A new material consisting of only one sheet of carbon atoms can give rise to new and unique designs of optical quantum computing devices. Researchers from the University of Vienna and Institute of Photonic Sciences, Barcelona have proved that tailored structures of graphene lead to the interaction of singular photons. The study has been published in the npj Quantum Information.
Photons interact with the environment to a very less degree, which makes it quite suitable for the storage and transmission of quantum information. However this same property makes it very difficult to interpret the information which has been stored in them.
For building a quantum photonic computer, it is essential for a photon to alter the state of second. This is called a quantum logic gate and a quantum computer requires millions of these. This can be achieved with the help of a ‘non-linear material’, in which there is interaction of two photons. But the standard non-linear materials are not efficient to construct a quantum logic gate.
However it has been recently understood that the nonlinear interactions can be highly improved with the help of plasmons. Plasmons make the light bind to the electrons which are located at the surface. Then these electrons facilitate a very strong interaction between the photons. In presence of these positives, a drawback is that the plasmons decay in the standard materials before the actual quantum effects can occur.
Philip Walther, from University of Vienna who led the team of researchers made a proposal to manufacture plasmons in the graphene material. Graphene has been only discovered in 2004 by Andre Geim and Konstantin Novoselov at University of Manchester. Though it was observed way back in 1962, it had not been independently isolated and studied then. For their work, the duo was awarded the Nobel Prize in Physics in 2010.
The unique arrangement of electrons in graphene leads to strong nonlinear interactions, which allows the plasmons to remain for a long duration. In the graphene quantum logic gate, scientists have demonstrated that if singular plasmons in nanoribbon are made from graphene, then it allows for the interaction of electrical fields of two plasmons in different nanoribbons. This makes way for quantum computation if each of the plasmons remain in their ribbons, since many gates can be applied to them.
Irati Alonso Calafell, who is the first author on this paper remarked that strong non linear interaction in graphene does not allow two plasmons to be in the same ribbon.