Rodin Bogdan A, Bengs Christian, Kiryutin Alexey S, Sheberstov Kirill F, Brown Lynda J, Brown Richard C D, Yurkovskaya Alexandra V, Ivanov Konstantin L, Levitt Malcolm H
International Tomography Center SB RAS, Novosibirsk, Russia.
Department of Chemistry, Southampton University, Southampton SO17 1BJ, United Kingdom.
J Chem Phys. 2020 Apr 30;152(16):164201. doi: 10.1063/5.0006742.
Algorithmic cooling methods manipulate an open quantum system in order to lower its temperature below that of the environment. We achieve significant cooling of an ensemble of nuclear spin-pair systems by exploiting the long-lived nuclear singlet state, which is an antisymmetric quantum superposition of the "up" and "down" Zeeman states. The effect is demonstrated by nuclear magnetic resonance experiments on a molecular system containing a coupled pair of near-equivalent C nuclei. The populations of the system are subjected to a repeating sequence of cyclic permutations separated by relaxation intervals. The long-lived nuclear singlet order is pumped well beyond the unitary limit. The pumped singlet order is converted into nuclear magnetization which is enhanced by 21% relative to its thermal equilibrium value.
