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Despite being the smallest constituent of light, photons hold enormous potential for revolutionising communication technology. In quantum networks, these particles act as flying qubits\u2014the basic building blocks of information in such systems\u2014and can be transmitted over long distances via fibre optic cables, enabling secure quantum communication.<\/p>\n
Essential to realising scalable and efficient quantum networks is quantum key distribution, a secure communication method that relies on advanced components such as superconducting nanowire single-photon detectors (SNSPDs). Now, new research published in\u00a0Nature Nanotechnology<\/strong>\u00a0and led by Dr Ilya Charaev and Professor Karl Berggren (Massachusetts Institute of Technology), Assistant Professor Denis Bandurin (National University of Singapore, former Pappalardo Fellow at MIT), and Prof Ivan Bo\u017eovi\u0107 (Brookhaven National Laboratory and Yale University), has achieved a trailblazing milestone in the area of SNSPDs.<\/p>\n Focusing on the materials used to construct the photon detectors, the team has fabricated novel light sensors using two cuprate compounds, materials that host superconducting electron systems with the highest critical temperature. Utilising such materials has enabled the operation of the detectors at elevated temperatures \u2014 a long-standing challenge in the field.<\/p>\n This breakthrough brings a range of benefits, including reduced cooling requirements, extended operating lifetimes, and improved performance, extending the potential applications of SNSPDs in areas from quantum cryptography and neuroimaging to gas sensing and space exploration.<\/p>\n <\/p>\n Artistic representation of the high-temperature superconducting nanowire single-photon detectors. Credit: Maxim Karmantsov<\/em><\/span><\/p>\n <\/p>\n \u201cFor more than a century, superconductivity has been at the epicentre of research in condensed matter physics, giving rise to numerous practical devices that bring us convenience every day,\u201d says Dr Ilya Charaev, one of the principal authors of the paper. \u201cAmong them, SNSPDs have recently become a cornerstone of quantum communication and sensing, owing to their high detection efficiency, broadband operation, exceptional signal-to-noise ratio, and fast recovery times.\u201d<\/p>\n The operation of SNSPDs requires cooling the mounted nanowires to near absolute zero \u2014coaxing them to enter a superconducting state. When a photon strikes the wire, it disrupts a Cooper pair of electrons \u2014 the building blocks of superconductivity. That generates a small amount of electricity that is quickly detected by the wire, indicating the presence of a photon.<\/p>\n Nonetheless, the challenge in operating SNSPDs lies in creating an optimal environment for their functioning. Conventional superconducting materials need to be cooled to extremely low critical temperatures at which they achieve superconductivity\u2014a process achieved using expensive and bulky cryocoolers, which severely limits the practicality of the devices.<\/p>\n \u201cSuch limitations formed the impetus for our research goal to innovate novel SNSPDs based on high-temperature superconductors that do not require ultra-chilled conditions as traditional detectors,\u201d says Asst Prof Denis Bandurin. Asst Prof Baldurin (Materials Science and Engineering Department, College of Design and Engineering, NUS, one of the principal and corresponding authors of the paper.<\/p>\n The researchers discovered that the difficulty is not in overcoming the fundamental limits of the superconducting material itself but rather in how it is processed and fabricated into the nanowire. To work around this, the team devised a technique for shaping two cuprate compounds into nanowires using a focused beam of helium ions, demonstrating their ability to detect photons at elevated temperatures up to 25 K. \u201cOne type of such devices can be fabricated via a process called atomic-layer-by-layer molecular beam epitaxy \u2014 an advanced method that enables precise control of the device\u2019s structure and material composition and scalable manufacturing of the devices,\u201d says Prof Ivan Bo\u017eovi\u0107, the world expert in this unique technology.<\/p>\n \u201cDespite two decades of experimental efforts to develop superconductors with high critical temperatures for SNSPDs, no workable devices were successfully created,\u201d adds Prof. Denis Bandurin. \u201cThis fact, together with some discouraging theories, fueled beliefs that SNSPDs made of such materials are infeasible.\u201d<\/p>\n![\"\"](\"https:\/\/cde.nus.edu.sg\/mse\/wp-content\/uploads\/sites\/4\/2023\/03\/Artistic-representation-superconducting-nanowire-single-photon-detectors-e1679305917686-300x151.png\")
<\/p>\nInnovation and ingenuity make the impossible possible<\/strong><\/h3>\n
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