Stochastic optimal control: Designing dynamic nuclear polarization in large open quantum systems

Stochastic optimal control: Designing dynamic nuclear polarization in large open quantum systems.

While being one of the most important analytical technologies ever invented nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) suffer a major challenge in terms of sensitivity. Orders of magnitude higher sensitivity – and access to long-range structure information - may be obtained by excitation and detection via much higher polarized electron spins using dynamic nuclear polarization (DNP) with prospects of the next breakthrough in magnetic resonance. To realize this potential, we need to combine advanced pulsed microwave technology with clever pulse engineering capable of handling large electron-nuclear spin systems influenced by MHz to GHz electron-spin interactions, extensive spin diffusion, and relaxation/dissipative processes in nanosecond time scales. This complexity calls for novel mathematical, data-driven design strategies involving stochastic optimal control, to develop experiments where advanced microwave and radio-frequency pulse sequences drive polarization from the electrons through resolved nuclear spin states and back to electrons in multiple-dimensional experiments encoded with information about structure and dynamics.