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1. Higher-group symmetry of (3+1)D fermionic $$\mathbb{Z}_2$$ gauge theory: Logical CCZ, CS, and T gates from higher symmetry

   https://doi.org/10.21468/SciPostPhys.16.5.122  

   Barkeshli, Maissam; Hsin, Po-Shen; Kobayashi, Ryohei (January 2024, SciPost Physics)

   It has recently been understood that the complete global symmetry of finite group topological gauge theories contains the structure of a higher-group. Here we study the higher-group structure in (3+1)D\mathbb{Z}_2 ${\mathbb{Z}}_2$gauge theory with an emergent fermion, and point out that pumping chiralp+ip $p+ip$topological states gives rise to a\mathbb{Z}_{8} ${\mathbb{Z}}_8$0-form symmetry with mixed gravitational anomaly. This ordinary symmetry mixes with the other higher symmetries to form a 3-group structure, which we examine in detail. We then show that in the context of stabilizer quantum codes, one can obtain logical CCZ and CS gates by placing the code on a discretization ofT^3 $T^3$(3-torus) andT^2 \rtimes_{C_2} S^1 $T^2{⋊}_{C_2}{S}^1$(2-torus bundle over the circle) respectively, and pumpingp+ip $p+ip$states. Our considerations also imply the possibility of a logicalT $T$gate by placing the code on\mathbb{RP}^3 ${ℝ\mathbb{P}}^3$and pumping ap+ip $p+ip$topological state. 

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2. Ultra-high extinction ratio polarization beam splitter with extreme skin-depth waveguide

   https://doi.org/10.1364/OL.420824  

   Ahmed, Syed_Z; Ahmed, Ishtiaque; Mia, Md_Borhan; Jaidye, Nafiz; Kim, Sangsik (April 2021, Optics Letters)

   In this Letter, we present a high extinction ratio and compact on-chip polarization beam splitter (PBS), based on an extreme skin-depth (eskid) waveguide. Subwavelength-scale gratings form an effectively anisotropic metamaterial cladding and introduce a large birefringence. The anisotropic dielectric perturbation of the metamaterial cladding suppresses the TE polarization extinction via exceptional coupling, while the large birefringence efficiently cross-couples the TM mode, thus reducing the coupling length. We demonstrated the eskid-PBS on a silicon-on-insulator platform and achieved an ultra-high extinction ratio PBS ( $\approx <\#comment/>60\mathrm{d}\mathrm{B}$for TE and $\approx <\#comment/>48\mathrm{d}\mathrm{B}$for TM) with a compact coupling length ( $\approx <\#comment/>14.5\text{µ<\#comment/>}\mathrm{m}$). The insertion loss is also negligible ( $<<\#comment/>0.6\mathrm{d}\mathrm{B}$). The bandwidth is $><\#comment/>80$(30) nm for the TE (TM) extinction ratio $><\#comment/>20\mathrm{d}\mathrm{B}$. Our ultra-high extinction ratio PBS is crucial in implementing efficient polarization diversity circuits, especially where a high degree of polarization distinguishability is necessary, such as photonic quantum information processing. 

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3. Polarized lidar and ocean particles: insights from a mesoscale coccolithophore bloom

   https://doi.org/10.1364/AO.389845  

   Collister, Brian_L; Zimmerman, Richard_C; Hill, Victoria_J; Sukenik, Charles_I; Balch, William_M (May 2020, Applied Optics)

   Oceanographic lidar can provide remote estimates of the vertical distribution of suspended particles in natural waters, potentially revolutionizing our ability to characterize marine ecosystems and properly represent them in models of upper ocean biogeochemistry. However, lidar signals exhibit complex dependencies on water column inherent optical properties (IOPs) and instrument characteristics, which complicate efforts to derive meaningful biogeochemical properties from lidar return signals. In this study, we used a ship-based system to measure the lidar attenuation coefficient ( $\mathrm{\alpha <\#comment/>}$) and linear depolarization ratio ( $\mathrm{\delta <\#comment/>}$) across a variety of optically and biogeochemically distinct water masses, including turbid coastal waters, clear oligotrophic waters, and calcite rich waters associated with a mesoscale coccolithophore bloom. Sea surface IOPs were measured continuously while underway to characterize the response of $\mathrm{\alpha <\#comment/>}$and $\mathrm{\delta <\#comment/>}$to changes in particle abundance and composition. The magnitude of $\mathrm{\alpha <\#comment/>}$was consistent with the diffuse attenuation coefficient ( $K_{\text{d}}$), though the $\mathrm{\alpha <\#comment/>}$versus $K_{\text{d}}$relationship was nonlinear. $\mathrm{\delta <\#comment/>}$was positively related to the scattering optical depth and the calcite fraction of backscattering. A statistical fit to these data suggests that the polarized scattering properties of calcified particles are distinct and contribute to measurable differences in the lidar depolarization ratio. A better understanding of the polarized scattering properties of coccolithophores and other marine particles will further our ability to interpret polarized oceanographic lidar measurements and may lead to new techniques for measuring the material properties of marine particles remotely. 

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4. Calibration method for an extended depth-of-field microscopic structured light system

   https://doi.org/10.1364/OE.448019  

   Chen, Liming; Hu, Xiaowei; Zhang, Song (December 2021, Optics Express)

   This paper presents a calibration method for a microscopic structured light system with an extended depth of field (DOF). We first employed the focal sweep technique to achieve large enough depth measurement range, and then developed a computational framework to alleviate the impact of phase errors caused by the standard off-the-shelf calibration target (black circles with a white background). Specifically, we developed a polynomial interpolation algorithm to correct phase errors near the black circles to obtain more accurate phase maps for projector feature points determination. Experimental results indicate that the proposed method can achieve a measurement accuracy of approximately 1.0 $\mathrm{\mu <\#comment/>}$m for a measurement volume of approximately 2,500 $\mathrm{\mu <\#comment/>}$m (W) × 2,000 $\mathrm{\mu <\#comment/>}$m (H) × 500 $\mathrm{\mu <\#comment/>}$m (D). 

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5. Lidar measurements of the diffuse attenuation coefficient in Yellowstone Lake

   https://doi.org/10.1364/AO.389169  

   Roddewig, Michael_R; Churnside, James_H; Shaw, Joseph_A (March 2020, Applied Optics)

   Airborne lidar study of lake ecosystems is still a relatively unexplored field. In this paper we present measurements of the diffuse attenuation coefficient of downwelling irradiance ( $K_d$) obtained using a 532 nm airborne lidar in flights during 2004 and 2016 over Yellowstone Lake, Yellowstone National Park, Wyoming, USA. We compare the lidar measurements with MODIS $K_d$data, discuss the impact that local weather and river inflows/outflows may have had on the data, compare to previous models of the diffuse attenuation coefficient, and examine several published relationships converting $K_d$to Secchi disk depth. 

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