Cluster-state quantum computing enhanced by high-fidelity generalized measurements

TL;DR

This paper demonstrates how replacing projective measurements with generalized quantum measurements (POVMs) in cluster states enhances quantum computational capabilities, achieving high-fidelity results with minimal error contributions in photonic systems.

Contribution

The authors experimentally implement a tunable POVM and active feedforward on a two-qubit photonic cluster state, extending the computational power of cluster states.

Findings

Average output fidelity of 0.9832 with over 206 computations

Error contribution from POVM device and feedforward is less than 10^-3

Achieved thresholds relevant for fault-tolerant cluster computing

Abstract

We introduce and implement a technique to extend the quantum computational power of cluster states by replacing some projective measurements with generalized quantum measurements (POVMs). As an experimental demonstration we fully realize an arbitrary three-qubit cluster computation by implementing a tunable linear-optical POVM, as well as fast active feedforward, on a two-qubit photonic cluster state. Over 206 diferent computations, the average output fidelity is 0.9832 +/- 0.0002; furthermore the error contribution from our POVM device and feedforward is only of order 10e-3, less than some recent thresholds for fault-tolerant cluster computing.