May 2024
Abstracts of the Quantum Center Lunch Seminar
Date: Thursday, May 2, 2024
Place: ETH Zurich, Hönggerberg, HPF G 6
Time: 12:00 - 13:30
Twenty-zone surface ion trap with fully integrated photonics
Tereza Viskova - Ion Trap Quantum Computing (Hempel group), ETHZ-PSI Quantum Computing Hub
One of the obstacles in scaling up trapped ion quantum computing is the increasing number of free-space lasers with increasing numbers of ions. These lasers are necessary for cooling the ions as well as performing quantum state manipulation and readout. In QCCD architectures, where ions are moved in two-dimensional trap arrays, individual addressing by free-space lasers further increases the system complexity. A promising avenue to address this challenge is the delivery of light through on-chip integrated waveguides, as previously demonstrated in the Home group at ETH Zurich [Mehta, 2019] for infrared light. Jointly with the ETH team, our group at PSI, is exploring this approach now in a 2D array that incorporates both UV and infrared light delivery through integrated photonics, combining Si3N4 and Al2O3 for the first time in an ion trap.
Electron paramagnetic resonance of isolated and coupled spins probed with atomic resolution
Aishwarya Vishwakarma - Magnetism and Interface Physics (Gambardella group), ETH Zurich
Scanning tunneling microscopy (STM) stands as a versatile tool for the investigation of surfaces and individual molecules and atoms on surfaces. It offers access to the local conductance through tunneling spectroscopy, with energy resolution limited by the electronic temperature. On the other hand, electron paramagnetic resonance (EPR) is commonly used for characterizing the magnetic properties of solid-state materials and molecular compounds. Recent advances have combined STM and EPR, extending sub-µeV energy resolution to the atomic scale. EPR-STM thus provides a powerful platform for coherent/incoherent control of individual spin qubits and their interactions within the local environment. Moreover, in-situ atom manipulation allows for the assembly of artificial quantum systems to study spin interactions in engineered and self-assembled structures.
In this talk, I will introduce the EPR-STM measurements of spins hosted in localized orbitals of single atoms and extended molecular orbitals of organic radicals. Depending on the distribution of the spin density, either a time-dependent electromagnetic field or a spin-polarized current can drive the EPR inside the STM junction. Furthermore, in the case of µeV-coupled spin structures, the effect of molecular orbital overlap can be precisely and directly sensed. Transitions involving singlet-triplet states and quantum interference effects can be probed in coupled two-level systems.