Using optimal control methods with constraints to generate singlet states in NMR.

Area of Science:

• Magnetic Resonance Spectroscopy
• Quantum Control

Background:

• Adiabatic-Passage Spin Order Conversion (APSOC) is crucial for manipulating singlet spin states in NMR.
• Current APSOC techniques often rely on simplified radiofrequency (RF) field ramps, limiting conversion efficiency.

Purpose of the Study:

• To optimize the APSOC technique for improved performance in NMR experiments.
• To enhance the efficiency of magnetization-to-singlet conversion using advanced pulse engineering.

Main Methods:

• Proposed an optimization method for APSOC utilizing the Gradient Ascent Pulse Engineering (GRAPE) approach.
• Assumed monotonicity of the RF-field envelope within a fixed search area for optimization.
• Applied adiabatically ramped RF-fields for magnetization-to-singlet and singlet-to-magnetization conversion.

Main Results:

• Achieved significantly better performance for APSOC compared to simple linear ramps.
• Demonstrated greatly improved efficiency in magnetization-to-singlet conversion.
• Showcased robustness of the optimization method against inaccuracies in NMR parameters and RF-field settings.

Conclusions:

• The GRAPE-optimized APSOC technique offers superior performance for singlet spin state manipulation in NMR.
• This optimized approach is robust and applicable to various NMR and EPR experiments involving adiabatic spin Hamiltonian switching.