Early Career Researchers Receive High Energy Physics Awards

The Department of Energy (DOE) recently announced funding for research on quantum information science-enabled discoveries in high energy physics. Two projects involving Pacific Northwest National Laboratory (PNNL) researchers were selected for support under this award. 

Erik Lentz will serve as the principal investigator for “The Very Entangled Bose Array eXperiment (VEBAX): A Pathfinder for Multi-mode Quantum Enhancement of Arrayed Cavity Axion Haloscopes” project. Christian Boutan will support that project as well as “Accelerating high mass axion searches using Kinetic Inductance Traveling Wave Parametric Amplifiers,” led by Corey McRae from the University of Colorado Boulder. 

Both projects involve the search for dark matter axions, which are feebly interacting low mass particles. The hunt for axions typically involves a haloscope—a microwave signal-detector connected to a resonant cavity placed inside a large superconducting magnet that converts axions passing through the cavity into detectable microwaves. The cavity and magnet are cooled to milli-Kelvin and 4 Kelvin temperatures with a dilution refrigerator and pulse tube cryocoolers, respectively.

Both projects will expand upon the capabilities of current haloscopes, such as the one used in the Axion Dark Matter eXperiment (ADMX), improving sensitivities to classical dark matter axions. 

The PNNL-led project, VEBAX, will search for axions with masses of 10-15 meV (4-6 GHz) using an array of identical cavities, in contrast to ADMX which operates near 1 GHz with a single, much larger cavity. More importantly, VEBAX will reduce the total noise of the cavity array by correlating the cavity backgrounds via quantum entanglement, improving the sensitivity scaling to the Heisenberg limit, imposed by quantum theory. 

“The bottom line is we want to improve a sensitivity measure called the signal-to-noise ratio, SNR. VEBAX will reduce the noise—the denominator of SNR—in the array, pushing towards the Heisenberg limit, thereby raising the sensitivity and keeping the cavity haloscope technique competitive when searching for axions at higher masses and frequencies,” said Lentz. 

Boutan will collaborate with University of Colorado Boulder on another project that will also search for axions at higher frequencies. This collaborative project focuses on demonstrating the operation of quantum noise limited amplifiers in high magnetic fields—a feat that has thus far been impossible with conventional superconductors.  

“Looking for axions involves two things that don’t play well together: large magnetic fields and superconductors—we need both,” said Boutan. “The magnetic field sets the conditions to produce our dark matter signal, while superconducting devices amplify that tiny yocto-watt signal. We want these devices near the magnetic field to boost our sensitivity, but the field destroys superconductivity. By using exotic materials, such as niobium-titanium nitride, we expect to solve this problem and it could be a game changer.”

Both of these newly-awarded projects bring the search for axions to PNNL’s campus, necessitating the building of new hardware to be combined with existing instrumentation, such as the superconducting qubit testbed. The DOE, Office of Science, High Energy Physics program will support each project for a total of five years. 

“After we demonstrate the successful use of these brand-new quantum noise limited amplifiers in a magnetic field, we plan to use them in our own in-house axion search” said Boutan. 

Over the past year, Boutan has been using his own DOE Early Career Research program award to design a novel two cavity axion search that operates under the ADMX banner. This is currently scheduled to be the first axion search ever performed at PNNL. 

Lentz and Boutan met in graduate school at the University of Washington and continue to work closely together on PNNL’s axion research program today. Over the last two years, the duo has collaborated on several proposals in the areas of physics, quantum information science, and artificial intelligence.

“Erik and Christian are bringing ground-breaking developments to PNNL,” said John L. Orrell, manager for high energy physics research at PNNL. “Their creativity in addressing the challenges of searching for axion dark matter may revolutionize the field and our Lab’s role in future work.”