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1. Mode-multiplexed photonic integrated vector dot-product core from inverse design

   https://doi.org/10.1364/PRJ.524419  

   Zhu, Zheyuan; Sarma, Raktim; Smith-Dryden, Seth; Li, Guifang; Pang, Shuo_S (October 2024, Photonics Research)

   Photonic computing has the potential to harness the full degrees of freedom (DOFs) of the light field, including the wavelength, spatial mode, spatial location, phase quadrature, and polarization, to achieve a higher level of computing parallelism and scalability than digital electronic processors. While multiplexing using the wavelength and other DOFs can be readily integrated on silicon photonics platforms with compact footprints, conventional mode-division multiplexed (MDM) photonic designs occupy areas exceeding tens to hundreds of microns for a few spatial modes, significantly limiting their scalability. Here, we utilize inverse design to demonstrate an ultracompact photonic computing core that calculates vector dot products based on MDM coherent mixing. Our dot-product core integrates the functionalities of two-mode multiplexers and one multimode coherent mixer within a nominal footprint of 5  μm×3  μm. We have experimentally demonstrated computing examples on the fabricated dot-product core, including complex number multiplication and motion estimation using optical flow. The compact dot-product core design enables large-scale on-chip integration in a parallel photonic computing primitive cluster for high-throughput scientific computing and computer vision tasks. 

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2. Hybridization and deconfinement in colloidal quantum dot molecules

   https://doi.org/10.1063/5.0112443  

   Verbitsky, Lior; Jasrasaria, Dipti; Banin, Uri; Rabani, Eran (October 2022, The Journal of Chemical Physics)

   The structural, electronic, and optical properties of CdSe/CdS core–shell colloidal quantum dot molecules, a new class of coupled quantum dot dimers, are explored using atomistic approaches. Unlike the case of dimers grown by molecular beam epitaxy, simulated strain profile maps of free-standing colloidal dimers show negligible additional strain resulting from the attachment. The electronic properties of the relaxed dimers are described within a semiempirical pseudopotential model combined with the Bethe–Salpeter equation within the static screening approximation to account for electron–hole correlations. The interplay of strain, hybridization (tunneling splitting), quantum confinement, and electron–hole binding energies on the optical properties is analyzed and discussed. The effects of the dimensions of the neck connecting the two quantum dot building blocks, as well as the shell thickness, are studied. 

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3. Calamitic ligand design for quantum dot assembly

   https://doi.org/10.1063/5.0263810  

   Liba, Samia_I; Wheeler, Alauna_C; Ochoa, Jocelyn; Licauco, Nicholas_Javier_C; Reyes, Isabella_C; Stokes, Benjamin_J; Atherton, Timothy_J; Hirst, Linda_S (June 2025, Journal of Applied Physics)

   We report the design and use of calamitic ligands for quantum dot surface modification and nanoparticle assembly. Ligands incorporating a rigid aromatic rod-like core have previously been shown to facilitate the formation of porous nanoparticle-based structures, such as solid-walled capsules and multi-compartment quantum dot foams and networks via liquid crystal phase transition templating—a process in which the host phase is quenched through the isotropic-nematic phase transition. The effect of the calamitic ligand structure on particle dispersion, transport, and subsequent assembly, however, requires further investigation, particularly in the case of anisotropic liquid crystal solvents. In this report, we vary the structure of six new calamitic ligands and characterize quantum dot size and packing into superstructures when modified with each ligand. Dynamic light scattering is used to measure the effective nanoparticle size for each ligand in dilute toluene solution. Transmission electron microscopy reveals nanoparticle distribution in dense drop-cast films for each ligand, and small-angle x-ray scattering is used to measure interparticle separations in the assembled porous structures. Together, these methods provide a full picture of particle packing for each ligand. Notably, our findings demonstrate that while longer, more rigid aromatic cores promote a closer packing structure in drop-cast films (a slow quasi-equilibrium process)—such effects are not evident using a rapid quenching method. This study highlights the fact that when nanoparticles are formed into macroscopic assemblies, both ligand design and the particular method of assembly can contribute significantly to the final packing structure. 

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4. Teaching quantum formalism and postulates to first-year undergraduates

   https://doi.org/10.1119/5.0209945  

   Levy, Jeremy; Singh, Chandralekha (January 2025, American Journal of Physics)

   Traditional approaches to undergraduate-level quantum mechanics require extensive mathematical preparation, preventing most students from enrolling in a quantum mechanics course until the third year of a physics major. Here we describe an approach to teaching quantum formalism and postulates that can be used with first-year undergraduate students and even high school students. The only pre-requisite is a familiarity with vector dot products. This approach enables students to learn Dirac notation and core postulates of quantum mechanics at a much earlier stage in their academic career, which can help students prepare for careers in quantum science and engineering and advance the Second Quantum Revolution. 

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5. Carbon–TiO2 Hybrid Quantum Dots for Photocatalytic Inactivation of Gram-Positive and Gram-Negative Bacteria

   https://doi.org/10.3390/ijms25042196  

   Dong, Xiuli; Liu, Yamin; Adcock, Audrey F; Sheriff, Kirkland; Liang, Weixiong; Yang, Liju; Sun, Ya-Ping (February 2024, International Journal of Molecular Sciences)

   Carbon–semiconductor hybrid quantum dots are classical carbon dots with core carbon nanoparticles doped with a selected nanoscale semiconductor. Specifically, on those with the nanoscale TiO2 doping, denoted as CTiO2-Dots, their synthesis and thorough characterization were reported previously. In this work, the CTiO2-Dots were evaluated for their visible light-activated antibacterial function, with the results showing the effective killing of not only Gram-positive but also the generally more resistant Gram-negative bacteria. The hybrid dots are clearly more potent antibacterial agents than their neat carbon dot counterparts. Mechanistically, the higher antibacterial performance of the CTiO2-Dots is attributed to their superior photoexcited state properties, which are reflected by the observed much brighter fluorescence emissions. Also considered and discussed is the possibility of additional contributions to the antibacterial activities due to the photosensitization of the nanoscale TiO2 by its doped core carbon nanoparticles. 

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