Macroscopic Hyperpolarization Enhanced with Quantum Optimal Control

TL;DR

This paper demonstrates a macroscopic hyperpolarization technique using quantum optimal control, achieving significant signal enhancement and faster polarization, with a novel adaptive sequence optimization method called ARISE.

Contribution

It introduces a macroscopic optimal control approach for hyperpolarization and the ARISE method for robust sequence optimization under experimental uncertainties.

Findings

28% increase in signal strength

15% faster polarization rate

ARISE improves hyperpolarization robustness

Abstract

Hyperpolarization of nuclear spins enhances nuclear magnetic resonance signals, which play a key role for imaging and spectroscopy in the natural and life sciences. This signal amplification unlocks previously inaccessible techniques, such as metabolic imaging of cancer cells. In this work, electron spins from the photoexcited triplet state of pentacene-doped naphthalene crystals are used to polarize surrounding protons. As existing strategies are rendered less effective by experimental constraints, they are replaced with optimal control pulses designed with RedCRAB. In contrast to previous optimal control approaches, which consider an average single nucleus, this closed-loop optimization is macroscopic. A 28% improvement in signal and 15% faster polarization rate is observed. Additionally, a strategy called Autonomously-optimized Repeated Linear Sweep (ARISE) is introduced to efficiently tailor existing hyperpolarization sequences in the presence of experimental uncertainty to enhance their performance. ARISE is expected to be broadly applicable in many experimental settings.