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Abhinav Patra

Cardiff University

Supervisors: Hartmut Grote (Cardiff University) – Animesh Datta (University of Warwick)

Short Bio: I earned my BS-MS from IISER Kolkata, with a major in physics and a minor in mathematics. As part of my master’s project, I picked-up modeling optical systems for the Laser Interferometer Gravitational Wave Observatory (LIGO) and have been doing the same since. I moved to Cardiff, UK in 2021, to pursue a PhD in physics with a focus on modern optical interferometry for probing fundamental science signals. With my time here, I had the pleasure to meet and work with great people, visit LIGO and improve my understanding on various topics, from quantum gravity theory to RF electronics and FPGA programming. I plan to use my time with the Enrico Fermi Fellowship to the fullest and bring together the fields of precision interferometry and quantum gravity.

The QUEST experiment and search for signatures of Quantum Gravity

Project summary: 

The search for signatures of quantum gravity has been at the forefront of fundamental physics research for the last decades. Measurement techniques varying from levitated diamonds to cosmological surveys have been proposed and are in active development to test for models of quantum gravity. The contemporary advancements in precision interferometry, especially in the context of gravitational waves, have opened paths to study fluctuations of space-time at scales that were otherwise inaccessible, allowing for verification of various quantum gravity models.

The Quantum Enhanced Space-Time (QUEST) experiment, hosted at Cardiff University, is advancing the search for quantum gravity by commissioning two state-of-the-art table-top interferometers. The instruments in QUEST are operated at quantum shot noise limited sensitivities, targeting radio frequencies between 1 and 200 MHz. The main science target for the experiment is to search for signatures of quantum gravity, dark matter and high frequency gravitational waves, which are encoded as correlated signals between the outputs of the two interferometers. As part of an initial observing run, we have demonstrated the ability to search for new physics by setting new upper limits on stochastic length fluctuations between 13 and 80 MHz.

Correlated space-time fluctuation signals, if observed, provide strong evidence for new physics beyond our current understanding of space-time. Quantum gravity models, especially the class of models that emerge from the holographic principal have predicted signals of this nature and the QUEST experiment is designed to be sensitive to them. We are commissioning the interferometers, in preparation for another observation run that is planned for this summer. A 1 million-second (2 weeks) observation run will be conducted and data analysed to constrain various quantum gravity models.

The nature of the work during the fellowship period is inherently a cross-training between the experimental development of quantum optics and the verification of quantum gravity theories. As part of the fellowship, along with further commissioning of the QUEST experiment, I will also work towards developing a quantum Fisher information-based theory framework to aid in the design of future interferometric experiments. This will provide a path forward to optimally search for fluctuations predicted by various quantum gravity and correlated space-time models.