Sr atom interferometry with the optical clock transition as a gravimeter and a gravity gradiometer

Abstract

We characterize the performance of a gravimeter and a gravity gradiometer based on the 1 S 0 -3 P 0 clock transition of strontium atoms. We use this new quantum sensor to measure the gravitational acceleration with a relative sensitivity of 1.7 × 10 −5 , representing the first realisation of an atomic interferometry gravimeter based on a single-photon transition. Various noise contributions to the gravimeter are measured and characterized, with the current primary limitation to sensitivity seen to be the intrinsic noise of the interferometry laser itself. In a gravity gradiometer configuration, a differential phase sensitivity of 1.53 rad/ √ Hz was achieved at an artificially introduced differential phase of π/2 rad. We experimentally investigated the effects of the contrast and visibility based on various parameters and achieve a total interferometry time of 30 ms, which is longer than previously reported for such interferometers. The characterization and determined limitations of the present apparatus employing 88 Sr atoms provides a guidance for the future development of large-scale clock-transition gravimeters and gravity gradiometers with alkali-earth and alkali-earth-like atoms (e.g., 87 Sr, Ca, Yb).

Circulating pulse cavity enhancement as a method for extreme momentum transfer atom interferometry

“…With a beam to cloud diameter ratio of 20, residual intensity variations have a negligible contribution to fidelity loss. A typical cloud of radius of 200 µm would require a 1/e 2 beam radius of 4 mm (42), and a total input power of 1.1 W (31,35). However, divergence of the Gaussian beam over the 1 km arm length is the more stringent constraint.…”

“…The 698 nm optical clock transition in 87 Sr is a suitable candidate for single photon interferometry. With an excited state lifetime of 150s (Γ = 2π • 1 mHz), spontaneous emission is a negligible source of decoherence (34,35). With microsecond π-pulses and therefore MHz Rabi frequencies, the 10 4 k pulse sequence is completed in a small fraction of the total interrogation time.…”

Measuring gravitational time dilation with delocalized quantum superpositions

“…[31] involves a combination of simultaneous pairs of pulses driving single-photon transitions between the two clock states. The application of these single-photon transitions to atom interferometry has already been demonstrated for 88 Sr atoms [47,48], but a large magnetic field was necessary to turn the otherwise forbidden transition for bosonic isotopes into a weakly allowed one. Since the use of such magnetic fields does not seem viable for high-precision measurements, fermionic isotopes, which are harder to cool down to the required ultra-low temperatures, will need to be employed instead.…”

Watt-level blue light for precision spectroscopy, laser cooling and trapping of strontium and cadmium atoms

“…high-precision optical atomic clocks and for atom interferometry. Strontium has received considerable attention, especially in the atomic clock community [1][2][3], but also more recently for atomic interferometry, with recent demonstrations on the narrow 1 𝑆 0 → 3 𝑃 1 intercombination [4,5] and ultra-narrow 1 𝑆 0 → 3 𝑃 0 clock transitions [6,7], as well as being suggested as the test species for both ground-based [8,9] and satellite missions [10,11] for gravitational wave and dark matter detection. Cadmium is presently less well developed, though it has attracted renewed interest due to its low susceptibility to background blackbody radiation [12,13].…”