JQI Seminar November 4, 2024: Scott Diddams

"Quantum Metrology with Optical Frequency Combs" Speaker: Scott Diddams, University of Colorado Boulder 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)."