Spin coherence and optical properties of alkali-metal atoms in solid parahydrogen
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Authors
Upadhyay, Sunil
Issue Date
2020
Type
Dissertation
Language
Keywords
alkali atoms , magnetic resonance , optical pumping , parahydrogen , spin coherence
Alternative Title
Abstract
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.