11/09/2024
By Rajkumar CharanSingh Singharia

The Kennedy College of Sciences, Department of Physics and Applied Physics, invites you to attend a master's thesis defense by Rajkumar Singharia titled "Advantages of IAS Protocol in Squeezed State."

Date: Thursday, Nov. 22, 2024
Time: 11 a.m. to 1 p.m.
Location: Olney Hall, Room 430, North Campus

Advisor: Hugo Ribeiro, Ph.D., Assistant Professor, Department of Physics and Applied Physics, UMass Lowell
Committee Members:
Peter Bender, Ph.D., Assistant Professor, Department of Physics and Applied Physics, UMass Lowell
Viktor Podolskiy, Ph.D., Professor, Department of Physics and Applied Physics, UMass Lowell

Brief Abtract:
Quantum sensing is an emergent field that explores how quantum phenomena, e.g., entanglement, can be used to measure a physical quantity. The goal is to develop measurements protocols that utilize quantum resources to achieve sensitivity and high precision, surpassing “classical” sensors that are limited by the Standard Quantum Limit (SQL). A single qubit is considered as a “classical” sensor in the field since superposition states can be realized with systems obeying classical laws of physics like, for example, coupled harmonic oscillators. The most well-known “classical” sensing protocol is Ramsey Interferometry, which allows one to measure an unknown frequency. Recently, a Ramsey Interferometry-based Iterative Adaptive Sensing (IAS) protocol has been proposed to overcome some of the shortcomings associated with a standard Ramsey measurement. The main feature of IAS is that it allows one to estimate with high accuracy an unknown frequency from a short signal.
This work investigates the potential enhancement of atomic interferometer precision through the use of spin-squeezed states, which are uniquely quantum and lack classical analogs. We demonstrate that, despite the effects of noise, it is feasible to develop a spin-squeezed-state Ramsey protocol that produces a signal enabling high-precision estimation of an unknown frequency with minimal uncertainty. The frequency estimation relies on measurements of an optimized spin operator, ensuring that the uncertainty remains unaffected by the ”unsqueezed” quadrature of the spin-squeezed state.
In our study, we analyzed signals from three distinct spin numbers, N = 20, 200, and 2000, utilizing both a conventional Ramsey protocol and the initial iteration of the IAS protocol for comparative purposes. Our findings indicate multiple squeezing strengths that enhance the Signal-to-Noise Ratio (SNR), achieving a remarkable relative error in frequency estimation of 10^(-7) across all three spin systems.