About
I am a Physics PhD student at the University of Iowa, working in the Quantum Light Control Lab led by Prof. Ravitej Uppu. My research is highly interdisciplinary, investigating both fundamental principles and applied implementations of physics involving quantum optics, nanophotonics, and hybrid spin-photon interfaces. Broadly, my research is concerned with understanding and developing scalable, chip-integrated photonic quantum technologies for use in a quantum repeater, which is an essential component in the long-distance transmission of quantum information. My work is primarily experimental, where day-to-day I am involved with sample development (growth and nanofabrication), computational electrodynamics simulations, cryogenic optical spectroscopy, and various other room-temperature quantum optics experiments. Prior to my PhD, I completed my BS in Physics (Honors) and Mathematics at the University of Iowa, graduating with Highest Distinction. My undergraduate research experience focused on studying a novel manifestation of spatiotemporal correlations in multimode optical fibers using complex wavefront shaping techniques.
Research Interests
My research spans several interconnected areas in quantum physics and optics/photonics, with applications in quantum information science and long-distance communication.
Multimode Quantum Optics
Multimode quantum optics explores the quantum nature of light in systems with hundreds or even thousands of electromagnetic modes such as multimode optical fibers or integrated waveguide arrays. Rather than attempting to eliminate losses, I am developing techniques to harness exceptional points (EPs) in non-Hermitian quantum systems with reduced symmetry (PT-symmetry) to suppress decoherence in multiphoton systems. This approach provides a tuning mechanism to manipulate dissipative fields in photonic circuits through complex optical wavefront shaping methods that employ spatial light modulators, potentially enabling perfect transfer of multiphoton states in photonic lattices despite the inherent presence of loss. Image credit: COPS @ UTwente
Nanophotonics
Nanophotonics explores how light behaves and propagates within materials at the nanoscale. My research involves designing, simulating, fabricating and optically characterizing nanophotonic structures such as photonic crystal cavities and waveguides that facilitate near-deterministic (>99.8%) light-matter interactions. Understanding and harnessing these engineered structures are important in realizing efficient, scalable, chip-integrated quantum repeater architectures.
Hybrid Spin-photon Interfaces
Spin-photon interfaces bridge the worlds of quantum optics and solid-state quantum information processing. My research employs a novel approach to overcome the inherent tradeoff between spin coherence and radiative properties in solid-state defect platforms by combining III-V semiconductor quantum dots (QDs)—which are extremely bright and indistinguishable single-photon sources—with highly coherent rare-earth ionic spin defects (REIs) such as erbium (Er3+) and thulium (Tm3+) in a heterogeneous light-matter interface. My lab work focuses on growing and characterizing the microstructural properties of these interfaces as well as studying how interfacial electronic noise affects the optical and spin coherence properties of the embedded QDs and REIs. Successfully preserving both the radiative properties of QDs and the spin coherence properties of REIs in this hybrid architecture would enable scalable and efficient generation of multiphoton entangled states, including linear cluster states and tree graph states.
Research Experience
Quantum Light Control Lab, University of Iowa
As a graduate researcher in Prof. Ravitej Uppu's lab, I focus on:
- Growing and characterizing the microstructural properties of Er3+:TiO2, Er3+:CeO2 and Er3+:PbWO4 thin films on GaAs/GaSb substrates using Pulsed Laser Deposition, X-Ray Diffraction, Atomic Force Microscopy, Raman Spectroscopy and Transmission Electron Microscopy
- Performing coherent spin control to investigate the role of interfacial electronic noise on the coherence properties of 4f intraband optical transitions of Er3+ ions in heterogeneous light-matter interfaces
- Developing nanofabrication protocols for creating various nanophotonic structures in a heterogeneous oxide thin film on III-V semiconductor substrate sample, including micropillars, grating outcouplers, (photonic crystal) nanobeam waveguides and photonic crystal cavities
- Performing 3D computational electrodynamics simulations using active Dirichlet boundary conditions to model the β-factors of electric and magnetic dipole optical transitions of quantum emitters in homogeneous and heterogeneous (photonic crystal) nanobeam waveguides and photonic crystal cavities with <5% error
- Constructing cryogenic-compatible optical setups for performing various optical spectroscopy techniques including resonance fluorescence, photoluminescence excitation and RT spectroscopy
- Developing and performing room-temperature experiments studying programmable many-photon interference in multimode optical fibers and integrated waveguide arrays
- Studying the frequency correlations of single and entangled photons in highly multimode optical fibers and integrated waveguide arrays
Quantum Light Control Lab, University of Iowa
As an undergraduate researcher, I:
- Designed a complex wavefront shaping optical system utilizing a Digital Micromirror Device (DMD) to modulate the spatial wavefront of coherent laser light and focus it through Multimode Fibers (MMFs)
- Implemented a feedback-based wavefront shaping algorithm in Python to study the dependence of wavefront shaping enhancement and frequency correlations on the core geometry of multimode fibers
- Constructed object-oriented Python scripts for automating data acquisition by integrating various lab devices and detectors
- Discovered a novel manifestation of spatiotemporal correlations in multimode fibers demonstrating that rectilinear (i.e., square or rectangular) core MMFs provide enhanced prospects for high-dimensional spatially multiplexed optical communication schemes
Spectrum Lab, Montana State University
During this summer research program, I:
- Designed an optical system using spatial light modulators (SLMs) to perform space-division multiplexing communication protocols via the combination of Dammann Vortex Gratings and 4-core multicore fibers (MCFs)
- Built a tabletop optical setup including a heat plate to quantify and simulate strong environmental turbulence
- Assessed the viability of active and passive OAM mode sorters for use in various optical communication protocols
Publications
"Effect of core geometry on frequency correlations and channel capacity of a multimode optical fiber"
H. C. Hammer and R. Uppu, Adv. Photonics Res., 2400156 (2025)
Talks & Posters
March 4, 2025
"Efficient Coupling of Single Quantum Emitters in Heterogeneous Photonic Nanostructures"
University of Iowa Department of Physics & Astronomy Acevedo Poster Competition, Iowa City, IA
November 15, 2023
"Heterogeneous Light-matter Interfaces for Photonic Quantum Communication & Computation"
University of Iowa Department of Physics & Astronomy Condensed Matter Seminar, Iowa City, IA
May 5, 2023
"Effect of Core Geometry on the Channel Capacity of a Multimode Optical Fiber"
University of Iowa Department of Physics & Astronomy Awards Ceremony Seminar, Iowa City, IA
Senior Thesis Talk
August 4, 2022
"Using Light's Orbital Angular Momentum to Transmit Information"
Montana State University Quantum and Materials Physics REU Symposium, Bozeman, MT
November 10, 2021
"Wavefront Shaping Through Circular & Non-circular Multimode Fiber Core Geometries"
University of Iowa Department of Physics & Astronomy Condensed Matter Seminar, Iowa City, IA
November 10, 2021
"Wavefront Shaping Through Circular & Non-circular Multimode Fiber Core Geometries"
University of Iowa Fall Undergraduate Research Festival, Iowa City, IA
Received Andrew Nelson Undergraduate Research Prize for best Physics major poster
September 29, 2021
"Frequency Correlation Measurements of Wavefront-shaped Light in Round, Square, & Rectangular Multimode Fiber Core Geometries"
University of Iowa Department of Physics & Astronomy Summer Undergraduate Research Colloquium, Iowa City, IA
Education
August 2023 - January 2029 (Expected)
Doctorate of Philosophy in Physics
University of Iowa, Iowa City, IA
Thesis Advisor: Prof. Ravitej Uppu
GPA: 4.06/4.00
August 2019 - May 2023
Bachelor of Science in Physics (Honors), Mathematics
University of Iowa, Iowa City, IA
Graduated With Highest Distinction
GPA: 4.08/4.00 (Physics GPA: 4.11/4.00; Mathematics GPA: 4.01/4.00)
Senior Thesis: Effect of core geometry on frequency correlations and channel capacity of a multimode optical fiber
Honors and Awards
- Iowa Graduate Recruitment Fellowship
- James A. Van Allen Award for Excellence in Undergraduate Research
- Iowa Flagship Scholarship
- Charles E. Fahrney Scholarship
- Andrew Nelson Undergraduate Research Prize
- Charles A. Wert Summer Research Grant
- Phi Beta Kappa
Graduate Coursework
- Quantum Mechanics I-II
- Classical Electrodynamics I-II
- Classical Mechanics
- Statistical Mechanics
- Quantum Field Theory
- Quantum Optics & Nanophotonics
- Microfabrication & Thin Films
- Semiconductor Physics
- Advanced Condensed Matter
- Independent Study: Photonic Crystals
Student Memberships
- American Physical Society
- Optica
Skills
Programming Languages
- Python (numpy, scipy, matplotlib)
- C
- MATLAB
- Mathematica
Electrodynamics Simulation Software
Nanofabrication Design Software
- Klayout
- CNST Nanolithography Toolbox
Operating Systems
- Linux (Ubuntu, Fedora)
- Windows
- macOS/OS X
Applications/Typesetters
- Inkscape
- GIMP
- Microsoft Office
- LaTeX
Hardware
- Spatial Light Modulators (DMDs, LCOS-SLMs)
- Avalanche Photodiodes (APDs)
- Superconducting Nanowire Single Photon Detectors (SNSPDs)
- Cryostats (4K helium closed-cycle)
- Lasers (Ti:Sapphire, Generic Tabletop Fiber-coupled/Free Space)
- Single/Multimode Optical Fibers and Fiber-Optic Components
- Free Space Optical Components (Lenses, Objectives, Diffraction Gratings, etc.)
- Lock-in Amplifiers
- Digital Pulse Delay Generators
- Function/Arbitrary Waveform Generators
- Electronic Circuit Board Components (Amplifiers, Switches, etc.)
- Semiconductor Optical Amplifiers
- Acousto- and Electro-optic Modulators (Fiber-coupled/Free Space)
- RF Amplifiers and Switches
- Microcontrollers (Arduino, Adafruit, Raspberry Pi)
- Oscilloscopes
Experimental/Measurement Techniques
- Resonance Fluorescence Spectroscopy
- Confocal Microscopy
- Hanbury Brown and Twiss Interferometry
- Time-Correlated Single Photon Counting
- Wavefront Shaping
- Lock-in Amplification
- Arbitrary Pulse Generation and Sequencing
- Optical Coherent Spin Control (Raman, Ultrafast)
- RF Coherent Spin Control (Split Ring Resonators)
- X-Ray Diffraction
- Atomic Force Microscopy
- Raman Spectroscopy
- Ramsey Interferometry
- Hahn Echo
- Dynamical Decoupling (XY-N, CPMG)
Growth/Nanofabrication Techniques
- Pulsed Laser Deposition
- UV Photolithography
- Electron-Beam Lithography
- Electron-Beam Deposition
- Wet Etching
- Dry Etching (ICP RIE, RIE)
Personal
Outside of the lab, some of my favorite pastimes include spending time with friends, skiing, hiking and watching various sports teams including the Iowa Hawkeyes, Chicago Blackhawks, Chicago Cubs and Minnesota Vikings. I am also an avid listener of electronic music.