Quantum interference of tunnel trajectories between states of different spin length in a dimeric molecular nanomagnet

Abstract

Tunable electron spins in solid media are among the most promising candidates for qubits. In this context, molecular nanomagnets have been proposed as hardware for quantum computation. The flexibility in their synthesis represents a distinct advantage over other spin systems, enabling the systematic production of samples with desirable properties, for example, with a view to implementing quantum logic gates. Here, we report the observation of quantum interference associated with tunnelling trajectories between states of different total spin length in a dimeric molecular nanomagnet. We argue that the interference is a consequence of the unique characteristics of a molecular Mn"1"2 wheel, which behaves as a molecular dimer with weak ferromagnetic exchange coupling: each half of the molecule acts as a single-molecule magnet, whereas the weak coupling between the two halves gives rise to an extra internal spin degree of freedom within the moleculethat is, its total spin may fluctuate. More importantly, the observation of quantum interference provides clear evidence for quantum-mechanical superpositions involving entangled states shared between both halves of the wheel. © 2008 Nature Publishing Group.