Demonstration and Application of Long-lived state in a four-spin system hyperpolarized at room temperature*

A solution with hyperpolarized nuclear spins encoded into a long-lived state has been utilized for sensing chemical phenomena in vivo and in vitro. In a conventional way, nuclear spins are hyperpolarized at very low temperatures, and it needs a large-scale setup with a cryogenic instrument. In this work, we demonstrate the encoding of a four-nuclear-spin system hyperpolarized at room temperature into a long-lived state in a solution. Both room temperature hyperpolarization and quantum encoded sensor are a hot topic in quantum sensing. Experiments are performed for the aromatic protons in p-chlorobenzoic acid. The lifetime of spin polarization was increased 2.4 times by the quantum encoding. We apply the solution with the long-lived state as a sensor in ligand--receptor binding experiments.