July 2014
Abstracts of the QSIT Lunch Seminar, Thursday July 3, 2014
Strain Coupling of a Nitrogen-Vacancy Center Spin to a Diamond Mechanical Oscillator
Arne Barfuss, Quantum Sensing Lab, University of Basel
Significant progress in control and understanding of quantum two-level systems has been made within the last decade In order to employ such two-level systems for quantum information processing or quantum sensing, it is important to engineer a controllable coupling to their environment. As a result, long-range coupling of two-level systems could be enabled. A possible approach to that end is the coupling of two-level systems to mechanical oscillators. Several such hybrid spin-oscillator systems have been proposed and implemented within the past. However, most existing hybrid spin-oscillator systems are based on complex coupling mechanisms and suffer from relatively low coupling strengths compared to the systems’ relevant decoherence rates.
To overcome these limitations, we implemented a novel hybrid system consisting of an electronic spin in form of a Nitrogen-Vacancy center intrinsically coupled to a single-crystalline diamond mechanical oscillator through crystal strain. In this talk, I will discuss our experimental investigations of this novel hybrid spin-oscillator system. In particular, I will present experiments in which we determined the former unknown spin-strain coupling constants for Nitrogen-Vacancy centers in diamond. We furthermore demonstrate that our system allows us to enter the resolved sideband regime. With future experimental improvement, our system has the potential to reach the strong coupling regime. The results therefore establish our diamond-based hybrid spin-oscillator system as a valuable resource for future experiments in the quantum regime.
Single Photon Emitters in Monolayer WSe2
Meinrad Sidler, Quantum Photonics Group, ETH Zurich
co-authors:
Ajit Srivastava, Atac Imamoglu: Institute for Quantum Electronics, ETH Zürich
Adrien Allain, Dominik Lembke, Andras Kis:Electrical Engineering Institute, EPF Lausanne
Optical properties of monolayer transition metal dichalcogenides (TMD) as a two-dimensional semiconductor have attracted considerable interest [1,2]. We report localized, spectrally narrow (~ 100 ueV), photoluminescence (PL) in monolayer WSe2 flakes. The different emitters lie within a wavelength range which is lower in energy than both the exciton and the trion PL of the WSe2 flake. The sharp peaks we observe are within the wavelength range that was previously assigned to the impurity-bound excitonic complexes [3]. We have carried out photon correlation measurements exhibiting strong anti-bunching and thereby unequivocally proving the 0-dimensional nature of the emitters. We measure surprisingly long PL lifetime of ~ 5 ns and saturation behavior at much lower excitation power (few uWs) compared to unbound exciton and trion emission, consistent with quantum dot-like emission.
References:
[1]H. Zhang, J. Dai, W. Yao, D. Xiao, X. Cui, Nature Nanotechnology, 7, 490-493, (2012).
[2] K.F. Mak, K. He, J. Shan and Tony F. Heinz, Nature Nanotechnology, 7, 494-498, (2012).
[3] A.M. Jones, H. Yu, N.J. Ghimire, S. Wu, G. Aivazian, J.S. Ross, B. Zhao, J. Yan, D. G. Mandrus, D. Xiao, W. Yao and X. Xu, Nature Nanotechnology, 8, 634-638, (2013).