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

This research project is in competition for funding with one or more projects available across the EPSRC Doctoral Training Partnership (DTP). Usually the projects which receive the best applicants will be awarded the funding. Find out more information about the DTP and how to apply.

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) to determine the coherent coupling structure in few-quantum-dot systems by two-dimensional four-wave mixing, 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.

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 and between quantum dots mediated by a cavity.

Recent work showed the multi-wave coherent control and the radiatively limited dephasing of excitons in WS2. The project is embedded in an ongoing EPSRC grant 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.

Project aims and methods

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 and viva.


Professor Wolfgang Langbein

Professor Wolfgang Langbein

Head of Condensed Matter and Photonics Group

+44 (0)29 2087 0172

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