Quantum coherence of steered states

Area of Science:

• Quantum Information Theory
• Quantum Mechanics
• Quantum Correlations

Background:

• Coherence is a key resource in quantum information theory.
• Quantum steering, a concept by Schrödinger, involves one party influencing another's quantum state remotely.
• Recent attention has focused on steering and coherence as fundamental quantum phenomena.

Purpose of the Study:

• Introduce maximal steered coherence as a measure of steering's ability to generate coherence.
• Quantify the remote creation of coherence via quantum steering.
• Investigate the relationship between maximal steered coherence and other quantum correlations like discord.

Main Methods:

• Define maximal steered coherence as the maximum coherence of a steered state over all possible local measurements.
• Analyze the behavior of maximal steered coherence for different quantum states, including quantum-classical and entangled states.
• Examine the effect of local quantum channels on maximal steered coherence in a two-qubit system.

Main Results:

• Maximal steered coherence is zero for quantum-classical states and maximal for pure entangled states with full Schmidt rank.
• Maximal steered coherence is invariant under local unitary operations.
• Bob's local channel can increase maximal steered coherence if it is neither unital nor semi-classical, a condition also linked to increasing quantum discord.

Conclusions:

• Maximal steered coherence provides a novel way to quantify the coherence-generating power of quantum steering.
• The measure distinguishes itself from existing quantum correlation measures, including discord.
• Understanding maximal steered coherence deepens insights into the fundamental nature of quantum correlations and information processing.