Summary
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.
Figure 1. Bloch sphere depiction of the optical addressability of bright excitons in a Single-Layer TMDC. Bright excitons with pseudospin ├ |↑⟩ or ├ |↓⟩ are created (annihilated) via absorption (emission) of a right-handed or a left-handed circularly polarized photon (red and blue arrows, respectively). The equator corresponds to equal superpositions of bright excitons in the two valleys and are therefore generated by absorption of linearly polarized photons denoted by green arrows.
Related Content
Silicon Platform for Electron Spin Qubits
Summary Scaling solid-state quantum processors to a useful threshold while maintaining the requisite precision in quantum control remains a challenge. We propose a quantum metal-oxide-semiconductor (QMOS) architecture operating at cryogenic temperatures that is based on a network/node approach as a means to scalability. By working with QMOS, we benefit from the deep investments and […]
December 7, 2018
Chiral Quantum Antenna Based on Multilayer Metasurface
Summary Individual atoms can act as stationary qubits and thus serve as nodes in quantum computing networks or as memories for quantum repeaters. However, to successfully use qubits based on single atoms suspended in free space, photons emitted by a single atom need to be efficiently collected. Conventionally, this can be done with high […]
September 20, 2018
Reliably operating noisy quantum computers
Summary The overall goal of the project is to develop practical methods to be able to reliably run useful applications on near-term quantum computers. This requires identifying and overcoming the ubiquitous errors that currently limit quantum computing capabilities. Traditional methods of quantifying errors in quantum computers fail to predict how errors affect the output of […]
January 22, 2020
Identifying the Potential of Quantum Dots to Detect and Disrupt Tau Protein Aggregation in Alzheimer’s Disease
Specific tests for Alzheimer’s disease (AD) diagnosis are currently unavailable, despite AD being the leading cause of dementia. One hallmark of AD progression is the aggregation of tau proteins into paired helical filaments and neurofibrillary tangles, which is accelerated by the hyperphosphorylation of Tau proteins. However, the mechanism by which the hyperphosphorylated tau accelerates protein […]
March 27, 2023