Seconds-scale coherence on an optical clock transition in a tweezer array

Abstract

Coherent control of high-quality-factor optical transitions in atoms has revolutionized precision frequency metrology. Leading optical atomic clocks rely on the interrogation of such transitions in either single ions or ensembles of neutral atoms to stabilize a laser frequency at high precision and accuracy. In addition to absolute time-keeping, the precision and coherence afforded by these transitions has enabled observations of gravitational time dilation on short length-scales, and facilitated applications in quantum information. Here, we demonstrate a new platform for interrogation and control of an optical clock transition based on arrays of individual strontium atoms held within optical tweezers that combines key strengths of these two leading approaches. We report coherence times of 3.4 seconds, record single-ensemble duty cycles up to 96% through repeated interrogation, and 4.7 × 10 −16 (τ /s) −1/2 frequency stability commensurate with present-day leading platforms. These results establish optical tweezer arrays, and their associated capacity for microscopic control of neutral atoms, as a powerful tool for coherent control of optical transitions for metrology and quantum information science.

An Atomic-Array Optical Clock with Single-Atom Readout

“…We note the very recent, complementary results of Ref. [34] that show seconds-long coherence in a tweezer array filled with ≈5 88 Sr atoms using an ultra-low noise laser without feedback operation. In this and our system, a recently developed repetitive interrogation protocol [25], similar to that used in ion clocks, provides a short dead time of ≈100 ms between interrogation blocks, generally suppressing the impact of laser noise on stability stemming from the Dick effect [35].…”

“…The results presented here and in Ref. [34] provide the foundation for establishing a third optical clock platform promising competitive stability, accuracy, and robustness, while incorporating single-atom detection and control techniques in a natural fashion. We expect this to be a crucial development for applications requiring advanced control and read-out techniques in many-atom quantum systems, as discussed in more detail in the outlook section.…”

“…Reaching several hundreds of atoms is realistic with an upgrade to two-dimensional arrays, while Ref. [34] already demonstrated seconds-long interrogation. A further increase in atom number is possible by using a secondary array for readout, created with a non-magic wavelength for which higher power lasers exist [41,44].…”

“…In this context, we note the results of Ref. [34], where stability is evaluated by converting a spectroscopic signal into a frequency record (without a closed feedback loop). Based on interrogation with an ultra-low noise laser system, they achieve a short-term stability of 4.7×10 −16 / √ τ with ≈5 atoms in tweezers.…”

Number-resolved imaging of $^{88}$Sr atoms in a long working distance optical tweezer

“…These species have important applications in optical frequency standards [18] due to their extremely narrow (< 1 Hz) optical clock transitions. In combination with tweezer array technology, this highly coherent environment [19,20] offers new perspectives in quantum-enhanced metrology and quantum simulation. Furthermore, narrow intercombination cooling transitions provide powerful new methods for loading [15,16] and high-fidelity imaging in tweezer arrays [21], as well as cooling to the motional ground state [15,16,22].…”