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Quantum Sensors


The Quantum Sensors Project develops sensors based on quantum phenomena for spectroscopy, imaging, and other precision measurements for wavelengths from dc through gamma rays. We integrate these sensors with custom superconducting and room temperature electronics, cryogenic structures, and software to create complete measurement systems. We work with collaborators in industry, academia, and other government agencies to apply this measurement capability to applications including materials analysis, particle physics, nuclear nonproliferation and forensics, astronomy, cosmology, and homeland defense.


The Quantum Sensors Project is a world leader in developing new detector systems. We have developed transition edge sensors (TES) for use in a variety of applications. These devices utilize a strip of superconducting material, biased in its transition from normal to superconducting states, as an extremely sensitive thermometer. This thermometer is attached to an absorber that is isolated from a cold (~100 mK) heat sink by a micromachined structure. The heat deposited by incident photons is then measured to accurately determine their energy. These TES detectors and superconducting quantum interference device (SQUID) readout circuits are designed, fabricated, and implemented for use by a variety of different scientific and technical communities.

One example is the development of gamma-ray and alpha particle detectors based on TES technology that have more than 10 times better energy resolution than conventional detectors. These detectors can resolve more lines in the complicated gamma-ray spectra of nuclear materials such as uranium and plutonium isotopic mixtures. The gamma-ray devices are being developed specifically to help in the verification of international nonproliferation treaties, by determining the plutonium content of spent nuclear fuel. The alpha particle devices have similarly impressive performance and have demonstrated the ability to analyze mixed-actinide samples. These detectors are being developed for use in nuclear forensics. Prototypes of both systems have been delivered to our collaborators at Los Alamos National Laboratory.

In the infrared regime, our TES bolometers have achieved world-record sensitivity. This impressive result confirms the utility of TES technology for this application as well. We are actively collaborating with many groups and are providing either detectors or superconducting readout and multiplexing circuits to many infrared and sub-millimeter instruments. Most recently, our detector efforts are focused on developing new polarization sensitive bolometers for Cosmic Microwave Background measurements.

Major Accomplishments:

Development of superconducting x-ray sensor technology and its dissemination to U.S. synchrotron light sources. Synchrotrons are large facilities that provide x-ray beams of unmatched brightness and quality. As a result, they are heavily used by industrial and academic researchers to understand and develop advanced materials such as next-generation battery components. The Quantum Sensors Group has developed superconducting x-ray sensors that can provide a unique combination of spectral resolution, broad-band response, and collecting efficiency (see below Figure). In order to disseminate these sensors to users at U.S. light sources, the QSG has also developed the cryogenics, readout electronics, and control software needed to construct complete superconducting x-ray spectrometers. NIST deployed the first of these spectrometers to the National Synchrotron Light Source at Brookhaven National Laboratory in 2010 and recently deployed a second instrument to the Advanced Photon Source at Argonne National Laboratory in 2014 (see right Figure). NIST will deploy a third spectrometer to the Stanford Synchrotron Radiation Lightsource in 2016. An overview of this work was published in J. Ullom et al., Synchrotron Radiation News 27 (2014) 24. This work was also described in a recent PML highlight.

quantum sensor images
Left: Cover of the July/August 2014 issue of Synchrotron Radiation News showing an array of NIST’s superconducting x-ray sensors installed at the National Synchrotron Light Source. Right: NIST x-ray spectrometer installed at beamline 29-ID of the Advanced Photon Source synchrotron light source, Argonne National Laboratory. The spectrometer contains 240 x-ray sensors and demonstrates NIST’s ability to develop and deliver complete measurement systems.

scanning electron microscope
A scanning electron microscope (center-left) with a commercial superconducting x-ray spectrometer (left) developed at STAR Cryoelectronics. The energy resolution of the spectrometer enables elemental and, in some cases, chemical speciation. Credit: Robin Cantor.

Support of commercialization of superconducting x-ray sensors. These high energy resolution x-ray sensors were originally pioneered at NIST, and have considerable potential for materials analysis if they can be developed into spectrometers compatible with the ubiquitous scanning electron microscopes used throughout materials intensive industries. By measuring x-rays produced by the exciting electron beam, these sensors can provide improved elemental and chemical information, as well as information on thinner and smaller structures than is presently possible. The QSG has worked to disseminate this sensor technology so that it can be developed commercially. In particular, the QSG has supported STAR Cryoelectronics’ efforts to develop a spectrometer that can be mounted on an electron microscope. STAR Cryoelectronics is a small company located in Santa Fe, New Mexico. STAR now provides a complete commercial instrument based on an array of superconducting x-ray sensors and has already sold several spectrometers to private customers. STAR also provides commercial analysis services using a superconducting x-ray spectrometer located at STAR’s Santa Fe facility.

The red histogram shows approximately 100 independent measurements of the energy of the terbium Lβ1 x-ray energy performed using a superconducting x-ray spectrometer developed by NIST. The blue curve shows the centroid and uncertainty for this x-ray line in the existing tabulation of x-ray line energies, clearly demonstrating the potential for improvement in this important database.
Improving the X-Ray Reference Database:

The Quantum Sensors Group initiated a project in 2015 to produce improved x-ray reference data in order to support emerging needs in industrial and scientific materials analysis. A central goal of this work is an improved tabulation of x-ray line energies. The project is a collaboration between the QSG and three other Divisions at NIST. The QSG will use the high resolving power, broadband response, and high collecting efficiency of its superconducting x-ray sensors to perform absolute energy metrology on a wide range of x-ray lines, including lines that were too weak for exact measurement using previous techniques. Proof-of-principle measurements of lanthanide x-rays were highly successful, establishing the viability of this new technique.

Laboratory-Scale Picosecond X-ray Material Probe. X-rays are among the most common methods to probe materials and chemical reactions. Using picosecond x-ray pulses available at synchrotrons, it is possible to monitor the evolution of chemical changes in materials on the picosecond timescale. This capability is being used to study the pathways of photoreactions in environmentally and technologically relevant molecular systems, such as new solar cell materials. However, beam time at synchrotrons is very limited, making it possible to explore only a few materials systems with this technique. The QSP is working to develop a laboratory-scale picosecond x-ray probe system to compliment the more powerful (but much harder to access) synchrotron facilities. This project required the development of an x-ray source that produces picosecond duration pulses synchronized to optical laser pulses that can be used to photoexcite a material of interest. We have developed an x-ray source based on a laser-generated plasma in a water jet target that enables materials to be characterized using optical pump, x-ray probe techniques. The technique is made possible by the high energy resolution of the NIST-developed superconducting x-ray spectrometer. X-ray measurements are now being performed with this system, and it has already provided new information on structural and electronic photodynamics. This experimental path was outlined in J. Uhlig et al., Physical Review Letters 102 (2013) 082601 and details of the x-ray plasma source developed at NIST were recently described in L. Miaja-Avila et al., Structural Dynamics 2 (2015) 024301.

Examples of devices developed by the Quantum Sensors Group to measure the total energy of single radioactive decays. These devices are used by Los Alamos National Laboratory to determine the elemental and isotopic composition of trace radioactive samples. In both devices, a solid silicon platform is suspended by flexible silicon beams. Radioactive samples can be attached to the dark brown squares. The device at left also has an embedded thermometer. A U.S. dime in the background provides scale. Photo credit: Daniel Schmidt.

Development of sensors to measure the total energy of single radioactive decay events. The energy released by a single radioactive decay can be used to identify the specific element involved. However, measuring such a small energy is extremely difficult. The superconducting sensors developed at NIST have the energy resolution to perform this measurement, provided they can be engineered into a system compatible with total energy measurements. We have developed new sensors are fabricated on micromachined silicon (rather than silicon nitride) to simultaneously achieve good thermal isolation while preserving mechanical robustness. Robustness is needed to allow the easy attachment of metal foils containing embedded radioactive material, including particulates. The energy of single radioactive decays is sufficient to produce a measureable temperature rise in the sensors. Performed in collaboration with Los Alamos National Laboratory, the goal of this work is to develop new capabilities for nuclear forensics, treaty verification, and environmental monitoring. These sensors have shown their suitability for a wide range of analytical measurements. The attractions of the technique are spectral simplicity, the ability to simultaneously measure multiple isotopes including both alpha- and beta-emitters, and greatly reduced sample preparation. The ability of this technique to accurately measure the mass ratio of the isotopes 240Pu and 239Pu was published in A. Hoover et al, Analytical Chemistry 87 (2015) 3996. This work was also described in a recent PML highlight.

Fabrication and delivery of arrays of low temperature microbolometers for use in polarization-sensitive millimeter-wave cameras. The millimeter wave band is used to study relic radiation from the early universe called the Cosmic Microwave Background (CMB). Intense scientific activity worldwide is presently focused on measuring and understanding the detailed properties of the CMB, including searches for so-called B-mode polarization signals. If detected, these signals will be a signature of gravity waves and an inflationary epoch in the early universe. The Quantum Sensors Group fabricates some of the largest, most sophisticated, and most sensitive cameras in the world for this vigorous area of science. NIST sensors were delivered to the SPTPol (2012) and ACTPol (2012-2014) instruments located in Antarctica and Chile, respectively. The ACTPol camera incorporates the first deployed multi-chroic detector array, meaning a detector array that is simultaneously sensitive to more than one frequency band. The Quantum Sensors Group is presently working on a major expansion to the ACTPol instrument that will be deployed to Chile in 2016.

Left: Image of the South Pole Telescope Polarimeter (SPTpol) focal plane reproduced from “Particle Physics and the Cosmic Microwave Background” which appeared in the March 2015 issue of Physics Today. NIST delivered the central seven detector arrays. Right: The first ever deployed array of multichroic millimeter-wave detectors, which was installed in 2015 on the ACTpol camera.

BLAST balloon
BLAST balloon (center-left) and scientific payload (right) in Antarctica. Support vehicles and Mt. Erebus are visible in the background. The Quantum Sensors Group is developing polarization-sensitive detectors for an upcoming flight. Photo Credit: Mark Halpern.

Kinetic Inductance Detectors for the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST).

Demonstration of photon-noise limited sensitivity in feedhorn-coupled. A new type of superconducting sensor based on changes in the kinetic inductance rather than changes in resistance has recently been explored as an alternative to the standard transition edge sensor used in most superconducting detector systems. Kinetic inductance detectors are an attractive technology for making submillimeter cameras but achieving satisfactory sensitivity has been challenging until now. The QSP has undertaken to develop this new technology for the upcoming Balloon-borne Large-Aperture Submillimeter Telescope (BLAST) program. The BLAST instrument is launched from Antarctica and is used to study the role of magnetic fields in star formation. By measuring the intensity and polarization of submillimeter radiation emitted by dust in star-forming clouds, BLAST will map the magnetic field geometry in these clouds. NIST’s detectors will be used in an upcoming flight called BLASTpol and will provide unprecedented polarization sensitivity. See J. Hubmayr et al, Applied Physics Letters 106 (2015) 073505.

747 jet
The SOFIA airborne observatory is contained in a modified 747 jet. NIST’s superconducting current amplifiers are used in the HAWC instrument that provides SOFIA with a far-infrared imaging capability. Photo credit: NASA.

Development and dissemination of superconducting readout electronics for low temperature sensors. In addition to the superconducting detectors developed in the QSP, any practical instrument based on these devices must include superconducting readout electronics to measure and amplify the signals from the detectors. The QSP is nearly unique in the world in its ability to develop and fabricate this readout electronics, and provides these amplifiers world-wide to programs that have developed their own arrays of superconducting sensors. The QSG has supplied readout circuits to experiments including Bicep2, Bicep3, ACTpol, ABS, Advanced ACT, BETTII, HAWC (see Figure at right), PIPER, SPTpol, SPT3G, PolarBear, HEATES, HOLMES, ZEUS2, MUSTANG1.5, Simons Array, Keck Array, and SPIDER. The QSG has supplied readout circuits to institutions including Los Alamos National Laboratory, Jyväskylä University, Lund University, NASA Goddard Space Flight Center, Stanford University, the Advanced Photon Source, the National Synchrotron Light Source, the SLAC National Accelerator Laboratory, Princeton University, Cornell University, the University of Chicago, the University of Pennsylvania, and the Jet Propulsion Laboratory.

SQUID-based multiplexer for SCUBA-2:  This 1280 pixel (32 column x 40 row) multiplexer is used as the readout circuit for a submillimeter-wavelength astronomical camera for the SCUBA2 instrument currently operating on Mauna Kea in Hawaii.
SQUID-based multiplexer for SCUBA-2: This 1280 pixel (32 column x 40 row) multiplexer is used as the readout circuit for a submillimeter-wavelength astronomical camera for the SCUBA2 instrument.

End Date:


Lead Organizational Unit:


Source of Extramural Funding:



  • Los Alamos National Laboratory
  • Jet Propulsion Laboratory, SQUID multiplexer for IR detectors
  • NASA Goddard Space Flight Center, SQUID multiplexer for IR detectors
  • NASA Goddard Space Flight Center, X-ray microcalorimeter arrays
  • NASA Goddard Space Flight Center, Magnetic Microcalorimeters
  • UK Astronomy Technology Center, SCUBA2 camera
  • University of Edinburgh /Scottish Microelectronics Centre, SCUBA2 camera
  • Raytheon Vision Systems Inc., SCUBA2 camera
  • University of Cardiff, SCUBA2 camera
  • Lockheed Martin, X-ray detector development for solar physics
  • Stanford University, X-ray detector development for solar physics
  • Star Cryoelectronics, X-ray detector development
  • Princeton University, IR Detector and SQUID multiplexer development, deployment of SQUID multiplexers on the Atacama Cosmological Telescope
  • University of Chicago, Detector and SQUID multiplexer development for CMB
  • University of Colorado, Detector and SQUID multiplexer development for CMB
  • University of Pennsylvania, Detector and SQUID multiplexer development for CMB, deployment of SQUID multiplexers ant the Greenbank Telescope


Joel Ullom, Project Leader
James Beall
Daniel Becker
Douglas Bennett
Edward Denison
William "Randy" Doriese
Susan "Lisa" Ferreira
Colin Fitzgerald
Joseph Fowler
Jiansong Gao
Jonathon Gard
James Hays-Wehle
Gene Hilton
Johannes Hubmayr
Vincent Kotsubo
Dale Li
Peter Lowell
John "Ben" Mates
Galen O'Neil
Carl Reintsema
Daniel Schmidt
Daniel Swetz
Leila Vale
Jeffrey Van Lanen



Joel Ullom

325 Broadway
Boulder, CO 80305-3328