JILA SrI optical lattice clock with uncertainty of $2.0 \times 10^{-18}$

Abstract

We report on an improved systematic evaluation of the JILA SrI optical lattice clock, achieving a nearly identical systematic uncertainty compared to the previous strontium accuracy record set by the JILA SrII optical lattice clock (OLC) at 2.1 × 10 −18 . This improves upon the previous evaluation of the JILA SrI optical lattice clock in 2013, and we achieve a more than twenty-fold reduction in systematic uncertainty to 2.0 × 10 −18 . A seven-fold improvement in clock stability, reaching 4.8 × 10 −17 / √ τ for an averaging time τ in seconds, allows the clock to average to its systematic uncertainty in under 10 minutes. We improve the systematic uncertainty budget in several important ways. This includes a novel scheme for taming blackbody radiation-induced frequency shifts through active stabilization and characterization of the thermal environment, inclusion of higher-order terms in the lattice light shift, and updated atomic coefficients. Along with careful control of other systematic effects, we achieve low temporal drift of systematic offsets and high uptime of the clock. We additionally present an improved evaluation of the second order Zeeman coefficient that is applicable to all Sr optical lattice clocks. These improvements in performance have enabled several important studies including frequency ratio measurements through the Boulder Area Clock Optical Network (BACON), a high precision comparison with the JILA 3D lattice clock, a demonstration of a new all-optical time scale combining SrI and a cryogenic silicon cavity, and a high sensitivity search for ultralight scalar dark matter. * Equal Contributions

Characterization of Errors in Interferometry with Entangled Atoms

“…Neutral atoms are used in some of the most precise, state-of-the-art quantum sensors, including atomic clocks [1][2][3][4], optical atomic magnetometers [5][6][7], and atom interferometers (AIs) [8][9][10][11]. Looking forward, an ambitious goal is to harness the power of quantum entanglement to decrease the phase uncertainty in these atomic sensors [12], first, beyond the standard quantum limit (SQL), N −1/2 , which arises in measurements with independent atoms, and, ultimately, as close as possible to the Heisenberg limit (HL), N −1 , where N is the number of atoms used in the measurement.…”

Optical atomic clock comparison through turbulent air

“…Optical atomic clocks, with stabilities and accuracies now approaching 10 −18 [1][2][3][4][5][6][7][8][9][10], have created new opportunities for precision measurements in physics. These include the redefinition of the SI second, relativistic geodesy, investigation of possible variations in fundamental constants, and searches for dark matter, among others [11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”

“…The frequency ratio measurements discussed in this paper were performed during a measurement campaign conducted by the Boulder Area Clock and Optical Network (BACON) collaboration [51]. This campaign compared three state-of-the-art optical atomic clocks: a ytterbium (Yb) lattice clock [4], an aluminum ion (Al + ) clock [5], and a strontium (Sr) lattice clock [7]. Here, we describe measurements of the ratio of 171 Yb and 87 Sr transition frequencies, obtained over six days using O-TWTFT across a freespace optical link.…”

Keeping Time with Light

“…In this Letter, we report on the first realization of a timescale based on an optical local oscillator (OLO) which outperforms state-of-the-art microwave oscillators steered to either microwave or optical frequency standards. This all-optical timescale consists of an ultrastable laser based on a cryogenic silicon reference cavity that is steered daily to an accurate 87 Sr lattice clock [20] over a monthlong campaign. During this period, the frequency stability of the OLO surpasses that of the hydrogen masers in the UTC (NIST) timescale at all averaging intervals up to multiple days [21], demonstrating the requisite stability for improved timescale performance.…”

“…We combine our local oscillator with an accurate optical frequency standard to form an all-optical timescale. Over a 34 day interval, a strontium lattice clock with systematic uncertainty of 2.0 × 10 −18 [20] is used to track the OLO frequency with 25% uptime. Daily measurements of the OLO allow us to build a reliable predictive model of its frequency evolution.…”