Abstract: A new type of atom-photon interface is proposed that can be used as a resource for processing quantum information. Individual organic dye molecules will be deposited close to optical waveguides on a photonic chip.
At cryogenic temperature, the molecules act as simple two-level atoms with a strong electric dipole transition. They can be individually addressed and they remain trapped indefinitely in the solidified solvent. We demonstrated that a single molecule can obscure a substantial part of the light in a beam whose cross section is comparable to the scattering cross section of the molecule [i]. In such a beam, we showed that the molecule behaves as a two-level quantum emitter whose nonlinear response is appreciable even at very low light intensity. This was seen through the appearance of Mollow sidebands in the fluorescence spectrum of the molecule. The relative merits of absorption and fluorescence as a method of detecting single molecules were discussed in ref [ii]. In another proof of the large dipolar coupling we were able to observe Rabi flopping of the two-level molecule in weak light pulses, where only a few hundred photons were enough to generate a p-pulse [iii]. Most recently, we showed that the single molecule can act as an absorber whose absorption coefficient can be manipulated by a control laser and can also be turned into gain when the population of the molecule is inverted [iv]. All-optical nonlinear operation at the single emitter level has been deemed exceptionally challenging and only been considered in high-finesse microcavities. Here, we demonstrate that such operation is possible with single molecules with a propagating laser beams and discuss the possibility of building a quantum network on an optical waveguide chip.
At cryogenic temperature, the molecules act as simple two-level atoms with a strong electric dipole transition. They can be individually addressed and they remain trapped indefinitely in the solidified solvent. We demonstrated that a single molecule can obscure a substantial part of the light in a beam whose cross section is comparable to the scattering cross section of the molecule [i]. In such a beam, we showed that the molecule behaves as a two-level quantum emitter whose nonlinear response is appreciable even at very low light intensity. This was seen through the appearance of Mollow sidebands in the fluorescence spectrum of the molecule. The relative merits of absorption and fluorescence as a method of detecting single molecules were discussed in ref [ii]. In another proof of the large dipolar coupling we were able to observe Rabi flopping of the two-level molecule in weak light pulses, where only a few hundred photons were enough to generate a p-pulse [iii]. Most recently, we showed that the single molecule can act as an absorber whose absorption coefficient can be manipulated by a control laser and can also be turned into gain when the population of the molecule is inverted [iv]. All-optical nonlinear operation at the single emitter level has been deemed exceptionally challenging and only been considered in high-finesse microcavities. Here, we demonstrate that such operation is possible with single molecules with a propagating laser beams and discuss the possibility of building a quantum network on an optical waveguide chip.
[ii] G. Wrigge, J. Hwang, I. Gerhardt, G. Zumofen, V. Sandoghdar, Opt. Express 16, 17358 (2008).
[iii] I. Gerhardt, G. Wrigge, G. Zumofen, J. Hwang, A. Renn, V. Sandoghdar, Phys. Rev. A. 79 011402(R) (2009).
[iv] J. Hwang, M. Pototschnig, R. Lettow, G. Zumofen, A. Renn, S. Goetzinger, V. Sandoghdar, Nature 76 460 (2009).
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