Aerospace & Defense Technology - May 2024 - 28

Tech Briefs
NRL Scientists Deliver Quantum Algorithm to Develop New
Materials and Chemistry
U.S. Naval Research Laboratory scientists unveil the Cascaded Variational Quantum Eigensolver
(CVQE) algorithm expected to become a powerful tool to investigate the physical properties in electronic
systems for disruptive defense technologies.
U.S. Naval Research Laboratory, Washington D.C.
U
.S. Naval Research Laboratory (NRL)
scientists published the Cascaded Variational
Quantum Eigensolver (CVQE)
algorithm in a recent Physical Review
Research article, expected to become a
powerful tool to investigate the physical
properties in electronic systems.
The CVQE algorithm is a variant of the
Variational Quantum Eigensolver (VQE)
algorithm that only requires the execution
of a set of quantum circuits once rather
than at every iteration during the parameter
optimization process, thereby increasing
the computational throughput.
" Both algorithms produce a quantum
state close to the ground state of a system,
which is used to determine many of the
system's physical properties, " said John
Stenger, Ph.D., a Theoretical Chemistry
Section research physicist. " Calculations
that previously took months can now be
performed in hours. "
The CVQE algorithm uses a quantum
computer to probe the needed probability
mass functions and a classical computer to
perform the remaining calculations,
including the energy minimization.
" Finding the minimum energy is computationally
hard as the size of the state
space grows exponentially with the system
size, " said Steve Hellberg, Ph.D., a Theory of
Advanced Functional Materials Section
Research Physicist. " Except for very small
systems, even the world's most powerful
supercomputers are unable to find the
exact ground state. "
To address this challenge, scientists use a
quantum computer with a qubit register,
whose state space also increases exponentially,
in this case with qubits. By representing
the states of a physical system on the
state space of the register, a quantum computer
can be used to simulate the states in
the exponentially large representation
space of the system.
Data can subsequently be extracted by
quantum measurements. As quantum
28
NRL researchers have developed the Cascaded Variational Quantum Eigensolver (CVQE) algorithm expected
to become a powerful tool to investigate the physical properties in electronic systems featured in
ships and other naval assets, platforms and technologies. (Image: NRL)
measurements are not deterministic, the
quantum circuit executions must be
repeated multiple times to estimate
probability distributions describing the
states, a process known as sampling.
Variational quantum algorithms, including
the CVQE algorithm, identify trial
states by a set of parameters that are optimized
to minimize the energy.
" The key difference between the original
VQE method and the new CVQE
method is that the sampling and optimization
processes have been decoupled in
the latter such that the sampling can be
performed exclusively on the quantum
computer and the parameters processed
exclusively on a classical computer, " said
Dan Gunlycke, D.Phil., Theoretical
Chemistry Section Head, who also leads
the NRL quantum computing effort.
" The new approach also has other benefits.
The form of the solution space does
not have to comport with the symmetry
requirements of the qubit register, and
therefore, it is much easier to shape the
solution space and implement symmetries
of the system and other physically
motivated constraints, which will ultimobilityengineeringtech.com
mately
lead to more accurate predictions
of electronic system properties. "
Quantum computing is a component of
quantum science, which has been designated
as a Critical Technology Area by the
Under Secretary of Defense for Research
and Engineering, Heidi Shyu.
" Understanding the properties of quantum-mechanical
systems is essential in the
development of new materials and chemistry
for the Navy and Marine Corps, " Gunlycke
said. " Corrosion, for instance, is an
omnipresent challenge costing the Department
of Defense billions every year. The
CVQE algorithm can be used to study the
chemical reactions causing corrosion and
provide critical information to our existing
anticorrosion teams in their quest to develop
better coatings and additives. "
This research was performed by John
Stenger, Ph.D., a Theoretical Chemistry
Section Research Physicist, for the Naval
Research Laboratory (Washington D.C.).
For more information, download the
Technical Support Package (free white
paper) at mobilityengineeringtech.
com/tsp under the Materials category.
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