High-dimensional spin-orbital single-photon sources

Abstract

Hybrid integration of solid-state quantum emitters (QEs) into nanophotonic structures opens enticing perspectives for exploiting multiple degrees of freedom of single-photon sources for on-chip quantum photonic applications. However, the state-of-the-art single-photon sources are mostly limited to two-level states or scalar vortex beams. Direct generation of high-dimensional structured single photons remains challenging, being still in its infancy. Here, we propose a general strategy to design highly entangled high-dimensional spin-orbital single-photon sources by taking full advantage of the spatial freedom to design QE-coupled composite (i.e., Moiré/multipart) metasurfaces. We demonstrate the generation of arbitrary vectorial spin-orbital photon emission in high-dimensional Hilbert spaces, mapping the generated states on hybrid-order Bloch spheres. We further realize single-photon sources of high-dimensional spin-orbital quantum emission and experimentally verify the entanglement of high-dimensional superposition states with high fidelity. We believe that the results obtained facilitate further progress in integrated solutions for the deployment of next-generation high-capacity quantum information technologies.

Fig. 1.. High-dimensional spin-orbital quantum light sources.

(A) Direct on-chip generation of high-dimensional spin-orbital quantum light with the QE coupled composite metasurfaces. (B) The VSH-based approach for generation of high-dimensional spin-orbital quantum light illustrating the recording and reconstruction process. (C) Design of the QE-coupled Moiré metasurface by superimposing two interference patterns of arbitrary spin-orbital signal waves (ℓ₁ = +2 and ℓ₂ = −2) and QE-excited SPPs. (D) Intensity cross sections of the Moiré interference patterns marked by dashed lines with corresponding colors in (C).

Fig. 2.. Generation of arbitrary vectoral spin-orbital quantum emission in high-dimensional Hilbert spaces.

(A) HOBSs presenting structured photon emission vortex beams with vectoral spin-orbital states, ∣L⟩ (left) and ∣R⟩ (right). The insets show the far-field emission intensity patterns (NA = 0.5) and the corresponding phase profiles of three QE-coupled Moiré metasurfaces. The metasurfaces are related to the signal beams with ℓ₁ = +2 and ℓ₂ = −2. (B) The scanning electron microscope (SEM) images of three QE-coupled Moiré metasurfaces with (θ, φ) being set as (π/6, π/4), (π/2, π/4), and (2π/3, π/4), from the left to the right. Scale bars, 2 μm. (C) The modal spectrum changing with the azimuthal angle θ (analytic with lines and simulation with histogram) of ∣L⟩ (left) and ∣R⟩ (right).

Fig. 3.. Generation of composite high-dimensional spin-orbital quantum emission.

(A) SEM (top) and AFM (bottom) images of the sample. Scale bar, 2 μm. The metasurfaces is related to the signal beams with ℓ₁ = +5 and ℓ₂ = +11. (B) Simulation and experimental results of the emission patterns (NA = 0.9) and corresponding phase profiles of LCP (top row) and RCP (bottom row) states. (C) HOBSs presenting composite photon emission vortex beams in high-dimensional Hilbert spaces of LCP (top row) and RCP (bottom row) states.

Fig. 4.. Demonstration of entanglement of single-photon emission with composite high-dimensional superposition states.

(A) The simulated density matrices density matrix for the entangled state. (B) The experimentally measured density matrix recovered for the entangled state by using QST. (C) Spectrum and (D) autocorrelation comparison of QE before and after coupling with metasurfaces.