What Optical Atomic Clocks Tell Us About Space-Time | Jun Ye

Times have changed. And cesium clocks can't keep up. In this episode, we sit down with Jun Ye, Joint Institute for Laboratory Astrophysics (JILA) Fellow and pioneer of optical lattice clocks, whose work has pushed timekeeping far beyond traditional cesium atomic clocks. Ye explains how combining ultra-stable lasers, frequency combs, and ultra-cold atoms produces clocks more than 100× more precise than today’s standards: so sensitive they can detect gravitational time dilation across the width of a human hair. We explore how this next generation of atomic clocks may open windows onto gravitational waves, test Einstein’s relativity in new regimes, and even help build a GPS for space travel. Ye also shares his personal journey from growing up during China’s Cultural Revolution to becoming a leader in precision measurement, and what that experience taught him about resilience, mentorship, and protecting scientific inquiry. Whether you’re curious about time, relativity, quantum physics, GPS technology, or the frontiers of precision measurement, this conversation offers a rare insider’s look at how breakthroughs in timekeeping can lead to entirely new physics. Follow us for more technical interviews with the world’s greatest scientists: Twitter: https://x.com/632nmPodcast Instagram: https://www.instagram.com/632nmpodcas... LinkedIn:   / about   Substack: https://632nmpodcast.substack.com/ Follow our hosts! Mikhail Shalaginov:   / mikhail-shalaginov   Michael Dubrovsky: https://x.com/MikeDubrovsky Xinghui Yin: https://x.com/XinghuiYin Subscribe: Apple Podcasts: https://podcasts.apple.com/us/podcast... Spotify: https://open.spotify.com/show/4aVH9vT... Website: https://www.632nm.com Timestamps: 00:00 - Intro 01:17 - Why Haven't Optical Clocks Replaced Cesium Clocks? 10:45 - Fundamentals of Optical Atomic Clocks 17:34 - History of Atomic Clocks 30:18 - What is JILA? 35:01 - What brought Jun to JILA? 39:33 - What does it take to get a PhD in Physics? 42:40 - Jun Ye's PhD work 44:36 - Limitations of Laser Stabilization 50:38 - How Do We Make the Most Stable Lasers? 57:28 - How to Measure Laser Coherence Times 1:04:24 - Building Atomic Clocks from First Principles 1:08:59 - Jun's Notable Accomplishments 1:14:00 - Magic Frequencies for Optical Traps 1:21:04 - Can AI Improve Atomic Clocks? 1:24:00 - How Does Quantum Entanglement Affect Clocks? 1:30:29 - Development of Quantum Computers 1:34:23 - Pros and Cons of Nuclear Clocks 1:43:49 - What Would Jun Do With Unlimited Research Funding? 1:47:09 - Lessons from China's Cultural Revolution #quantumcomputing #quantumphysics #atomicclock #laser #physics #optics #astrophysics #astronomy #spacetime