Crossed Andreev reflection in a d-wave superconductor with two quantum point contacts

TL;DR

This paper theoretically investigates crossed Andreev reflection in a d-wave superconductor with two quantum point contacts, revealing sharp conductance peaks from Andreev bound states that could serve as a qubit.

Contribution

It introduces the formation of Andreev bound states as a two-level quantum system in a d-wave superconductor with quantum contacts, a novel approach for qubit implementation.

Findings

Sharp conductance peaks below the gap due to Andreev bound states

Formation of bonding and antibonding Andreev states

Proposal of these states as a two-level quantum system (qubit)

Abstract

We theoretically study the crossed Andreev reflection in a hybrid nanostructure which comprises a d-wave superconductor and two normal-metal quantum wires. When the superconductor of the (110) oriented surface is in contact with the wires parallel and placed close to each other, the Andreev bound state is formed by the crossed Andreev reflection. When the contact barrier potential is sufficiently large, two sharp peaks appear in the conductance well below the gap structure, which originate from the bonding and antibonding Andreev bound states. We propose that these Andreev bound states form a two-level quantum system (qubit).