How does experience rewire the brain—and why is vision the ideal system for understanding neuroplasticity?

In this episode, we speak with Mark Bear, MIT neuroscientist and a pioneer in the study of experience-dependent plasticity. Bear explains how the visual cortex became a model system for uncovering the synaptic mechanisms that allow the brain to change, adapt, and learn, especially during early development.

We explore how visual experience shapes neural circuits, why the brain undergoes critical periods of heightened plasticity, and what classic experiments in visual deprivation revealed about how connections are strengthened or lost. Bear walks us through the discovery of binocular vision in the cortex, the role of inhibition in closing critical periods, and how these ideas reshaped our understanding of learning and memory.

The conversation also covers modern views of cortical plasticity, including perceptual learning, visual recognition memory, and how the brain distinguishes familiar from novel stimuli. Bear discusses how insights from vision extend to broader questions about brain development, neurological disorders such as amblyopia, and whether adult plasticity can be reopened.

Whether you’re interested in neuroscience, brain development, neuroplasticity, learning and memory, or the biology of vision, this episode offers a clear and authoritative look at how experience shapes the brain at the level of neural circuits and synapses.

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Website: https://www.632nm.com

Timestamps:
00:00 - Intro
00:54 - Neuroplasticity in the Visual Cortex
05:45 - Critical Periods for Neuroplasticity
16:50 - Brain Development in Blind People
19:25 - Hallucinations and Sensory Deprivation
25:36 - How Mark’s Vision Disorder Led Him to a Career in Neuroscience
31:35 - Intro to the Visual System
35:52 - Visual System Processing
40:52 - Pop Science Neuroplasticity
45:00 - Memory Enhancing Pharmaceuticals
50:18 - Other Ways of Modifying the Visual Cortex
1:14:50 - Declarative vs Procedural Memory
1:22:36 - Neural Networks and Memory Degradation
1:25:16 - Neuron Transplants and Neurogenesis
1:28:58 - Brain-Machine Interfaces
1:33:46 - Most Prominent Issues in the Field
1:40:47 - Fragile X Syndrome
1:51:10 - Advice for Young Scientists

#neuroplasticity #neuroscience #hubermanlab #braindevelopment #brainplasticity

How can flat surfaces shape light as powerfully as bulky lenses?

In this episode, we speak with Federico Capasso, Harvard physicist and pioneer of metasurfaces, metalenses, and nanophotonics. Capasso traces the path from his work at Bell Labs on quantum cascade lasers to the invention of metasurface optics, showing how a practical challenge—collimating light without traditional lenses—sparked a new way to control light.

We explore the physics behind metasurfaces and generalized Snell’s law, explaining how subwavelength structures enable precise control of wavefronts, phase, and polarization beyond what conventional diffractive optics or Fresnel lenses allow. Capasso clarifies common misconceptions, contrasts metasurfaces with diffraction gratings and phased arrays, and emphasizes the importance of physical intuition and simplicity.

The conversation covers metalenses, polarization optics, holography, and how these ideas moved from theory to large-scale manufacturing in semiconductor foundries, ultimately appearing in consumer devices like smartphones. Capasso also reflects on commercialization, the legacy of Bell Labs, and the blurred boundary between basic science and real-world technology.

Whether you’re interested in metasurfaces, metalenses, nanophotonics, optics, or the process behind breakthrough discoveries, this episode offers a clear and insightful look at how modern optical physics becomes transformative technology.

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Apple Podcasts: https://podcasts.apple.com/us/podcast/632nm/id1751170269
Spotify: https://open.spotify.com/show/4aVH9vT5qp5UUUvQ6Uf6OR
Website: [https://www.632nm.com](https://www.632nm.com/)

Timestamps:
00:00 - Intro
01:53 - Transition from Bell Labs to Harvard
09:45 - Generalized Snell's Law
21:25 - Facing the Diffractive Optics Community
31:07 - Benefits of Well-Rounded Education
45:16 - Metalenses
55:55 - Can AI do Physics?
1:07:39 - Industry vs Academia
1:11:44 - Nanophotonics
1:14:44 - What Allowed for the First Metalenses?
1:17:38 - 632nm and Other Lasers
1:20:47 - Quantum applications of Metalenses
1:30:14 - Quantum Entanglement Redefines Spacetime
1:43:22 - Stokes Parameters
1:48:28 - Limits of Metasurface Pixel Size
1:55:20 - Advice for Young Scientists
2:01:45 - Critique of the H Index

#metasurface #metalenses #quantumphysics #materialscience #optics #photonics

How do electrons behave when they’re confined to a single layer, and why do entirely new laws of physics emerge when dimensions shrink?

Papers discussed in this episode:
Experimental observation of the quantum Hall effect and Berry's phase in graphene: https://www.nature.com/articles/nature04235
Tunable Fractional Quantum Hall Phases in Bilayer Graphene: https://arxiv.org/abs/1403.2112
Room-Temperature Quantum Hall Effect in Graphene: https://arxiv.org/abs/cond-mat/0702408

In this episode, we speak with Philip Kim, Harvard physicist and a leading experimentalist in low-dimensional quantum materials. Kim traces the experimental path from high-temperature superconductors and charge-density waves to carbon nanotubes and the earliest graphene devices, revealing how advances in nanofabrication and quantum transport opened the door to modern 2D materials physics.

We dive deep into the Hall effect and quantum Hall effect, from their 19th-century origins to the discovery of quantized and fractional conductance, and explain why these effects were found experimentally before they were fully understood theoretically. Kim shares behind-the-scenes stories of early graphene experiments, mechanical exfoliation, Shubnikov–de Haas oscillations, and what it was like to be scooped by the work that launched graphene into the spotlight.

Along the way, we explore how disorder, dimensionality, and magnetic fields shape electronic behavior; why carbon nanotubes paved the way for graphene; and how many of the most important discoveries in condensed matter physics arise from intuition, timing, and new experimental tools.

Whether you’re interested in graphene, quantum transport, the quantum Hall effect, nanofabrication, superconductors, or the real stories behind breakthrough discoveries, this conversation offers a rare, technically rich look at how modern quantum materials research actually unfolds.

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Apple Podcasts: https://podcasts.apple.com/us/podcast/632nm/id1751170269
Spotify: https://open.spotify.com/show/4aVH9vT5qp5UUUvQ6Uf6OR
Website: [https://www.632nm.com](https://www.632nm.com/)

Timestamps:
00:00 - Intro
01:15 - How Philip Began Studying Graphene
20:06 - Old Methods of Creating Graphene
32:33 - Hall Effect and Quantum Hall Effect
48:29 - Philip's Work at Columbia
52:33 - Philip's First Experiments with Graphene
1:06:43 - Did Philip Get Scooped from a Discovery?
1:09:40 - The Power of Scotch Tape
1:24:57 - High Temperature Quantum Hall Effect
1:30:18 - Fractional Quantum Hall Effect
1:41:17 - Collaboration with Particle Physicists
1:54:13 - Single Layer Graphene
1:59:44 - Next Gen Electronics with 2D Materials
2:03:23 - Graphene Twisting
2:14:48 - Superconductivity in Other Materials
2:20:06 - Anyons
2:30:00 - Fault-Tolerant Quantum Computing
2:36:05 - Can AI and Big Data Help Physicists?
2:40:47 - What Would Philip Do with Unlimited Resources?
2:43:44 - Optimizing the Education System

#graphene #quantumphysics #materialscience #halleffect #electromagnetism

What makes high-temperature superconductors and “strange metals” some of the most perplexing systems in modern physics?

In this episode, we speak with Dr. Subir Sachdev: Harvard physicist and one of the leading architects of today’s understanding of quantum matter. Sachdev explains why strange metals refuse to behave like ordinary conductors, how quantum entanglement reshapes the landscape of many-body physics, and why the quest to understand cuprate superconductors continues to push both theory and experiment to their limits.

We explore the physics of the cuprate phase diagram, the collapse of quasiparticles, and the role of quantum criticality in creating universal, linear-in-temperature behavior. Sachdev walks us through the origins of the SYK model, its surprising connections to black-hole thermodynamics and holography, and how new lattice-based models may finally bridge the gap between solvable theory and real materials.

Whether you’re curious about superconductivity, quantum criticality, black-hole analogies, emergent gauge fields, or the deep physics behind strongly correlated electrons, this conversation offers a rare, accessible look at how frontier theoretical work is redefining our picture of quantum matter—from the lab bench to the edge of spacetime.

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Website: https://www.632nm.com

Timestamps:
01:22 - Subir’s Path to Condensed Matter Physics
06:24 - Challenges in Discovering Cuprates
09:53 - History of Superconductivity
20:07 - Subir's PhD work
27:09 - Development of the SYK model
41:09 - Strange Metals
56:43 - Derivation of SYK Model
1:03:53 - Signatures of Strange Metals
1:09:58 - How Quantum Mechanics Affects Black Holes
1:17:10 - What Brought Subir to Black Holes?
1:19:43 - Black Hole Connections to SYK
1:29:28 - ADS CFT Correspondence
1:37:04 - Can Quantum Computers Help Advance the SYK Model?
1:40:17 - Is AI Useful for Theoretical Physics?
1:46:40 - How does Quantum Criticality Play into Superconductivity?
1:49:11 - Derivation Quantum Criticality
1:52:49 - What is Holography?
1:55:07 - Holography
2:00:19 - Green’s Function
2:08:46 - Green’s equation slides
2:13:23 - Yukawa Model vs SYK
2:17:30 - Can AI Brute Force Physics Discoveries?
2:23:51 - What Would Subir Do With Unlimited Funding?
2:36:33 - Dissecting the Hype of Superconductivity
2:31:15 - Raising the Next Generation of Great Physicists

#theoreticalphysics #quantummaterials #astrophysics #superconductivity #superconductor #blackhole #quantumphysics #quantummechanics

Would we get a quantum computer sooner if everything was open source?

In this episode, we speak with Austin Fowler, one of the architects of quantum error correction and a pioneer of the surface code used in today’s leading quantum computers. Fowler helped lay the groundwork for scalable, fault-tolerant computation at Google Quantum AI, before leaving to advocate for a more open and collaborative model of research.

He explains why building a useful quantum computer will require millions of reliable qubits, why no known algorithm yet clearly outperforms classical computation, and why the field’s current competitive funding model may be slowing progress instead of accelerating it. From the engineering challenges of superconducting qubits to the economics of global research, Fowler offers a candid, inside look at the state of quantum technology.

We explore the history and promise of quantum error correction, the software bottlenecks that still stand in the way, and how an open-source, international approach — modeled on CERN or the International Space Station — could transform the field. Along the way, Fowler reflects on his time at Google, the importance of collaboration, and what it will really take to make quantum computing practical.

Whether you’re interested in quantum hardware, physics, computer science, or research policy, this conversation reveals the technical, ethical, and economic realities behind one of today’s most ambitious scientific pursuits.

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Apple Podcasts: https://podcasts.apple.com/us/podcast/632nm/id1751170269
Spotify: https://open.spotify.com/show/4aVH9vT5qp5UUUvQ6Uf6OR
Website: [https://www.632nm.com](https://www.632nm.com/)

Timestamps:
00:00 - Intro
01:40 - Austin’s Longevity in Quantum
02:31 - What’s the Goal of Quantum Computing?
05:01 - Creating Fault-Tolerant Qubits
06:55 - Advantages of 2D Surface Code
08:47 - Austin’s Journey into Quantum
16:32 - Working at Google
20:14 - Alternatives to Surface Codes
22:18 - Should Quantum Computing Be Open Source?
25:20 - Quantum Computing is Eating Itself
30:52 - Open Source as a Mission
35:46 - Advice for People Getting into TQEC
39:03 - Bit Flips vs Phase Flips
45:43 - History of Surface Codes
49:05 - From Surface Code to Fault Tolerance
57:19 - What Software do Quantum Computers Need?
1:00:17 - Quantum vs Classical Error Correction
1:05:57 - Manufacturing Superconducting Qubits
1:12:02 - Noise Models in Software
1:21:21 - How do NISQ Experiments help us Build Better Computers?
1:24:01 - State of the Art Topological QEC
1:31:38 - How did the TQEC Community Begin?
1:34:46 - Future of TQEC
1:36:03 - Quantum AI
1:37:58 - Advice for Young Scientists
1:41:35 - Underrated Quantum Research
1:47:21 - What are the Most Important Upcoming Developments?

Why is syncing atomic clocks still one of the hardest problems in physics and engineering?

In this episode, we speak with Judah Levine—legendary NIST physicist and one of the key architects of modern timekeeping—about the invisible systems that hold the digital world together. Levine explains why synchronizing atomic clocks across the planet is far more complex than the clocks themselves, and why seemingly simple ideas like “round-trip delay” break down in real-world media such as fiber optics and the internet.

We explore how UTC is built from hundreds of atomic clocks, the difference between keeping time and *transferring* time, and the surprising challenges introduced by asymmetric delays, chromatic dispersion, and environmental noise. Levine walks us through the evolution of cesium clocks, the rise of optical clocks, and the technologies that make GPS, finance, power grids, and global communication possible.

Along the way, we discuss the history of time synchronization, from railroad schedules to radio frequencies to modern satellite systems; the ongoing debate over leap seconds; and why the future of precision timing depends not just on better clocks, but on better *engineering* to deliver those clocks’ performance to the real world.

Whether you’re curious about atomic clocks, relativity, fiber optics, GPS, the structure of time itself, or the hidden physics behind everyday technology, this conversation offers a rare look at how science, engineering, and careful statistical thinking keep modern civilization in sync—down to the nanosecond.

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Subscribe:
Apple Podcasts: https://podcasts.apple.com/us/podcast/632nm/id1751170269
Spotify: https://open.spotify.com/show/4aVH9vT5qp5UUUvQ6Uf6OR
Website: [https://www.632nm.com](https://www.632nm.com/)

Timestamps:
00:00 – Intro
01:03 – What is UTC?
05:50 – Timekeeping for Satellites
07:08 – How Radio Created Better Clocks
18:32 – From Astronomy to Atoms
25:25 – Why are there 24 Hours in a Day?
29:55 – Why Synchronizing Clocks is so Hard
47:09 – How did Judah get into Clocks?
53:29 – Is UTC Vulnerable to Hackers?
1:06:41 – Cesium vs Optical Atomic Clocks
1:11:23 – How Cesium Clocks Work
1:23:35 – Why Cesium Clocks are Imperfect
1:26:17 – Judah’s 3 Year Experiment
1:29:30 – Statistics with Clocks
1:33:40 – Is Time Real?
1:36:29 – Is the Universe Slowing Down?
1:40:29 – Atomic Time and General Relativity
1:42:17 – What’s Left for Atomic Clocks?
1:54:34 – What would Judah do with Unlimited Funding?
1:58:57 – Judah's Past in Programming
2:02:55 – Advice for Young Scientists

Why do civilizations rise, prosper, and then collapse? Here's what the math tells us.

In this episode, we sit down with Peter Turchin, complexity scientist and founder of the field of cliodynamics, which uses data and mathematical models to study the long-term cycles of history. Turchin explains his theory of elite overproduction, how societies generate too many ambitious, educated elites competing for too few positions, and why this dynamic reliably leads to polarization, inequality, and political turmoil.

We explore how his structural-demographic theory maps the recurring “boom and bust” rhythms that have shaped civilizations from ancient Rome to modern America, the role of military competition in driving cooperation and social complexity, and how new tools—from AI-assisted historical databases to ancient DNA and LiDAR—are transforming the study of the past.

Whether you’re drawn to history, sociology, complexity science, or the fate of modern democracies, this conversation reveals how Turchin’s quantitative approach offers a new way to understand—and maybe even forecast—the forces that make societies rise and fall.

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Subscribe:
Apple Podcasts: https://podcasts.apple.com/us/podcast/632nm/id1751170269
Spotify: https://open.spotify.com/show/4aVH9vT5qp5UUUvQ6Uf6OR
Website: https://www.632nm.com

Timestamps:

00:00 - Intro
01:48 - Overproduction of Elites
10:56 - Did Models Predict the Rise of Trump?
20:43 - Is Russian History Repeating in the US?
26:48 - How Competition Stabilizes Societies
32:14 - What Data Goes into Cliodynamic Models?
38:13 - How New Technologies Shaped Archaeology
43:28 - Can Historians Build Mathematical Intuitions?
47:59 - What Questions can be Answered with Cliodynamics?
52:23 - Does the NYC Mayoral Race Fit into Turchin's Theory?
56:37 - Is Fear of China Bringing Us Together?
58:29 - Do Historians Reject Turchin’s Work?
1:00:03 - Trends in Civilizations and Outliers
1:03:29 - Calvary and the Evolution of Societies
1:10:03 - Is Evolution via Natural Selection a Suitable Analog for History?
1:15:16 - Could Turchin's Ideas Be Misinterpreted Dangerously?

You can’t copy a qubit. So how do quantum computers remember anything?

In this episode, we sit down with Mikhail Lukin, Harvard physicist and co-director of the Harvard Quantum Initiative, whose lab is building quantum computers from arrays of individually trapped atoms. Lukin explains the paradox of quantum error correction—how you can safeguard quantum information even though it can’t be copied or measured directly—and why this breakthrough may be the key to making large-scale quantum computers possible.

We dive into the strange logic of superposition, entanglement, and “small cat states,” explore what makes quantum evolution inherently analog, and learn how Lukin’s team uses optical tweezers and Rydberg interactions to engineer stable, reconfigurable qubits—atoms literally held and moved by light.

Whether you’re fascinated by quantum mechanics, computing, Schrödinger’s cat, or the future of information, this conversation reveals how physicists are turning the weirdness of quantum physics into working technology—and why building a fault-tolerant quantum computer is one of the hardest and most exciting challenges in science today.

Follow us for more technical interviews with the world’s greatest scientists:
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LinkedIn: https://www.linkedin.com/company/632nm/about/
Substack: https://632nmpodcast.substack.com/

Follow our hosts!
Michael Dubrovsky: https://x.com/MikeDubrovsky
Misha Shalaginov: https://x.com/MYShalaginov
Xinghui Yin: https://x.com/XinghuiYin

Subscribe:
Apple Podcasts: https://podcasts.apple.com/us/podcast/632nm/id1751170269
Spotify: https://open.spotify.com/show/4aVH9vT5qp5UUUvQ6Uf6OR
Website: https://www.632nm.com

Timestamps:
00:00 - Intro
01:32 - Fundamentals of Quantum Computers
04:09 - Transistors vs Quantum Gates
10:07 - What is Quantum Error Correction?
14:23 - State of the Art QEC
22:19 - Quantum Research Before Lukin
27:35 - Lukin’s Breakout Work
31:10 - From Quantum Optics to Quantum Computing
36:59 - Working with Neutral Atoms
48:17 - Funding Quantum Computers
50:00 - Transverse Gate Operations
58:22 - Is Quantum Computing All Hype?

#quantumcomputing #quantumerrorcorrection #mikhaillukin #qubits #schrodingerscat #entanglement #superposition #quantumphysics