Superconducting Cavity-Based Sensing of Band Gaps in 2D Materials.

The superconducting coplanar waveguide (SCPW) cavity plays an essential role in various areas like superconducting qubits, parametric amplifiers, radiation detectors, and studying magnon-photon and photon-phonon coupling. Despite its wide-ranging applications, the use of SCPW cavities to study various van der Waals 2D materials has been relatively unexplored. The resonant modes of the SCPW cavity exquisitely sense the dielectric environment. In this work, we measure the charge compressibility of bilayer graphene coupled to a half-wavelength SCPW cavity. Our approach provides a means to detect subtle changes in the capacitance of the bilayer graphene heterostructure, which depends on the compressibility of bilayer graphene, manifesting as shifts in the resonant frequency of the cavity. This method holds promise for exploring a wide class of van der Waals 2D materials, including transition metal dichalcogenides (TMDs) and their moiré, where DC transport measurement is challenging.

Quantum-noise-limited microwave amplification using a graphene Josephson junction.

Josephson junctions (JJs) and their tunable properties, including their nonlinearities, play an important role in superconducting qubits and amplifiers. JJs together with the circuit quantum electrodynamics architecture form many key components of quantum information processing1. In quantum circuits, low-noise amplification of feeble microwave signals is essential, and Josephson parametric amplifiers (JPAs)2 are the widely used devices. The existing JPAs are based on Al-AlOx-Al tunnel junctions realized in a superconducting quantum interference device geometry, where magnetic flux is the knob for tuning the frequency. Recent experimental realizations of two-dimensional (2D) van der Waals JJs3-5 provide an opportunity to implement various circuit quantum electrodynamics devices6-8 with the added advantage of tuning the junction properties and the operating point using a gate potential. While other components of a possible 2D van der Waals circuit quantum electrodynamics architecture have been demonstrated, a quantum-noise-limited amplifier, an essential component, has not been realized, to the best of our knowledge. Here we implement a quantum-noise-limited JPA using a graphene JJ, that has a linear resonance gate tunability of 3.5 GHz. We report 24 dB amplification with 10 MHz bandwidth and -130 dBm saturation power, a performance on par with the best single-junction JPAs2,9. Importantly, our gate-tunable JPA works in the quantum-limited noise regime, which makes it an attractive option for highly sensitive signal processing. Our work has implications for novel bolometers; the low heat capacity of graphene together with JJ nonlinearity can result in an extremely sensitive microwave bolometer embedded inside a quantum-noise-limited amplifier. In general, this work will open up the exploration of scalable device architectures of 2D van der Waals materials by integrating a sensor with the quantum amplifier.

The dexmedetomidine "augmented" sedato analgesic cocktail: An effective approach for sedation in prolonged endoscopic retrograde cholangio-pancreatography.

BACKGROUND AND AIMS: In absence of any published standard guideline for sedation or anesthesia practice for prolonged therapeutic "endoscopic retrograde cholangio-pancreatography (ERCP)", safe and cost-effective sedation protocol is the need of the hour. Our study aims to evaluate the efficacy of a dexmedetomidine as an add-on for prolonged deep sedation for ERCP and to compare three deep sedation regimens regarding safety and efficacy. MATERIAL AND METHODS: Forty-five consecutively enrolled patients planned for therapeutic ERCP and assumed to have prolonged procedural duration (>50 min) were divided into three groups in a randomized assessor blinded fashion. Group 1 received propofol and midazolam, Group 2 received the sedato-analgesic cocktail containing ketamine-propofol-midazolam-pentazocine, and the Group 3 received sedate-analgesic cocktail plus dexmedetomidine infusion under monitoring of vital parameters and according to the judgment of the concerned anesthesiologist. Total propofol requirement, episodes of gagging, oxygen desaturation, changes in mean blood pressure (MBP), recovery and satisfaction score of endoscopist, anesthetist and patient were noted and analyzed statistically using one way ANOVA with Bonferroni correction and Chi-square test. RESULTS: Mean propofol requirement, incidences of gagging and oxygen desaturation was significantly less in Group 2 and 3 compared to Group 1. MBP was more stable and recovery was faster in Group 3. Anesthetist's satisfaction was more with Group 2 and even more with Group 3. CONCLUSIONS: The sedato-analgesic cocktail was superior to the conventional propofol-midazolam regimen, dexmedetomidine as add-on increased the efficacy and safety of sedate-analgesic cocktail. It reduces propofol requirement, helps to maintain the patient in a safe and more stable level of sedation and increases satisfaction of the anesthetist.