We report on the realization of a matter-wave interferometer based on single-photon interaction on the ultranarrow optical clock transition of strontium atoms. We experimentally demonstrate its operation as a gravimeter and as a gravity gradiometer. No reduction of interferometric contrast was observed for a total interferometer time up to ∼10 ms, limited by geometric constraints of the apparatus. Single-photon interferometers represent a new class of high-precision sensors that could be used for the detection of gravitational waves in so far unexplored frequency ranges and to enlighten the boundary between quantum mechanics and general relativity.
We report on the realization of a matter-wave interferometer based on single-photon interaction on the ultranarrow optical clock transition of strontium atoms. We experimentally demonstrate its operation as a gravimeter and as a gravity gradiometer. No reduction of interferometric contrast was observed for a total interferometer time up to ∼10 ms, limited by geometric constraints of the apparatus. Single-photon interferometers represent a new class of high-precision sensors that could be used for the detection of gravitational waves in so far unexplored frequency ranges and to enlighten the boundary between quantum mechanics and general relativity.
Abstract We characterize the performance of a gravimeter and a gravity gradiometer based on the 1S0–3P0 clock transition of strontium atoms. We use this new quantum sensor to measure the gravitational acceleration with a relative sensitivity of after 150 s of integration time, 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 was achieved at an artificially introduced differential phase of rad. We experimentally investigated the effects of the contrast and visibility based on various parameters and achieved 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 88Sr 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. 87Sr, Ca, Yb, Cd).
We report the first realization of large momentum transfer (LMT) clock atom interferometry. Using single-photon interactions on the strontium ^{1}S_{0}-^{3}P_{1} transition, we demonstrate Mach-Zehnder interferometers with state-of-the-art momentum separation of up to 141 ℏk and gradiometers of up to 81 ℏk. Moreover, we circumvent excited state decay limitations and extend the gradiometer duration to 50 times the excited state lifetime. Because of the broad velocity acceptance of the interferometry pulses, all experiments are performed with laser-cooled atoms at a temperature of 3 μK. This work has applications in high-precision inertial sensing and paves the way for LMT-enhanced clock atom interferometry on even narrower transitions, a key ingredient in proposals for gravitational wave detection and dark matter searches.
We present a gradiometer based on matter-wave interference of alkaline-earth-metal atoms, namely 88 Sr. The coherent manipulation of the atomic external degrees of freedom is obtained by large-momentum-transfer Bragg diffraction, driven by laser fields detuned away from the narrow 1 S 0 – 3 P 1 intercombination transition. We use a well-controlled artificial gradient, realized by changing the relative frequencies of the Bragg pulses during the interferometer sequence, in order to characterize the sensitivity of the gradiometer. The sensitivity reaches 1.5 × 10 −5 s −2 for an interferometer time of 20 ms, limited only by geometrical constraints. We observed extremely low sensitivity of the gradiometric phase to magnetic field gradients, approaching a value 10 4 times lower than the sensitivity of alkali-atom based gradiometers, limited by the interferometer sensitivity. An efficient double-launch technique employing accelerated red vertical lattices from a single magneto-optical trap cloud is also demonstrated. These results highlight strontium as an ideal candidate for precision measurements of gravity gradients, with potential application in future precision tests of fundamental physics.
Matter-wave interferometers operating as clocks and gravimeters allow for precision measurements of time and gravity at unprecedented levels. In all these sensors, the exquisite control of both the internal (electronic) and external (center-of-mass motion) degrees of freedom of ultracold atomic samples enable interactions at their most basic, quantum level to be studied, paving the way for new tests of fundamental physics. For all these applications, novel interferometric schemes based on the narrow intercombination transitions of alkali-earth (and alkali-earth like) atoms have recently gained considerable attention. Here we present the work towards the realization of a simultaneous atom interferometer with cadmium and strontium atoms and the potential physics such a system could explore, along the idea of the ERC - “TICTOCGRAV” EU research project. In particular, we present the design and implementation of the high-power UV laser sources necessary for performing atom interferometry with cadmium and the prospects for developing a high-flux, cold source of cadmium. Potential applications of a simultaneous cadmium and strontium atom interferometer, including to weak equivalence principle and quantum time dilation tests, are discussed.
Atom interferometry is a maturing quantum technology which provides one of the most precise approaches to explore fundamental physics, e.g. to search for dark matter, and one day to observe gravitational waves in the frequency range from 10 mHz - 10 Hz. Standard atom interferometers use Bragg or Raman two-photon transitions for the coherent manipulation of matter waves. In a Michelson configuration for atom-aided gravitational waves detection, two orthogonal arms are built to reject laser noise, in the same way as optical interferometers. Atom interferometers utilizing an optical clock transition for coherent manipulation are less affected by the technical noise of the laser, and as a result that single baseline detectors become feasible.At LP2N, we are building a vertical gravity-gradiometer based on atom interferometry using strontium atoms probed on such a clock transition. The final experimental setup will implement a 6-meter tall atomic fountain to realize gradiometry with two or more separated atomic clouds.In my dissertation, I present the realization of the experimental setup in all its sub-systems, and the first experiments with atoms at millikelvin temperature obtained with the first cooling stage with blue light. The laser system for the second red cooling phase and for the coherent manipulation is ready; meanwhile, we realized a dual-frequency Zeeman slower that improves the atomic flux by a factor of six. We also present a study of an original scheme to achieve pulsed and fast light-atom interaction in a narrow-linewidth cavity by exploiting the Stark shift as a high bandwidth switch; this technique could open to the use of narrow-linewidth cavities – and notably their high power buildup - in several contexts, like atom interferometry and quantum information.
The interplay between quantum mechanics and gravity is almost as mysterious today as it was half a century ago despite remarkable progress in either field. Putting aside exotic topics like quantum theories of gravity, even a purely classical quantity, such as Newton’s gravitational constant (or “big G”), has not been measured to a precision and accuracy close to that of other fundamental constants (e.g. speed of light, fine structure constant, etc.). Moreover, until recently [1], most measurements of big G have been classical in nature. Therefore, using a quantum sensor, such as an atomic gradiometer, to perform precision measurements of big G not only adds another (quantum) dimension to said measurement, but also opens a window into studying other fundamental classical gravitational phenomena, like measuring gravitational waves [2]. Furthermore, due to the quantum nature of the sensor apparatus, the interplay of gravity and quantum mechanics can be explored by studying effects such as gravitational decoherence [3]. In this talk, I will discuss ongoing progress on the construction of a 2 meter tall atom interferometer using Strontium. By virtue of the bosonic isotope (Strontium-88) having a zero nuclear spin, the demands on magnetic shielding of the apparatus are relaxed compared to (say) alkali atoms. Once operational over the 2 meter baseline, this atom interferometer will be used to perform short-distance tests (10 centimeters to 1 meter) of gravity using source (or proof) masses in the 100 kilogram range or higher. The distance between the gravitational sensor (i.e. atom interferometer) and the proof masses can be varied using appropriate translation stages. This measurement configuration will allow us to perform precision measurements of big G. [1] Rosi et al. (2014). Nature 510, 518-521. [2] Abe et al. (2021) Quantum Science and Technology 6, 044003. [3] Roura (2020). Physical Review X 10, 021014.