Developments in quantum technology for portable strontium atomic systems

Bass, Jonathan (2022). Developments in quantum technology for portable strontium atomic systems. University of Birmingham. Ph.D.

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Cold atomic experiments have reached a level of maturity where they are no longer required to be contained in a laboratory environment. This opens up the opportunity to develop portable quantum systems for use in science and industry but there is still a requirement to improve the methodology and technology to decrease the size and/or increase the performance to allow useful deployment in the field. Portable optical clocks are moving towards the prospect of remote frequency comparison where optical fibres links cannot be established [1], and measurements of gravitational redshift utilising the change in clock frequency with height [2]. This thesis focuses on systems utilising neutral strontium, detailing work on a portable strontium lattice clock, compact laser systems and an alternative atom source to current methods for next generation systems.

The clock detailed in the thesis is designed with tophat beams and prisms to generate the 6 orthogonal directions of light for cooling and trapping of atoms; allowing a compact and robust atomic package to be designed. The progress in the experiment from a blue to a red magneto optical trap (MOT) is shown and it is described how the results found affect the future of the experiment. This work also inspired research into future technologies for portable strontium systems. Specifically, lasers of dimensions $ 77 \times 34 \times 57$ mm (length $\times$ width $\times$ height) were built and used to trap and cool atoms. These stable and compact lasers offer a low cost alternative to commercial lasers while providing the performance required for the trapping of atoms. Of note is the 461 nm laser that was constructed, producing 40 mW of single frequency light.

The final experimental section covers the novel MOT loading with optically activated, strontium oxide powder that is successfully used as a atomic source for a cold atomic experiment. The source is held within the science chamber and sublimated to a gas with a focused 405 nm emission laser. This allows unique and compact designs be made as the source no longer needs be held and heated outside of the chamber, requiring line of sight from the point of release to capture. The flux released from the source has proven to trap twice as many atoms in the blue MOT compared to a commonly used dispenser, both without pre-cooling. The characterisation and limitation of this source is presented with considerations of how it will be used within an experiment.

[1] T. Akatsuka et al. “30-km-long optical fiber link at 1397 nm for frequency comparison between distant strontium optical lattice clocks”. In: Jpn. J. Appl. Phys. 53.032801 (Feb. 2014). doi: 10.7567/JJAP.53. 032801. url: 032801.
[2] M. Takamoto et al. “Test of general relativity by a pair of transportable optical lattice clocks”. In: Nature Photonics 14.411-415 (Apr. 2020). doi: 10.1038/ s41566 - 020 - 0619 - 8. url: articles/s41566-020-0619-8.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Licence: All rights reserved
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Physics and Astronomy
Funders: Engineering and Physical Sciences Research Council
Subjects: Q Science > QC Physics


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