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. Trivalent lanthanide atoms have protected core F-electrons whose electronic transitions have found applications in lasing, telecom, and biological imaging. Simultaneously, many Ln (III) ions have microwave transitions that are amenable to qubit operations. Inorganic complexes of these ions can be stabilized in the condensed phase and show intense and narrow peak optical absorption and photoluminescence in a variety of chemical environments. We probe a new ytterbium (III) complex with a ferrocene-derived ligand which demonstrates a surprisingly narrow absorption peak near the gas phase 2F5/2 to 2F7/2 transition at 980 nm at room temperature. To our knowledge this Yb (III) complex demonstrates one of the narrowest absorption peaks (FWHM= 1.2 meV) ever seen in room-temperature solution. I plan to explore the stability and applicability of this particularly narrow transition in both solution and solid phase across a wide range of temperatures, ultimately to achieve optical quantum state preparation and measurement in the condensed phase.
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.