Quantum Nanoscopy and Optical Control: From Single Molecules to Entangled Pairs

Jean-Baptiste Trebbia, Quentin Deplano, Philippe Tamarat +1 more

The control and manipulation of quantum-entangled states is crucial for the development of quantum technologies. A promising route is to couple solid-state quantum emitters through their optical dipole-dipole interactions. Entanglement in itself is challenging, as it requires both nanometric distances between emitters and nearly degenerate electronic transitions. Here we implement hyperspectral imaging to identify pairs of coupled dibenzanthanthrene molecules, and find distinctive spectral signatures of maximally entangled superradiant and subradiant electronic states by tuning the molecular optical resonances with Stark effect. We demonstrate far-field selective excitation of the long-lived subradiant delocalized state with a laser field tailored in amplitude and phase. Optical nanoscopy of the coupled molecules unveils spatial signatures that result from quantum interferences in their excitation pathways and reveal the location of each emitter. Controlled electronic-states superposition will help deciphering more complex physical or biological mechanisms governed by the coherent coupling and developing quantum information schemes.

Mario Agio

S. Ya. Kilin

Jean-Baptiste Trebbia, Quentin Deplano, Philippe Tamarat +1 more

Abstract The control and manipulation of quantum-entangled states is crucial for the development of quantum technologies. A promising route is to couple solid-state quantum emitters through their optical dipole-dipole interactions. Entanglement in itself is challenging, as it requires both nanometric distances between emitters and nearly degenerate electronic transitions. Here we implement hyperspectral imaging to identify pairs of coupled dibenzanthanthrene molecules, and find distinctive spectral signatures of maximally entangled superradiant and subradiant electronic states by tuning the molecular optical resonances with Stark effect. We demonstrate far-field selective excitation of the long-lived subradiant delocalized state with a laser field tailored in amplitude and phase. Optical nanoscopy of the coupled molecules unveils spatial signatures that result from quantum interferences in their excitation pathways and reveal the location of each emitter. Controlled electronic-states superposition will help deciphering more complex physical or biological mechanisms governed by the coherent coupling and developing quantum information schemes.

Quentin Deplano, Jean-Baptiste Trebbia, Philippe Tamarat +1 more

Using quantum emitters (such as quantum dots, atoms, NV defects in diamond ...) in order to create quantum logic gates, is a widely studied topic in modern physics. Among all of those objects, organic molecules trapped in condensed matter are nearly ideal quantum emitters dispensing single indistinguishable photons. Moreover, at low temperature (≈ 2K), molecules are very well modelized by a two-level system. At nanometric distances, two molecules can be coupled by the dipole-dipole interaction leading to the apparition of two delocalized states respectively sub- and super-radiant. The observation of two coupled dipoles has been reported only once in the literature in 2002, despite of numerous interesting applications for quantum computing. The major limitation is the low probability to find an entangled pair in a sample. For this purpose, we lately developed an optical nanoscopy method based on the saturation of the excited state by a scanned donut shaped beam, and operating at cryogenic temperature, allowing us to find some pairs of coupled dipoles. We obtained a sub 10-nm resolution for a single dipole imaging. When the donut is scanned over an entangled pair, the Rabi frequencies seen by the two emitters varies which modifies the four energy levels of the pair by AC lightshift and leads to the apparition of fluorescence dips in the final image, when two levels become degenerated. With this technique we succeeded in doing specific images of an entangled system delocalized over 20 nm. The goal of the research activity presented here is to manipulate, on demand, the degree of entanglement of such a system. The latter could only be changed by applying an external electric field on the pair, which tunes the energy difference of the two emitters by Stark effect. We have been able to put at resonance the two emitters and observed a broadening and shrinking of the symmetric and antisymmetric transitions compatible with a modification of theirs relative lifetimes.

Ch. Brunel, Philippe Tamarat, Brahim Lounis +1 more