Contextuality as a resource for models of quantum computation on qubits

TL;DR

This paper demonstrates that quantum contextuality is a necessary resource for certain quantum computation schemes on qubits, extending the understanding of what enables quantum speed-up.

Contribution

It establishes the necessity of contextuality in magic states for a broad class of qubit-based quantum computations, addressing a key open question.

Findings

Contextuality is necessary for quantum speed-up in qubit models.

The result applies to measurement-based quantum computation schemes.

State-independent contextuality does not obstruct the role of contextuality as a resource.

Abstract

A central question in quantum computation is to identify the resources that are responsible for quantum speed-up. Quantum contextuality has been recently shown to be a resource for quantum computation with magic states for odd-prime dimensional qudits and two-dimensional systems with real wavefunctions. The phenomenon of state-independent contextuality poses a priori an obstruction to characterizing the case of regular qubits, the fundamental building block of quantum computation. Here, we establish contextuality of magic states as a necessary resource for a large class of quantum computation schemes on qubits. We illustrate our result with a concrete scheme related to measurement-based quantum computation.