Tečer Matija, Di Liberto Marco, Silvi Pietro, Montangero Simone, Romanato Filippo, Calajó Giuseppe
Dipartimento di Fisica e Astronomia "G. Galilei", via Marzolo 8, I-35131 Padova, Italy.
Padua Quantum Technologies Research Center, Universitá degli Studi di Padova.
Phys Rev Lett. 2024 Apr 19;132(16):163602. doi: 10.1103/PhysRevLett.132.163602.
One-dimensional confinement in waveguide quantum electrodynamics (QED) plays a crucial role to enhance light-matter interactions and to induce a strong quantum nonlinear optical response. In two or higher-dimensional settings, this response is reduced since photons can be emitted within a larger phase space, opening the question whether strong photon-photon interaction can be still achieved. In this study, we positively answer this question for the case of a 2D square array of atoms coupled to the light confined into a two-dimensional waveguide. More specifically, we demonstrate the occurrence of long-lived two-photon repulsive and bound states with genuine 2D features. Furthermore, we observe signatures of these effects also in free-space atomic arrays in the form of weakly subradiant in-band scattering resonances. Our findings provide a paradigmatic signature of the presence of strong photon-photon interactions in 2D waveguide QED.
波导量子电动力学（QED）中的一维限制对于增强光与物质的相互作用以及诱导强烈的量子非线性光学响应起着至关重要的作用。在二维或更高维的情况下，这种响应会降低，因为光子可以在更大的相空间内发射，这就引发了一个问题，即是否仍然可以实现强光子 - 光子相互作用。在本研究中，对于耦合到限制在二维波导中的光的二维正方形原子阵列的情况，我们对这个问题给出了肯定的答案。更具体地说，我们展示了具有真正二维特征的长寿命双光子排斥态和束缚态的出现。此外，我们还在自由空间原子阵列中以弱亚辐射带内散射共振的形式观察到了这些效应的特征。我们的发现为二维波导QED中存在强光子 - 光子相互作用提供了一个典型的特征。
