Qudit Colour Codes and Gauge Colour Codes in All Spatial Dimensions

TL;DR

This paper extends color codes and gauge color codes to qudits, demonstrating their ability to support advanced transversal gates and phase gates in higher dimensions, thus enhancing fault-tolerant quantum computation.

Contribution

It generalizes color codes to qudits, supporting higher-level gates and saturating theoretical bounds across all but a few cases, using a novel methodology based on triorthogonal matrices.

Findings

Qudit color codes support transversal non-Clifford gates in higher dimensions.

Gauge fixing enables Clifford gates without state distillation.

Supports phase gates from higher Clifford hierarchy levels, saturating bounds.

Abstract

Two-level quantum systems, qubits, are not the only basis for quantum computation. Advantages exist in using qudits, d-level quantum systems, as the basic carrier of quantum information. We show that color codes, a class of topological quantum codes with remarkable transversality properties, can be generalized to the qudit paradigm. In recent developments it was found that in three spatial dimensions a qubit color code can support a transversal non-Clifford gate, and that in higher spatial dimensions additional non-Clifford gates can be found, saturating Bravyi and K\"onig's bound [Phys. Rev. Lett. 110, 170503 (2013)]. Furthermore, by using gauge fixing techniques, an effective set of Clifford gates can be achieved, removing the need for state distillation. We show that the qudit color code can support the qudit analogues of these gates, and show that in higher spatial dimensions a color code can support a phase gate from higher levels of the Clifford hierarchy which can be proven to saturate Bravyi and K\"onig's bound in all but a finite number of special cases. The methodology used is a generalisation of Bravyi and Haah's method of triorthogonal matrices [Phys. Rev. A 86 052329 (2012)], which may be of independent interest. For completeness, we show explicitly that the qudit color codes generalize to gauge color codes, and share the many of the favorable properties of their qubit counterparts.