June 2021

Abstracts of the QSIT Lunch Seminar, Thursday, June 3, 2021

Scheduled Zoom meeting

How to reach the motional ground state of a nanoparticle?

Nadine Meyer – Nanophotonic Systems Laboratory (Quidant group), Quantum Center, ETH Zurich

During the last decades, the rule book of quantum mechanics has been observed and tested extensively in many platforms using atoms, ions and electrons. Despite this success story, our everyday macroscopic world is a classical world. This raises the question where does quantum mechanics break down? To be able to study this question, we need dierent experimental platforms. In this talk here I will present our experimental approach to control and cool a nanoparticle, that is orders of magnitude larger than an atom, close to its motional ground state, a goal that has only recently been achieved [1]. In our setup, we use optical tweezers to levitate a nanoparticle in an optical, high nesse cavity [2]. Levitated particles stand out among the plethora of optomechanical systems due to their detachment, and therefore high degree of isolation from the environment. The tailored interaction between the nanoparticle motion and the cavity light eld reduces the kinetic energy of the particle, so cooling its centre-of-mass motion, by using the so-called coherent scattering technique. I will briefly discuss the concept of coherent scattering and decoherence sources present in our system.

Thanks to our large optomechanical coupling rates, we enter the so-called strong coupling regime [2], which in cavity optomechanics corresponds to an optomechanical coupling strength larger than cavity decay rate and mechanical damping. Here, we demonstrate the strong coupling regime at room temperature between a levitated particle and a high nesse optical cavity [2]. Finally, I discuss the feasibility of entering the regime of quantum control with our system.

[1] U. Delic, M. Reisenbauer, K. Dare, D. Grass, V. Vuletic, N. Kiesel, M. Aspelmeyer, Science 367, 6480 (2020)
[2] A. de los Ros Sommer, N. Meyer, and R. Quidant, Nature Communications 12, 276 (2021)

Universal quantum computing using electro-nuclear wavefunctions of rare-earth ions

Manuel Grimm – Condensed Matter Theory Group, Paul Scherrer Institut & Quantum Center, ETH Zurich

For certain computationally hard problems, quantum computers have a huge speedup advantage compared to their classical counterparts and their successful implementation may lead to drastic advances in solid state physics, quantum chemistry and biomedicine, among others.

In this seminar I discuss why rare-earth compounds might be ideal candidates for solid state quantum computation. I address the challenge to realize long-lived, coherent quantum memories, and efficient ways to unprotect those qubits and realize high fidelity gates between them [1].

[1] MG, Adrian Beckert, Gabriel Aeppli, and Markus Müller, PRX Quantum 2, 010312 (2021)