Real-time optimal quantum control of mechanical motion at room temperature

Area of Science:

• Quantum mechanics
• Nanotechnology
• Control engineering

Background:

• Accurate control of physical systems via measurement and feedback is crucial for modern engineering.
• Applied quantum technologies necessitate control at the individual quantum system level.
• Optimal control requires quantum-limited measurements and tailored state estimation/feedback algorithms.

Purpose of the Study:

• To demonstrate real-time optimal control of a quantum trajectory for an optically trapped nanoparticle.
• To achieve quantum ground-state cooling of a mechanical oscillator.

Main Methods:

• Utilized confocal position sensing near the Heisenberg limit.
• Employed optimal state estimation via Kalman filtering for real-time phase space tracking.
• Implemented optimal feedback control strategies.

Main Results:

• Achieved real-time tracking of nanoparticle motion with a position uncertainty of 1.3 times the zero-point fluctuation.
• Stabilized the quantum harmonic oscillator to a mean occupation of 0.56 ± 0.02 quanta.
• Realized quantum ground-state cooling from room temperature.

Conclusions:

• Established quantum Kalman filtering as a viable method for quantum control of mechanical motion.
• Demonstrated potential implications for quantum sensing across various scales.
• Paved the way for full-scale control over macroscopic quantum object wavepacket dynamics.