Source-linked AI summary
Interpreting quantum discord through quantum state merging
Vaibhav Madhok, Animesh Datta
TL;DR
The paper asks for an operational interpretation of quantum discord beyond its definition as the difference between total and classical correlations. It uses quantum state merging to show that discord is the communication-cost markup caused by discarding information, and relates this interpretation to other correlation measures and selected single-copy cases.
Problem
Quantum discord needs an operational interpretation that does not rely on defining it as the difference between total and classical correlations.
Method
The paper analyzes quantum state merging after simulating arbitrary quantum operations, including measurements, on the receiving party's subsystem.
Results
Quantum discord equals the minimum increase in quantum communication cost for state merging when measurement on the receiving party discards relevant information.
Takeaways & Limitations
The state-merging perspective also gives operational interpretations of local purity and quantum deficit, with quantum deficit coinciding with discord asymptotically and lower-bounding it for finite copies under stated measurement restrictions.
Takeaways & Limitations
The information-theoretic task yields regularized quantum discord because single-copy state merging does not generally produce the conditional von Neumann entropy.
Abstract
from arXiv · showhide
We present an operational interpretation of quantum discord based on the quantum state merging protocol. Quantum discord is the markup in the cost of quantum communication in the process of quantum state merging, if one discards relevant prior information. Our interpretation has an intuitive explanation based on the strong subadditivity of von Neumann entropy. We use our result to provide operational interpretations of other quantities like the local purity and quantum deficit. Finally, we discuss in brief some instances where our interpretation is valid in the single copy scenario.