Information Gain and Loss for a Quantum Maxwell's Demon

Area of Science:

• Quantum Information Science
• Quantum Thermodynamics
• Superconducting Circuits

Background:

• The Maxwell's demon paradox explores the relationship between information and thermodynamics.
• Quantum systems introduce unique challenges and possibilities for information processing and energy conversion.
• Superconducting qubits offer a controllable platform for studying fundamental quantum phenomena.

Purpose of the Study:

• To experimentally investigate the information dynamics of a quantum Maxwell's demon using a superconducting qubit.
• To explore the conversion of information into work via quantum coherent feedback.
• To verify quantum fluctuation theorems in the presence of feedback and imperfect measurements.

Main Methods:

• Utilized continuous weak measurements on a driven superconducting qubit.
• Employed quantum coherent feedback to process information gained from measurements.
• Analyzed single quantum trajectories to verify theoretical predictions.

Main Results:

• Demonstrated the conversion of information into work using quantum feedback on a superconducting qubit.
• Verified a quantum fluctuation theorem by analyzing information from single quantum trajectories.
• Showed that quantum backaction in imperfect measurements can lead to information loss.

Conclusions:

• Experimental evidence supports the thermodynamic cost of information in quantum systems.
• Quantum feedback provides a mechanism to extract work from information, consistent with fluctuation theorems.
• The study highlights the role of measurement backaction and initial state purity in quantum information dynamics.