Two qubit gate with macroscopic singlet-triplet qubits in synthetic spin-one chains in InAsP quantum dot nanowires

TL;DR

This paper proposes a theoretical framework for implementing a two-qubit gate using macroscopic singlet-triplet qubits in synthetic spin-one chains within InAsP quantum dot nanowires, leveraging topological protection and tunable coupling methods.

Contribution

It introduces a novel approach to realize two-qubit gates with macroscopic singlet-triplet qubits in synthetic spin-one chains, including methods for tunable coupling and high-precision gate generation.

Findings

Effective low-energy model captured by antiferromagnetic spin-one chain Hamiltonian.

Method for tunable coupling via an intermediate control dot.

Two approaches for generating accurate two-qubit gates.

Abstract

We present a theory of a two qubit gate with macroscopic singlet-triplet (ST) qubits in synthetic spin-one chains in InAsP quantum dot nanowires. The macroscopic topologically protected singlet-triplet qubits are built with two spin-half Haldane quasiparticles. The Haldane quasiparticles are hosted by synthetic spin-one chain realized in chains of InAsP quantum dots embedded in an InP nanowire, with four electrons each. The quantum dot nanowire is described by a Hubbard-Kanamori (HK) Hamiltonian derived from an interacting atomistic model. Using exact diagonalization and Matrix Product States (MPS) tools, we demonstrate that the low-energy behavior of the HK Hamiltonian is effectively captured by an antiferromagnetic spin-one chain Hamiltonian. Next we consider two macroscopic qubits and present a method for creating a tunable coupling between the two macroscopic qubits by inserting an intermediate control dot between the two chains. Finally, we propose and demonstrate two approaches for generating highly accurate two-ST qubit gates : (1) by controlling the length of each qubit, and (2) by employing different background magnetic fields for the two qubits.