Comparison of Two Independent Sr Optical Clocks with 1x10-17 Stability at 10^3 s

Author
Abstract
Many-particle optical lattice clocks have the potential for unprecedented measurement precision and stability due to their low quantum projection noise. However, this potential has so far never been realized because clock stability has been limited by frequency noise of optical local oscillators. By synchronously probing two 87Sr lattice systems using a laser with a thermal noise floor of 1×10-15, we remove classically correlated laser noise from the intercomparison, but this does not demonstrate independent clock performance. With an improved optical oscillator that has a 1×10-16 thermal noise floor, we demonstrate an order of magnitude improvement over the best reported stability of any independent clock, achieving a fractional instability of 1×10-17 in 1000 s of averaging time for synchronous or asynchronous comparisons. This result is within a factor of 2 of the combined quantum projection noise limit for a 160 ms probe time with ∼103 atoms in each clock. We further demonstrate that even at this high precision, the overall systematic uncertainty of our clock is not limited by atomic interactions. For the second Sr clock, which has a cavity-enhanced lattice, the atomic-density-dependent frequency shift is evaluated to be -3.11×10-17 with an uncertainty of 8.2×10-19.
Year of Publication
2012
Journal
Physical Review Letters
Volume
109
Start Page
230801
Issue
23
Number of Pages
230801
Date Published
2012-12
ISSN Number
0031-9007
DOI
10.1103/PhysRevLett.109.230801
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