Quantum Information with NV Centres

Lead Research Organisation: University of Warwick
Department Name: Physics

Abstract

The aim of QINVC is to exploit the superior quantum coherence of the spins of the negatively charged Nitrogen-Vacancy (NV) colour centres in diamond, at both room and low temperature, for quantum information processing (QIP). This system is indeed among the best solid-state quantum systems in terms of coherence, ease of manipulation by ESR, and addressability down to the single spin using optical microscopy. Our project first focuses on two hybrid strategies for QIP (WP1). The first one consists in fabricating regular arrays of single NV centres, with gate operation performed using a movable NV spin placed at the apex of a cantilever, coming close enough to get entangled with a NV spin on the lattice using magnetic dipolar interaction. The fabrication method is based on pulsed ion beam implantation through a tiny hole threading the tip of an AFM cantilever, or through the voids of a mask deposited at the surface of the diamond sample. The second strategy implements a hybrid architecture for QIP based on circuit QED and ensembles of NV spins: transmon qubits are coupled to ensembles of NV spins through the resonator in which they are embedded. The NV spins will be used as a long-coherence time quantum memory for the transmon qubits which will be used to process quantum information.

QINVC will investigate in WP2 the optical properties of NV centres at low temperature. The first goal of WP2 is to transfer the optical techniques used at room temperature to control electron and nuclear spins to low-temperatures, in the purpose of applying them to hybrid quantum circuits (WP1). A second goal is to investigate the potential of NV centres ensembles to build a quantum memory for optical photons. These ambitious goals will request the optimisation of NV centre production and their spin properties in synthetic diamond (WP3) using state-of-the-art methods and beyond. This will be done in collaboration with the world industrial leader on the production of synthetic diamond Element6 Ltd. Engineered implantation of single N impurities with nanometer resolution will be performed for WP1, and suitable concentrations will be prepared for both WP1 and WP2. Sample processing will be developed for these two WPs in order to minimize the unwanted defects that cause decoherence. Innovative fabrication techniques will be also developed, such as the preferential alignment of NV centres under uniaxial stress, an appealing possibility.

Planned Impact

The QINVC project is a frontier research project that aims at developing a quantum technology in the domain of quantum information. Indeed, quantum mechanics does make a difference with classical physics in this domain. Although present day research is still very far from providing useful quantum processors, the impact of the QINVC project is sizeable. The project will impact on all academic and industrial researchers striving to exploit the remarkable properties of the NV centre.

An innovative road towards Quantum Information: hybrid structures Despite about a decade of intensive research, the systems investigated up to now do not match all the required criteria for making quantum processors. The innovative research on hybrid structures proposed by our QINVC consortium offers a chance to succeed where other systems have not. Is it possible to take the best of the microscopic quantum systems, namely their superior quantum coherence, and of the quantum electrical circuits, namely their ease of operation? QINVC will probe the whole issue of the hybrid way for quantum information.

Linking microscopic entities to macroscopic objects
In the wider context of quantum physics, the primary outcome will be to establish a direct link between microscopic entities, the NV spins, and macroscopic electrical circuits. Although quantum mechanics rules both worlds, they are not very often in speaking terms. This is what QINVC will achieve, and this would have an impact on our understanding of quantum mechanics.

Innovative truly quantum materials
On the material side, improving materials with a well affirmed quantum character is also very important. Indeed, quantum properties of NV centres are not only considered for quantum information, but also for numerous applications. Sample optimisation and characterisation will thus have an impact in other more applied areas such as magnetometry or magnetic microscopy. The close link already established with Element Six Ltd will be very useful in this respect.

Publications

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Description In recent years negatively charged nitrogen vacancy (NV-) centre in diamond has emerged as one of the post promising candidates for solid-state implementations of quantum information and computing. NV- centres are defects in the diamond lattice consisting of a substitutional nitrogen atom and a neighbouring vacancy having trapped an additional electron. They present many unique features that make it particularly attractive for quantum information protocols. The spin of an individual NV- centre can be readout optically at room-temperature using standard confocal microscopy. It has among the longest coherence times ever reported in the solid-state even at room-temperature. NV- centres are coupled to neighbouring nuclear spins, offering the possibility of creating a quantum register based on nuclear spins. Finally, at low-temperatures, they have a narrow optical line (the zero-phonon line) promising for quantum communication protocols. However, before NV- centres can really form the basis for a scalable implementation of quantum information and communication protocols, one challenging issue absolutely needs to be solved: how to make NV centres communicate with each other in a quantum-coherent way.
Our European consortium CEA and ENS Cachan in France, Universities of Stuttgart and Leipzig in Germany and the University of Warwick focused on hybrid quantum systems (WP1), optical properties of NV centres at low temperatures (WP2), and the materials science associated with producing diamond samples with optimised quantum defects for particular applications (WP3). Research at Warwick focused on WP3 where we developed new knowledge pertaining to the NV- production (important for applications such as bulk magnetometry or ensemble memories), investigating the production of aligned NV- centres, and provide new insights into alternate colour centres in diamond for quantum technologies.
Exploitation Route The research advances achieved in the CHIST-ERA QINVC project have been taken forward in both national and international follow on projects. Worldwide efforts to exploit the remarkable quantum properties of the negatively charged nitrogen vacancy (NV-) centre in diamond have grown considerably since the inception of this project. Warwick researchers now lead the EPSRC Centre for Doctoral Training in Diamond Science and Technology (EP/L015315/1), which has a strong quantum technologies theme, and are partners in the NQIT Quantum Technology Hub (EP/M013243/1). Funding was won with Element Six Ltd (EP/M508305/1), to develop processing methodologies to produce diamond with near surface NV- centres with good quantum properties for applications such as nano-magnetometry. Follow on Funding was subsequently secured from Innovate UK (Scalable Quantum Diamond Devices TSB: 102676). Working with the CHIST-ERA QINVC Stuttgart, Warwick and other European partners have bid for an Innovative Training Networks in diamond based Quantum Technology.
Sectors Digital/Communication/Information Technologies (including Software),Pharmaceuticals and Medical Biotechnology

URL http://www.chistera.eu/projects/qinvc
 
Description We have been involved in outreach activities related to educating the public about the potential impact of Diamond Science and Technologies. This included participating in a Science Lates event (June 2015, Science Museum) and we exhibited at the 2016 Royal Society Summer Exhibition. The latter included a specific exhibit/demonstration of a diamond quantum spin magnetometer
First Year Of Impact 2015
Sector Education
Impact Types Societal

 
Description Innovate UK Exploring the commercial applications of quantum technologies - Feasibility study
Amount £95,983 (GBP)
Funding ID EP/M508305/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 06/2015 
End 05/2016
 
Description NICOP - Towards a picotesla DC diamond magnetometer
Amount $200,000 (USD)
Organisation US Navy 
Department US Office of Naval Research Global
Sector Public
Country United States
Start 10/2016 
End 09/2024
 
Description Technology Strategy Board -CR&D PROPOSAL
Amount £281,000 (GBP)
Funding ID TSB102676 
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 09/2016 
End 08/2017
 
Description UK Quantum Technology Hub: NQIT - Networked Quantum Information Technologies
Amount £38,029,961 (GBP)
Funding ID EP/M013243/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 12/2014 
End 11/2019
 
Description De Beers Technologies 
Organisation De Beers Group
Department DTC Research Centre
Country United Kingdom 
Sector Private 
PI Contribution New knowledge relating to nature of defects in diamond.
Collaborator Contribution Provision of diamond samples with engineered properties and sample processing
Impact Improved identification strategies for synthetic diamond
Start Year 2014
 
Description Element Six Ltd (UK) 
Organisation De Beers Group
Department Element Six
Country Luxembourg 
Sector Private 
PI Contribution Understanding of defect incorporation in CVD diamond
Collaborator Contribution Provision of samples
Impact Further research on defects in diamond
Start Year 2014