Absolute measurement of the 1S0 − 3P0 clock transition in neutral 88Sr over the 330 km-long stabilized fibre optic link

Abstract

We report a stability below 7 × 10−17 of two independent optical lattice clocks operating with bosonic 88Sr isotope. The value (429 228 066 418 008.3(1.9)syst (0.9)stat Hz) of the absolute frequency of the 1S0 – 3P0 transition was measured with an optical frequency comb referenced to the local representation of the UTC by the 330 km-long stabilized fibre optical link. The result was verified by series of measurements on two independent optical lattice clocks and agrees with recommendation of Bureau International des Poids et Mesures.

Absolute frequency determination of molecular transition in the Doppler regime at kHz level of accuracy

“…The first is the PDH-locked FS-CRDS used for probing the P7 P7 transition [11,20]. The second one is the optical atomic clock which provides the optical frequency reference [12,13]. The third one is the optical frequency comb, which transfers optical frequency between other subsystems [21].…”

“…The first is a 10 MHz RF signal of a hydrogen maser [24]. This signal serves as a link to the UTC(AOS) and is delivered to our laboratory by a 330 km long, frequency-stabilized fibre link [13,25] from Astro-Geodynamic Observatory (AOS) in Borowiec. All frequency counters and generators used in the PDH-locked FS-CRDS as well as in the OFC are referenced to this signal [26].…”

“…The clock laser shifted by an AOM is digitally locked [27] to the 1 S 0 − 3 P 0 clock transition in ultracold 88 Sr atoms confined in a 1D optical lattice [12,13]. Long term frequency instability is below 10 −15 after 3 hours of averaging.…”

“…The experimental spectra were collected here with an optical frequency comb (OFC) assisted, Pound-Drever-Hall locked frequency-stabilized cavity ring-down spectrometer (PDH-locked FS-CRDS) [11]. An 88 Sr optical atomic lattice clock [12,13] served as a frequency reference in most of the performed measurements. The spectrometer was optically linked to the optical atomic clock via the OFC [14,15].…”

Terahertz Frequency Metrology for Spectroscopic Applications: a Review

“…This is the main reason why the development and characterization of long-haul optical fiber links (OFLs), rather than microwave satellite links, recently featured a substantial thrust [186][187][188][189][190]. Indeed, in the last years, OFLs have shown undoubted effectiveness in comparing remote atomic clocks beyond the ultimate limit of GPS-based comparisons, attaining precision levels not limited by the frequency transfer method [191][192][193][194][195][196], and are also envisioned as key elements for the development of a new kind of high-accuracy relativistic geodesy [195,197]. Besides optical clock comparisons, short-range OFLs have recently been exploited in order to increase the spectral performance of a local laser and to allow for precision molecular spectroscopy [198].…”