As monolayers, transition metal dichalcogenides (TMDCs) – such as tungsten diselenide (WSe2) – become direct-bandgap semiconductors capable of emitting light. Compared to conventional direct-bandgap semiconductors, such as III-V semiconductors like GaAs, excitons (quasiparticles made of an electron hole bound with an electron) and single-layer TMDCs (SL-TMDCs) have much stronger binding energy. Excitons and SL-TMDCS also have an extra degree of freedom called “k-valley index” or “pseudospin”, which couples with their spin in the presence of light. Due to the way the spin and valley degrees of freedom couple together, excitons in SL-TMDCs can act as a two-level quantum system, whose quantum state can be initialized and controlled with photons of specific polarization, either collectively or as individual excitons confined in quantum dots. To utilize these two-level quantum systems as solid-state qubits in a quantum device, the spectral and temporal dynamics of SL-TMDC excitons in the presence of electric and optical fields needs to be investigated. However, some of the exciton processes in SL-TMDCs happen at timescales that are beyond the resolution of streak cameras used for studies of excitons in conventional semiconductors. To overcome this problem, this research will use femtosecond photoluminescence up-conversion (fsPLupC). This technique relies on sum frequency generation that arises when the photoluminescence signal overlaps with a reference femtosecond (fs) pulse inside a non-linear crystal. It can reveal both temporal and spectral information about the studied processes, potentially with a resolution better than 100 fs. This work will provide a greater fundamental understanding of TMDC monolayers and explore their potential use as ‘valleytronic’ based quantum devices.
Quantum Information Processing with Molecular Lattices
The aim of the work is to develop theoretical tools to simulate and predict the behaviour of a one-dimensional chain of trapped dipolar molecules and to study the nature of entanglement as a design resource.
June 1, 2017
Entangled Photon Orbital Angular Momentum Arrays
Summary Arrays of orbital angular momentum (OAM) states of light are a new form of structured light so far relatively unexplored in quantum information science. Unlike spin angular momentum of light, which is related to light’s polarization and covers two dimensions, OAM states, sometimes described as ‘donut beams’ due to the shape of the field […]
September 19, 2019
Topological Properties of Exciton-Polaritons in a Kagome Lattice as a Solid-state Quantum Simulator
Summary In this project, we build a solid-state quantum simulator for engineering a specific Hamiltonian. Quantum simulators are purpose-built devices with little to no need for error correction, thereby making this type of hardware less demanding than universal quantum computers. Our platform consists of exciton-polariton condensates in multiple quantum-wells sandwiched in a semiconductor Bragg […]
December 8, 2018
Next Generation Quantum Sensors
We are developing new semiconductor p-n junctions and designing novel nanowire arrays that have the potential to significantly enhance the ability to detect light at the single photon level over an unprecedented wavelength range from the ultraviolet to infrared.
June 1, 2017