Abstract: Shadow tomography provides a means to infer properties of unknown repeatedly produceable quantum states such as an output of a quantum circuit. Repeated random projective measurements can be made on these to produce a large volume of data from which the operator expectation values can be estimated in an unbiased manner with guaranteed error bounds. This suggests that the state itself can be inferred in principle using a similar scheme. Inference of the best estimate state instead of the operator expectation values allows learning operator expectation values without violating positivity or other constraints. In particular, interesting 1D area law states of n sites have an efficient MPS representation and can be inferred efficiently by learning O(n) parameters. We ask whether these parameters can be directly inferred from the projective measurement data. I will briefly discuss the idea of shadow tomography and general formalism of MPS variation ansatz. I will then discuss the variational inference schemes for MPS by gradient descent solutions of non-linear optimization equations that allow inference of the state in an MPS form from the random Pauli measurements. I demonstrate that finite depth locally Haar unitary circuits can improve on the simplest local measurement schemes.

Abstract: Metalenses are ultracompact optical elements that enable precise control of light using subwavelength nanostructures, offering a fundamentally new approach to imaging system design. In this talk, I will begin by introducing the underlying physics of metalenses and will then dwell on the practical aspects of their design and fabrication. I will then discuss applications of metalenses, including compact medical imaging systems and astronomical instrumentation, where reduced size and weight are particularly advantageous. Finally, I will address strategies for achieving reconfigurability in metalenses, with an emphasis on active tuning mechanisms. I will present our recent work on a varifocal metalens based on phase-change materials, capable of diffraction-limited operation at the edge of the visible spectrum.

Abstract: Niels Bohr's principle of complementarity asserts that certain physical properties of a quantum system — such as path information and interference visibility in the double-slit experiment — cannot be simultaneously revealed within a single experimental arrangement. While originally formulated as a profound philosophical insight into the nature of quantum phenomena, complementarity now admits a precise operational formulation in terms of measurement incompatibility and joint measurability. In this talk, I will discuss how complementarity acquires new structure in multi-copy scenarios, where multiple identical quantum systems are probed collectively. By analyzing the joint measurability of incompatible qubit observables on ensembles of parallel and antiparallel spin-½ pairs, we obtain a sharper operational understanding of how incompatibility transforms under collective measurements. I will also briefly discuss connections to the Mean King retrodiction problem, Jeffrey Bub's quantum cryptographic protocol, and quantum estimation theory, illustrating how complementarity continues to inform both conceptual advances and practical tasks in quantum information science.

Abstract: The interaction between two seemingly antagonistic phases—magnetism and superconductivity—and novel emergent phenomena that arise at thin-film interfaces between them, form the basis of the rapidly developing field of superconducting spintronics1. Early experimental efforts focused primarily on the realization of theoretically predicted exotic phenomena, such as odd-frequency triplet superconductivity2,3 and 0–π transitions4. More recently, the emphasis has shifted toward the development of functional devices aimed at enabling large-scale, non-dissipative computing architectures, with all components compatible with fully superconducting digital electronics. In this talk, I will first provide a brief introduction to the field of superconducting spintronics, outlining its central concepts and motivations. I will then present recent results from the Quantum Materials and Devices Laboratory at IIT Bombay. In particular, I will show that - analogous to metallic spintronics, where spin-dependent scattering is harnessed to engineer current-in-plane (CIP) giant magnetoresistance (GMR) and current-perpendicular-to-plane (CPP) tunnelling magnetoresistance (TMR) devices; similar device functionalities can berealized within superconducting spintronics, with much larger MR effects. However, in contrast to the normal metallic case, these effects emerge from the fundamentally different physics of a superconducting state that is, in its conventional form, intrinsically spin-agnostic. I will discuss how interfacial exchange fields and proximity effects enable the engineering of superconducting analogues of GMR and TMR devices, opening new pathways for dissipation less spin-based electronics

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Abstract: Neutrinos make the Sun shine, the stars explode, and bring us news from corners of the Universe. However, they are elusive particles that pass through almost everything. Therefore, detecting them requires ingenious techniques, exploiting physics concepts suitable for specific purposes. These combine ideas from nuclear physics, atomic physics, particle physics, chemistry, electrodynamics, materials science, etc. The talk will discuss some examples of successful, planned, as well as unexplored ideas.

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Abstract: Cell migration is the main driver of the evolutionarily conserved process of gastrulation, which shapes metazoan embryo morphology. The molecular and cellular mechanisms of cell migration during gastrulation though well researched lacks an understanding of the contribution of cell sizes to collective cell migration. This is especially important during the early phase of metazoan development, which is dominated by constantly changing cell sizes in the background of which cells migrate en mass to shape the embryo. Here we investigate this phenomenon in zebrafish embryos, a model system in which early cell divisions causes cell sizes to decrease naturally over time as cells migrate collectively to sculpt the embryonic body plan. Because mutations that can perturb cell sizes so early in development do not exist, we generate haploid and tetraploid zebrafish embryos and show that cell sizes in such embryos are smaller and larger than the diploid norm, respectively. Cells in embryos made of smaller or larger than normal cells migrate sub-optimally, leading to gastrulation defects. Gene expression analysis suggests that the observed defects originate from altered cell size, and not from pleiotropic effects of altered ploidy. This interpretation is strengthened when gastrulation defects are rescued by increasing cell sizes in embryos wherein cell sizes are smaller than normal. We show that the migration defects are cell-autonomous by live imaging migrating haploid and tetraploid cells during gastrulation in chimeric diploid embryos. Analysis of membrane protrusion dynamics in single cells shows that cells normally extend protrusions non-uniformly during migration, a phenomenon which is perturbed when cell sizes deviate from the norm. Thus, an optimal range of developmental stage-specific cell sizes appears necessary for collective cell migration to correctly position cells in space and time to shape an amorphous ball of blastoderm into an embryo.