A team of Irish-based researchers has announced a breakthrough that could take us one step closer to a more efficient quantum computer.

One of the ‘holy grails’ of computer science is to achieve a stable, small-scale quantum computer that would exceed the capability of even the most powerful binary supercomputer. Now, researchers from the SFI AMBER centre, the Trinity College Dublin (TCD) School of Physics and the CRANN Institute have announced a breakthrough that takes us one step closer to that goal.

Unlike a traditional binary computer that uses binary ‘bits’ – which can be either one or zero – a quantum bit (qubit) can be one, zero or both at the same time. One common two-state qubit is the spin of the electron, in which the two levels can be spin up and spin down.

However, one problem that has faced researchers in our understanding of this phenomenon – called coherent superposition – is the issue of decoherence. In this state, qubits don’t behave as predicted when interacting with their surroundings.

So, if qubits store information based on being in both states simultaneously, then decoherence means data will be lost. Using electronic structure calculations, the AMBER team said that one possible source of this decoherence is vibrations in material used in the quantum computer.

‘At the very forefront of the research field’

Working alongside experimental teams based in the UK and Italy, Dr Alessandro Lunghi and Prof Stefano Sanvito from TCD conducted theoretical and modelling work.

“What makes this research unique was that the experimental teams were able to observe vibrations of molecular qubits for the first time,” Sanvito explained. “And our TCD team made it possible to understand the nature and the details of how the observed vibrations couple to spin.”

Lunghi added: “This is at the very forefront of the research field and sheds new light on a fundamental phenomenon such as the interaction between spin and atomic motion.

“This is a major step for us as it validates the models we have developed and means that we can understand and predict spin coherence in molecular spins starting from simulations. We can now use these models to design new compounds and set the starting point for the design of more efficient molecular qubits.”

A paper on this research has been published to Nature Communications.