The optical frequency comb is one of the most significant advances in laser physics since the
development of the laser itself. It has made routine the counting and synthesis of the oscillations
of light on the femtosecond time scale, and it is an essential component of all present and future
optical clocks and time-transfer systems. It further enables the most accurate measurement of any
fundamental physical quantity—that of the quantized energy states of atoms and ions with 18
digits of precision. Despite this powerful connection to quantum systems, there are few examples
of how an optical frequency comb can yield a quantum advantage for metrology. The most
important limitation remains in photodetection, where shot noise sets the fundamental signal-to-
noise ratio. In this context, we seek to define and extend the quantum limit for metrology with
optical frequency combs. Over a decade ago, we showed that breaking time stationarity in the
detection of frequency comb light can lead to a new shot-noise limit [1]. More recently we
employ soliton squeezing to control the distribution of quantum noise in a frequency comb,
generating 15 mW of frequency comb light that has its amplitude fluctuations suppressed more
than 3 dB relative to the time-stationary shot noise limit. As a first application, we use this
squeezed comb to perform simultaneous spectroscopy of trace gases with 2500 modes spanning
2.5 THz, yielding a twofold reduction in averaging time to achieve the same shot-noise-limited
precision [2]. We expect these results will drive additional advances in frequency comb
measurement scenarios that impact applications in clock networks, climate science, health
diagnostics, and perhaps even the discovery and characterization of exoplanets.
1. F. Quinlan, et al., Nature Photonics 7, 290 (2013).
2. D. Herman, et al., arXiv:2408.16688 (2024).
*You will need to bring your cell phone, so you can sign in using the QR code outside of ATL 2400. You will need to submit your first and last name, email, and affiliation on the form by 11:15am to be able to get lunch after the seminar. Lunch is first come, first served.*
Scott Diddams holds the Robert H. Davis Endowed Chair at the University
of Colorado Boulder, where he is also Professor of Electrical Engineering
and Physics. He carries out experimental research in the fields of precision
spectroscopy and quantum metrology, nonlinear optics, microwave
photonics and ultrafast lasers. Diddams received the Ph.D. degree from the
University of New Mexico in 1996. From 1996 through 2000, he did
postdoctroral work at JILA, NIST and the University of Colorado.
Subsequently, Diddams was a Research Physicist, Group Leader, and
Fellow at NIST (the National Institute of Standards and Technology). In
2022 he transitioned to his present position where he also assumed the role
of Faculty Director of the Quantum Engineering Initiative in the College of
Engineering and Applied Science. As a postdoc Diddams built the first
optical frequency combs in the lab of Nobel laureate John Hall, and
throughout his career, he has pioneered the use of these tools for optical
clocks, tests of fundamental physics, novel spectroscopy, and astronomy. His research has been
documented in more than 750 peer-reviewed publications, conference papers, and invited talks. The work
of Dr. Diddams and his research group has also been recognized by multiple awards. These include the
Distinguished Presidential Rank Award, the Department of Commerce Gold and Silver Medals for
"revolutionizing the way frequency is measured”, as well as the Presidential Early Career Award in
Science and Engineering (PECASE), the OPTICA C.E.K. Mees Medal, the IEEE Photonics Society Laser
Instrumentation Award, and the IEEE Rabi award. He is a Fellow of OPTICA (formerly OSA), the
American Physical Society, and IEEE.