Plasmonics guide the way to entanglement

Ying Gu, LuoJia WANG, Qihuang Gong

Marie-Christine Dheur, Benjamin Vest, Éloïse Devaux +5 more

Quantum entanglement is a stunning consequence of the superposition principle. This universal property of quantum systems has been intensively explored with photons, atoms, ions, and electrons. Collective excitations such as surface plasmons exhibit quantum behaviors. We report the remote preparation of a single plasmon state through the projective measurement of a photon entangled with the plasmon. We achieved photon-plasmon entanglement by converting one photon of an entangled photon pair into a surface plasmon. The plasmon is tested on a plasmonic platform in a Mach-Zehnder interferometer. A projective measurement on the polarization of the photon allows the remote preparation of the interference state of the plasmon. Entanglement between particles of various nature paves the way to the design of hybrid systems in quantum information networks.

A. Köster, P. Martinot, Fabrice Pardo +3 more

Most of the intrinsic optical devices which have been studied in recent years consist of a Fabry-Perot resonator containing a nonlinear medium. The response time of such devices is determined by the transients associated with the high-Q resonator and the response time of the nonlinear medium. The fastest devices must be free of any Fabry-Perot cavity. The excitation of either surface plasmons at a nonlinear interface or guided waves in thin nonlinear films is a way to obtain an ultrafast bistable optical device. These two kinds of device have been studied.

Ναταλία Δομένικου, Nikos Iliopoulos, Andreas Terzis +2 more

Benjamin Vest, Marie-Christine Dheur, Éloïse Devaux +7 more

Surface plasma waves are collective oscillations of electrons that propagate along a metal-dielectric interface. In the last ten years, several groups have reproduced fundamental quantum optics experiments with surface plasmons. Observation of single-plasmon states, waveparticle duality, preservation of entanglement of photons in plasmon-assisted transmission, and more recently, two-plasmon interference have been reported. While losses are detrimental for the observation of squeezed states, they can be seen as a new degree of freedom in the design of plasmonic devices, thus revealing new quantum interference scenarios. Here we report the observation of two-plasmon quantum interference between two freely-propagating, non-guided SPPs interfering on lossy plasmonic beamsplitters. As discussed in the article "Quantum optics of lossy beam splitters" by Barnett et al. (Phys. Rev. A 57, 2134 (1998)) , the presence of losses (scattering or absorption) relaxes constraints on the reflection and transmission factors of the beamsplitter, allowing the control of their relative phase. By using this degree of freedom, we are able to observe either coalescence or anticoalescence of identical plasmons.

E. Altewischer, Martin P. van Exter, J. P. Woerdman