C Voisin

Graphene Centre Seminar with Christophe Voisin

Title: Carbon nano-structures as quantum-light sources
Lecturer: Christophe Voisin, Physics Laboratory of Ecole Normale Supérieure, Paris, France
Coffee and cake will be served from 12:40 outside Kollektorn. 

Welcome to attend!

The Graphene Center at Chalmers (GCC) will organize a monthly GCC seminar on the recent advances in the field of graphene and 2D materials. The seminars will be on a monthly basis and will take place every last Monday in the month. ​

​Abstrac​t:
Single-photon sources are a key building block for secured quantum telecommunications or for future quantum information processing. In most protocols, this source is required to be on-demand and to show a large anti-bunching puritytogether with high brightness. In addition, technological integration in long range telecommunication networks requires near-infrared operation. Room temperature operation together with electrical injection would also be highly valuable for large scale integration.
Carbon nano-structures and in particular carbon nanotubes and graphene quantum dots have strong assets in this perspective. They were shown to be excellent single-photon emitters (both at low-temperature and room temperature for chemically grafted nanotubes or graphene quantum dots) [1, 2]. In addition, their emission wavelength can be chosen over a wide range, including the telecom O and C bands for nanotubes, by selecting appropriate chiral species. Finally, electro-luminescence has been reported by several teams [1]. Nevertheless, whatever the excitation scheme, the reported luminescence quantum efficiency is consistently small and the linewidth may be strongly broadened by interactions with phonons or by local environment electrical fluctuations.
Here, we show that these key properties can be drastically improved by coupling the nanostructure to a small volume, high-finesse micro cavity, through the so-called Purcell effect [3].
In order to tackle the so-called spatial and spectral mode matching issues (that become especially critical in high Q applications), we used a tunable cavity designed at the apex of an optical fiber for further integration in telecom networks. We show that the emission rate of the nanotube can be enhanced by a factor 60 leading to an effective luminescence quantum yield of about 40% and a coupling factor close to 100% [4].
In addition, the original tuning capability of our open cavity, allows us to exploit the spectral broadening of the emitter line and to achieve a widely tunable single-photon source. This new feature is possibly valuable for multiplexing applications in telecommunications or for indistinguishability engineering from remote nano-sources for quantum computing [4].

References:
[1] X. He et al., Nature Materials, 17, 663 (2018)
[2] S. Zhao et al., Nature Com. 9, 3470 (2018)
[3] A. Jeantet et al., Phys. Rev. Lett. 116, 247402 (2016).
[4] A. Jeantet, et al., Nano Lett. 17, 4184 (2017).
[5] Y. Chassagneux et al., Phys. Rev. B 97, 205124 (2018)

Preliminary list of future speakers:
25 March: Annick Loiseau, France
29 April: Christoph Stampfer, Aachen, Germany
27 May: Wang Yao, Hong Kong​

Category Seminar; Lecture
Location: Kollektorn, lecture room, Kemivägen 9, MC2-huset
Starts: 25 February, 2019, 13:00
Ends: 25 February, 2019, 14:00

Published: Tue 08 Jan 2019. Modified: Mon 18 Feb 2019