The discovery of a nano-Hz stochastic gravitational wave background by Pulsar Timing Array (PTA) collaborations can be interpreted as arising from a strongly supercooled phase transition in a nearly conformal dark sector. I will show that such strong supercooling generically dilutes any pre-existing baryon asymmetry and dark matter abundance, and discuss how this problem can be turned into a solution by exploiting the built-in out-of-equilibrium dynamics of the transition to generate both after the phase transition. I will present a neutron portal framework connecting the resulting dark baryon asymmetry to the visible sector, discuss its ultraviolet completion, and outline the resulting phenomenological signatures at beam-dump and collider experiments.

Quantum measurements need amplifiers that boost weak signals without adding noise. Today's best amplifiers rely on strong microwave pump tones, which makes them bulky, costly and hard to scale. In this talk, I introduce Inelastic Cooper-pair Tunneling Amplifiers (ICTAs), superconducting amplifiers powered by a simple DC voltage. I'll explain how a superconducting junction can amplify microwave signals using only DC power, then cover three challenges we tackled: simulating and optimizing gain, designing circuits that suppress excess noise, and widening the bandwidth despite the gain-bandwidth trade-off.
Joint work with Eva Dupont-Ferrier and Max Hofheinz, Université de Sherbrooke

Quantum measurements need amplifiers that boost weak signals without adding noise. Today's best amplifiers rely on strong microwave pump tones, which makes them bulky, costly and hard to scale. In this talk, I introduce Inelastic Cooper-pair Tunneling Amplifiers (ICTAs), superconducting amplifiers powered by a simple DC voltage. I'll explain how a superconducting junction can amplify microwave signals using only DC power, then cover three challenges we tackled: simulating and optimizing gain, designing circuits that suppress excess noise, and widening the bandwidth despite the gain-bandwidth trade-off.
Joint work with Eva Dupont-Ferrier and Max Hofheinz, Université de Sherbrooke

Combining optical fibers with frequency combs provides a versatile platform for high-speed, remote, and distributed sensing of our
environment. In this talk, I will present a fiber-based electro-optic dual-frequency comb source operating at a 10 GHz repetition rate and
generating mutually coherent ultrashort (60 fs) pulses capable of multimodal sensing. Its capabilities are demonstrated through rapid
linear and nonlinear spectroscopy applications, such as opto-mechanical ultrasound sensing and coherent anti-Stokes Raman spectroscopy. I will
also discuss potential application avenues across multiple scales, including distributed monitoring of agriculture through ultrasound,
fiber-integrated particulate matter sensing and potentially quantum enhanced sensing. Integrating these techniques with India’s extensive
public fiber infrastructure could enable multipurpose networks that combine communication with large-scale environmental monitoring.

A PhD in Physics typically takes 4.5–5.5 years. Students face many ups and downs during this period. This period is often marked by significant intellectual challenges, setbacks, and uncertainty. Maintaining a consistently high level of enthusiasm throughout this journey is indeed very challenging, which requires continuous feedback and support from both within and outside the research environment. The present talk addresses how you can become a high performer during your PhD and afterward. Actually, it is not very difficult—one simply needs to follow basi c steps with a positive and purposeful mindset. Setting goals for tangible outputs, focusing on preparedness, and sustaining efforts can make a significant difference. This requires small changes in your daily routine. Keeping good physical and mental well-being is essential, which requires conscious and continuous attention. The talk will discuss these principles and practical strategies with illustrations from my own academic and professional journey.

In general relativity, electromagnetic waves in the geometric-optics approximation follow null geodesics independently of polarization, while the polarization itself is transported along the ray. I will review this standard picture, including ambiguities in defining gravitational polarization rotation, and then discuss how birefringence can arise through modified classical couplings or quantum corrections.
I will then turn to finite-frequency corrections within ordinary general relativity and Maxwell theory, where photon helicity affects ray propagation beyond leading geometric optics. Recent results on the resulting gravitational birefringence, formal aspects of null-particle dynamics, and some observational implications will be presented.

Helical-coil (HC) targets provide a unique all-optical approach for manipulating laser-driven proton beams using electromagnetic pulses generated during the laser-target interaction itself. By tailoring the interaction between the propagating pulse and the proton beam, HC targets can simultaneously guide, energy-select and post-accelerate laser-accelerated protons within a compact target-integrated structure. Over the past decade, this concept has evolved from proof-of-principle demonstrations to a versatile beam-conditioning platform capable of controlling both the transverse and longitudinal phase space of laser-driven ion beams. This talk will provide an overview of the HC concept and its development, covering experimental demonstrations of beam collimation, spectral shaping, post-acceleration, scaling to higher-power laser systems, multi-stage acceleration schemes, and recent advances in longitudinal phase-space rotation and temporal compression. The prospects of HC-based manipulation for next-generation laser-ion accelerators and emerging applications will also be discussed.