Chaos K = 1.0

Bidhi Vijaywargia

PhD Candidate, University of Connecticut
Advisor: Prof. Lea F. Santos

"Reading quantum mechanics with a classical accent"

CV Scholar Contact
Bidhi Vijaywargia

How does a simple quantum system generate such rich dynamical behavior? My research looks at quantum chaos, nonlinear dynamics, open quantum systems, and quantum sensing, mostly in collective spin models such as the Lipkin-Meshkov-Glick model, and in Kerr parametric oscillators. I look for the quantum signatures of classical structures, like saddle points, separatrices, unstable trajectories, and critical regions, and how they show up in energy spectra, wavepacket dynamics, and squeezing. I'm especially interested in when instability, criticality, and dissipation turn into a resource for quantum technology.

Research Interests

Quantum Chaos Quantum-Classical Correspondence Many-Body Spin Systems Open Quantum Systems Entanglement & Spin Squeezing Quantum Metrology

Journey

2024 - Present PhD Candidate University of Connecticut, Storrs, CT
2023 - 2024 Junior Research Fellow IIT Madras, Chennai
2021 - 2023 M.Sc. Physics IIT Madras, Chennai Thesis
2017 - 2020 B.Sc. Physics (Honours) University of Delhi, New Delhi

Research

Instability-Enhanced Quantum Sensing

Quantum sensors are fundamentally limited by the standard quantum limit (SQL). Several strategies push beyond it, including spin squeezing, entanglement-based protocols, and dynamical instability. I focus on instability-driven sensing in collective spin systems, where chaos and unstable fixed points both amplify weak signals and rapidly generate entanglement, with my recent work showing how multibody interactions reshape phase space to accelerate this gain.

Live simulation of the quartic twist-and-turn model from Vijaywargia et al., arXiv:2604.05047 (2026)

Many-Body Spin Systems and Infinite-Range Interactions

Infinite-range interactions in cavity QED and trapped-ion platforms make collective spin models a powerful testbed for many-body quantum dynamics. Beyond the symmetric collective sector, the full spin Hilbert space hosts richer dynamics that are often overlooked. I study how multibody interactions, dissipation, and dynamics across different spin sectors shape entanglement, chaos, and metrologically useful behavior in these systems.

Quantum-Classical Correspondence

How much of quantum behavior in chaotic systems can be read from classical structure? The semiclassical correspondence has long been studied for unitary dynamics, but extending it to open and dissipative evolution remains active. My work develops this correspondence at the level of quantum channels, comparing them with classical Koopman channels in chaotic maps to show how phase-space features such as scars, regular islands, and unstable manifolds dictate the quantum spectrum.

Three quantum-channel eigenmode Husimi functions alongside the classical phase space (upper-left), showing imprints of stable period-2 orbits, a length-6 resonance chain, and a torus

Fig. 6 from Vijaywargia & Lakshminarayan, Phys. Rev. E 111, 014210 (2025)

Publications

Preprint

Instability-Enhanced Quantum Sensing with Tunable Multibody Interactions

Bidhi Vijaywargia, Jorge Chávez-Carlos, Francisco Pérez-Bernal, Lea F. Santos

arXiv preprint (under review at PRL) (2026)

A quartic extension of the twist-and-turn Hamiltonian reshapes phase space and accelerates metrological gain in collective-spin sensors. Strikingly, multibody interactions outperform the quadratic case even at equal Lyapunov exponents, identifying phase-space curvature as a resource for quantum sensing.

arXiv
Preprint

Universal spectral correlations in open Floquet systems with localized leaks

Edson M. Signor, Miguel A. Prado Reynoso, Bidhi Vijaywargia, Sandra D. Prado, Lea F. Santos

arXiv preprint (2025)

Opening a chaotic Floquet system with a localized leak yields universal short-range spectral correlations governed by the non-Hermitian symmetry class AI† (transpose-symmetric Ginibre), not the unconstrained Ginibre ensemble previously assumed.

arXiv
Published

Quantum-classical correspondence in quantum channels

Bidhi Vijaywargia, Arul Lakshminarayan

Physical Review E 111, 014210 (2025)

Compares quantum channels with their classical Koopman counterparts in the coupled standard map to study quantum-classical correspondence at the subunitary level. Surviving channel eigenmodes carry imprints of classical phase-space structure, including regular islands smaller than the effective Planck constant and scars along unstable manifolds.

arXiv Journal

Presentations

Contributed Talk

Instability-Enhanced Quantum Sensing with Tunable Multibody Interactions

APS Global Physics Summit 2026 • Denver, CO • March 15-20, 2026

Session: Entanglement-Enhanced Quantum Sensing

Contributed Talk

Quantum Metrology Enhancement via Higher-Order Spin Interactions

57th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics • Providence, RI • June 2, 2026

Conferences & Schools

Summer School

Summer School on Quantum Sensing and Precision Science

Johns Hopkins University • Baltimore, MD • August 2025

Conference

Progress in Quantum Science and Technologies

Centre for Quantum Information, Communication and Computing, IIT Madras • Chennai, India • January 23-27, 2023

Winter School

ACM India Winter School on Advanced Quantum Computing

IIT Madras & IBM Research India • Chennai, India • December 5-16, 2022

Summer School

Summer School in Computational Physics

IAPT Mumbai (Indian Association of Physics Teachers) • Online • May 17-29, 2021

Teaching

I find teaching physics genuinely fun, partly because so many students walk in expecting to hate it. My favorite moments are when a coffee swirl, a phone screen, or a sunset suddenly becomes a piece of physics they can explain themselves.

Lab Instructor

PHYS 1502 — Physics for Engineers II

University of Connecticut • Fall 2024, Fall 2025, Spring 2026

Lab Instructor

PHYS 1202 — General Physics II

University of Connecticut • Spring 2025

Volunteer Science Teacher

Ek-Ummid NGO

2021 - 2023

Awards & Achievements

Summer Research Fellowship Award

$5,000 competitive fellowship from the KMS Nagavarapu Graduate Award and Fay & Philip Mannheim Fellowship, awarded to outstanding incoming physics PhD students

University of Connecticut • 2024

Pre-doctoral Fellowship

Department of Physics, University of Connecticut • Aug 2024

V. Kalyanasundram Memorial Prize

Best Woman in M.Sc. Physics (based on CGPA)

IIT Madras • 2023

Usha Krishnaswamy Scholarship

Top-ranking female student based on CGPA

IIT Madras • 2022

MCM Scholarship

Top 10% of class, all four semesters

IIT Madras • 2021-2023

Beyond Physics

From Chaibasa, a small town in Jharkhand, India. First in my family to pursue graduate study. Physics took me from there to Delhi, then Chennai, and now to Storrs in the USA, and I'd like that route to feel less unusual for whoever comes next.

Chaibasa
Delhi
Chennai
Storrs, CT

Badminton, piano lessons that started as grad-school therapy, hikes and museums for the breathing room, and a fitness habit I'm slowly building.