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Detecting and manipulating Majorana bound states in nanowires

Speaker: 
Thomas Schmidt (University of Luxembourg)
Date: 
Wed, 20/01/2016 - 11:00am to 12:00pm
Location: 
Physics Conference Room (S11-02-07)
Host: 
Quek Su Ying
Event Type: 
Seminars

Abstract

It has been shown recently that the interplay of spin-orbit coupling, magnetic fields, and the superconducting proximity effect can lead to the emergence of zero-energy Majorana bound states (MBS) at the ends of a nanowire. These states are interesting because of their non-Abelian exchange statistics and their potential usefulness for quantum computation applications. However, detecting and manipulating them remains a challenge.

In the first part of the talk, I will present multi-terminal networks hosting MBS which could be useful for their identification. In particular, I will discuss T-shaped junctions of two Majorana nanowires. When the wires are in the topologically nontrivial regime, three MBS are localized near the outer ends of the wires, while one MBS is localized near the crossing point, and when the lengths of the wires are finite adjacent MBS can overlap. A combination of current and cross-correlation measurements can then be used to reveal the predicted coupling of four MBS in a topological T junction. Interestingly, the elementary transport processes at the central lead are different compared to the outer leads, giving rise to characteristic nonlocal signatures in electronic transport [1].

MBS have also been proposed as building blocks for qubits on which certain operations can be performed in a topologically protected way using braiding. However, the set of these protected operations is not sufficient to realize universal quantum computing. In the second part of the talk, I will show that the electric field in a microwave cavity can induce Rabi oscillations between adjacent MBS. These oscillations can be used to implement an additional single-qubit gate. Supplemented with one braiding operation, this gate allows one to perform arbitrary single-qubit operations [2,3].

[1] Luzie Weithofer, Patrik Recher, and Thomas L. Schmidt, Phys. Rev. B 90, 205416 (2014)
[2] Thomas L. Schmidt, Andreas Nunnenkamp, and Christoph Bruder, Phys. Rev. Lett. 110, 107006 (2013)
[3] Thomas L. Schmidt, Andreas Nunnenkamp, and Christoph Bruder, New J. Phys. 15, 025043 (2013)

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