Enhanced coherence by coupling spins through a delocalised pi-system

Data and illustration of pi conjugated j mediators

Using certain molecules, the authors of 'Enhanced coherence by coupling spins through a delocalised pi-system: Vanadyl porphyrin dimers' (published in Chem) were able to create a delocalised electronic pathway through spins.  This made it possible to enhance the quantum coherence of the spin centres, instead of depleting them.

Units of quantum information, called qubits, must communicate with each other if they are to perform useful logic operations.  Finding suitable scaffolds for linking chemically synthesised qubits together is crucial for the development of molecular quantum technologies.  Pi-conjugated linkers allow efficient electron transport over relatively long distances, but can they be used to couple together qubits, such as vanadyl ions?

In the paper, the authors not only answer affirmatively but they also show that conjugated linkers can out-perform other types of bridges by preserving the quantum coherence.  They synthesise two families of porphyrins containing vanadyl ions and investigate their geometry, conjugation and quantum performance.  The discovery that a pi-conjugated backbone can protect from decoherence is valuable for the design of molecular materials for functional quantum devices operated by microwaves and with electrical readout.