Andrew Greentree

J. Jeske, D. Lau, X. Vidal, L. McGuinness, P. Reineck, B. Johnson, M. Doherty, J. McCallum, S. Onoda, F. Jelezko, T. Ohshima, T. Volz, J. Cole, B. Gibson, A. Greentree

Stimulated emission is the process fundamental to laser operation, thereby producing coherent photon output. Despite negatively charged nitrogen-vacancy (NV−) centres being discussed as a potential laser medium since the 1980s, there have been no definitive observations of stimulated emission from ensembles of NV− to date. Here we show both theoretical and experimental evidence for stimulated emission from NV− using light in the phonon sidebands around 700 nm. Furthermore, we show the transition from stimulated emission to photoionization as the stimulating laser wavelength is reduced from 700 to 620 nm. While lasing at the zero-phonon line is suppressed by ionization, our results open the possibility of diamond lasers based on NV− centres, tuneable over the phonon sideband. This broadens the applications of NV− magnetometers from single centre nanoscale sensors to a new generation of ultra-precise ensemble laser sensors, which exploit the contrast and signal amplification of a lasing system. Here Jeskeet al. show both theoretical and experimental evidence for stimulated emission from negatively charged nitrogen vacancy centres using light in the phonon sidebands around 700 nm, demonstrating its suitability as a laser medium.

Scarlett R. Howard, A. Avarguès-Weber, Jair E. Garcia, A. Greentree, A. Dyer

Understanding zero It has been said that the development of an understanding of zero by society initiated a major intellectual advance in humans, and we have been thought to be unique in this understanding. Although recent research has shown that some other vertebrates understand the concept of the “empty set,” Howard et al. now show that an understanding of this concept is present in untrained honey bees (see the Perspective by Nieder). This finding suggests that such an understanding has evolved independently in distantly related species that deal with complexity in their environments, and that it may be more widespread than previously appreciated. Science, this issue p. 1124; see also p. 1069 Honey bees display an understanding that zero is an empty set at the base of the number line. Some vertebrates demonstrate complex numerosity concepts—including addition, sequential ordering of numbers, or even the concept of zero—but whether an insect can develop an understanding for such concepts remains unknown. We trained individual honey bees to the numerical concepts of “greater than” or “less than” using stimuli containing one to six elemental features. Bees could subsequently extrapolate the concept of less than to order zero numerosity at the lower end of the numerical continuum. Bees demonstrated an understanding that parallels animals such as the African grey parrot, nonhuman primates, and even preschool children.

Scarlett R. Howard, A. Avarguès-Weber, Jair E. Garcia, A. Greentree, A. Dyer

Honeybees learn to add or subtract one item from a set using color cues and can interpolate operations to a novel number. Many animals understand numbers at a basic level for use in essential tasks such as foraging, shoaling, and resource management. However, complex arithmetic operations, such as addition and subtraction, using symbols and/or labeling have only been demonstrated in a limited number of nonhuman vertebrates. We show that honeybees, with a miniature brain, can learn to use blue and yellow as symbolic representations for addition or subtraction. In a free-flying environment, individual bees used this information to solve unfamiliar problems involving adding or subtracting one element from a group of elements. This display of numerosity requires bees to acquire long-term rules and use short-term working memory. Given that honeybees and humans are separated by over 400 million years of evolution, our findings suggest that advanced numerical cognition may be more accessible to nonhuman animals than previously suspected.

A. Manian, M. de Vries, Daniel Stavrevski, Qiang Sun, S. Russo, A. Greentree

Hexagonal diamond, often called lonsdaleite, is an exotic allotrope of carbon, predicted to be harder than cubic (conventional) diamond with a wider bandgap. Due to its pure sp3 bonded lattice, it should be expected to host sub-bandgap defect centres (colour centres). Here, we perform ab initio modeling of nitrogen-vacancy (NV) colour centres in hexagonal diamond nanocrystals for both the neutral and negatively charged species (NV0 and NV-). We identify three distinct configurations for the NV center: two of which are analogous to the NV in diamond, and one which is a configuration that can only exist in the hexagonal form. Diamond-like NV systems comprise three symmetry equivalent centers which reside on the same carbon plane, and one defect that is split across two planes and replaces a carbon-carbon bond. There is an additional NV centre where the N and V each have four nearest neighbour carbon atoms. The presence of this latter configuration would provide an unambiguous determination of the hexagonal nature of lonsdaleite. Quantum chemical analysis show that all derivatives are thermochemically stable, and each with their own unique photophysical properties, spectral profiles, and magneto-optical characteristics. By assuming that the ground state properties of the NV- in hexagonal diamond are comparable to those of the NV- in cubic diamond, albeit with increased strain, we predict ground state fine structure splitting for two of the centres to be 2.74 GHz and 4.56 MHz, compared with 2.87 GHz for cubic diamond. The possibility of optically detected magnetic resonance with the NV- in lonsdaleite would provide a new carbon-based quantum sensing system, and an unambiguous method to resolve outstanding issues around the structure of lonsdaleite as hexagonal diamond.

M.R. Hutchinson, Daniel T. Barratt, Charlotte H Johnston, Melissa A. Humphries, Carolyn Semmler, G. Tettamanzi, A. Greentree, Paul Rolan

ABSTRACT Persistent pain represents a significant global health challenge, necessitating innovative biomarker technologies that facilitate personalised prediction, prevention, and treatment. Recent advances in omics, encompassing genomics, proteomics, transcriptomics, lipidomics, epigenomics, and metabolomics, now permit high-resolution mapping of neuroimmune pathways implicated in pain chronification. Yet, biomarkers must transcend isolated molecular or sensory indicators, integrating emotional, cognitive, functional, and social dimensions of pain. Emerging quantum sensing technologies, such as diamond nitrogen-vacancy sensors and portable magnetoencephalography systems, promise precise and wearable tools capable of real-time, multimodal assessment of pain. Concurrently, transparent machine learning methods combining explainable artificial intelligence with physiologically informed modelling are crucial for managing the vast data complexity inherent to these multidimensional omics approaches. Ultimately, achieving economically viable, environmentally sustainable, and universally accessible pain management solutions requires strategically streamlined methods. Here, we outline a visionary framework of measurement-enabled understanding that enables precision pain medicine with rapid feedback that points toward actionable clinical outcomes, harnessing interdisciplinary innovation to address persistent pain comprehensively, just as genomics and immunotherapy have transformed cancer care.