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TT: Fachverband Tiefe Temperaturen

TT 40: Topological Josephson Junctions

TT 40.7: Vortrag

Mittwoch, 18. März 2020, 16:30–16:45, HSZ 103

Manipulation of Majorana qubits in the Josephson junction on helical edges — •Sang-Jun Choi, Calzona Alessio, and Trauzettel Bjoern — Institute of Theoretical Physics and Astrophysics, University of Würzburg, Würzburg, Germany

Topological Josephson junctions constitute a promising platform to observe the exotic properties of Majorana fermions (MFs). Hosting MFs – especially in a Josephson junction setup – enables us (i) to manipulate the coupling between MFs via the phase difference of the superconductors and (ii) measure the fermion parity of two MFs by the sign of the supercurrent. First experimental hints for the existence of MFs in Josephson junctions have recently been established by a measurement of the fractional Josephson effect.

We theoretically study the Josephson effect on a U-shaped quantum spin Hall edge channel which hosts four MFs and hence describes a single Majorana qubit. Two distinct knobs – chemical potential and superconducting phase difference – are used to tune the various couplings among the MFs. As a result, we find two kinds of finite rotations of the Majorana qubit around x- and z-axis. We identify signatures of Lamor precession and Rabi oscillations in this setup. Additionally, we show that the rotated (Majorana qubit) state can be read-out by measuring the supercurrent. Finally, we propose an experimental protocol that is able to detect the non-Abelian nature of the MFs.