Controlled long-range coherent coupling of solid-state qubits

Lead Research Organisation: Cardiff University
Department Name: School of Physics and Astronomy

Abstract

Information technology has gained importance over the last 20 years due to the improving user-friendliness, capability and affordability of the related hardware and software. Today, the internet is the dominant information source for a majority of society, and is likely to be the dominant way of communication within the next decade. This has revolutionised the way society works, improving efficiency and personal choice. The underlying technology is based on classical computing, which faces fundamental limits of its power consumption dictated by the thermodynamics of the implemented classical algorithms. Quantum computing is seen as the next generation technology to augment classical computing, enabling new types of algorithms for more efficient and rapid processing.
This proposal is underpinning this next generation technology. It aims to develop and characterise controlled coherent and incoherent long-range coupling between qubits. The experimental realisation in a quantum dot - optical cavity system integrated with semiconductor technology is one of the promising routes for the implementation of quantum information technology. The physical mechanisms of the coherent coupling researched in this project have however a wide range of importance across physics and biosciences, beyond the specific material system and application investigated.

Planned Impact

The proposed research will characterise and develop controlled coherent and incoherent long-range coupling between qubits. The physical mechanisms of the coherent coupling researched in this project have also a wide range of importance across physics and biosciences.
Economy
The coherent coupling technology resulting from the research will enable applications in quantum information processing, which is expected to revolutionise information and communication technology (ICT) over the next 30 years, with the related impact in the high-tech industry. The optical HSI technique developed further within this project has the potential to be commercialised as a general characterisation instrument of coherence of individual quantum systems.
Society
ICT has gained importance over the last 20 years in society due to the improving user-friendliness, capability and affordability of the related hardware and software. Today, the internet is the dominant information source for a majority of society, and is likely to be the dominant way of communication within the next decade. This has revolutionised the way society works, improving efficiency and personal choice. The underlying technology is based on classical computing, which faces fundamental limits of its power consumption limited by the thermodynamics of the implemented classical algorithms. Quantum computing is seen as the next generation technology to augment classical computing, enabling new types of algorithms for more efficient and rapid processing. This present proposal is part of the development of this next generation technology. We will engage in outreach activities to raise the awareness and enthusiasm in the public for these developments.
 
Description We have measured the beta factor and the circularity of the emission of quantum dots in a photonic crystal waveguide. For the first time, this has been done using directly the emission power measurements, removing the uncertainty of lifetime mesurements used in the past. beta factors of above 95% have been measured in the fast light regime, which is a step towards using these devices in quantum information processing on chip.

We have measured the coherent dynamics of excitons in colloidal quantum dot systems of InP/ZnSe, and perovskite materials. These properties are important for the use of these materials in quantum technology, and as phophors in displays.

The phonon-assisted dephasing of quantum dots strongly coupled to optical cavities was treated theoretically on a rigorous basis using a trotter decomposition methods, suited for all regimes of coupling strengths

A method to measure the quantum dot size, the material deformation potential, and the temperature using a fit to the emission lineshape was developed - this can be important for temperature sensors and material characterization
Exploitation Route The high beta factor and directional emission can be employed to build quantum photonic circuits.
The long dephasing times found in the colloidal quanum dots highlights them for use in quantum technologies.
The rigorous theory of quantum dot / cavity / phonon coupling allows to predict and design the properties of such systems in quantum technology.
The method to measure the quantum dot size, the material deformation potential, and the temperature can be used for temperature sensors and material characterization.
Sectors Digital/Communication/Information Technologies (including Software),Electronics

 
Description 4PI Two-photon Lithography for Isotropic 3D Nanostructure Fabrication
Amount £771,658 (GBP)
Funding ID EP/R009147/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2018 
End 12/2020
 
Description Forster transfer in quantum dots
Amount £80,000 (GBP)
Organisation Cardiff University 
Sector Academic/University
Country United Kingdom
Start 10/2020 
End 03/2024
 
Description Multiphoton Microscopy and Ultrafast Spectroscopy: Imaging meets Quantum (MUSIQ)
Amount € 4,034,447 (EUR)
Funding ID 812922 
Organisation Marie Sklodowska-Curie Actions 
Sector Charity/Non Profit
Country Global
Start 04/2019 
End 03/2023
 
Description Quantum coherence in single biomolecules measured by multidimensional optical micro-spectroscopy
Amount £80,000 (GBP)
Organisation Cardiff University 
Department School of Physics and Astronomy
Sector Academic/University
Country United Kingdom
Start 10/2021 
End 03/2025
 
Description Responsive Mode
Amount £1,200,000 (GBP)
Funding ID EP/P011470/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 04/2017 
End 03/2020
 
Description Solid State Superatoms
Amount £653,988 (GBP)
Funding ID EP/P011470/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 05/2017 
End 04/2021
 
Title Resonant-state expansion of three-dimensional open optical systems: Light scattering 
Description The data contains calculated reflection and scattering cross-section coefficients, as well as related accuracies. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Resonantly excited exciton dynamics in two-dimensional MoSe2 monolayers 
Description The data contains results of four-wave mixing and transmission experiments on MoSe2 monolayers and their analysis. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Description Bristol / Oulton 
Organisation University of Bristol
Department Bristol Research Unit
Country United Kingdom 
Sector Academic/University 
PI Contribution We have measured the directional emission of the quantum dots in the provided samples, and coordinated the interpretation of results and publication.
Collaborator Contribution The group of Ruth Oulton has contributed to the a collaboration on quantum dot emission in photonic crystal waveguides which lead to the publication [10.1103/PhysRevB.100.035311]. A sample, fabricated in the University of Wurzburg during a previous project, was made available for measurements. A PhD student in the group, Ben Lang, was working with us to develop electromagnetic simulations of the coupling and emission , and was running them on the compute cluster in Bristol.
Impact 10.1103/PhysRevB.100.035311
Start Year 2017
 
Description Cork Pelucchi 
Organisation University College Cork
Department Department of Chemistry
Country Ireland 
Sector Academic/University 
PI Contribution Investigating dephasing and coherent coupling of vertically coupled quantum dots
Collaborator Contribution Growth and characterization of bespoke vertically coupled quantum dots for our investigations
Impact None yet
Start Year 2015
 
Description Grenoble Jacek Kasprzak 
Organisation NEEL Institute
Country France 
Sector Public 
PI Contribution Contributed to Experimental Design and Software, Data interpreations and publications
Collaborator Contribution Made the measurements and analyzed data, prepared publications.
Impact 10.1088/2053-1583/aabc1c 10.1364/OPTICA.3.000377 10.1021/acs.nanolett.6b01060 10.1038/NPHOTON.2016.2
Start Year 2015
 
Description PHONSI IBM 
Organisation IBM
Department IBM Research Zurich
Country Switzerland 
Sector Private 
PI Contribution Measurement of dephasing in peroskite quantum dots, analyzed data, contributed to publication
Collaborator Contribution Provided quantum dot sample, seconded PhD student, analyzed data, contributed to publication
Impact 10.1021/acs.nanolett.8b03027
Start Year 2017
 
Title Jitter correlation factorization 
Description A software to factorize emission spectra of single quantum dots undergoing jitter into the temporal shift and the intrinsic lineshape. It ises Non-negative matrix factorization. The jitter can be additionally constrained using a multiple charge trap model, returning the respective energy shifts affected by each charged site. 
Type Of Technology Software 
Year Produced 2018 
Impact This software has been used to analyze data from different quantum dots (e.g. CdSe, InP, Perovskites), and will be made publically available this year, for other researchers or indistrial applications.