The record of atomic clock frequency comparisons at NIST over the past half-decade provides one of the tightest constraints of any present-day, temporal variations of the fundamental constants. Notably, the 6-year record of increasingly precise measurements of the absolute frequency of the Hg+ single-ion optical clock (using the cesium primary frequency standard NIST-F1) constrains the temporal variation of the fine structure constant α to less than 2 • 10-16yr-1 and offers Local Position Invariance test in the framework of General Relativity. The most recent measurement of the frequency ratio of the Al+ and Hg+ optical clocks is reported with a fractional frequency uncertainty of (5.2 • 10-17). The record of such measurements over the last year sensitively tests for a temporal variation of α and constraints (α/α = (–1.6 ± 2.3) • 10-17yr-1), consistent with zero.
Citation: European Journal of Physics
Pub Type: Journals
atom trapping and cooling, quantum computation:quantum information processing, quantum superpositions, quantum-state engineering, trapped ions