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Physica Scripta

Tunable formation of cold atomic clouds via dynamic detuning in the launch of 133Cs atoms

H Peña, Cristian López-Monjaraz, Karina Jiménez-García, José Mauricio López-Romero, Neil Corzo

Published Apr 25, 2025• 0 citations
Publisher

Abstract

Abstract The ballistic launch of cold atoms is crucial to a range of advanced investigations, serving as a highly precise source for timekeeping, gravimetry, and fundamental studies in quantum technologies. A detailed understanding of atomic dynamics during these launches is essential for furthering research in these fields. In this study, we investigate the ballistic launch of cold 133Cs atoms and observe a remarkable behavior in the launched atomic cloud. Following the launch, an abrupt change in frequency detuning caused the cold atomic cloud to segment into two parts with distinct velocities. Our work details and characterizes the effect of segmentation on the thermal and velocity properties of the atomic cloud. This non-adiabatic segmentation phenomenon has significant implications for improving the precision of quantum devices that rely on the precise control of free-flying atomic clouds.

DOI
10.1088/1402-4896/add0f1

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Abstract The ballistic launch of cold atoms is crucial to a range of advanced investigations, serving as a highly precise source for timekeeping, gravimetry, and fundamental studies in quantum technologies. A detailed understanding of atomic dynamics during these launches is essential for furthering research in these fields. In this study, we investigate the ballistic launch of cold 133Cs atoms and observe a remarkable behavior in the launched atomic cloud. Following the launch, an abrupt change in frequency detuning caused the cold atomic cloud to segment into two parts with distinct velocities. Our work details and characterizes the effect of segmentation on the thermal and velocity properties of the atomic cloud. This non-adiabatic segmentation phenomenon has significant implications for improving the precision of quantum devices that rely on the precise control of free-flying atomic clouds.
We propose a method for precise control of the launch velocity vector of a cold atomic cloud. By independently adjusting the relative detuning of three pairs of orthogonal counter-propagating laser beams in moving optical molasses, this method achieves accurate regulation of three-dimensional velocity components, thereby realizing precise calibration of atomic launch direction. It can significantly reduce the complexity of mechanical adjustments and mitigate residual errors caused by mechanical tuning, with the advantages of simplicity and easy implementation. Experimental verification on an 87Rb atomic fountain clock shows that the spatial distribution of the cold atomic cloud is obtained via horizontal velocity scanning, and the tilt deviation of the fountain clock is evaluated and corrected. Ultimately, the angles between the cold atom launch direction, the central axis of the fountain clock, and the vertical direction are all less than 0.1 mrad. Time-of-flight signal analysis indicates that under 3% laser power fluctuation, the long-term instability (5000 s) of the velocity reaches 62 μm/s. This method holds significant application value for atomic fountains, atomic gravimeters, atomic gyroscopes, and other cold atomic precision instruments based on moving molasses.
We have employed an intuitive model and 3D Monte Carlo simulations to study the effect of ballistic expansion of the atomic cloud on the collision energies and the resulting frequency shift in a fountain clock. In particular, we show that the energies relevant for collisions contributing to the clock shift correspond to temperatures which may be significantly smaller than the temperature of the cloud at launch. Both the assumptions and predictions of our model are related to realistic parameters of operating caesium fountain clocks.
This paper introduces the concept of Atomic Quantum Boundary Drift (AQBD), a novel observation suggesting a persistent, albeit minute, movement of electron cloud boundaries surrounding individual atoms. The theoretical underpinning of AQBD posits that atoms, under specific conditions, exhibit a slow, directional drift, leading to a measurable change in their apparent position within a quantum system. This phenomenon is explored through the application of highly precise atomic clocks and is presented as a potentially groundbreaking discovery with implications for our fundamental understanding of atomic structure and dynamics. The core hypothesis is that the observed drift is not random fluctuation but a systematic movement influenced by quantum interactions. We detail the methodology, focusing on the use of atomic clocks to detect these subtle shifts, and discuss the potential significance of this finding, suggesting a dynamic rather than static view of atomic structure. The paper concludes with a discussion of the implications for future research and the potential for this discovery to reshape our understanding of quantum mechanics.
Atom-based sensors have the potential to enhance inertial navigation in Global Positioning System (GPS)-denied environments, providing an alternative to traditional accelerometers, gyroscopes, and sensors. Accurate temperature characterization is critical for atom interferometry, which relies on precise control of atomic motion to achieve high sensitivity. This research develops a model to infer the temperature of laser-cooled rubidium vapor by analyzing its ballistic expansion. The release and recapture method is employed to track atomic cloud dynamics after trap release, refining temperature inference through comparison with theoretical models. A magneto-optical trap is used to cool and confine the atoms, followed by sub-Doppler cooling to achieve lower temperatures. By characterizing expansion dynamics, this study improves temperature measurement techniques for cold atomic samples, addressing sources of systematic uncertainty that affect precision in quantum sensors. These findings contribute to advancements in laser cooling methodologies and atomic interferometry at the Naval Postgraduate School, with direct defense applications in inertial navigation, precision measurement, and sensing.
Background:Understanding the dynamics of ultracold quantum gases in an anharmonic potential is essential for applications in the new field of cold-atom scanning probe microscopy. Therein, cold atomic ensembles are used as sensitive probe tips to investigate nanostructured surfaces and surface-near potentials, which typically cause anharmonic tip motion. Results:Besides a theoretical description of this anharmonic tip motion, we introduce a novel method for detecting the cold-atom tip dynamics in situ and real time. In agreement with theory, the first measurements show that particle interactions and anharmonic motion have a significant impact on the tip dynamics. Conclusion:Our findings will be crucial for the realization of high-sensitivity force spectroscopy with cold-atom tips and could possibly allow for the development of advanced spectroscopic techniques such as Q-control.
This paper has developed and characterized a method to produce a velocity-tunable 87 Rb cold atomic source for atomic interferometry application. Using a high speed fluorescence imaging technology, it reports that the dynamic process of the atomic source formation is observed and the source performances including the flux and the initial velocity are characterized. A tunable atomic source with the initial velocity of 1.4∼2.6 m/s and the atomic source flux of 2 × 10 8 ∼ 6 × 10 9 atoms/s has been obtained with the built experimental setup.