QuTech360 w/Guanzhong Wang and Tom Dvir

In this QuTech360 seminar, Guanzhong Wang (PhD student) and Tom Dvir (postdoc researcher) present their research in the Kouwenhoven Lab (Qubit Research Division) at QuTech.
In the first talk, Guanzhong Wang presents 'Singlet vs triplet Cooper-pair splitting in InSb nanowires'. In the second talk, Tom Dvir presents 'Realizing a minimal Kitaev chain in InSb hybrid nanowire'.
For bio and abstracts, please see the description below.

Title:
Singlet vs triplet Cooper-pair splitting in InSb nanowires.

Speaker:
Guanzhong Wang

Abstract:
Cooper pairs are a natural source of entangled electrons provided by superconductors. Semiconducting-superconducting hybrid systems allow the splitting of Cooper pairs into separate single electrons and their subsequent manipulation. Using two few-electron InSb nanowire quantum dots separated by a narrow strip of proximitized superconducting Al, we achieve a high degree of control in Cooper-pair splitting via selecting for the single electron's desired charge as well as spin. The resulting Cooper-pair splitting signal is free of contributions from the competing process, elastic co-tunneling. Under an applied magnetic field parallel to the Rashba spin-orbit field of InSb, we observe complete blockade of the equal-spin splitting process due to spin-singlet superconducting pairing. Rotating the applied field to be perpendicular to the Rashba field introduces a triplet component in the effective superconducting pairing between electrons and lifts this blockade. The spin blockade results open new pathways to the precise manipulation and entanglement testing of the split electrons.

Bio:
Guanzhong Wang received his MSc degree in Applied Physics from TU Delft in 2017. Since then, he has been a PhD student in the group of Leo Kouwenhoven at QuTech, working on electron transport in hybrid semiconducting-superconducting nanowires.
Title:
Realizing a minimal Kitaev chain in InSb hybrid nanowire.

Speaker:
Tom Dvir

Abstract:
Majorana bound states constitute one of the simplest examples of emergent non-Abelian excitations in condensed matter physics. A toy model proposed by Kitaev shows that such states can arise on the edges of a spinless p-wave superconducting chain. Practical proposals for its realization require coupling neighboring quantum dots in a chain via both electron tunneling and crossed Andreev reflection simultaneously. Here we demonstrate for the first time the simultaneous presence of all necessary ingredients for an artificial Kitaev chain: two spin-polarized quantum dots in an InSb nanowire strongly coupled by both elastic co-tunneling and crossed Andreev reflection. Our system can be further fine-tuned to a sweet spot where a pair of Majorana bound states is predicted to appear. In this sweet spot, the transport characteristics satisfies all accessible theoretical predictions for a Majorana bound state platform for the first time, including pairwise correlation, zero charge and the expected phase diagram. While the simple system presented here can be scaled to simulate a full Kitaev chain with an emergent topological order, it can also be used imminently to study the physics of Majorana bound states and non-abelian anyons.

Bio:
Tom Dvir graduated from the Hebrew University of Jerusalem in 2019, where he studied superconductivity in ultra-thin van der Waals materials. He later joined the group of Leo Kouwenhoven in QuTech to study topological superconductivity in hybrid systems of superconductors and semiconducting nanowires.

Видео QuTech360 w/Guanzhong Wang and Tom Dvir канала QuTech Academy