arXiv subjects

Srikar Gadamsetty

Publications and source records attributed to Srikar Gadamsetty.

5 recordsLinked to original sources

arXiv2026

Sixth-order time-convolutionless master equation and beyond: Late-time resummations, two types of divergences, and the limits of validity

Perturbative master equations are essential for modeling open quantum systems but often exhibit late-time divergences when environmental correlations decay algebraically. In this work, we analyze the time-convolutionless (TCL) master equation, expanded to order 2n and demonstrate that, while van Kampens cumulants suppress early-time secular growth, they ultimately diverge at long times. To overcome this, we introduce a resummation technique based on the Hadamard trick, which incorporates time integrals directly into the bath spectral density via element-wise multiplication. This approach establishes a maximum expansion order, nmax, and defines a precision limit of the asymptotic states. The resummed master equation features renormalized Bohr frequencies that capture decoherence and spectral overlap effects. In the unbiased spin-boson model, this results in secular inflation of the generator at a temperature-independent rate equal to the decoherence rate and a finite validity time. For exponentially decaying correlations, the method recovers a proper Markovian limit below a critical coupling threshold.

quant-ph↗

arXiv2025

The Extreme Universe Observatory on a Super-Pressure Balloon II: Mission, Payload, and Flight

The Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) is a pathfinder mission toward a space-based observatory such as the Probe of Extreme Multi-Messenger Astrophysics (POEMMA). The aim of POEMMA is the observation of Ultra High Energy COsmic Rays (UHECRs) in order to elucidate their nature and origins and to discover $\gtrsim$ 20 PeV very high energy neutrinos that originate from transient and steady astrophysical sources. EUSO-SPB2 was launched from Wānaka New Zealand on May 13th, 2023 as a NASA Balloon Program Office test flight. The mission goals included making the first near-space altitude observations of the fluorescence emission from UHECR-induced extensive air showers (EASs) and making the first direct Cherenkov light emission from PeV cosmic rays traversing Earth's atmosphere. In addition, a Target of Opportunity program was developed for selecting and scheduling observations of potential neutrino sources as they passed just below the Earth's limb. Although a leaky balloon forced termination over the Pacific Ocean after 37 hours, data was collected to demonstrate the successful commissioning and operation of the instruments. This paper includes a description of the payload and the key instruments, pre-flight instrument characterizations in the lab and in the desert, flight operations and examples of the data collected. The flight was too short to catch a UHECR event via fluorescence, however about 10 candidate EAS events from cosmic rays were recorded via Cherenkov light.

astro-ph.HE↗

arXiv2025

Commissioning and Performance of the Trinity Demonstrator

The Trinity Demonstrator is a proof of concept prototype for the Trinity Neutrino Observatory, which is sensitive to astrophysical neutrinos above PeV energies. The Demonstrator is a one-square meter class imaging atmospheric Cherenkov telescope deployed on Frisco Peak, Utah, and remotely operated. The light-collection surface is equipped with 77 mirror facets with 15 cm diameter, and its $3.87^\circ\times3.87^\circ$ field of view is instrumented with a 256-pixel camera yielding a $0.24^\circ$ angular resolution. The camera signals are digitized with a 100 MS/s, and 12-bit resolution switched capacitor array readout. We discuss the Demonstrator's design, the telescope's deployment on Frisco Peak, and its commissioning.

astro-ph.IM↗

arXiv2024

The Camera and Readout for the Trinity Demonstrator and the EUSO-SPB2 Cherenkov Telescope

We developed a modular silicon photomultiplier camera to detect Earth-skimming PeV to EeV tau neutrinos with the imaging atmospheric Cherenkov technique. We built two cameras, a 256-pixel camera with S14161-6050HS SiPMs for the Trinity Demonstrator located on Frisco Peak, Utah, and a 512-pixel camera with S14521-6050AN SiPMs for the EUSO-SPB2 Cherenkov Telescope. The front-end electronics are based on the eMUSIC ASIC, and the camera signals are sampled and digitized with the 100MS/s and 12-bit AGET system. Both cameras are liquid-cooled. We detail the camera concept and the results from characterizing the SiPMs, bench testing, and calibrating the two cameras.

astro-ph.IM↗

arXiv2024

Invalidation of the Bloch-Redfield Equation in Sub-Ohmic Regime via a Practical Time-Convolutionless Fourth-Order Master Equation

Despite recent advances in quantum sciences, a quantum master equation that accurately and simply characterizes open quantum dynamics across extremely long timescales and in dispersive environments is still needed. In this study, we optimize the computation of the fourth-order time-convolutionless master equation to meet this need. Early versions of this master equation required computing a multidimensional integral, limiting its use. Our master equation accounts for simultaneous relaxation and dephasing, resulting in coefficients proportional to the system's spectral density over frequency derivative. In sub-Ohmic environments, this derivative induces infrared divergence in the master equation, invalidating the second-order Bloch-Redfield master equation findings. We analyze the approach to a ground state in a generic open quantum system and demonstrate that it is not reliably computed by the Bloch-Redfield equation alone. The optimized fourth-order equation shows that the ground-state approach is accurate to second order in bath coupling regardless of the dispersion, even though it can diverge in the fourth order at zero temperature.

quant-ph↗