With each breakthrough in developing processors that work on multiple-state quantum bits as opposed to binary-state ones and zeros, the era of quantum computing – with machines capable of far greater computational capacity than today’s computers -- gets more in focus.

Silicon, which of course is widely used in transistors and within nearly all electronic devices, has been seen as a promising material for quantum technology. Using electrical fields, single electrons can be captured as quantum bits in silicon, where they will store information for a long period. The drawback, however, is that those quantum bits, or qubits, could only make direct contact with their immediate neighbors. Until now.

As published in the journal Science, a team of scientists at TU Delft has shown that the quantum information of a single electron spin can be coupled to a single photon within the context of a silicon chip. Photons have been used in quantum systems for long-distance interactions. Transporting information from an electron spin to a photon allows qubits to be connected across the chip, and scaled up to large numbers – an essential prerequisite for making useful computations.

"To use a lot of qubits at the same time, they need to be connected to each other; there needs to be good communication,” said researcher Nodar Samkharadze.

The group’s progress is very much a homegrown creation.

“The substrate is made in Delft, the chip created in the Delft cleanrooms and all measurements carried out at QuTech," said Samkharadze.

QuTech is an advanced research center for quantum computing and quantum internet, a collaboration founded by TU Delft and TNO, the Netherlands Organization for Applied Scientific Research. Team leader Prof. Lieven Vandersypen, of QuTech/Kavli Institute of Nanoscience at Delft, notes that the team achieved their result in a relatively short time and under great pressure from worldwide competition. Next up?

“The goal now is to transfer the information via a photon from on electron spin to another," he said.