October 2021
Abstracts of the QSIT Lunch Seminar, Thursday, October 7, 2021
Higgs analysis with quantum classifiers
Vasileios Belis - Institute of Particle Physics and Astrophysics (Dissertori group), ETH Zurich
We have developed two quantum classifier models for the identification of the Higgs boson production in the ttH(bb) channel. Both models fall into the category of hybrid quantum-classical algorithms for Noisy Intermediate Scale Quantum devices (NISQ). Our results, along with other studies, serve as a proof of concept that Quantum Machine Learning (QML) methods can have similar or better performance, in specific cases of low number of training samples, with respect to conventional ML methods even with a limited number of qubits available in current hardware. Τo accommodate for limitations in both simulation hardware and real quantum hardware we investigated different feature reduction methods. Their impact on the performance of both the classical and quantum models was assessed. We addressed different implementations of two QML models, representative of the two main approaches to supervised quantum machine learning today: a Quantum Support Vector Machine (QSVM), a kernel-based method, and a Variational Quantum Circuit (VQC), a variational approach.
Membrane-based scanning force microscopy
Thomas Gisler - Spin Physics Group (Degen group), ETH Zurich
Recent advances in fabrication and development of micro- and nanomechanical resonators push the boundaries of detectable forces. Among other techniques, phononic engineering of silicon nitride membranes enables unprecedented high quality factors. Using these membranes as force sensors may lead to a new generation of scanning force microscopes.
In this talk, I will discuss the experimental realization of a membrane-based scanning force microscope. The interaction of a scannable-static tip with the vibrating membrane enables to capture topographical images of samples placed on the membrane surface. The measured data reveals that silicon nitride membranes retain their excellent force sensitivity in presence of the scanning tip and when loaded with a sample [1].
To overcome the limited displacement sensitivity of the optical interferometer in the current setup, an optical cavity is implemented. This leads to an enhanced readout of the membrane motion which is one of the necessary steps towards single nuclei spin detection. The improved displacement sensitivity allows to feedback cool the membrane mode and increases the mechanical response time of the resonator.
[1] David Hälg, Thomas Gisler, Yeghishe Tsaturyan, Letizia Catalini, Urs Grob, Marc-Dominik Krass, Martin Héritier, Hinrich Mattiat, Ann-Katrin Thamm, Romana Schirhagl, Eric C. Langman, Albert Schliesser, Christian L. Degen, and Alexander Eichler
Phys. Rev. Applied 15, L021001 – Published 5 February 2021