Graduate Research

Molecules Functionalized with Optical Cycling Centers for Quantum Information Science

A quantum computer uses quantum states to store and process information, able to tackle questions that are intractable in classical computers. As modern day computers use bits to represent information, quantum computers use qubits (quantum bits) that can achieve a “mixed state” and become entangled with one another. Trapped ions (gas phase atoms trapped in an external magnetic field) make an effective qubit because they can optically cycle (i.e. be excited by laser radiation and de-excited back to the ground state multiple times). However, the stability of the gas phase atoms relies on cryogenic cooling, electric field traps, and complex interfaces, rendering ionic qubits unscalable in their current paradigm. While cycling transitions in trapped atoms have been crucial for early works in quantum information, the extension of this idea to molecular substrates has been hindered by the lack of systems that have cycling transitions. Alkaline earth (AE) metal atoms are known to optically cycle in gas phase and to bond with fluorine, hydroxyl, and even alkoxyl groups while retaining their cycling properties. This project aims to tether the AE atoms to molecular substrates as OCCs. The OCC will then be activated by resonant, narrow-band light, and the presence or absence of laser induced fluorescence will enable projective measurements of the system’s quantum state. This design combines the efficiency of trapped ions and the stability of room-temperature surface chemistry, essentially creating a network of molecular qubits on a surface.

Spectroscopic Studies of 2D Colloidal Nanoplatelets

Colloidal semiconducting nanocrystals have broad applications in biological imaging, energy conversion, and optoelectronics. Nanoplatelets (NPLs) are two-dimensional nanostructures that show uniform quantum confinement in their thickness while having large lateral dimensions. NPLs exhibit photoluminescence behaviors similar to that of quantum wells with localization of states. There are a few nanoscale crystals that absorb and emit light efficiently in the shortwave infrared (SWIR, 1000-2000 nm or 1.24-0.63eV), and none that demonstrate tunable mid-gap state emission. This project conducts spectroscopic characterization of mercury telluride nanoplatelets that have tunable bandgaps with high quantum yield through the SWIR. Spectrally resolved photoluminescence demonstrates energy-dependent lifetimes, and further investigation of temperature-dependent fluorescence measurements reveal the thermodynamic properties of the chemical process that lead to this tunable mid-gap state. Photophysical studies of mercury chalcogenide nanoplatelets with tunable emission will lead to a new class of emitters that lead to novel optoelectronics targeted to the SWIR.

In my first year in Prof. Justin Caram’s lab, I helped set up an original spectroscopic instrument that employs an interferometric approach to obtain correlated lifetime and photoluminescence measurements.

Undergraduate Research