Time-optimal excitation of maximum quantum coherence: Physical limits and pulse sequences

Area of Science:

• Quantum Information Science
• Quantum Control Theory
• Magnetic Resonance Spectroscopy

Background:

• Exciting maximum quantum (MaxQ) coherence is crucial for quantum information processing and spectroscopy.
• Conventional methods often face limitations in efficiency and speed.

Purpose of the Study:

• To investigate optimal control strategies for efficient MaxQ coherence excitation.
• To determine the theoretical limits of MaxQ amplitude and minimum excitation time.
• To develop novel pulse sequences for enhanced coherence preparation.

Main Methods:

• Analytical and numerical methods based on optimal control theory.
• Optimization of arbitrary pulse shapes and practical pulse sequence families.
• Modeling of coupled spin systems up to five spins.

Main Results:

• Substantial gains in MaxQ amplitude and reduced pulse sequence durations compared to conventional approaches.
• Experimental demonstration of a threefold gain in a model system.
• Discovery of two novel analytical transfer schemes, including faster double-quantum and triple-quantum coherence generation.

Conclusions:

• Optimal control theory provides a powerful framework for enhancing MaxQ coherence excitation.
• Novel pulse sequences offer significant improvements in speed and efficiency for quantum coherence preparation.
• These advancements have implications for improving quantum sensing and computation.