Probing Scalar Coupling Differences via Long-Lived Singlet States

TL;DR

This paper demonstrates a method to detect tiny scalar coupling differences in organic molecules by using long-lived nuclear spin singlet states and the SLIC technique, revealing potential for quantum memory applications.

Contribution

It introduces a novel approach combining SLIC with singlet states to measure small J coupling differences with high precision.

Findings

Measured J coupling differences of 8 mHz and 2.57 Hz in specific molecules.

Showed coherent transfer of singlet order between spin pairs.

Characterized long-lived singlet state coherence in glutamate.

Abstract

We probe small scalar coupling differences via the coherent interactions between two nuclear spin singlet states in organic molecules. We show that the spin-lock induced crossing (SLIC) technique enables the coherent transfer of singlet order between one spin pair and another. The transfer is mediated by the difference in cis and trans vicinal J couplings among the spins. By measuring the transfer rate, we calculate a J coupling difference of $8 \pm 2$ mHz in phenylalanine-glycine-glycine and $2.57 \pm 0.04$ Hz in glutamate. We also characterize a coherence between two singlet states in glutamate, which may enable the creation of a long-lived quantum memory.