Diddams' group develops optical frequency combs (fiber, microresonator, and mid-IR) and applies them to quantum metrology, optical clocks, precision spectroscopy from UV to THz, low-noise microwave photonics, and astronomical spectrograph calibration; he directs CU's Quantum Engineering Initiative. For context, this complements the established paradigm of NV-diamond ensemble magnetometry (Hahn-echo/DEER, nanoscale NMR, T1 relaxometry) operating near pT/√Hz sensitivity.