Lifetime-limited Coherence Between Two 27Al+ Clocks using Correlation Spectroscopy
Abstract
In optical clock comparisons, measurement stability is often limited by the coherence time of the local oscillator. Correlation spectroscopy is a technique for performing frequency measurements between two atomic clocks with an interrogation time beyond this limit. By interrogating with the same local oscillator and measuring correlations in the atomic states, the common-mode phase noise of the local oscillator is removed. Here, we demonstrate correlation spectroscopy between two independent 27Al+ optical clocks. We observe coherence between the two systems (operating at a frequency of 1 . 121 PHz) with interrogation times up to 8s, beyond the capability of state-of-the-art cavity-stabilized lasers. This increase in the interrogation time requires active control of differential noise sources such as magnetic field noise and optical-path-length fluctuations. We obtain a fractional comparison measurement instability below 4 ×10-16 /√{ τ} where τ is the averaging time, a factor of ∼10 improvement from previous Al+ clock comparisons.
This work was supported by the National Institute of Standards and Technology, the Defense Advanced Research Projects Agency, and the Office of Naval Research.- Publication:
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APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts
- Pub Date:
- 2020
- Bibcode:
- 2020APS..DMPP07005C