Exponentially Localized Magnetic Fields for Single-Spin Quantum Logic Gates

TL;DR

This paper demonstrates that a finite array of superconducting nanowires can generate highly localized magnetic fields suitable for fast, single-spin quantum logic gates, compatible with current quantum computing architectures.

Contribution

It introduces a practical design for nanowire arrays that produce exponentially localized magnetic fields for quantum logic operations.

Findings

Peak magnetic field of 10mT achieved

Field decays by a factor of 10^4 over 500nm

Quantum gate times of 5ns possible

Abstract

An infinite array of parallel current-carrying wires is known, from the field of neutral particle optics, to produce an exponentially localized magnetic field when the current direction is antiparallel in adjacent wires. We show that a finite array of several tens of superconducting Nb nanowires can produce a peak magnetic field of 10mT that decays by a factor of 10^4 over a length scale of 500nm. Such an array is readily manufacturable with current technology, and is compatible with both semiconductor and superconducting quantum computer architectures. A series of such arrays can be used to individually address single single-spin or flux qubits spaced as little as 100nm apart, and can lead to quantum logic gate times of 5ns.