Nathan Lemke

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Optical atomic clocks promise timekeeping at the highest precision and accuracy, owing to their high operating frequencies. Rigorous evaluations of these clocks require direct comparisons between them. We have realized a high-performance remote comparison of optical clocks over kilometer-scale urban distances, a key step for development, dissemination, and(More)
Atomic clocks have been instrumental in science and technology, leading to innovations such as global positioning, advanced communications, and tests of fundamental constant variation. Timekeeping precision at 1 part in 10(18) enables new timing applications in relativistic geodesy, enhanced Earth- and space-based navigation and telescopy, and new tests of(More)
At ultracold temperatures, the Pauli exclusion principle suppresses collisions between identical fermions. This has motivated the development of atomic clocks with fermionic isotopes. However, by probing an optical clock transition with thousands of lattice-confined, ultracold fermionic strontium atoms, we observed density-dependent collisional frequency(More)
We present an optical frequency divider based on a 200 MHz repetition rate Er:fiber mode-locked laser that, when locked to a stable optical frequency reference, generates microwave signals with absolute phase noise that is equal to or better than cryogenic microwave oscillators. At 1 Hz offset from a 10 GHz carrier, the phase noise is below -100 dBc/Hz,(More)
• Derived a theoretical framework that describes many-body effects in a lattice clock. • Validated the analysis with recent experimental measurements. • Demonstrated the importance of beyond mean field corrections in the dynamics. a b s t r a c t We present a unifying theoretical framework that describes recently observed many-body effects during the(More)
1. Experimental setup for generation and cross-spectrum phase noise measurement of two 10 GHz hybrid microwave sources. LF denotes loop filter and PD denotes photodiode. Abstract— We demonstrate a 10 GHz hybrid oscillator comprised of a phase stabilized optical frequency comb divider and a room temperature dielectric sapphire oscillator. Characterization of(More)
Quantum state engineering of ultracold matter and precise control of optical fields have together allowed accurate measurement of light-matter interactions for applications in precision tests of fundamental physics. State-of-the-art lasers maintain optical phase coherence over one second. Optical frequency combs distribute this optical phase coherence(More)
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