Demonstration of a trapped-ion atomic clock in space

Abstract

Atomic clocks, which lock the frequency of an oscillator to the extremely stable quantized energy levels of atoms, are essential for navigation applications such as deep space exploration 1 and the Global Positioning System (GPS) 2 and as scientific tools for addressing questions in fundamental physics 3,4,5,6 . Atomic clocks that can be launched into space are an enabling technology for GPS, but to date have not been applied to deep space navigation and have seen only limited application to scientific questions due to performance constraints imposed by the rigors of space launch and operation 7 . The invention of methods to electromagnetically trap and cool ions has revolutionized atomic clock performance 8,9,10,11,12,13 . Terrestrial trapped ion clocks have achieved orders of magnitude improvements in performance over their predecessors and have become a key component in national metrology laboratories 13 . However, transporting this new technology into space has remained elusive. Here we show the results from the first-ever trapped ion atomic clock to operate in space. Launched in 2019, NASA's Deep Space Atomic Clock (DSAC) has operated for more than 12 months, demonstrating a short-term fractional frequency stability of between 1 and 2 x 10 -13 at 1 second of averaging time (measured on the ground), a long-term stability of 3 x 10 -15 at 23 days, and an estimated drift of 3.0(0.7) x 10 -16 per day. Each of these exceeds current space clock performance by as much as an order of magnitude 14,15,16 . We found the DSAC clock to be particularly amenable to the space environment, having low sensitivities to variations in radiation, temperature, and magnetic fields, and we were able to characterize these in detail. This level of space clock performance will enable new types of space navigation. In particular, the DSAC mission has demonstrated a process called one-way navigation whereby signal delay times are measured in-situ making near-real-time deep space probe navigation possible 17 .

Design, implementation, and qualification of high-performance time and frequency reference for the MeerKAT telescope

“…The GNSS at minimum form the basic part of high-accuracy time transfer to GPS and UTC(k). It is not inconceivable that a European laboratory or the SARAO might in fact be able to run a robust, and compact commercial cold atom clock or a robust mercury ion clock 103 at the Losberg astronomy site 104 to further help to locally monitor/calibrate the masers, to ensure continued low uncertainty on a bi-weekly basis before the UTC is published. 9 Appendix A: Calculation of KTT's Uncertainty…”

High precision differential clock comparisons with a multiplexed optical lattice clock

“…3c, with a relative stability of 9.7(4) × 10 −18 / √ τ in agreement with the QPN limit (red dashed line), and a fractional frequency uncertainty of 8.9(3) × 10 −20 at the full 3.3 hours of averaging time. This demonstration of precision below the 10 −19 level with a rack-mounted, commercially-available local oscillator with a stability of 1 × 10 −15 at 1 s is encouraging for future applications that require portable or spaced-based clocks such as relativistic geodesy, and gravitational wave detection [6,[11][12][13]22].…”

“…The unique capabilities offered by this platform pave the way for future studies of precision isotope shift measurements, spatially resolved characterization of limiting clock systematics, development of clock-based gravitational wave and dark matter detectors [6][7][8][9], and novel tests of relativity including measurements of the gravitational redshift at sub-centimeter scales [10][11][12][13] Neutral atom optical lattice clocks (OLCs) have recently reached stability and accuracy at the 10 −18 level [1-5, [14][15][16] largely due to the ultra-narrow linewidths (∼ 1 mHz) of optical frequency (∼ 400 THz) forbidden clock transitions in alkaline-earth(-like) atoms. This performance enables novel clock applications such as relativistic geodesy, searches for dark matter, gravitational wave detection, and tests of fundamental physics [6][7][8][9][10][11][12][13][17][18][19][20][21][22].…”

Deterministic loading of a single strontium ion into a surface electrode trap using pulsed laser ablation

“…Trapped ion systems, in which atomic ions are levitated in a vacuum by electric and/or magnetic field, are promising platform for the development of quantum technologies such as quantum metrology [1][2][3], quantum communication [4][5][6] and quantum computation [7][8][9]. Precise quantum operations on trapped ions as quantum bits (qubits) are indispensable ingredients for such a purpose.…”