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ABSTRACT Of the 61 kinesins annotated inArabidopsis thaliana, many are still without assigned function. Here, we have screened an insertional mutant library of Arabidopsis pollen‐expressed kinesins for fertility defects. Insertional mutants for three kinesins showed a significant reduction in seed set. Among them, we focused on the sole kinesin‐4 expressed in pollen (kinesin‐4C, here Pollen‐Expressed Kinesin 14, PEK14). We show a seed‐set defect in the three independent allelespek14‐1, pek14‐2, and pek14‐3. This defect is male‐derived and is equally distributed throughout the silique. Maturepek14‐1anthers contain about 10% inviable pollen grains.pek14‐1pollen tubes grow 20% more slowly and show reduced pollen tube bending. Analysis of the male germ unit (MGU), as it travels through the pollen tube, demonstrates an aberrant organization of thepek14‐1MGU in 30% of pollen tubes and an increase in the distance of the MGU to the tip by 24%. Expression of GFP‐tagged PEK14 successfully complemented the observed seed set defect, as well as the growth rate, bending, and MGU organization defects observed inpek14‐1. In pollen, PEK14‐GFP is located diffusely at the pollen tube tip. PEK14‐GFP is also expressed in the root meristematic zone and is located at the mid‐zone of the phragmoplast, but no apparent root growth phenotype was observed, likely due to redundancy in this organ. 

When a low flux of time-frequency-entangled photon pairs (EPP) illuminates a two-photon transition, the rate of two-photon absorption (TPA) can be enhanced considerably by the quantum nature of photon number correlations and frequency correlations. We use a quantum-theoretic derivation of entangled TPA (ETPA) and calculate an upper bound on the amount of quantum enhancement that is possible in such systems. The derived bounds indicate that in order to observe ETPA the experiments would need to operate at a combination of significantly higher rates of EPP illumination, molecular concentrations, and conventional TPA cross sections than are achieved in typical experiments. 

Abstract The authors demonstrate a form of two‐photon‐counting interferometry by measuring the coincidence counts between single‐photon‐counting detectors at an output port of a Mach–Zehnder Interferometer (MZI) following injection of broad‐band time‐frequency‐entangled photon pairs (EPP) generated from collinear spontaneous parametric down conversion into a single input port. Spectroscopy and refractometry are performed on a sample inserted in one internal path of the MZI by scanning the other path in length, which acquires phase and amplitude information about the sample's linear response. Phase modulation and lock‐in detection are introduced to increase detection signal‐to‐noise ratio and implement a “down‐sampling” technique for scanning the interferometer delay, which reduces the sampling requirements needed to reproduce fully the temporal interference pattern. The phase‐modulation technique also allows the contributions of various quantum‐state pathways leading to the final detection outcomes to be extracted individually. Feynman diagrams frequently used in the context of molecular spectroscopy are used to describe the interferences resulting from the coherence properties of time‐frequency EPPs passing through the MZI. These results are an important step toward the implementation of a proposed method for molecular spectroscopy—quantum‐light‐enhanced 2D spectroscopy.