Optical Magnetometry Using Multiphoton Transitions

Optical magnetometry plays a critical role in low-energy precision measurements and numerous other applications. In particular, permanent electric dipole moment (EDM) searches impose strict requirements on magnetic field sensitivity of the underlying atomic or molecular species. Other magnetometer properties -- such as chemical reactivity, dielectric strength, and interaction cross-sections with other species -- also impose limitations on experimental conditions. Here, we explore a novel approach to optical magnetometry, using multiphoton transitions of diamagnetic atoms to detect Larmor precession of polarized nuclei. Resonant probes are possible at moderate ultraviolet wavelengths, and hyperfine structure couples spin precession to fluorescence transitions with negligible backgrounds; paramagnetic rotation due to intensity-dependent dispersion may also be detectable. Nuclear spins and nonlinear optical excitation introduce new degrees of freedom, and evade limitations arising from rapid electronic decoherence. This dissertation reports progress towards two-photon optical magnetometry using ytterbium, rubidium, and xenon. We characterize the influence of probe polarization and magnetic fields on fluorescence spectra, for one- and two-photon continuous-wave (cw) excitation of ytterbium. Resolved hyperfine and isotope structure allow us to use spin-zero isotopes for diagnostics and normalization, and we develop analysis for overlapping two-photon resonances. We also report measurements of two-photon excitation in ytterbium and rubidium using picosecond laser pulses, and in xenon using a cw laser. Although hyperfine structure is unresolved, the rubidium measurements are sensitive to probe field polarization. Fluorescence spectra from two-photon excitation of ytterbium with femtosecond pulses show modulation when the repetition rate changes. Although techniques for polarizing noble gas nuclei are mature, existing cell designs are incompatible with two-photon magnetometry. We describe development of silicate-assisted hydroxide-catalysis bonding for both aluminosilicate EDM cells with silicon electrodes, and sapphire-windowed cells that transmit ultraviolet excitation light. Progress in measuring the 129Xe nuclear EDM is discussed. Absolute referencing of the picosecond laser to potassium transitions is proposed for two-photon spectroscopy of ytterbium and xenon, and a compatible frequency-tripling method is outlined to produce excitation light for xenon. Novel possibilities including spatial resolution and multiphoton optical pumping of nuclear spins are considered.PHDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135807/1/sdegen_1.pd

Frequency shifts in noble-gas magnetometers

Polarized nuclei are a powerful tool in nuclear spin studies and in searches for beyond-the-standard model physics. Noble-gas comagnetometer systems, which compare two nuclear species, have thus far been limited by anomalous frequency variations of unknown origin. We studied the self-interactions in a $^3$He-$^{129}$Xe system by independently addressing, controlling and measuring the influence of each component of the nuclear spin polarization. Our results directly rule out prior explanations of the shifts, and demonstrate experimentally that they can be explained by species dependent self-interactions. We also report the first gas phase frequency shift induced by $^{129}$Xe on $^3$He.Comment: v.

Optical Lattices for Atom Based Quantum Microscopy

We describe new techniques in the construction of optical lattices to realize a coherent atom-based microscope, comprised of two atomic species used as target and probe atoms, each in an independently controlled optical lattice. Precise and dynamic translation of the lattices allows atoms to be brought into spatial overlap to induce atomic interactions. For this purpose, we have fabricated two highly stable, hexagonal optical lattices, with widely separted wavelengths but identical lattice constants using diffractive optics. The relative translational stability of 12nm permits controlled interactions and even entanglement operations with high fidelity. Translation of the lattices is realized through a monolithic electro-optic modulator array, capable of moving the lattice smoothly over one lattice site in 11 microseconds, or rapidly on the order of 100 nanoseconds.Comment: 7 pages, 9 figure

Ultracold neutron storage in a bottle coated with the fluoropolymer CYTOP

The fluoropolymer CYTOP was investigated in order to evaluate its suitability as a coating material for ultracold neutron (UCN) storage vessels. Using neutron reflectometry on CYTOP-coated silicon wafers, its neutron optical potential was measured to be 115.2(2) neV. UCN storage measurements were carried out in a 3.8 l CYTOP-coated aluminum bottle, in which the storage time constant was found to increase from 311(9) s at room temperature to 564(7) s slightly above 10 K. By combining experimental storage data with simulations of the UCN source, the neutron loss factor of CYTOP is estimated to decrease from 1.1(1)$$\times 10^{-4}$$ to 2.7(2)$$\times 10^{-5}$$ at these temperatures, respectively. These results are of particular importance to the next-generation superthermal UCN source SuperSUN, currently under construction at the Institut Laue-Langevin, for which CYTOP is a possible top-surface coating in the UCN production volume

The PanEDM neutron electric dipole moment experiment at the ILL

The neutron's permanent electric dipole moment dn is constrained to below 3 × 10−26e cm (90% C.L.) [1, 2], by experiments using ultracold neutrons (UCN). We plan to improve this limit by an order of magnitude or more with PanEDM, the first experiment exploiting the ILL's new UCN source SuperSUN. SuperSUN is expected to provide a high density of UCN with energies below 80 neV, implying extended statistical reach with respect to existing sources, for experiments that rely on long storage or spin-precession times. Systematic errors in PanEDM are strongly suppressed by passive magnetic shielding, with magnetic field and gradient drifts at the single fT level. A holding-field homogeneity on the order of 10−4 is achieved in low residual fields, via a high static damping factor and built-in coil system. No comagnetometer is needed for the first order-of-magnitude improvement in dn, thanks to high magnetic stability and an assortment of sensors outside the UCN storage volumes. PanEDM will be commissioned and upgraded in parallel with SuperSUN, to take full advantage of the source's output in each phase. Commissioning is ongoing in 2019, and a new limit in the mid 10−27e cm range should be possible with two full reactor cycles of data in the commissioned apparatus

The PanEDM Neutron Electric Dipole Moment Experiment at the ILL

International audienceThe neutron's permanent electric dipole moment dn is constrained to below 3 × 10−26e cm (90% C.L.) [1, 2], by experiments using ultracold neutrons (UCN). We plan to improve this limit by an order of magnitude or more with PanEDM, the first experiment exploiting the ILL's new UCN source SuperSUN. SuperSUN is expected to provide a high density of UCN with energies below 80 neV, implying extended statistical reach with respect to existing sources, for experiments that rely on long storage or spin-precession times. Systematic errors in PanEDM are strongly suppressed by passive magnetic shielding, with magnetic field and gradient drifts at the single fT level. A holding-field homogeneity on the order of 10−4 is achieved in low residual fields, via a high static damping factor and built-in coil system. No comagnetometer is needed for the first order-of-magnitude improvement in dn, thanks to high magnetic stability and an assortment of sensors outside the UCN storage volumes. PanEDM will be commissioned and upgraded in parallel with SuperSUN, to take full advantage of the source's output in each phase. Commissioning is ongoing in 2019, and a new limit in the mid 10−27e cm range should be possible with two full reactor cycles of data in the commissioned apparatus