In the 1920s, physicists like Schrödinger, Heisenberg, Einstein, Planck—and many others—realized something deeply unsettling and beautiful: the universe at microscopic scales is nothing like what we observe in everyday life. This was the era when quantum mechanics was discovered. And I’m intentionally saying discovered, not born, because that word choice matters. Quantum mechanics isn’t just a framework we invented—it’s closer to the idea that we uncovered something that was already true about reality.

What makes this discovery so fascinating is that quantum mechanics feels so far away from how we perceive the world… and yet, it is literally what the world is. The universe is fundamentally governed by quantum laws. And what we experience in daily life—objects with definite properties, predictable motion, a world that feels stable and classical—can be thought of as an emergent phenomenon.

And the way we’re taught physics reflects that. When we start learning physics in high school, we begin with the rules of the world we directly experience: classical physics. Only later do we “upgrade” to quantum mechanics, and we try to map our classical intuition onto this quantum world. And we do that for a very human reason: from birth, we’ve trained our intuition on the classical world. So when quantum mechanics tells us something that doesn’t match that intuition, it feels non-intuitive.

But what if we flipped the script?

If the universe is fundamentally quantum, why don’t we start there? Why don’t we build our intuition from the quantum picture first—and then understand classical reality as something that emerges in the right circumstances? That question—this idea of taking a quantum-first approach—is exactly what our guest today, Ashmeet Singh, is thinking about.

Ashmeet is a theoretical physicist who completed his PhD at Caltech and is now a professor of physics at the Indian Institute of Technology, Delhi. Along with being a brilliant physicist, Ashmeet is also an avid science communicator—someone who has a real gift for explaining complex ideas in physics in a way that’s clear, intuitive, and genuinely exciting.

In this episode, we also talk to Ashmeet about his personal journey through academia: how he navigated his path from IIT to Caltech to IIT, what that transition felt like, and what he learned along the way about doing research, and finding a place in physics.
We’re genuinely grateful to IIT Delhi for hosting us—both giving us this beautiful space to sit in and record and for inviting us to give colloquium talks while we were in India. And a special thanks to Saarthak Parik for being a wonderful host and organizing everything so smoothly.

So if you’ve ever wondered what it would mean to understand the universe starting from quantum mechanics—treating classical reality not as the default, but as the thing that has to be explained—then you are in for a treat.

Ashmeet's Website: https://www.quantumfirst.space/

Ashmeet's Youtube (The Scribbled Equation): https://www.youtube.com/@TheScribbledEquation

Recently, I came across a definition of a good theory: it should explain as much as possible, with as few ingredients as possible, and with as much accuracy as possible. I think that is something every serious physicist can relate to. And really, that is what modern theoretical physics is striving for — not just identifying what the universe is made of, but understanding the mathematical framework that makes the laws of nature hang together. That is why the mathematical formulation of quantum field theory is so important. It reveals the hidden structures behind particles, forces, symmetry, and even space itself, and it opens surprising connections to geometry, topology, and information. That is precisely the kind of frontier our guest explores, through research spanning string theory, gauge theory, Seiberg–Witten theory, matrix models, quantum curves, knot theory, and even biophysics through the topology of biomolecules. We’re thrilled to welcome Professor Piotr Sułkowski, a theoretical physicist at the University of Warsaw and a visiting faculty member at Caltech. He leads the Chair of Quantum Mathematical Physics, and his work explores some of the most elegant and fundamental structures in modern physics. Alongside that, he has also been actively involved in making science accessible to broader audiences through outreach projects like “Ask a Physicist.” Professor Sułkowski, it’s such a pleasure to have you with us today.

Important links:

Piotr's Website: https://psulkows.fuw.edu.pl/

Most of what we know about the universe actually comes from what we can’t see.
Only a tiny fraction of the cosmos is made of “normal” matter—the stuff that makes up stars, planets, and us. The rest is a mysterious combination we call dark matter and dark energy, which, although invisible to our telescopes, is absolutely crucial for how the universe expands and how structures form over billions of years.

So how do we even study something we cannot see?

One of the most powerful tools we have is weak gravitational lensing. As light from distant galaxies travels through the cosmic web, the gravity of dark matter gently stretches and shears those galaxy images. The effect on any single galaxy is tiny, almost imperceptible. But when you measure this across millions or even billions of galaxies, a pattern emerges—a subtle cosmic fingerprint that tells us how matter is distributed and how fast the universe is expanding.

This is what our guest today, Dr. Nikolina Sarcevic, works on. She is a cosmologist working at the intersection of data and theory. Nikolina is part of the LSST Dark Energy Science Collaboration, and her work focuses on understanding and modelling the systematics that can bias our measurements—things like how galaxies are intrinsically aligned, how we infer their redshift distributions, and how all of that feeds into weak lensing and dark energy constraints.

So if you’ve ever wondered how we really know that dark energy exists, or what kinds of experiments are used to learn about this invisible matter, you’re going to be thrilled. So with that, let’s go.