Necessary and sufficient condition for non-zero quantum discord

Abstract

Quantum discord characterizes "non-classicality" of correlations in quantum mechanics. It has been proposed as the key resource present in certain quantum communication tasks and quantum computational models without containing much entanglement. We obtain a necessary and sufficient condition for the existence of non-zero quantum discord for any dimensional bipartite states. This condition is easily experimentally implementable. Based on this, we propose a geometrical way of quantifying quantum discord. For two qubits this results in a closed form of expression for discord. We apply our results to the model of deterministic quantum computation with one qubit, showing that quantum discord is unlikely to be the reason behind its speedup.

minor changes, published version

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Cited by in corpus (9)

• Operational interpretations of quantum discord
• Quantum discord for general two--qubit states: Analytical progress
• Linking Quantum Discord to Entanglement in a Measurement
• Quantum discord and geometry for a class of two-qubit states
• Optimal measurements to access classical correlations of two-qubit states
• Frozen discord in non-Markovian dephasing channels
• Detecting Multipartite Classical States and their Resemblances
• Measurement-induced disturbance and thermal entanglement in spin models
• Witness to detect quantum correlation of bipartite states in arbitrary dimension