Demonstration of a universal one-way quantum quadratic phase gate

TL;DR

This paper demonstrates a universal one-way quantum quadratic phase gate for continuous-variable quantum computation, showcasing controllability and nonclassical state generation, advancing the implementation of Gaussian transformations.

Contribution

It introduces a fully controlled quadratic phase gate in the continuous-variable regime, enabling universal Gaussian transformations in measurement-based quantum computation.

Findings

Successful experimental demonstration of the quadratic phase gate.

Observation of sub-shot-noise quadrature variances in output states.

Confirmation of nonclassical state creation through cluster computation.

Abstract

We demonstrate a quadratic phase gate for one-way quantum computation in the continuous-variable regime. This canonical gate, together with phase-space displacements and Fourier rotations, completes the set of universal gates for realizing any single-mode Gaussian transformation such as arbitrary squeezing. As opposed to previous implementations of measurement-based squeezers, the current gate is fully controlled by the local oscillator phase of the homodyne detector. Verifying this controllability, we give an experimental demonstration of the principles of one-way quantum computation over continuous variables. Moreover, we can observe sub-shot-noise quadrature variances in the output states, confirming that nonclassical states are created through cluster computation.