Quantum effects improve the energy efficiency of feedback control

Area of Science:

• Thermodynamics
• Quantum Mechanics
• Quantum Information

Background:

• Thermodynamic laws apply to both classical and quantum systems.
• Quantum effects do not inherently alter the fundamental efficiency limits of classical thermodynamic devices like refrigerators or engines.

Purpose of the Study:

• To investigate if quantum mechanics enables thermodynamically more efficient feedback control protocols compared to classical ones.
• To analyze the thermodynamic costs and benefits of measurement-based and coherent feedback control in quantum systems.

Main Methods:

• Detailed thermodynamic accounting of unitary feedback control.
• Analysis of measurement-based and coherent feedback protocols.
• Comparison of quantum and classical feedback control efficiencies.

Main Results:

• Quantum mechanics permits measurement-based feedback control protocols that surpass classical counterparts in thermodynamic efficiency.
• Identified sources of inefficiency in both measurement-based and coherent feedback mechanisms.
• Demonstrated that quantum feedback can achieve higher thermodynamic performance.

Conclusions:

• Despite fundamental thermodynamic efficiencies remaining unchanged by quantum effects, quantum feedback control offers a pathway to enhanced performance.
• Measurement-based feedback control in quantum systems presents a promising avenue for improving thermodynamic efficiency.