world's largest supercomputer.

Taking up the challenge, a team at the University of Bristol's Quantum Engineering Technology Labs (QET Labs), in collaboration with researchers
at Imperial College London and Hewlett Packard Enterprise, have reduced
this simulation time down to just a few months, a speedup factor of
around one billion.

Their paper "The boundary for quantum advantage in Gaussian boson
sampling," published today in the journal Science Advances, comes at
a time when other experimental approaches claiming quantum advantage,
such as from the quantum computing team at Google, are also leading to
improved classical algorithms for simulating these experiments.

Joint first author Jake Bulmer, PhD student in QET Labs, said: "There
is an exciting race going on where, on one side, researchers are trying
to build increasingly complex quantum computing systems which they
claim cannot be simulated by conventional computers. At the same time, researchers like us are improving simulation methods so we cansimulate
these supposedly impossible to simulate machines!" "As researchers
develop larger scale experiments, they will look to make claims of quantum advantage relative to classical simulations. Our results will provide an essential point of comparison by which to establish the computational
power of future GBS experiments," said joint first author, Bryn Bell,
Marie Curie Research Fellow at Imperial College London, now Senior
Quantum Engineer at Oxford Quantum Circuits.

The team's methods do not exploit any errors in the experiment and so one
next step for the research is to combine their new methods with techniques
that exploit the imperfections of the real-world experiment. This would
further speed up simulation time and build a greater understanding of
which areas require improvements.

"These quantum advantage experiments represent a tremendous achievement
of physics and engineering. As a researcher, it is exciting to
contribute to the understanding of where the computational complexity
of these experiments arises. We were surprised by the magnitude of the improvements we achieved - - it is not often that you can claim to find
a one-billion-fold improvement!" said Jake Bulmer.

Anthony Laing, co-Director of QET Labs and an author on the
work, said: "As we develop more sophisticated quantum computing
technologies, this type of work is vital. It helps us understand
the bar we must get over before we can begin to solve problems in
clean energy and healthcare that affect us all. The work is a great
example of teamwork and collaboration among researchers in the UK
Quantum Computing and Simulation Hub and Hewlett Packard Enterprise." ========================================================================== Story Source: Materials provided by University_of_Bristol. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Jacob F. F. Bulmer, Bryn A. Bell, Rachel S. Chadwick, Alex E. Jones,
Diana Moise, Alessandro Rigazzi, Jan Thorbecke, Utz-Uwe Haus, Thomas
Van Vaerenbergh, Raj B. Patel, Ian A. Walmsley, Anthony Laing. The
boundary for quantum advantage in Gaussian boson sampling. Science
Advances, 2022; 8 (4) DOI: 10.1126/sciadv.abl9236 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220126143957.htm

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