Research Projects

Single-photon detection lies at the heart of modern quantum technologies, including quantum communication, LiDAR, astronomy, and biomedical imaging. Superconducting (Sc) nanowire single-photon detectors (SNSPDs) have emerged as the most promising detectors due to their ultrafast response, high detection efficiency (DE), low dark count rate (DCR), and timing jitter. However, their dependence on low Tc Sc such as NbN or WSi restricts their operation to sub-3 K temperatures, demanding costly He-based cryogenic setup. This limits scalability and practical deployment, of SNSPDs. This project aims to overcome these limitations by designing and fabricating high-performance SNSPDs using high-Tc (e.g., YBCO, LSCO) and intermediate-Tc (e.g., MoSi, NbTiN, MoGe) superconductors, capable of operating in the 4–77 K range, including LN2-temperature. The central hypothesis is that judicious nanostructure engineering—combined geometry optimization, can enable efficient detection in these materials, despite their inherent anisotropy and vulnerability to defects. The research will test whether fabrication-induced defects such as edge roughness, oxygen depletion, or grain boundary voids create new phase-slip centers, suppress Sc or destabilize device performance. Furthermore, the project will examine if certain layout geometries (e.g., spiral or constricted wires) can mitigate these effects and enhance jitter, DE, and reset time. The project objectives include: (1) developing optimized nanofabrication protocols for ultrathin superconducting films; (2) engineering device geometries to minimize kinetic inductance and hotspot latching; (3) investigating nanoscale defect formation during lithography and etching (4) correlating these defects with changes in superconducting parameters (Tc, Jc, coherence length, penetration depth); and (5) demonstrating single-photon response across the 4–77 K range using time-correlated single-photon counting (TCSPC) techniques. The experimental plan involves film growth of YBCO/LSCO via PLD or MBE, and of MoSi/NbTiN via sputtering, followed by patterning into nanowires using EBL and RIE. Devices will be tested for photon response under cryogenic conditions using laser pulse excitation and electrical readout of timing jitter and DCR. A theoretical model based on Ginzburg–Landau formalism and electrothermal simulations will be developed to understand phase-slip and vortex dynamics in high-Tc nanostructures. If successful, this work will significantly advance the fundamental understanding of how disorder and nanoscale geometry influence superconductivity and photon detection in complex materials. It will establish a design and fabrication framework for high-Tc SNSPDs that can be integrated into scalable, cost-effective quantum sensing platforms. The outcomes will be relevant to India’s National Mission on Quantum Technologies and will contribute directly to building indigenous capabilities in deployable photonic quantum devices