Controlled coherent coupling of single quantum dots in photonic crystal cavity networks

Outline

The proposed project spans from the field of optical spectroscopy of semiconductor nanostructures, specifically coherent spectroscopy of single quantum dots, to quantum computing, specifically the implementation of quantum operations in quantum dots.

Technological advances in light detectors and microscopy techniques during the last decade have allowed the investigation of the emission properties of individual localized light emitters such as dye molecules, defects in semiconductors, or semiconductor quantum dots. The observation of coherence in these systems and their manipulation by coherent control is presently at the forefront of the research in the field, driven by the expectation that these techniques allow the implementation of quantum information processing using optical transitions in single quantum dots as qubits or to control spin q-bits. The goal of the project is the application of the unique experimental technique of heterodyne spectral interferometry (HSI) [Optics Letters 31, 1151 (2006)] to determine the coherent coupling structure in few-quantum-dot systems by two-dimensional four-wave mixing [Nature Photonics 5, 57 (2011)], and then use this knowledge to design optical control pulses to implement simple quantum gates in the few-quantum-dot system, again using HSI to read the result of the gate operations [Phys. Rev. Lett. 95, 266401 (2005)]. The detailed information about the quantum system gained by this detection scheme will be used to design the control pulse to a quantum gate of high fidelity. Previous experiments by the supervisor detected the coherent coupling between localized excitons in quantum wells [Nature Photonics 5, 57 (2011] and between quantum dots mediated by a cavity [Nature Communications 4, 1747 (2013)]. Recent work showed the multi-wave coherent control [Nature Photonics 10, 155 (2016)] and the radiatively limited dephasing of excitons in WS2 [2D Materials 5, 031007 (2018)]. The project is embedded in an ongoing EPSRC grant [EP/M020479/1] and will benefit from the support by one ongoing PhD and two PDRAs working on related topics and supporting the required experimental setups and theoretical predictions.

References:

L. Scarpelli et al., Phys. Rev. B 96, 045407 (2017) DOI 10.1103/PhysRevB.96.045407

F. Fras, et al., Nature Photonics 10, 155 (2016) DOI 10.1038/nphoton.2016.2

F. Albert et al, Nature Communications 4, 1747 (2013) DOI 10.1038/ncomms2764

What is funded

Self-Funded PhD Students Only

This PhD position is opening for self-funded student only, which means the candidate with own funding to cover the living cost and tuition fees will be considered.

Duration

Feasibility of completion within 3.5 years: The project outline plan is as follows; Month 1-9: literature review, training on HSI setup and data analysis. Month 10-18: Coherent coupling between QDs in a PCC. Incoherent coupling via phonons. Publication. Month 19-27: Coupling between QDs in separated coupled PCC. Publication. Month 28-33: Control of coherent coupling via electrical tuning. Publication. Month 35-38: thesis writing, submission,viva

Eligibility

 Candidates should hold a good bachelor’s degree (first or upper second-class honours degree) or a MSc degree in Physics or a related subject. Applicants whose first language is not English will be required to demonstrate proficiency in the English language (IELTS 6.5 or equivalent).

How to Apply

Applicants should submit an application for postgraduate study via the Cardiff University webpages (https://www.cardiff.ac.uk/study/postgraduate/research/programmes/programme/physics-and-astronomy) including:

• an upload of your CV

• a personal statement/covering letter

• two references

• Current academic transcripts

Applicants should select Doctor of Philosophy, with a start date of October 2020. In the research proposal section of your application, please specify the project title and supervisors of this project and copy the project description in the text box provided.