Mötesplats Rydberg: Martin Leijnse "A quest for nonlocal and nonabelian quasiparticles"

Tuesday 28 Jan 2020, 15:15 → 16:15 Europe/Stockholm

Rydbergsalen (Fysiska institutionen-Physics Department Hus H)

I will present a recently started research project aiming to realize quasiparticles with properties that are fundamentally different from anything observed in experiments so far, namely being nonlocal and nonabelian. Nonlocal means that the quantum state encoded in a set of quasiparticles is hidden from any set of local measurements. Nonabelian means that exchanges of particle positions result in nontrivial changes to the quantum state and that the result of several exchanges depends on their order. In addition to being of fundamental interest, these properties might be useful in future quantum computers.

It was theoretically predicted already around 30 years ago that so-called Majorana modes should have nonlocal and nonabelian properties, but despite intensive efforts this has never been experimentally demonstrated. Early attempts were based on trying realize Majorana modes in fractional quantum Hall states. There is now new hope because recent theoretical and experimental developments have led to increasing evidence for Majorana modes in a different platform, based on hybrid superconductor-semiconductor structures. But showing evidence for the existence of Majorana modes is one thing, experimentally demonstrating their (possibly) nonlocal and nonabelian properties is a challenge on an entirely different level. I will discuss how we are now taking on this challenge in a joint effort with groups from the Center for Quantum Devices at University of Copenhagen. The project involves a tight collaboration between material science, advanced nanofabrication, low-temperature measurements and theoretical physics.