Scientists at TU Delft, working in collaboration with German colleagues, have succeeded in controlling individual photons in a way that brings an efficient memory for quantum computers a step closer. This week Dr Nika Akopian and his colleagues published an article about their research in the online edition of Nature Photonics.

Speed
The researchers, based at the Kavli Institute of Nanoscience at TU Delft and the Institute for Integrative Nanosciences at the IFW Dresden, were able to control the speed of individual light particles (photons) and to reduce it to less than 4 percent of the speed of light in a vacuum. They achieved this by guiding photons one by one through a vapour of rubidium atoms that has precisely the right physical properties to decelerate the photons.

Quantum computer
By drastically reducing this speed, the scientists can ‘keep’ individual photons with their properties in a controlled manner for a short period. This temporary storage of information is a first step towards the creation of a quantum memory based on slow photons. A quantum memory has the same function as a usual  computer memory but can be applied within a quantum computer: a (future) super-efficient computer that functions on the basis of the physical laws in quantum mechanics.

Secure
There are major advantages in working with single photons in this type of quantum application. Indeed, in current technology most information is transmitted via photons (in optical fibres). Moreover, individual photons can transmit quantum information over very large distances in a manner that is 100 percent secure and cannot be hacked.

Semiconductor material
The photons are generated and emitted by tiny objects known as quantum dots. Since they are fabricated from well-known semiconductor material, they can easily be integrated in modern electronics.

The research is supported by the Foundation for Fundamental Research on Matter.
The research was published in the online edition of Nature Photonics on 20 February.