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Nonzero Classical Discord
Vlad Gheorghiu1,2, Marcos C de Oliveira2,3, Barry C Sanders1,2,4
1Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Physical Review Letters
|August 1, 2015
Summary
Quantum discord quantifies the disturbance in quantum states from local measurements. This study defines classical discord similarly, revealing a quantum-classical separation through noisy measurements and negative conditional entropy.
Area of Science:
- Quantum Information Theory
- Quantum Foundations
Background:
- Quantum discord quantifies quantum correlations beyond entanglement.
- Mutual information can be expressed using different conditional entropies, leading to discord.
- Classical systems can also exhibit discord-like phenomena.
Purpose of the Study:
- To define and understand classical discord.
- To establish an operational meaning for classical discord.
- To demonstrate the quantum-classical separation in information theory.
Main Methods:
- Constructing a stochastic model for shared states.
- Defining classical discord analogous to quantum discord.
- Analyzing state merging with noisy measurements.
Main Results:
- Classical discord quantifies stochasticity in measurement processes.
- An operational meaning for classical discord is established.
- A quantum-classical separation is shown via negative conditional entropy.
Conclusions:
- Discord, both quantum and classical, quantifies state disturbance from local measurements.
- Classical discord provides a framework for understanding noise in classical information processing.
- The concept of negative conditional entropy highlights fundamental differences between quantum and classical information.
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