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Spin coherence and optical properties of alkali-metal atoms in solid parahydrogen
AdvisorWeinstein, Jonathan D.
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Trapped gas phase atoms and molecules are the leading experimental platformsfor applications such as quantum computation, quantum sensing, and tests of fundamental physics. There is active research in solid-state electron spin systems for these applications. Nitrogen-vacancy centers in diamond, phosphorus donors in silicon, and molecular nanomagnets are some of the leading examples of the latter case. In this thesis, I will discuss development of a system consisting of trapped alkali atoms in a cryogenic parahydrogen solid as a candidate system for the aforementioned applications. In this experiment, we have studied the relevant properties of Rb-85, Rb-87, Cs-133, and K-39 trapped in the solid.First we discuss experiments where we studied optical spectra, optical pumping,and longitudinal relaxation of spins in the ground state. We find a large variation in the magnitude of the ground state spin polarization from one alkali species to another; however, all the species exhibit similar longitudinal relaxation times on the order of 1 s. We present a series of measurements motivated to understand the interaction mechanisms that lead to the variations across the alkali species.Next we discuss experiments where we studied transverse relaxation of Zeemancoherences in the ground hyperfine manifolds. We find that the transverse relaxation times vary over an order of magnitude across the alkali species. The longest measured transverse relaxation times are about four orders of magnitude shorter than the corresponding longitudinal relaxation times. Based on further study of Rb-85 and Rb-87, we establish that the dominant mechanism that limits the transverse relaxation of the ground state Zeeman coherences is an inhomogeneous electrostatic-like interaction with the host parahydrogen solid. With this understanding, we can choose a combination of Zeeman states that are mostly insensitive to the electrostatic-like interaction. This has allowed us to improve the transverse relaxation times by more than a factor of 6, thereby making this system more attractive for DC sensing applications.In the concluding part we describe experiments on spin echo decay of the correspondingZeeman coherences. The measured spin echo lifetimes are about two orders of magnitude longer than their transverse relaxation counterparts. We present results from a series of experiments which show that unlike the transverse relaxation, the spin echo relaxation is dominated by time-varying magnetic-like interactions. We conclude with a discussion of the ongoing efforts where we are investigating the origin of the magnetic-like interactions in the system.