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Quantum sensing deals with quantum measurement, exploring the use of quantum properties in single particles to measure a broad range of physical quantities, and to set higher levels of measurement accuracy, far beyond what was the limit previously perceived by uncertainty principle (Degen, Reinhard & Cappellaro, 2017). Quantum sensing uses quantum technologies to design and engineer drastically improved sensors and measuring devices (Pirandola et al., 2018). Quantum sensors promise far more accuracy in measurements than conventional sensors. Quantum sensors promise new detection capabilities, detecting even the tiniest electrical signals in the human body, monitoring brain activity on the go, and detecting underground signals that will have applications in civil engineering and resource extraction including oil and gas. It will now be possible to have ultra-accurate navigation, even underwater, and sense changes in gravity thereby revealing potential earthquakes or volcanic activity, climate change. Above all, it will be possible to measure physical quantities against atomic properties, so there is no drift or need to calibrate (CNRS, 2021; NATO, 2020; Tetienne & Hall, 2021). In brief, quantum sensing finds innovative applications in as diverse fields as metrological standards, biological imaging, navigation systems, detailed underground mapping, next generation detectors, and autonomous cars (Fuentes & Bouyer, 2021). Quantum sensing not only have important commercial applications, they have potential to improve our everyday life and will also deepen our understanding of nature. Given the disruptive role that quantum sensing technologies are going to play in the near future, it will be worthwhile that a bibliometric study be undertaken to analyze and evaluate the global literature in quantum science research with the aim to identify the key players in this research at global, national, institutional, and individual scientist level.

As seen from the literature, no bibliometric study has been published till date on the topic assessment and evaluation of national and global research on quantum sensing. However, quite a few studies on similar topics have already been undertaken, such as quantum technologies, quantum computing (4703 global publications during 2007-16) quantum machine learning (1374 global publications during 1999-20), quantum neural networks (546 global records during 1990-19), quantum cryptography (10801 publications during 1992-20), quantum electronics (10115 records since 2008), quantum information processing (2000-17), quantum robotics (650 global records during 1993-20) and quantum dots (Dhawan, Gupta & Mamdapur, 2018; Dhawan, Gupta & Mamdapur, 2021; Gupta & Dhawan, 2020a; Dhawan, Gupta & Mamdapur, 2021; Ibrahim, Julius & Choudhury, 2021; Terekhov, 2020; Gupta & Dhawan, 2020b; Gupta, Dhawan & Mamdapur, 2021; Seskir & Aydinoglu, 2021; Tolcheev, 2018). Given the fact that no study has been undertaken till date in quantum sensing, the authors thought it appropriate to fill the gap and accordingly undertake this study to assess and evaluate global literature in the subject on metrics.

The study seeks to understand the status and performance of global research in the domain of quantum sensing at global, national, institutional, and individual author level based on select indicators derived from publications and citation data in the subject. The data for the study has been sourced from the Scopus international database for the period 1991-2020. For research evaluation, the publications data on quantum sensing will be analyzed on a number of parameters (i) distribution of publications by type and source, (ii) publication growth rate- annual and cumulative, (iii) quantify citation impact of publications in terms of citations per paper, relative citation index, and share of highly-cited papers (iv) identify the most productive countries in the world, (v) distribution of publications by broad subjects and significant keywords, (vi) identify and profile of most productive organizations and the most productive authors in the world, (vii) identify top channels for research communication, and (viii) describe the bibliographic characteristics of highly-cited papers in the subject.

The Scopus database (https://www.scopus.com) is used in this study for sourcing publication and citation data on the topic of quantum sensing research. A comprehensive search strategy was developed for identifying, retrieving, and downloading publications metadata. The keywords “quantum sensing” and “quantum sensors” were clubbed to field tags “Keyword” and “Title” (Article Title). The search output was confined to global search limited to the publication period ‘1991-20’. Subsequently, the search output was refined by the publication country name, one by one, to identify and generate a list of top 10 most productive countries of the world in this subject. The search yielded 588 global records, which were downloaded in csv file format to be further analyzed using statistical methods. The analytical provisions of the Scopus database were used to generate statistics on the publications output by broad subject areas, collaborating countries, contributing authors, affiliating organizations, and source journals, etc. The citations to each publication were counted from the date of their publication till 27.2.2021. The study examined the performance of the most productive countries, organizations, authors and journals on select bibliometric indicators. The VOS viewer and biblioshiny app for bibliometrix were used to evaluate and visualize the interactions among most productive countries/territories, organizations, authors and keywords. (TITLE (“quantum sensor*” or “quantum sensing”) OR KEY (“quantum sensor*” or “quantum sensing”)) AND (EXCLUDE (PUBYEAR, 2021)).

The study analyses the global output in quantum sensing research on metrics with the aim to understand its status and performance at national, institutional, and author level. The study identified key players in quantum sensing research such as key countries, key institutions, key authors, and key areas of research. The study also presented a visual view of network collaborative relationships between key players. The global research on this theme comprised a total of 588 publications in the 30-year period 1991-2020. The global research registered a 14.85% annual average growth, its 15-year cumulative output increased by 16.37%, and its research received an average of 12.04 citations per paper (CPP) since publication during the period. A 43.03% share of global output appeared as sponsored research papers. Although participation in quantum sensing research is global (with a participation of 48 countries), but only the top two countries (the USA and Germany) account for a 50% share. The other productive countries in the list of top-10 are the U.K., China, Italy, Japan, France and Australia but their global share is comparatively small ranging from 5.27% to 9.86% share of world output. Although a total of 389 authors from 293 organizations had participated in global quantum sensing research, but a significant share (35.52% and 34.18%) of global output is dominated by the top 15 most productive organizations and top 15 most productive authors respectively. Among the top 15 participating organizations, 4 each come from the USA, Germany and Italy and 3 from France). Among top 15 most productive authors, 6 come from Germany, 4 each from Italy and USA and 1 from Israel. The journals such as Physical Review A (30 papers), Physical Review Letters (28 papers), New Journal of Physics (23 papers) and Physical Review Applied (17 papers) lead in global publication productivity. In addition, in terms of most cited journals, Agriculture & Forest Meteorology (69.67), Science (42.17), Physical Review A (34.0) and Nature Communication (30.56) top the most cited journals list. The global research in the field of quantum sensors is distributed across seven disciplines. Of these, Physics & Astronomy, Engineering and Materials Science accounted for a major share (76.02%, 45.07% and 42.52% respectively) to the global output.

The research in the field of quantum sensing is still at a nascent stage of its development. Even after 30-year research into quantum sensing area the body of literature in the subject is still very small, standing just at a total of 588 publications, nearly 19.6 publications globally per year. The USA, Germany, and Italy are the top three countries that have come to dominate the domain of quantum sensing research at a global level. This conclusion is based on country-wise research productivity, organization-wise productivity, and publication of research output that appeared mainly in research journals that have country of their publication in western countries. Further, this study finds that Massachusetts Institute of Technology, USA and University of Ulm, Germany have emerged both as most productive organizations and the most cited organizations. In addition, ETH, Zurich, though it is not ranking the list of top 15 most productive organizations, but it emerged as one of top three highly cited organizations. This confirms the view that there is very little correlation between most cited organizations and most productive organizations. The contribution of Asian countries in the growth and development of research in the subject is marginal. The findings in this study should be of interest to researchers, policy formulators and other actors, especially those from the developing countries. The findings in this study should be of interest to stakeholders in the country in planning R&D investments for strengthening research infrastructure, initiating new programmes aimed at international collaboration, and in undertaking fresh programmes for manpower development in the domain of quantum sensing research.