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Abstract Multipartite entanglement is an essential aspect of quantum systems, needed to execute quantum algorithms, implement error correction and achieve quantum-enhanced sensing. In solid-state quantum registers such as nitrogen-vacancy centres in diamond, entangled states are typically created using sequential, pairwise gates between the central electron and individual nuclear qubits. This sequential approach is slow and suffers from crosstalk errors. Here we demonstrate a parallelized multi-qubit entangling gate to generate a four-qubit Greenberger–Horne–Zeilinger state using a room-temperature nitrogen-vacancy centre in only 14.8 μs—ten times faster than that using sequences of two-qubit gates and close to the fundamental limit set by the hyperfine coupling frequencies. Parallel three-qubit gates are also realized with all-nuclear-qubit subsets. The entangled states are verified by measuring multiple quantum coherences. The four-qubit parallel gate has a fidelity of 0.92(4), whereas the sequential four-qubit gate fidelity is only 0.69(3). The approach is generalizable to other solid-state platforms, and it lays the foundation for scalable generation and control of entanglement in practical devices. 

Europium-doped gallium nitride (GaN:Eu) is a promising platform for classical and quantum optoelectronic applications. When grown using organometallic vapor-phase epitaxy, the dominant red emission from Eu exhibits an inhomogeneous photoluminescence (PL) spectrum due to contributions from several nonequivalent incorporation sites that can be distinguished with combined excitation-emission spectroscopy. Energy transfer from the GaN bandgap to the majority site is inefficient, limiting the performance of GaN:Eu light-emitting diodes (LEDs) and resulting in an inhomogeneous emission spectrum dominated by disproportionate contributions from minority sites. In this work, we use site-selective spectroscopy to characterize the photoluminescence properties of delta-doped structures with alternating doped and undoped layers of varying thicknesses and demonstrate that they selectively enhance emission from the majority site when compared to uniformly doped samples. Samples with 2- and 10-nm doped layers show much greater PL intensity per Eu concentration as well as more efficient energy transfer to the majority site, which are both highly desirable for creating power-efficient LEDs. Meanwhile, a sample with 1-nm doped layers shows emission only from the majority site, resulting in a narrow, homogeneous emission spectrum that is desirable for quantum technologies. This utilization of delta-doping has the potential to be broadly applicable for engineering desirable defect properties in rare-earth doped semiconductors. 

Abstract Microscopy approaches are frequently used to decipher the localization and quantify the abundance of biologically relevant molecular targets within single cells. Recent research has applied many optical imaging techniques to specifically visualize epigenetic modifications, the mechanisms by which organisms control gene expression in response to environmental factors. While many molecular and omics-based approaches are used to understand epigenetic mechanisms, imaging approaches provide spatial information that supplies greater context for discerning function. Thus, labeling approaches have been developed to quantify and visualize epigenetic targets using various fluorescence microscopy, electron microscopy, and super-resolution microscopy techniques. Here, we synthesize information about microscopy methods that enable visualization of epigenetic marks including DNA methylation, histone modifications, and localization of RNAs, which provide insights into mechanisms involved in chromatin remodeling and gene expression. The ability to determine how and where specific epigenetic marks manifest structurally and functionally in cells demonstrates the power of microscopy in aiding our understanding of epigenetic processes. 

American bison (Bison bison) were nearly hunted to extinction by the 20th century. This rapid decline and the fragmented nature of remnant populations pose challenges to their recovery and resilience, as does human-facilitated admixture between bison subspecies and cattle (Bos taurus). To contextualize current diversity, we sequenced 115 ancient and 45 modern bison genomes from the past ~20,000 years. Our results show that past bison populations were connected, in contrast to structured modern herds. Modern wood bison (B. b. athabascae), a northerly distributed subspecies, carry plains bison (B. b. bison) ancestry from 1920s translocations, and many sampled bison lack cattle ancestry. Our findings reveal the legacy of human impacts on bison and highlight the applicability of ancient DNA for guiding wildlife restoration. 

Abstract We report results of characterizing the response and light transport of wavelength-shifting (WLS) and scintillating-wavelength-shifting (Sci-WLS) fibers under irradiation by radioactive α, β, and γ sources. Light yield and light transmission were measured for the WLS fiber BCF-91A from Saint-Gobain and for a new Sci-WLS fiber EJ-160 from Eljen Technology. The two variants with different fluor mixtures, EJ-160I and EJ-160II, exhibited approximately five and seven times higher light yield than BCF-91A, respectively, while their attenuation lengths were 3.80 m for BCF-91A, 4.00 m for EJ-160I, and 2.50 m for EJ-160II.