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

Abstract

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 a coupled pair of near-equivalent 13C 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, and the nuclear magnetization is enhanced by 21% relative to its thermal equilibrium value. To our knowledge this is the first demonstration of algorithmic cooling using a quantum superposition state and without making a distinction between rapidly and slowly relaxing qubits.

22 pages, 6 figures

References in corpus (5)

• Quantum Computing with NMR
• A spin based heat engine: demonstration of multiple rounds of algorithmic cooling
• Robust conversion of singlet spin order in coupled spin-1/2 pairs by adiabatically switched RF-fields
• The Asymptotic Cooling of Heat-Bath Algorithmic Cooling
• Constant-adiabaticity RF-pulses for generating long-lived singlet spin states in NMR

Cited by in corpus (2)

• Long-Lived Singlet State in an Oriented Phase and its Survival across the Phase Transition Into an Isotropic Phase
• Symmetry-Based Singlet-Triplet Excitation in Solution Nuclear Magnetic Resonance