Practical effects in the preparation of cluster states using weak non-linearities

TL;DR

This paper analyzes practical experimental effects impacting the implementation of bus-mediated entangling operations for cluster state preparation using weak non-linearities, focusing on error sources and fault-tolerance.

Contribution

It provides a detailed error analysis of a scheme for entangling qubits via weak Kerr interactions and quadrature measurements, highlighting realistic experimental challenges.

Findings

Post-selection errors significantly affect entanglement fidelity.

Qubit and bus losses reduce success probability and fidelity.

Error models relate experimental imperfections to fault-tolerant thresholds.

Abstract

We discuss experimental effects in the implementation of a recent scheme for performing bus mediated entangling operations between qubits. Here a bus mode, a strong coherent state, successively undergoes weak Kerr-type non-linear interactions with qubits. A quadrature measurement on the bus then projects the qubits into an entangled state. This approach has the benefit that entangling gates are non-destructive, may be performed non-locally, and there is no need for efficient single photon detection. In this paper we examine practical issues affecting its experimental implementation. In particular, we analyze the effects of post-selection errors, qubit loss, bus loss, mismatched coupling rates and mode-mismatch. We derive error models for these effects and relate them to realistic fault-tolerant thresholds, providing insight into realistic experimental requirements.