Experimental generation of a high-fidelity four-photon linear cluster state

TL;DR

This paper reports the experimental creation of a high-fidelity four-photon linear cluster state using a novel scheme that can be extended to larger systems, optimizing success probability and simplicity.

Contribution

The authors introduce a new method for generating high-fidelity N-photon linear cluster states with maximal success probability and minimal complexity.

Findings

Achieved a state fidelity of 0.9517±0.0027 for the four-photon cluster state.

Scheme can be extended to generate larger N-qubit linear cluster states.

Optimal success probability of (1/4)^(N-1) for N-photon states.

Abstract

Cluster state plays a crucial role in the one-way quantum computation. Here, we propose and experimentally demonstrate a new scheme to prepare an ultrahigh-fidelity four-photon linear cluster state via spontaneous parametric down-conversion process. The state fidelity is measured to be $0.9517\pm0.0027$. Our scheme can be directly extended to more photons to generate N-qubit linear cluster state. Furthermore, our scheme is optimal for generating photonic linear cluster states in the sense of achieving the maximal success probability and having the simplest strategy. The key idea is that the photon pairs are prepared in some special non-maximally entangled states instead of the normal Bell states. To generate a 2N-qubit linear cluster state from N pairs of entangled photons, only (N-1) Hong-Ou-Mandel interferences are needed and a success probability of $(\frac{1}{4})^{N-1}$ is achieved.