Speaker: Scott Diddams (University of Colorado Boulder)
Title: Quantum Metrology with Optical Frequency Combs
Abstract: 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).
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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.