Quantum macroscopicity versus distillation of macroscopic superpositions

Understand

We suggest a way to quantify a type of macroscopic entanglement via distillation of Greenberger-Horne-Zeilinger states by local operations and classical communication.

• We analyze how this relates to an existing measure of quantum macroscopicity based on the quantum Fisher information in several examples.
• Both cluster states and Kitaev surface code states are found to not be macroscopically quantum but can be distilled into macroscopic superpositions.
• We look at these distillation protocols in more detail and ask whether they are robust to perturbations.