Strong Light Reflection from Few Atoms

Nikolai B. Delone, В. П. Крайнов

Philip Ball

Up to 75% of light reflects from just 2000 atoms aligned along an optical fiber, an arrangement that could be useful in photonic circuits.

P. Domokos, Péter Horák, Helmut Ritsch

We present a time-dependent quantum calculation of the scattering of a few-photon pulse on a single atom. The photon wave packet is assumed to propagate in a transversely strongly confined geometry, which ensures strong atom-light coupling and allows a quasi-one-dimensional treatment. The amplitude and phase of the transmitted, reflected, and transversely scattered part of the wave packet strongly depend on the pulse length (bandwidth) and energy. For a transverse mode size of the order of ${\ensuremath{\lambda}}^{2},$ we find nonlinear behavior for a few photons already, or even for a single photon. In a second step we study the collision of two such wave packets at the atomic site and find striking differences between the Fock state and coherent state wave packets of the same photon number.

S. Swain

Tarun Patel, Matteo P. Pennacchietti, Sayan Gangopadhyay +4 more

Abstract Single-atom waveguide-QED systems have emerged as a leading platform for demonstrating non-linear optics in the few-photon regime. Devices with such non-linear behavior are necessary for developing deterministic gates for photonic quantum computing. Artificial atoms coupled to nanophotonic or superconducting waveguides can be used to engineer highly efficient light-matter interfaces for such non-linear interactions, where every photon in the system interacts with the quantum emitter. However, it has been a challenge to access the reflection port of the waveguide due to the inability of rejecting stray electromagnetic fields that do not interact with the artificial atom. Here, we show coherent reflection of single photons from a semiconductor quantum dot strongly coupled to the fundamental waveguide mode of a nanowire. We utilize the tapered end of the nanowire for ideal mode-matching in a vertical geometry, enabled by a novel extinction technique. This mode-matching allows for efficient transfer of photons from the input to the reflection port while having all interacted with the quantum dot. Such a high-efficiency scalable photonic platform opens up applications in few-photon quantum nonlinear optics and has been proposed for creating key resource states for universal photon-based quantum computing.