Protocols for creating and purifying GHZ states*

The distribution of high quality Greenberger-Horne-Zeilinger (GHZ) states is at the heart of many applications in quantum information and the upcoming quantum internet, ranging from extending the baseline of telescopes to secret sharing. They also play an important role in error-correction architectures for distributed quantum computation, where EPR pairs are leveraged to create an entangled network of quantum computers.

Here, we investigate the creation of GHZ states over quantum networks. In particular, we introduce an algorithm based on dynamical programming to optimize over a large class of protocols that create and purify GHZ states. The new protocols outperform previous proposals for relevant scenarios, by reducing the resources necessary for GHZ creation, thus bringing the aforementioned applications closer to reality.