Xiran Bai successfully defends thesis, "Quantum Squeezing to Accelerate Axion Dark Matter Searches: From Demonstration to Broad Scan Range"

On June 17, Xiran Bai successfully defended the thesis “Quantum Squeezing to Accelerate Axion Dark Matter Searches: From Demonstration to Broad Scan Range” (advisor: Reina Maruyama).

Bai explained, “My thesis focuses on improving the search for axions, a hypothetical particle that could help explain dark matter, the invisible matter that makes up most of the matter in the Universe. Axions were also proposed as a solution to a long-standing puzzle in particle physics: why the strong interaction appears not to violate CP symmetry.” 

“My thesis work uses quantum techniques to reduce detector noise and make the search faster and more sensitive. My thesis reports the broadest quantum enhanced axion search to date in a well-motivated mass and coupling range. More broadly, it shows that quantum technology can be turned into a practical tool for dark matter searches at a data production scale, bringing us closer to detecting one of the most elusive particles in modern physics.”

Bai will join Fermilab as a research associate, developing the next generation of quantum sensors for axions and fundamental searches. 

Thesis Abstract: Advances in quantum sensing have opened new pathways for the search for dark matter, which comprises about 85% of the total matter in our universe. The axion stands out as a leading dark matter candidate. However, axion detection is exceptionally challenging: their interactions with ordinary matter are exceedingly weak, and traditional searches are fundamentally limited by the standard quantum limit (SQL). Without going beyond the SQL, a complete scan of the axion parameter space would take tens of thousands of years. The Haloscope At Yale Sensitive To Axion CDM (HAYSTAC) experiment overcomes this barrier using quantum squeezing with dual Josephson parametric amplifiers, surpassing the SQL and achieving a two-fold improvement in scan rate. I will present recent results and discuss efforts that enabled broad range scans that go beyond just small scale demonstrations. 

Thesis Committee: Reina Maruyama (advisor), Karsten Heeger, David Moore, David Poland, Julieta Gruszko (University of North Carolina at Chapel Hill)