25 JANUARY 2018

Two groups of scientists from TU Delft in the field of quantum nanotechnology have, independently of one another, found a way to convert spin information to light. The groups are led by professors Kobus Kuipers and Lieven Vandersypen, who both work at the Kavli Institute of Nanoscience. Their research has been published in Science. The discovery by Kuipers can lead to green ICT, for example energy-efficient data processing in data centres. The aim of Vandersypen's research is to allow large numbers of qubits on a chip to work together, bringing the quantum computer one step closer.

Discoveries in science are sometimes made by several researchers at the same time. The English term for this particular phenomenon is 'multiple discovery', and there are many examples to be found. A famous example is that in 1902 two scientists independently hypothesized that hereditary information is stored in chromosomes. A simultaneous discovery within one university, and even within one institute, is much more unlikely. Yet that is exactly what happened in Delft.

Connecting qubits
Electrons trapped in silicon as qubits can now only make direct contact with their nearest neighbours. Lieven Vandersypen shows that an electron spin used as a qubit can be linked to a single photon. This coupling makes it theoretically possible to transfer quantum information from an electron spin to a photon. This is an important step in connecting quantum bits in silicon and thus in making large numbers of qubits available on a chip. The discovery contributes to the development of the quantum computer.

Predictable light signal
Kobus Kuipers describes a way to convert spin information into a predictable light signal in a 2D material. This discovery, which works at room temperature, brings together the worlds of spintronics and nanophotonics, and may lead to' green ICT', for example energy-efficient ways of processing data.

Opto-electronic switches
And so a direct link is created between the spin information and the propagation direction of the light along the nanowire. It works almost perfectly: the spin information is ‘launched’ in the right direction along the thread in 90% of cases. In this way, fragile spin information can be carefully converted into a light signal and transported over far greater distances. Thanks to this technique, which works at room temperature, you can easily make new optoelectronic circuitry. Kuipers: ‘You don't need a stream of electrons, and no heat is released. This makes it a very low-energy way of transferring information.’

The discovery clears the way for combining the worlds of spintronics and nanophotonics. Kuipers: ‘This combination may well result in green information processing strategies at the nanoscale.’

****

More information: 

‘Nanoscale chiral valley-photon interface through optical spin-orbit coupling’, Su-Hyun Gong, Filippo Alpeggiani, Beniamino Sciacca, Erik C. Garnett, L. Kuipers 
DOI:10.1126/science.aan8010