Optimizing EPR pulses for broadband excitation and refocusing

Area of Science:

• Quantum control
• Magnetic resonance
• Pulse shaping

Background:

• Hahn echo techniques are crucial for preserving quantum coherence.
• Optimizing broadband pulse shapes is essential for maximizing echo amplitudes in magnetic resonance.
• Conventional pulse shapes like hyperbolic secant (HS) have limitations.

Purpose of the Study:

• To numerically optimize broadband pulse shapes for maximizing Hahn echo amplitudes.
• To compare the performance of novel pulse parameterizations against conventional methods.
• To investigate the impact of power constraints and realistic distortions on pulse performance.

Main Methods:

• Pulse shapes were parameterized using neural networks (NN), nonlinear Fourier series (FS), and discrete time series (DT).
• Numerical optimization was performed under power constraints.
• Realistic distortions from power amplifier nonlinearity and resonator transfer functions were included.

Main Results:

• NN, FS, and DT parameterizations demonstrated equivalent performance.
• These novel parameterizations outperformed optimized HS pulses.
• A large number of equivalent optimal maxima were found, indicating design flexibility.

Conclusions:

• Advanced parameterizations offer superior broadband pulse shaping for Hahn echo maximization.
• The flexibility of these methods allows for incorporating additional constraints in future pulse designs.
• This work advances quantum control strategies in magnetic resonance.