Experimental realization of atom-mediated photon-pair-generation processes

• Applicant: Dr. Sina Saravi
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 537709534

A longstanding challenge for largescale realization of optical quantum computation and simulation protocols has been the realization of integrated and high-quality sources of single photons. There are two main approaches for on-chip single-photon generation: Using solid-state emitters, such as quantum dots and color centers, or using nonlinear sources of photon pairs, made from nonlinear optical elements. Each approach has its own advantages and disadvantages, which are rather complementary to one another, and currently neither system exhibits the needed performance to the full extend. In this project, we aim for a proof-of-principle realization of the hybrid atom-mediated photon-pair generation (AMPG) scheme, a proposal that combines the two types of sources, in an effort to overcome their shortcomings. In the AMPG scheme, an atom-like system embedded into or placed onto a nonlinear micro- or nanostructured element, can modify the pair-generation dynamics and in theory relieve the nonlinear source of its undesirable probabilistic properties for single-photon production. More specifically, by utilizing the modes of an optical element with low optical density of states, such as off-resonance modes of a cavity, the atom-like system can lend its advantageous properties to the nonlinear source. For realizing this hybrid system, we choose color centers in 2D hexagonal boron nitride (hBN) flakes, which allow a large degree of versatility for hybridization. There has already been a long history of using solid-state emitters in micro- or nanostructured elements, but mainly in the linear regime of operation for the optical structure. Operating in the quantum nonlinear regime with the addition of the atom-like system, although investigated theoretically assuming ideal components, results in a new set of challenges for a practical implementation. The first objective of this project is therefore to study, both theoretically and experimentally, the different practical aspects of such an implementation. The goal is to maximize our chances for a successful implementation of the AMPG effect, by optimizing the pumping regime for the operation of the color centers, and by optimally designing and realizing a fiber-based nonlinear microcavity, which is practically best suited for such an implementation. The next objective is to characterize the hybrid AMPG system of the hBN flake with a color center placed within the optimized nonlinear microcavity. Here we aim to measure for different signature behaviors of the AMPG effect, by performing spectral and correlation measurements on the generated single photons. The results of this project could open the way towards the realization of ideal sources of single-photons through the AMPG effect, which could in principle be extended to other optical platforms and atom-like systems.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Thomas Pertsch