Although linear optical quantum technologies are one of the more promising routes to achieve feasible quantum technologies, in part due to the robustness and mobility of single photons, the creation of a two-qubit logic gate remains a challenge. In this talk, I will present our theoretical proposal to implement a universal quantum “root- swap” gate by encoding qubits in graphene surface plasmons which interact nonlinearly . In principle, this gate does not require any cryogenic or vacuum technology, and has a footprint of a few hundred nanometers, suggesting that graphene plasmonics offers a new route towards scalable quantum technologies. I will then present our recent experimental work demonstrating plasmon-mediated optical nonlinearities in graphene [2,3]: a first step towards our long-term goal of single-photon level nonlinearities.
1.I. Alonso Calafell, J.D. Cox, M. Radonjic, J. Garcia de Abajo, L. A. Rozema, and P. Walther. Quantum Computing with Graphene Plasmons. npj Quantum Information 5, 37 (2019).
2. I. Alonso Calafell, L. A. Rozema, D. Alcaraz Iranzo, A. Trenti, P.K. Jenke, J.D. Cox, A. Kumar, H. Bieliaiev, S. Nanot, C. Peng, D.K. Efetov, J.Y. Hong, J. Kong, D.R. Englund, F. J. García de Abajo, F. H. L. Koppens, P. Walther. Giant enhancement of third-harmonic generation in graphene-metal heterostructures. Nature Nanotechnology, (2021).
3. I. Alonso Calafell, L. A. Rozema, A. Trenti, J. Bohn, E. J. C. Dias, P. K. Jenke, D. Alcaraz Iranzo, F. J. Garcia de Abajo, F. H. L. Koppens, E. Hendry, and P. Walther. High-harmonic generation enhancement with graphene heterostructures. arXiv:2203.14644. To appear in Advanced Optical materials, (2022).