You are no doubt viewing this article on a digital device whose basic unit
of information is the bit, either 0 or 1. Scientists worldwide are racing to
develop a new kind of computer based on the use of quantum bits, or qubits,
which can simultaneously be 0 and 1 and could one day solve complex problems
beyond any classical supercomputers.
A team led by researchers at the U.S. Department of Energy's (DOE) Argonne
National Laboratory, in close collaboration with FAMU-FSU College of
Engineering Associate Professor of Mechanical Engineering Wei Guo, has
announced the creation of a new qubit platform that shows great promise to
be developed into future quantum computers. Their work is published in
Nature.
"Quantum computers could be a revolutionary tool for performing calculations
that are practically impossible for classical computers, but there is still
work to do to make them reality," said Guo, a paper co-author. "With this
research, we think we have a breakthrough that goes a long way toward making
qubits that help realize this technology's potential."
The team created its qubit by freezing neon gas into a solid at very low
temperatures, spraying electrons from a light bulb onto the solid and
trapping a single electron there.
While there are many choices of qubit types, the team chose the simplest
one—a single electron. Heating up a simple light filament such as you might
find in a child's toy can easily shoot out a boundless supply of electrons.
One important quality for qubits is their ability to remain in a
simultaneous 0 or 1 state for a long time, known as its "coherence time."
That time is limited, and the limit is determined by the way qubits interact
with their environment. Defects in the qubit system can significantly reduce
the coherence time.
For that reason, the team chose to trap an electron on an ultrapure solid
neon surface in a vacuum. Neon is one of only six inert elements, meaning it
does not react with other elements.
"Because of this inertness, solid neon can serve as the cleanest possible
solid in a vacuum to host and protect any qubits from being disrupted," said
Dafei Jin, an Argonne scientist and the principal investigator of the
project.
By using a chip-scale superconducting resonator—like a miniature microwave
oven—the team was able to manipulate the trapped electrons, allowing them to
read and store information from the qubit, thus making it useful for use in
future quantum computers.
Previous research used liquid helium as the medium for holding electrons.
That material was easy to make free of defects, but vibrations of the
liquid-free surface could easily disturb the electron state and hence
compromise the performance of the qubit.
Solid neon offers a material with few defects that doesn't vibrate like
liquid helium. After building their platform, the team performed real-time
qubit operations using microwave photons on a trapped electron and
characterized its quantum properties. These tests demonstrated that solid
neon provided a robust environment for the electron with very low electric
noise to disturb it. Most importantly, the qubit attained coherence times in
the quantum state competitive with other state-of-the-art qubits.
The simplicity of the qubit platform should also lend itself to simple,
low-cost manufacturing, Jin said.
The promise of quantum computing lies in the ability of this next-generation
technology to calculate certain problems much faster than classical
computers. Researchers aim to combine long coherence times with the ability
of multiple qubits to link together—known as entanglement. Quantum computers
thereby could find the answers to problems that would take a classical
computer many years to resolve.
Consider a problem where researchers want to find the lowest energy
configuration of a protein made of many amino acids. These amino acids can
fold in trillions of ways that no classical computer has the memory to
handle. With quantum computing, one can use entangled qubits to create a
superposition of all folding configurations—providing the ability to check
all possible answers at the same time and solve the problem more
efficiently.
"Researchers would just need to do one calculation, instead of trying
trillions of possible configurations," Guo said.
Reference:
Dafei Jin, Single electrons on solid neon as a solid-state qubit platform,
Nature (2022).
DOI: 10.1038/s41586-022-04539-x.