"Effect of the equation of state for dilute neutron matter on the composition of the inner crust of neutron stars"
Sunny Kumar Gupta and Michael Urban, Phys. Rev. C 109, 045806 (2024) (Physical Review C, American Physical Society)
"An FPGA-Based Feedback Loop for Magnetometry Using Nitrogen Vacancy Centres in Diamond"
At the ICFO-TIFRH International Schools on the Frontiers of Light: Hot Topics in Quantum and Nanophotonics
held at TIFR Hyderabad from 23rd - 25th October, 2024 (Certificate)
At the In-house Physics Symposium, the Department of Physics, IISER Bhopal, from 3rd - 4th March, 2025.
Worked under the supervision of Dr Phani Kumar Peddibhotla, Principal Investigator of Spin Microscopy Laboratory (website), for my year-long master's thesis project.
Learnt about NV-defect diamond and its use in quantum sensing and quantum metrology. Developed skills in LabVIEW programming, FPGA reconfiguration, electronics, and optics.
Abstract
Magnetometry has a wide range of applications. NV-centers are color centers in diamonds exhibiting exceptional sensitivity to the magnetic field and offer a promising magnetic field measurement platform due to their long coherence time, easy spin manipulation, and quick optical readout. The working principle of the NV-diamond magnetometer is based on measuring the Zeeman splitting of the spin sub-levels. Conventionally, microwave (MW) is swept across a range, exciting spin sub-levels on-resonance to obtain the Zeeman-splitted ODMR spectrum, which is impractical for real-time magnetometry. In the thesis, we demonstrate lock-in-based detection where application of frequency-modulated (FM) MW about the initial resonance frequency excites the NV spins sub-levels, producing modulated photoluminescence (PL) further demodulated by a lock-in amplifier, which is linear to the external field. There have been studies on the temperature dependence of resonance frequency, which leads to variation in measurement, which is eliminated by adopting dual resonance excitation. Additionally advantageous in improving signal contrast & sensitivity. The method is real-time and highly sensitive, but the dynamic range is limited to one-tenth of the linewidth of the spectrum, which makes the sensor impractical. We design an FPGA-based dual-channel PI-controller feedback loop that tracks the resonance frequencies, adapting to the fluctuating external magnetic field, and sends out analog signals to signal generators that shift the carrier frequencies of the FM microwaves in real-time. With the available FSK in the signal generator, we can achieve the desired dynamic range. Dual resonance excitation makes the NV-diamond magnetometer temperature robust, alongside integrating a feedback loop, enabling us to perform real-time magnetometry over a wide dynamic range, preserving the sensitivity.
Title: Atomic Gravimetry
Worked under Dr Sebestian Wüster, principle investigator of QuCoS group (website) IISER Bhopal, India.
Description: In this short-term project, I delved into understanding the matter-wave interferometry techniques and their application in measuring the gravitational field. I worked on computationally quantifying three-body losses of maximally entangled BEC states being employed in atom interferometers intended to measure gravity beyond the standard quantum limits. Working on this project, I developed a theoretical background on entanglement generation using Rydberg excited states and a strong foundation on the theory of Open Quantum Systems and Decoherence, sharpening my skills in scientific computing using Wolfram Mathematica.
Title: Effect of the equation of state for dilute neutron matter on the composition of the inner crust of neutron stars
Under supervision of Dr Michael Urban, Directeur de recherche at Physique nucléaire, Laboratoire de Physique des 2 infinis Irène Joliot-Curie – IJCLab, UMR9012 – CNRS / Université Paris-Saclay, France
Abstract
The composition of the inner crust of neutron stars is usually studied using phenomenological interactions such as Skyrme energy-density functionals. But most of these functionals do not agree well with ab initio calculations of very dilute neutron matter. In this work, we study the inner crust of neutron stars in the model of phase coexistence of dense neutron-rich nuclear clusters and dilute neutron gas, and we investigate how employing a realistic microscopic equation of state for the neutron gas alters the composition. Our results indicate that, with a functional that reproduces the correct equation of state of neutron matter at moderate densities, one can obtain a good description of the crust even if the functional does not have the correct behavior at extremely low density.
Find out more about my work in this recently published article Phys. Rev. C 109, 045806 (2024). It is co-authored with Dr M. Urban (his Google Scholar link).
I interned at the High Energy Gamma-Ray Lab (HEGR), Tata Institute of Fundamental Research (TIFR) Mumbai, India.
Under the supervision of Prof. Indranil Mazumdar, Principal Investigator of HEGR Lab.
I worked on improving the response of the Plastic Scintillation Detector in detecting gamma radiation. I also learned to work with oscilloscopes, electronics, and radioactive sources.
Title: Glauber-Model Analysis of Charge-Changing Cross Section to study the charge-distribution radii.
Under the supervision of Dr Soumya Bagchi, Assistant Professor of Physics at the Indian Institute of Technology - Indian School of Mines, Dhanbad, India.