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View article: Alternative approach to time-delay interferometry with optical frequency comb
Alternative approach to time-delay interferometry with optical frequency comb Open
Spaceborne gravitational wave observatories, exemplified by the Laser Interferometer Space Antenna (LISA) mission, are designed to remove laser noise and clock noise from interferometric phase measurements in postprocessing. The planned ob…
View article: Quantum gravity gradiometry for future mass change science
Quantum gravity gradiometry for future mass change science Open
A quantum gravity gradiometer in a low Earth orbit, operating in a cross-track configuration, could be a viable single-spacecraft measurement instrument to provide mass change data for Earth observation, at comparable or better resolutions…
View article: Classical and quantum frequency combs for satellite-based clock synchronization
Classical and quantum frequency combs for satellite-based clock synchronization Open
The next generation of space-based networks for communications, sensing, and navigation will contain optical clocks embedded within satellites. To fully realize the capabilities of such clocks, high-precision clock synchronization across t…
View article: Classical and Quantum Frequency Combs for Satellite-based Clock Synchronization
Classical and Quantum Frequency Combs for Satellite-based Clock Synchronization Open
The next generation of space-based networks will contain optical clocks embedded within satellites. To fully realize the capabilities of such clocks, high-precision clock synchronization across the networks will be necessary. Current exper…
View article: Ultra-low noise laser and optical frequency comb-based timing system for the Black Hole Explorer (BHEX) mission
Ultra-low noise laser and optical frequency comb-based timing system for the Black Hole Explorer (BHEX) mission Open
In this effort, we demonstrate the performance of a highly stable time reference for the proposed Black Hole Explorer (BHEX) mission, a space-based extension to the Event Horizon Telescope (EHT) Very Long Baseline Interferometry (VLBI) pro…
View article: Optical and microwave metrology at the 10-18 level with an Er/Yb:glass frequency comb
Optical and microwave metrology at the 10-18 level with an Er/Yb:glass frequency comb Open
Optical frequency combs are an essential tool for precision metrology experiments ranging in application from remote spectroscopic sensing of trace gases to the characterization and comparison of optical atomic clocks for precision time-ke…
View article: Optical coherence between atomic species at the second scale: improved clock comparisons via differential spectroscopy
Optical coherence between atomic species at the second scale: improved clock comparisons via differential spectroscopy Open
Comparisons of high-accuracy optical atomic clocks \cite{Ludlow2015} are essential for precision tests of fundamental physics \cite{Safronova2018}, relativistic geodesy \cite{McGrew2018, Grotti2018, Delva2019}, and the anticipated redefini…
View article: Optical coherence between atomic species at the second scale: improved\n clock comparisons via differential spectroscopy
Optical coherence between atomic species at the second scale: improved\n clock comparisons via differential spectroscopy Open
Comparisons of high-accuracy optical atomic clocks \\cite{Ludlow2015} are\nessential for precision tests of fundamental physics \\cite{Safronova2018},\nrelativistic geodesy \\cite{McGrew2018, Grotti2018, Delva2019}, and the\nanticipated re…
View article: High-performance, compact optical standard
High-performance, compact optical standard Open
We describe a high-performance, compact optical frequency standard based on a microfabricated Rb vapor cell and a low-noise, external cavity diode laser operating on the Rb two-photon transition at 778 nm. The optical standard achieves an …
View article: Optical atomic clock comparison through turbulent air
Optical atomic clock comparison through turbulent air Open
We use frequency comb-based optical two-way time-frequency transfer (O-TWTFT) to measure the optical frequency ratio of state-of-the-art ytterbium and strontium optical atomic clocks separated by a 1.5 km open-air link. Our free-space meas…
View article: Frequency Ratio Measurements with 18-digit Accuracy Using a Network of Optical Clocks
Frequency Ratio Measurements with 18-digit Accuracy Using a Network of Optical Clocks Open
Atomic clocks occupy a unique position in measurement science, exhibiting higher accuracy than any other measurement standard and underpinning six out of seven base units in the SI system. By exploiting higher resonance frequencies, optica…
View article: Coherent Optical Clock Down-Conversion for Microwave Frequencies with 10-18
Coherent Optical Clock Down-Conversion for Microwave Frequencies with 10-18 Open
Optical atomic clocks are poised to redefine the SI second, thanks to stability and accuracy more than one hundred times better than the current microwave atomic clock standard. However, the best optical clocks have not seen their performa…
View article: Demonstration of a Timescale Based on a Stable Optical Carrier
Demonstration of a Timescale Based on a Stable Optical Carrier Open
We report on the first timescale based entirely on optical technology. Existing timescales, including those incorporating optical frequency standards, rely exclusively on microwave local oscillators owing to the lack of an optical oscillat…
View article: Ramsey-Bordé Matter-Wave Interferometry for Laser Frequency Stabilization at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>−</mml:mo><mml:mn>16</mml:mn></mml:mrow></mml:msup></mml:math> Frequency Instability and Below
Ramsey-Bordé Matter-Wave Interferometry for Laser Frequency Stabilization at Frequency Instability and Below Open
We demonstrate Ramsey-Bordé (RB) atom interferometry for high performance laser stabilization with fractional frequency instability <2×10^{-16} for timescales between 10 and 1000s. The RB spectroscopy laser interrogates two counterpropagat…
View article: Measurements of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Al</mml:mi><mml:none/><mml:mo>+</mml:mo><mml:mprescripts/><mml:none/><mml:mn>27</mml:mn></mml:mmultiscripts></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Mg</mml:mi><mml:none/><mml:mo>+</mml:mo><mml:mprescripts/><mml:none/><mml:mn>25</mml:mn></mml:mmultiscripts></mml:math>magnetic constants for improved ion-clock accuracy
Measurements ofandmagnetic constants for improved ion-clock accuracy Open
We have measured the quadratic Zeeman coefficient for the ${^{1}S_{0} \leftrightarrow {^{3}P_{0}}}$ optical clock transition in $^{27}$Al$^{+}$, $C_{2}=-71.944(24)$~MHz/T$^{2}$, and the unperturbed hyperfine splitting of the $^{25}$Mg$^{+}…
View article: Towards the optical second: verifying optical clocks at the SI limit
Towards the optical second: verifying optical clocks at the SI limit Open
The pursuit of ever more precise measures of time and frequency motivates redefinition of the second in terms of an optical atomic transition. To ensure continuity with the current definition, based on the microwave hyperfine transition in…
View article: Optical-Clock-Based Time Scale.
Optical-Clock-Based Time Scale. Open
A time scale is a procedure for accurately and continuously marking the passage of time. It is exemplified by Coordinated Universal Time (UTC) and provides the backbone for critical navigation tools such as the Global Positioning System. P…
View article: Towards the optical second: Verifying optical clocks at the SI limit
Towards the optical second: Verifying optical clocks at the SI limit Open
The pursuit of ever more precise measures of time and frequency motivates redefinition of the second in terms of an optical atomic transition. To ensure continuity with the current definition, based on the microwave hyperfine transition in…
View article: Towards Adoption of an Optical Second: Verifying Optical Clocks at the SI Limit
Towards Adoption of an Optical Second: Verifying Optical Clocks at the SI Limit Open
The pursuit of ever more precise measures of time and frequency is likely to lead to the eventual redefinition of the second in terms of an optical atomic transition. To ensure continuity with the current definition, based on a microwave t…
View article: Optimizing the linearity in high-speed photodiodes
Optimizing the linearity in high-speed photodiodes Open
Analog photonic links require high-fidelity, high-speed optical-to-electrical conversion for applications such as radio-over-fiber, synchronization at kilometer-scale facilities, and low-noise electronic signal generation. Photodetector no…
View article: Hyperpolarizability and operational magic wavelength in an optical lattice clock
Hyperpolarizability and operational magic wavelength in an optical lattice clock Open
Optical clocks benefit from tight atomic confinement enabling extended interrogation times as well as Doppler- and recoil-free operation. However, these benefits come at the cost of frequency shifts that, if not properly controlled, may de…
View article: Single-branch Er:fiber frequency comb for precision optical metrology with 10^−18 fractional instability
Single-branch Er:fiber frequency comb for precision optical metrology with 10^−18 fractional instability Open
The comparison of optical atomic clocks with frequency instabilities reaching 1 part in 1016 at 1 s will enable more stringent tests of fundamental physics. These comparisons, mediated by optical frequency combs, require optical synthesis …
View article: Single-branch Er:fiber frequency comb for optical synthesis at the 10¯¹⁸ level
Single-branch Er:fiber frequency comb for optical synthesis at the 10¯¹⁸ level Open
As optical atomic clocks reach instabilities of 1 x 10^(-16) and below, many new tests of fundamental physics are enabled. These tests often require comparisons of clocks based on different atomic species, necessitating optical frequency c…
View article: Single-branch Er:fiber frequency comb for optical synthesis at the $10^{-18}$ level
Single-branch Er:fiber frequency comb for optical synthesis at the $10^{-18}$ level Open
Laser frequency combs based on erbium-doped fiber mode-locked lasers have shown great potential for compact, robust and efficient optical clock comparisons. However, to simultaneously compare multiple optical clock species, fiber laser fre…