Jeudi 16 mai 2013 à 10h15
Salle 234, Ecole de Physique

Quantum dots and Majorana bound states

Martin Leijnse, Lund University

Majorana fermions, particles which are their own antiparticles, may or may not exist as elementary particles in nature. However, it was shown theoretically a few years ago that they can appear as quasiparticle excitations in certain condensed matter systems, and a few ground-breaking recent experiments have reported likely Majorana sightings. This has quickly become one of the hottest topics in mesoscopic physics research, partly because of the possibility to use Majorana fermions for quantum information processing. In the first part of my talk, I will discuss the possibility to generate Majorana-like bound states in a double quantum dot system, where the dots are tunnel coupled to each other via a superconductor. The Majoranas in such a setup are not as protected as in other systems and we call them Poor Man's Majoranas. However, this may serve as an attractive setup in which to experimentally test some of the exciting theoretical predictions for Majorana physics. In the second part, I will focus on hybrid quantum devices, combining Majorana-based qubits and spin qubits defined in semiconducting quantum dots. I will describe how gated control of the charge on the quantum dots allows transfer of quantum information between the spin and Majorana qubits. Furthermore, the Majorana system can be used as a quantum bus to connect spatially separated quantum dots, allowing coherent transfer of spin states, generation of entangled spin-qubit pairs, and even two-spin-qubit gates.