Quantum
computing—considered the powerhouse of computational tasks—may have
applications in areas outside of pure electronics, according to a
University of Pittsburgh researcher and his collaborators.
Working
at the interface of quantum measurement and nanotechnology, Gurudev
Dutt, assistant professor in Pitt’s Department of Physics and Astronomy
in the Kenneth P. Dietrich School of Arts and Sciences, and his
colleagues report their findings in a paper published online Dec. 18 in Nature Nanotechnology.
The paper documents important progress towards realizing a nanoscale
magnetic imager comprising single electrons encased in a diamond
crystal.
“Think
of this like a typical medical procedure—a Magnetic Resonance Imaging
(MRI)—but on single molecules or groups of molecules inside cells
instead of the entire body. Traditional MRI techniques don’t work well
with such small volumes, so an instrument must be built to accommodate
such high-precision work,” says Dutt.
However,
a significant challenge arose for researchers working on the problem of
building such an instrument: How does one measure a magnetic field
accurately using the resonance of the single electrons within the
diamond crystal? Resonance is defined as an object’s tendency to
oscillate with higher energy at a particular frequency, and occurs
naturally all around us: for example, with musical instruments, children
on swings, and pendulum clocks. Dutt says that resonances are
particularly powerful because they allow physicists to make sensitive
measurements of quantities like force, mass, and electric and magnetic
fields. “But they also restrict the maximum field that one can measure
accurately.”
In
magnetic imaging, this means that physicists can only detect a narrow
range of fields from molecules near the sensor’s resonant frequency,
making the imaging process more difficult.
“It
can be done,” says Dutt, “but it requires very sophisticated image
processing and other techniques to understand what one is imaging.
Essentially, one must use software to fix the limitations of hardware,
and the scans take longer and are harder to interpret.”
Dutt—working
with postdoctoral researcher Ummal Momeen and PhD student Naufer Nusran
(A&S’08 G), both in Pitt’s Department of Physics and Astronomy—has
used quantum computing methods to circumvent the hardware limitation to
view the entire magnetic field. By extending the field, the Pitt
researchers have improved the ratio between maximum detectable field
strength and field precision by a factor of 10 compared to the standard
technique used previously. This puts them one step closer toward a
future nanoscale MRI instrument that could study properties of
molecules, materials, and cells in a noninvasive way, displaying where
atoms are located without destroying them; current methods employed for
this kind of study inevitably destroy the samples.
“This
would have an immediate impact on our understanding of these molecules,
materials, or living cells and potentially allow us to create better
technologies,” says Dutt.
These
are only the initial results, says Dutt, and he expects further
improvements to be made with additional research: “Our work shows that
quantum computing methods reach beyond pure electronic technologies and
can solve problems that, earlier, seemed to be fundamental roadblocks to
making progress with high-precision measurements.”
High-dynamic-range magnetometry with a single electronic spin in diamond
