Coherent coupling between distant two-level systems is a fundamental process in several physical contexts, from natural photosynthesis to quantum-information processing, where it enables two-qubit ...operations. For quantum information, qubits based on electronic degrees of freedom in a solid-state matrix are sensible candidates for scalable, integrated implementations. Clarifying the mechanisms underlying coherent coupling in solids is therefore an essential step in the development of such technology. Here, we demonstrate the existence of a long-range coherent coupling mechanism between individual localized excitons in a 5 nm GaAs/AlGaAs quantum well, introducing the novel tool of two-dimensional nonlinear coherent hyperspectral imaging. The coupling is shown to arise due to a biexcitonic renormalization, rather than a transition dipole (Förster) interaction. The long-range nature of the coupling is attributed to the existence of spatially extended exciton states up to the micrometre range, which are admixed in the biexciton state, as revealed in nonlinear imaging.
Abstract
Solid-state quantum light sources are being intensively investigated for applications in quantum technology. A key challenge is to extract light from host materials with high refractive ...index, where efficiency is limited by refraction and total internal reflection. Here we show that an index-matched solid immersion lens can, if placed sufficiently close to the semiconductor, extract light coupled through the evanescent field at the surface. Using both numerical simulations and experiments, we investigate how changing the thickness of the spacer between the semiconductor and lens impacts the collection efficiency (CE). Using automatic selection and measurement of 100 s of individually addressable colour centres in several aluminium nitride samples we demonstrate spacer-thickness dependent photon CE enhancement, with a mean enhancement factor of 4.2 and a highest measured photon detection rate of 743±4kcps.
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