Algorithmic Cooling of Nuclear Spin Pairs using a Long-Lived Singlet State

Algorithmic cooling methods manipulate an open quantum system in order to lower its temperature below that of the environment. We show that significant cooling is achieved on an ensemble of spin-pair systems by exploiting the long-lived nuclear singlet state, which is an antisymmetric quantum superposition of the up and down qubit states. The effect is demonstrated by nuclear magnetic resonance (NMR) experiments on a molecular system containing...