Spatial modes of light such as the Laguerre-Gauss modes are popular in free-space communication for spatial mode multiplexing and high-dimensional quantum communication protocols. One can also consider a pixel mode approach to spatial multiplexing, where the beam is subdivided into spatially separated circular modes which serve as orthogonal states for classical or quantum purposes. We investigate the limiting factors in both approaches with respect to the channel loss and mode crosstalk over long distances considering the effect of divergence and atmospheric turbulence. We then investigate the ability of an adaptive optics system to mitigate these challenges in both cases, and experimentally explore the results using a fast adaptive optics system in the lab.

Quantum light-matter interfaces are integral components of quantum communication protocols, such as quantum repeaters, and are proposed to enhance performance of quantum processors and sensors. Key figures-of-merit for such interfaces are the fidelity and efficiency with which quantum information is transferred between the optical and matter domain. For quantum memory, a common embodiment of quantum light-matter interfaces, storage time and multimode capacity are essential. Rare-earth-ion doped (REI) materials, have long been prime candidates for quantum light-matter interfaces, and several seminal demonstrations of quantum memory have been realized on this platform. The REI material properties that play key roles, are the long coherence times of spin and optical transitions as well as the inhomogeneously broadened transition lines, which allow efficient protocols, of the spin-echo family, to be implemented. Indeed, the ability to mix and match specific REI and host materials along with innovation in protocols has led to a steady improvement of quantum memory performance and features. In this talk, we present an overview of the platforms and applications with focus on experiments performed in the Quantum Cloud Lab on quantum memory for quantum networks. We will introduce a quantum memory protocol that allows on-demand and random-access retrieval of stored photonic modes and discuss the path towards real-world applications.

Quantum imaging is a research area that seeks to produce “better” images using quantum methods We review some recent research in the field of quantum imaging.