Session U05: Optical, Atomic, and Molecular Physics I

Bell Tests In the Moon-Earth Scale

Entanglement is measured in a so-called Bell Test, which puts a bound on the correlation between the states of two particles under a local-realist theory (hence “Bell’s Inequality”). We propose a Bell Test with a source halfway between the Earth and the Moon that would send a pair of entangled photons to a polarizer on the Moon and a polarizer on the Earth, the settings of which humans would adjust. At this large scale, humans would be space-like separated, meaning the decision on one side could not affect the photon’s measurement outcome on the other side. Moreover, humans could be given sufficient time to be presented with a choice, make a decision, and turn that decision into a polarizer setting after the pair of entangled photons were sent. We expect this experiment to violate Bell’s Inequality, but if it didn’t, it would mean entanglement could be explained through a hidden-variable theory. In any case, taking Bell Tests to this large scale might better validate non-locality and perhaps, combined with the effects of relativity, show us something new.   

Studying Spin Transport with Ultracold Atoms

Ultracold atoms can be used as a tool to study transport properties in quantum many-body systems. By inducing a magnetic field gradient, and thus a spin-dependent force, one can determine properties of spin diffusion at low temperatures close to the critical temperature for the superfluid phase transition. Studying ultracold fermions, like lithium-6, can reveal the impact that Cooper pairing has on spin transport.   

Polarized Drell-Yan Process to Study Sea Quarks at Fermilab E1039

The E1039/SpinQuest collaboration at Fermilab will measure the spin asymmetry in the quark sea. SpinQuest is the continuance of the E906/SeaQuest experiment which has studied the ratio of $\bar{u}$ to $\bar{d}$ in a proton using the Drell-Yan process to measure di-muons from quark-antiquark annihilation. The E1039 project has now upgraded the SeaQuest spectrometer with a polarized target and improved detectors to provide knowledge of the target proton’s spin. With this upgrade, SpinQuest can now search for a left-right spin asymmetry in Drell-Yan dimuons to make the world’s first measurement of the sea quark Sivers function, a correlation between the transverse momentum of the quark and the proton’s spin. Should the Sivers function turn out to be equal to zero, the spin of the proton and the transverse momentum of the sea quarks might then be independent of each other. However, if it is non-zero, this will suggest that sea quarks have orbital angular momentum, which may be one of the missing pieces to the proton spin puzzle. This presentation will discuss how the SpinQuest experiment will contribute to the understanding of the Sivers function in sea quarks.   

Developing Optical Control of Levitated Particles in A Thermophoretic Trap

We study the dynamics of levitated particles under illumination by a 405 nm wavelength laser. The particles are levitated and trapped using a thermophoretic force field generated in a vacuum chamber. Microspheres ranging from 5 to 50 $\mu $m in diameter are levitated at pressures between 4 and 15 Torr. Levitated microspheres exhibit different movements under illumination: movements in and opposite the direction of laser propagation (positive and negative photophoretic forces). To evaluate our experimental results vis-\`{a}-vis existing models of photophoresis, we report observations of the particle trajectories. We simulate the radiation field and temperature distribution of levitated spheres to understand the measurements quantitatively. This study of illumination-induced dynamics is a necessary first step towards use of the laser for optical control. With improved understanding of light forces, the laser can be used for novel measurements of the radial thermophoretic force and characterization of the thermophoretic potential. Optical control of levitated particles will widen the possibilities of our levitation scheme as a platform for studying micron-length dynamics and force fields in a microgravity environment.~   

Development of an optical system to determine impurity content & composition in a snowpack

Snow influences global temperatures due to its high reflectivity. This reflective property is called albedo, the fraction of solar radiation reflected off of a surface. Among other factors, light-absorbing particles (LAPs) such as black carbon, organic carbon, and dust can decrease snow albedo, subsequently accelerating snowmelt. Referencing previous studies, we built an optical system to measure LAP concentration in a snow sample following filtration through a Nuclepore filter. To do this, we used a light source ranging from 230 nm to 2500 nm, two integrating spheres, and a spectrometer to record light transmitted through a filter to measure LAP concentration. Following design and development, we have continued to characterize and quantitatively calibrate the system. Preliminary analysis of varying concentrations of black carbon show that this is a promising measurement technique for use on snow from the St. Olaf Natural Lands in Northfield, MN. These local measurements will be helpful in understanding the role of LAP concentration in Midwestern snow albedo and the implications for the timing of seasonal snowmelt as global temperatures continue to increase.   

Channel Competition in Single Ionization of CS$^+$ by Intense Laser Pulses

Employing a coincidence three-dimensional momentum imaging technique, we investigate the ultrafast, intense laser-induced ionization of CS$^+$. The analysis presented here focuses on the intensity-dependent branching ratio from 3$\times$10$^{14}$ to 3$\times$10$^{16}$ W/cm$^2$. The charge-symmetric C$^+$ + S$^+$ channel is dominant at all measured intensities, followed by CS$^{2+}$ and then C + S$^{2+}$, while C$^{2+}$ + S is not observed. The branching ratio measurement is assisted by {\it in situ} determination of the detection efficiency of all the product channels.   

Towards Cavity-Enhanced 2DIR Spectroscopy

We propose a new scheme for two-dimensional spectroscopy using cavity-enhancement techniques in the mid-infrared spectral region to study hydrogen bond networks. The scheme will use two pump beams and one probe beam, generated by several OPAs (optical parametric amplifiers). Phase cycling 2DIR spectroscopy will be achieved through using multiple frequency combs. This project focuses on planning the layout of the system, integrating all the necessary components as well as simulating necessary conditions for measurements.   

Optical buffering in a bottle microresonator on an optical fiber.

Manufacturing highly efficient optical communications and computing devices requires designing dense integrated photonic circuits. Unfortunately, surface roughness of microscopic optical signaling devices results in light attenuation, decreasing the efficiency of the optical devices. A microscopic optical buffer would alleviate these issues; a potential solution is the Surface Nanoscale Axial Photonics (SNAP) platform. The SNAP platform operates because of the propagation of whispering gallery modes (WGMs) around the surface of an optical fiber. Because WGMs undergo slow axial propagation, they can be mathematically described by the one-dimensional Schr\"{o}dinger equation. In this project, we calculate solutions to the effective wave equation to model the circulation of whispering gallery modes. We study the evolution of Gaussian-shaped wave pulses in a bottle microresonator on an optical fiber. By analyzing the propagation of WGMs within the bottle microresonator, we can examine the feasibility of creating a microscopic optical buffer for use in optical signal processing. In this project, we find analytical and numerical solutions to the effective wave equation. We then use the numerical solutions to the effective wave equation to develop a model of the system in Mathematica.   

Confining an ion in a surface electrode ion trap

Trapped ions are a promising platform for quantum information science, as they are easily manipulated using laser and microwave fields and well isolated from their environment. At Williams College, I have worked with Prof. Charlie Doret to begin installing the High Optical Access (HOA) Ion Trap 2.0 from Sandia Laboratories. The lab ultimately hopes to use the HOA trap to study mesoscopic heat transfer in chains of calcium ions. A deeper understanding of heat transfer on this scale could provide insights to the thermal regulation of nanoscale materials and microelectronics. We developed a MATLAB script that, given a target electric potential, calculates an optimal solution of voltages to apply to the HOA trap's DC electrodes that will match the target potential. This DC voltage solution, along with an AC field from radio frequency electrodes, will allow the lab to confine an ion in the HOA trap. The program has been further extended to calculate voltage solutions for the DC electrodes in order to trap chains of ions and to shuttle ions around in the trap. These calculations will be essential for efficiently running a future experiment with long chains of calcium ions.