Photo: An
artist's interpretation of ghost imaging. In this research technique,
scientists split an x-ray beam (represented by the thick pink line) into two
streams of entangled photons (thinner pink lines). Only one of these streams of
photons passes through the scientific sample (represented by the clear circle),
but both gather information. By splitting the beam, the sample being studied is
only exposed to a fraction of the x-ray dose.
Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National
Laboratory have begun building a quantum-enhanced x-ray microscope at the
National Synchrotron Light Source II (NSLS-II). This groundbreaking microscope,
supported by the Biological and Environmental Research progam at DOE’s Office
of Science, will enable researchers to image biomolecules like never before.
NSLS-II is
a DOE Office of Science User Facility where researchers use powerful x-rays to
“see†the structural, chemical, and electronic makeup of materials down to the
atomic scale. The facility’s ultrabright light already enables discoveries in
biology, helping researchers uncover the structures of proteins to inform drug
design for a variety of diseases—to name just one example.
Now, by
tapping into the quantum properties of x-rays, researchers at NSLS-II will be
able to image more sensitive biomolecules without sacrificing resolution. While
the high penetration power of x-rays enables superior resolution for imaging
studies, this powerful light can also damage certain biological samples, such
as plant cells, viruses, and bacteria. Low-dose x-ray studies can preserve
these samples, but the imaging resolution is reduced.
“If we are
successful in building a quantum-enhanced x-ray microscope, we will be able to
image biomolecules with very high resolution and a very low dose of x-rays,â€
said Sean McSweeney, manager of the structural biology program at NSLS-II.
The quantum-enhanced x-ray microscope at NSLS-II will achieve this remarkable combination of capabilities through an experimental technique called ghost imaging. Compared to typical x-ray imaging techniques, which send a single beam of photons (particles of light) through a sample and onto a detector, ghost imaging requires the x-ray beam be split into two streams of entangled photons—only one of which passes through the sample, but both gather information.
The
Coherent Hard X-ray Scattering (CHX) beamline at the National Synchrotron Light
Source II.
“One
stream goes through the sample and is collected by a detector that records the
photons with good time resolution, while the other stream of photons encodes
the exact direction in which the photons propagate,†said Andrei Fluerasu, lead
beamline scientist at NSLS-II’s Coherent Hard X-ray Scattering (CHX) beamline,
where the microscope will be developed. “It sounds like magic. But with
mathematical calculations, we’ll be able to correlate the information from the
two beams.â€
By
splitting the beam, the sample being studied is only exposed to a fraction of
the x-ray dose. And since the photons that do not pass through the sample are
correlated with the photons that do, the resolution of a full-dose x-ray beam
is maintained.
Ghost
imaging techniques have already been successfully developed using photons of
visible light, but translating this technique to x-ray light will be a major
scientific achievement.
The
quantum-enhanced x-ray microscope at Brookhaven Lab is being developed at
NSLS-II’s CHX beamline, which was chosen for its ability to manipulate the
coherence of the x-ray source, enabling scientists to tune the ghost imaging
experiments as needed. CHX’s existing setup was also flexible enough to
accommodate the addition of new and advanced equipment, such as a beam splitter
and a new detector. NSLS-II will collaborate with physicists at Brookhaven Lab
and Stony Brook University on the integration of these complex instruments.
“These
measurements will require imaging detectors with the best possible timing
resolution,†said Brookhaven physicist Andrei Nomerotski, “and this is
something we are already using for high energy physics experiments, quantum
information science projects like quantum astrometry, and fast optical
imaging.â€
The
quantum-enhanced x-ray microscope project team will also collaborate with
Brookhaven’s Computational Science Initiative (CSI) on data analysis. The Lab’s
biology department is partnering with NSLS-II to design experiments that
exploit the advanced capabilities of this microscope.
“Our
Biology colleagues at Brookhaven are excited to bring us complex problems to
solve using this new instrument,†McSweeney said. “With involvement from
Physics, Biology, and CSI, we have put an excellent team together for this
groundbreaking project.â€
“The
strong working relationship between Biology and NSLS-II scientists brings
together real-world scientific problems and advanced capabilities, delivering
cutting-edge solutions for problems relative to the DOE mission,†said John
Shanklin, Chair of the Lab’s biology department. “It’s a win-win situation.â€
The
team plans to gradually integrate new functionalities into the CHX beamline
over the next two to three years. The project will be complete upon
demonstrating ghost imaging of micron-sized objects with resolution below 10
nanometers, which is targeted for 2023.