Repeat-until-success cubic phase gate for universal continuous-variable quantum computation

TL;DR

This paper proposes a practical repeat-until-success method for implementing the cubic phase gate, a crucial non-Gaussian element needed for universal continuous-variable quantum computation, using photon subtraction and Gaussian operations.

Contribution

It introduces a novel repeat-until-success scheme for the cubic phase gate that improves success probability and practicality in continuous-variable quantum computing.

Findings

Scheme reduces expected time until success

Requires a primitive quantum memory

Offers a feasible route for non-Gaussian gate implementation

Abstract

In order to achieve universal quantum computation using continuous variables, one needs to jump out of the set of Gaussian operations and have a non-Gaussian element, such as the cubic phase gate. However, such a gate is currently very difficult to implement in practice. Here we introduce an experimentally viable 'repeat-until-success' approach to generating the cubic phase gate, which is achieved using sequential photon subtractions and Gaussian operations. We find that our scheme offers benefits in terms of the expected time until success, although we require a primitive quantum memory.