Atomic, Molecular and Optical Physics Commons^™

The Thermodynamic Fate Of Isolated Quantum Systems, John Keim, Isabel Martinez-Robles, Nicolaus A. Chlanda, Sage M. Thomas, Maja Teofilovska, Sarah E. Spielman, Jordyn Strunk, Tina Zhao, Juniper J. Bauroth-Sherman, Hannah Conley, Philip Conte, Aidan Kirk, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Summer Fellows

Isolated quantum systems are typically observed to come to thermal equilibrium. The weak Eigenstate Thermalization Hypothesis (wETH) states that the vast majority of eigenvectors are thermal. This implies that most initial states should thermalize. Studying the rare cases in which they fail to thermalize could reveal insight into quantum dynamics. In our experiment, we excite Rydberg atoms and allow them to exchange energy via dipole-dipole interactions. We find that they do not thermalize. We present numerical and theoretical results that show that our experimental initial state is not typical.

Nonthermalizing Dynamics Of Interacting Rydberg Atoms, Nicolaus A. Chlanda

Physics and Astronomy Honors Papers

An isolated system of ultracold Rydberg atoms can come to equilibrium by exchanging energy through dipole-dipole interactions. In our experiment, a static electric field of a few V/cm shifts the energy levels of the atoms, so that the energy levels are nearly degenerate at zero field and fan out with increasing field to form a manifold. We excite atoms to energy levels near the center of the manifold, where the spacing is nearly harmonic. We allow them to interact for a few microseconds, by which time the population of each energy level has reached a steady state. The population is …

Computational Analysis Of Proton Conductivity Factors In Grotthuss-Style Mechanisms, Brock Dyer

Physics and Astronomy Honors Papers

The mechanism and fundamental molecular properties involved in proton conduction are discussed. Four calculable properties are presented: the proton affinity, binding energy (between protonated and neutral forms), intramolecular tautomerization barrier, and proton hopping barrier. An overview of the computational methods used in this thesis, including an introduction to the many-body Schrödinger equation and Density Functional Theory, as well as a look at Plane-Wave Density Functional Theory and Gaussian-Type Orbital Density Functional Theory are presented. 4,5-dimethyl-[1,2,3]-triazole is used as a model system, with 10 variations being generated with varying amounts and positions of fluorine substitution on the methyl groups. Preliminary calculations …

Quantum Many-Body Scars In Few-Body Dipole-Dipole Interactions, Sarah E. Spielman, Alicia Handian, Nina P. Inman, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

We simulate the dynamics of Rydberg atoms resonantly exchanging energy via two-, three-, and four-body dipole-dipole interactions in a one-dimensional array. Using simplified models of a realistic experimental system, we study the initial-state survival probability, mean level spacing, spread of entanglement, and properties of the energy eigenstates. By exploring a range of disorders and interaction strengths, we find regions in parameter space where the three- and four-body dynamics either fail to thermalize or do so slowly. The interplay between the stronger hopping and weaker field-tuned interactions gives rise to quantum many-body scar states, which play a critical role in slowing …

Measuring The Density Of Ultracold Rydberg Atoms, Chakradhar Pulipaka, Philip Conte, Aidan Kirk

Physics and Astronomy Summer Fellows

The energy exchange between ultracold, highly-excited, or Rydberg, atoms can be used to model quantum mechanical systems. When interpreting the results of these systems, it is important to know the density of the Rydberg atoms. In a recent experiment, we have studied several clusters of states that form a nearly harmonic ladder of clusters. The Rydberg atoms all start in one energy cluster, and the interactions between them allows energy to spread to all the other states. We have developed new analysis software along with a method in which a simple four-level system can calibrate the density for our experiment. …

Density Dependence And Dynamics Of Dipole-Dipole Interactions Among Rydberg Atoms, Hannah Conley

Physics and Astronomy Summer Fellows

After trapping atoms, exciting them to an initial high-energy Rydberg state, and allowing them a brief time to exchange energy with each other through dipole-dipole interactions, we observe how their energies are redistributed among various energy levels. The measurements we make in this physical experiment do not give insight into how individual atoms interact or metrics like fidelity and entanglement entropy, which impact our results. For this reason, it is useful to compare our results from the physical experiment to those of our simulation on a supercomputer, in which we can track the final and initial energy of individual atoms …

Resonant Energy Exchange In Ultracold Rydberg Atoms, Samantha Grubb, Alan Okinaka

Physics and Astronomy Summer Fellows

Ultracold Rydberg atoms serve as good systems in which resonant dipole-dipole interactions can be observed. The goal of our work is to design a simulation in which energy exchange among many nearly evenly spaced energy levels is observed. These observations are useful for understanding the time evolution of complicated quantum systems, and have applications in quantum computing and simulating. We are utilizing a supercomputer to run our simulation as well as studying the system experimentally. Once we obtain simulated results, we plan to compare them with the results obtained in a lab.

54fe(D,P)55fe Single Neutron Transfer Presentation, Matthew Quirin, Raymond Saunders

Physics and Astronomy Presentations

During our summer research at the John D Fox Laboratory, we used the 9 MV Tandem van de Graaff accelerator and the Super Enge Split-Pole Spectrograph to make measurements of the neutron transfer reaction 54Fe(d,p) 55Fe to observe and explore excited states of 55Fe and shell structure beyond the magic number N=28. We have created momentum spectra and angular distribution plots of the protons from the reaction which will be analyzed to determine the angular momentum values of states and single-neutron energies in 55Fe in an effort to better understand nuclear structure.

54fe(D,P)55fe Single Neutron Transfer, Matthew Quirin, Raymond Saunders

Physics and Astronomy Summer Fellows

During our summer research at the John D Fox Laboratory, we used the 9 MV Tandem van de Graaff accelerator and the Super Enge Split-Pole Spectrograph to make measurements of the neutron transfer reaction 54Fe(d,p) 55Fe to observe and explore excited states of 55Fe and shell structure beyond the magic number N=28. We have created momentum spectra and angular distribution plots of the protons from the reaction which will be analyzed to determine the angular momentum values of states and single-neutron energies in 55Fe in an effort to better understand nuclear structure.

Simulating Many Body Localization With Rydberg Atoms, Alicia Handian

Physics and Astronomy Honors Papers

In thermodynamics, interacting systems are expected to achieve equilibrium with one another over the course of time. However, there are exceptions to this rule. When systems localize, or fail to reach equilibrium, information about the initial state of the system is preserved and locally observable after long periods of time. Many-body localization focuses on systems of interacting particles that fail to thermalize. We have developed a simulation that models the behavior of a many-body quantum system. The simulation is inspired by experiments conducted by Liu, et al., in their recent publication “Time Dependence of Few Body Forster Interactions Among Ultracold …

Time Dependence Of Few-Body Forster Interactions Among Ultracold Rydberg Atoms, Zhimin Cheryl Liu, Nina P. Inman, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

Rubidium Rydberg atoms in either |m_j| sublevel of the 36p_3/2 state can exchange energy via Stark-tuned Förster resonances, including two-, three-, and four-body dipole-dipole interactions. Three-body interactions of this type were first reported and categorized by Faoro et al. [Nat. Commun. 6, 8173 (2015)] and their Borromean nature was confirmed by Tretyakov et al. [Phys. Rev. Lett. 119, 173402 (2017)]. We report the time dependence of the N-body Förster resonance N×36p_3/2,|mj|=1/2→36s_1/2+37s_1/2+(N−2)×36p_3/2,|mj|=3/2, for N=2, 3, …

Perturbed Field Ionization For Improved State Selectivity, Vincent C. Gregoric, Jason Bennett, Bianca R. Gualtieri, Hannah P. Hastings, Ankitha Kannad, Zhimin Cheryl Liu, Maia R. Rabinowitz, Zoe A. Rowley, Maio Wang, Lauren Yoast, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

Selective field ionization (SFI) is used to determine the state or distribution of states to which a Rydberg atom is excited. By evolving a small perturbation to the ramped electric field using a genetic algorithm, the shape of the time-resolved ionization signal can be controlled. This allows for the separation of signals from pairs of states that would be indistinguishable with unperturbed SFI. Measurements and calculations are presented that demonstrate this technique and shed light on how the perturbation directs the pathway of the electron to ionization. Pseudocode for the genetic algorithm is provided. Using the improved resolution afforded by …

Improving The State Selectivity Of Field Ionization With Quantum Control, Vincent C. Gregoric, Jason Bennett, Bianca R. Gualtieri, Ankitha Kannad, Zhimin Cheryl Liu, Zoe A. Rowley, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

The electron signals from the field ionization of two closely spaced Rydberg states of rubidium-85 are separated using quantum control. In selective field ionization, the state distribution of a collection of Rydberg atoms is measured by ionizing the atoms with a ramped electric field. Generally, atoms in higher energy states ionize at lower fields, so ionized electrons which are detected earlier in time can be correlated with higher energy Rydberg states. However, the resolution of this technique is limited by the Stark effect. As the electric field is increased, the electron encounters numerous avoided Stark level crossings which split the …

Catalysis Of Stark-Tuned Interactions Between Ultracold Rydberg Atoms, A. L. Win, W. D. Williams, Thomas J. Carroll, C. I. Sukenik

Physics and Astronomy Faculty Publications

We have experimentally investigated a catalysis effect in the resonant energy transfer between ultracold 85Rb Rydberg atoms. We studied the time dependence of the process, 34p + 34p → 34s + 35s, and observed an enhancement of 34s state population when 34d state atoms are added.We have also performed numerical model simulations, which are in qualitative agreement with experiment and indicate that the enhancement arises from a redistribution of p-state atoms due to the presence of the d-state atoms.

Detecting Rydberg Interactions With Controlled Ionization, Lauren Yoast

Physics and Astronomy Summer Fellows

Rydberg atoms, which have a highly excited outer electron, are easily manipulated by electric fields. Using a magneto-optical trap, we cool Rubidium atoms to a few hundred millionths of a Kelvin above absolute zero and then excite to Rydberg states. Our first project looks at the dipole-dipole interactions of two atoms starting in the 33p state and ending in the 34s and 33s states. The standard technique is to apply an increasing electric field that ionizes the Rydberg electron and sends it to a detector, but unfortunately the signals overlap. A genetic algorithm is used to separate the signals by …

Quantum Control Via A Genetic Algorithm Of The Field Ionization Pathway Of A Rydberg Electron, Vincent C. Gregoric, Xinyue Kang, Zhimin Cheryl Liu, Zoe A. Rowley, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

Quantum control of the pathway along which a Rydberg electron field ionizes is experimentally and computationally demonstrated. Selective field ionization is typically done with a slowly rising electric field pulse. The (1/n^*)⁴ scaling of the classical ionization threshold leads to a rough mapping between arrival time of the electron signal and principal quantum number of the Rydberg electron. This is complicated by the many avoided level crossings that the electron must traverse on the way to ionization, which in general leads to broadening of the time-resolved field ionization signal. In order to control the ionization pathway, thus …

Optimizing An Electron's Path To Ionization Using A Genetic Algorithm, Jason Bennett, Kevin Choice

Physics and Astronomy Summer Fellows

A Rydberg atom is an atom with a highly excited and weakly bound valence electron. A widespread method of studying quantum mechanics with Rydberg atoms is to ionize the electron and measure its arrival time. We use a Genetic Algorithm (GA) to control the electron's path to ionization. The Rydberg electron's energy levels are strongly shifted by the presence of an electric field. The energy levels shift and curve, but never cross. At an avoided crossing the electron can jump from one level to the next. By engineering the electric field's time dependence, we thereby control the path to ionization. …

Microwave Assisted Dipole-Dipole Transitions, Jacob T. Paul

Physics and Astronomy Honors Papers

We explore this two photon assisted transition through computational and numerical analysis of possible energy levels. We calculate the matrix elements of the energy transition in detail discussing constants and the quantum mechanical possibilities of energy exchanges in these systems.

The goal is to better understand the energy exchange, so that moving forward we can control it. This paper covers the theoretical ends to controlling the energy transition by the way of two photon assisted transitions. The energy transitions take place between a dipole-dipole interaction, and a microwave photon.

Simulations Of The Angular Dependence Of The Dipole-Dipole Interaction Among Rydberg Atoms, Jacob L. Bigelow, Jacob T. Paul, Matan Peleg, Veronica L. Sanford, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

The dipole-dipole interaction between two Rydberg atoms depends on the relative orientation of the atoms and on the change in the magnetic quantum number. We simulate the effect of this anisotropy on the energy transport in an amorphous many atom system subject to a homogeneous applied electric field. We consider two experimentally feasible geometries and find that the effects should be measurable in current generation imaging experiments. In both geometries atoms of p character are localized to a small region of space which is immersed in a larger region that is filled with atoms of s character. Energy transfer due …

The Role Of Continuum States In The Field Ionization Of Rydberg Atoms, Michael P. Vennettilli

Physics and Astronomy Honors Papers

In an experiment performed by our collaborators at Bryn Mawr, we excite rubidium-85 to a coherent superposition of the different |m_j| splittings of the 37d_5/2 state induced by a small electric field. After waiting for some variable delay time, we apply a time-dependent electric field to ionize the atom and record the ionized current that arrives at the detector. Due to the initial superposition, we observe an interference pattern that depends on the delay time. This thesis describes my continued work with Dr. Carroll to develop a computational model of this experiment. Our initial method …

Quantum Mechanical Interference In The Field Ionization Of Rydberg Atoms, Jacob A. Hollingsworth

Physics and Astronomy Honors Papers

Rydberg atoms are traditionally alkali metal atoms with their valence electron excited to a state of very large principle quantum number. They possess exaggerated properties, and are consequently an attractive area of study for physicists. An example of their exaggerated properties is seen in their response to the presence of an applied electric field. In this work, we study the energy distribution of Rydberg atoms when subjected to a dynamic electric field intended to ionize them.

We excite ⁸⁵Rb atoms to a superposition of the 46D_5/2 |m_j| = 1/2 and |m_j| = 3/2 states …

Using A Genetic Algorithm To Optimize An Electric Field Ionization Pulse, Tamas Budner

Physics and Astronomy Honors Papers

Experimentally, we would like to demonstrate the process of selective field ionization of electrons as evidence of quantum control in a system of ultracold rubidium-85 Rydberg atoms. In order to accomplish this, an electric field pulse which is optimized to take an initial Rydberg electron state and produce the desired ionization spectra is necessary. We utilize techniques from artificial intelligence to develop a genetic algorithm for the optimization process. Our algorithm is computationally tested on an artificially constructed quantum system consisting of four energy states. In evaluating the viability of any given field pulse, we calculate the probability of an …

Quantum Interference In The Field Ionization Of Rydberg Atoms, Rachel Feynman, Jacob A. Hollingsworth, Michael Vennettilli, Tamas Budner, Ryan Zmiewski, Donald P. Fahey, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

We excite ultracold rubidium atoms in a magneto-optical trap to a coherent superposition of the three |mj | sublevels of the 37d5/2 Rydberg state. After some delay, during which the relative phases of the superposition components can evolve, we apply an electric field pulse to ionize the Rydberg electron and send it to a detector. The electron traverses many avoided crossings in the Stark levels as it ionizes. The net effect of the transitions at these crossings is to mix the amplitudes of the initial superposition into the same final states at ionization. Similar to a Mach-Zehnder interferometer, the three …

Simulations Of The Angular Dependence Of The Dipole-Dipole Interaction, Jacob T. Paul, Matan Peleg

Physics and Astronomy Summer Fellows

In our project we ran computations on a supercomputer to simulate experiments performed on highly excited atoms at μK temperatures. At μK temperatures the atoms are moving slowly so there are essentially no collisions of the atoms on the time scales at which we perform our experiments. In the absence of collisions the atoms exchange energy through long range dipole-dipole interactions. This exchange depends on the distances between and relative orientation of the atoms. The angular dependence between two atoms has recently been studied experimentally¹ . We simulate experimentally accessible spatial arrangements to see if the effect of the …

Simulations Of The Angular Dependence Of The Dipole-Dipole Interaction, Matan Peleg, Jacob T. Paul

Physics and Astronomy Summer Fellows

We conducted simulations of Rydberg atoms in a magneto-optical trap using the supercomputer available on campus and the COMET supercomputer provided by the NSF. Our research focused on the angular dependence of the long range interaction between Rydberg atoms. We simulated randomly distributed atoms alligned with a magnetic and electric field. We compared the simulated interaction rates for different electric field directions.

Toward Quantum Analog Computing: Simulating Designer Atomic Systems, Veronica L. Sanford, Jacob L. Bigelow

Physics and Astronomy Summer Fellows

We use a magneto-optical trap to cool rubidium atoms to temperatures in the _µK range. On the _µs timescales of our experiment, the atoms are moving slowly enough that they appear stationary. We then excite them to a Rydberg state, where the outer electron is loosely bound. In these high energy states, the atoms can exchange energy with each other. Since the energy exchange depends on the separation and the relative orientation of the atoms, we can potentially control their interactions by controlling the spatial arrangements of the atoms. We model this system using simulations on a supercomputer …

Toward Analog Quantum Computing: Simulating Designer Atomic Systems, Jacob L. Bigelow, Veronica L. Sanford

Physics and Astronomy Summer Fellows

We use a magneto-optical trap to cool rubidium atoms to temperatures in the _µK range. On the _µs timescales of our experiment, the atoms are moving slowly enough that they appear stationary. We then excite them to a Rydberg state, where the outer electron is loosely bound. In these high energy states, the atoms can exchange energy with each other. Since the energy exchange depends on the separation and the relative orientation of the atoms, we can potentially control their interactions by controlling the spatial arrangements of the atoms. We model this system using simulations on a supercomputer …

Imaging The Dipole-Dipole Energy Exchange Between Ultracold Rubidium Rydberg Atoms, Donald P. Fahey, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

The long-range, anisotropic nature of the interaction among atoms in an ultracold dipolar gas leads to a rich array of possibilities for studying many-body physics. In this work, an ultracold gas of highly excited atoms is used to study energy transport due to the long-range dipole-dipole interaction. A technique is developed to measure both the internal energy states of the interacting Rydberg atoms and their positions in space. This technique is demonstrated by observing energy exchange between two spatially separated groups of Rydberg atoms excited to two different internal states. Simulations confirm the general features of the energy transport in …

Dipole-Dipole Interaction Between Rubidium Rydberg Atoms, Emily Altiere, Donald P. Fahey, Michael W. Noel, Rachel J. Smith, Thomas J. Carroll

Physics and Astronomy Faculty Publications

Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (F¨orster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that …

Simulations Of The Dipole-Dipole Interaction Between Two Spatially Separated Groups Of Rydberg Atoms, Thomas J. Carroll, Christopher Daniel, Leah Hoover, Timothy Sidie, Michael W. Noel

Physics and Astronomy Faculty Publications

The dipole-dipole interaction among ultracold Rydberg atoms is simulated. We examine a general interaction scheme in which two atoms excited to the x and x states are converted to y and y states via a Förster resonance. The atoms are arranged in two spatially separated groups, each consisting of only one species of atom. We monitor the state mixing by recording the fraction of atoms excited to the y state as the distance between the two groups is varied. With zero detuning a many-body effect that relies on always resonant interactions causes the state mixing to have a finite range. …