Metasurface enabled quantum edge detection

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Science Advances  16 Dec 2020:
Vol. 6, no. 51, eabc4385
DOI: 10.1126/sciadv.abc4385
  • Fig. 1 The schematics of a metasurface enabled quantum edge detection.

    (A) The metasurface is designed to perform edge detection for a preferred linear polarization. |V〉, i.e., polarization state is orthogonal to the analyzer. The dashed light red line stands for the electrical path. The question mark means that polarization selection of idler photons of the heralding arm is unknown. If the Schrödinger’s cat is illuminated by unknown linear polarization photons from the polarization entangled source, the image would be a superposition of a regular “solid cat” and an edge-enhanced “outlined cat.” (B) The switch state ON or OFF of the heralding arm. When the idler photons of the heralding arm are projected to |H〉, it indicates the switch OFF state and leads to a solid cat captured. While the heralded photons are projected to |V〉, an edge-enhanced outlined cat is obtained with the switch ON state. (C and D) The calculated and experimental results of a solid cat, respectively. (E and F) The calculated and experimental results of the edge-enhanced outlined cat, respectively.

  • Fig. 2 Experimental setup and sample characterization.

    (A) Experimental setup of metasurface enabled quantum edge detection. BDM, broadband dielectric mirror; PBS, polarization beam splitter; DM, dichromatic mirror; FC, fiber coupler; BPF, band-pass filter; ICCD, intensified charge coupled device. By pumping a nonlinear crystal (type II phase-matched bulk PPKTP crystal) with a 405-nm laser, pairs of orthogonally polarized photons with 810-nm wavelength are generated through the spontaneously parametric down-conversion process. The blue (red) light path presents the 405-nm (810 nm) light. Edge detection switch is on the heralding arm. An edge detection imaging system is on the imaging arm. (B) Photograph of the partial metasurface sample. Scale bar, 4 mm. (C) Polariscopic analysis characterized by crossed linear polarizers of the sample area marked in 2a. The blue bars indicate the orientation of rotated nanostructures in one period, which represents the Pancharatnam-Berry phase induced by the laser writing dielectric metasurface. Scale bar, 50 μm. (D) The scanning electron microscopy image of the sample area marked in (C). Scale bar, 1 μm. Photo credit: Junxiao Zhou, University of California, San Diego.

  • Fig. 3 Characterizations of the entangled source.

    (A) Coincidence counts as a function of the HWP angle θ2 at one output port in 2 s. The red (blue) color of count data and interference corresponds to horizontal (diagonal) projection bases. The solid lines are sinusoidal fits to the data, error bars are estimated by assuming Poisson photon statistics in photon counting. Error bars are obtained from multiple measurements. (B and C) The real and imaginary parts of the reconstructed density matrix ρ of the two-photon states, respectively.

  • Fig. 4 The switchable edge detection demonstration.

    (A to D) The metasurface sample orientation, which is aligned with the xy plane. The inset yellow arrows indicate the phase gradient direction of the metasurface. (E to H) The images of the whole object comprising the separated LCP and RCP components, which is the OFF state of the edge detection mode. (I to L) The images reveal edges along different directions, which is the ON state of the edge detection mode. Photo credit: Junxiao Zhou, University of California, San Diego.

  • Fig. 5 Entanglement-enabled quantum edge detection has high SNR.

    (A and C) The edge detection images are triggered by the heralding detector. (B and D) Direct images where the ICCD is internally triggered. (C) and (D) are taken along the white dashed lines in (A) and (B), respectively.

Supplementary Materials

  • Supplementary Materials

    Metasurface enabled quantum edge detection

    Junxiao Zhou, Shikai Liu, Haoliang Qian, Yinhai Li, Hailu Luo, Shuangchun Wen, Zhiyuan Zhou, Guangcan Guo, Baosen Shi, Zhaowei Liu

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    • Notes S1 to S3
    • Figs. S1 to S3

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