Best Place To Build

Quantum Mechanics, qubits, superposition & superconductors with Prof. Prabha Mandayam | BP2B S2 E11

Join Prof. Prabha Mandayam on the Best Place to Build Podcast for a deep dive into how a Quantum Computer differ from a Classical Computer. What are Qubits, Quantum States, and Quantum Algorithms? How are Shor’s Algorithm and Grover’s Algorithm changing the future of computing? With this episode, we welcome you to step into the world of Quantum Processors, Quantum Gates, and cutting-edge concepts such as Entanglement, Decoherence, and Quantum Error Correction. What You’ll Learn: * The difference between a Classical Bit and a Quantum Bit (Qubit) * How Transistors and Binary Operations paved the way for modern computing * Types of Qubits: Superconducting Qubits, Photonic Qubits, Trapped Ion Qubits, Neutral Atom Qubits * The challenge of Noise, Decoherence, and why Error Correction matters * How Quantum Communication, Quantum Key Distribution (QKD), and Post-Quantum Cryptography (PQC) are shaping the future of cybersecurity * Emerging fields like Quantum Sensing and Variational Quantum Algorithms Tech giants like Google and IBM, along with research hubs such as IIT Madras, are pushing the boundaries of quantum innovation. Who will win the race to build a practical Quantum Processor? Whether you’re a beginner curious about the basics or a tech enthusiast exploring advanced Quantum Computing concepts, this episode breaks it down in simple, clear terms. Check out Prof. Prabha’s NPTEL lecture here: https://nptel.ac.in/courses/106106232 Department of Physics, IIT Madras: https://physics.iitm.ac.in/academics/engineeringphysics.html Head over to your favourite chapter here: 00:00 Introduction 00:50 Welcome to BP2B 01:30 Introducing Prof Prabha Mandayam 02:05 What is Quantum Computing? 05:00 Quantum Mechanics visualised 15:00 The Origin of Quantum Mechanics Studies - Photonics 101 16:20 The History of Quantum Mechanics | Algorithms Explained 22:00 What is Quantum Decoherence? 26:15 Google & IBM’s Experiments With Quantum Computation 31:50 Classical v/s Quantum Error Corrections 33:33 The No-Cloning Theory 37:50 Will We All Have Quantum Computers in Our Hands? 40:00 The Maths Behind it All 42:30 Variational Quantum Algorithms 44:50 The Interdisciplinary Nature of Quantum Computational Studies 49:30 Quantum Research in India 55:20 How Did Prof Prabha Get into Quantum Mechanics? 01:04:05 Do Women Pursue Quantum Computing Studies? 01:10:00 Closing Thoughts

PMPrabha Mandayamguest

Oct 10, 2025·1h 11m·Watch on YouTube ↗

📖 CHAPTERS

1. 1

   Setting the stage at IIT Madras + Prof. Prabha Mandayam’s focus

   The host introduces the Best Place To Build Podcast and frames the episode as a crash course in quantum computing. Prof. Prabha Mandayam is introduced along with her work in quantum information and (especially) quantum error correction.

2. 2

   From classical bits to qubits: the Bloch-sphere intuition

   Prof. Mandayam contrasts classical bits (0/1) with qubits using a sphere model (Bloch sphere). The key idea is that a qubit can occupy infinitely many states between 0 and 1, which is captured by the notion of superposition.

3. 3

   Superposition made tangible: coin-in-flight and polarization of light

   To make superposition feel less abstract, the discussion uses a coin toss analogy (capturing the coin mid-flight) and then a more physical example: photon polarization. This links the math of superposition to a real lab system people can imagine and measure.

4. 4

   Why it’s called ‘quantum’: single-particle physics and photons

   The word ‘quantum’ is tied to behavior at microscopic scales—single photons, single electron spins, single atoms—where outcomes become fundamentally probabilistic. The conversation explains how bulk light behaves classically, but reducing to single-photon regimes reveals quantum effects.

5. 5

   100 years of quantum mechanics + the birth of quantum algorithms

   The episode situates quantum mechanics historically (Schrödinger/Heisenberg era; roots in photoelectric effect) and then distinguishes modern quantum computing as ~40 years old. It highlights early algorithmic milestones that demonstrated computational advantage.

6. 6

   Why quantum computing mattered to the world: Shor, Grover, and RSA

   The discussion moves from toy speedups to real-world impact: Shor’s factoring algorithm threatens RSA-based security, while Grover’s algorithm accelerates search. These results are presented as catalysts for major government and industry investment.

7. 7

   Hardware reality check: architectures and the ‘transistor moment’

   Attention shifts from algorithms to building machines—what it takes to create controllable qubits on chips. The episode surveys leading qubit architectures and explains why superconducting qubits became prominent as an engineering path toward scalable processors.

8. 8

   Decoherence: why qubits are fragile and error correction is central

   Prof. Mandayam explains decoherence as the process by which quantum states leak into classical behavior due to environmental interactions. The conversation frames error correction as the defining challenge: isolate qubits enough to preserve states, but still control and measure them.

9. 9

   How many qubits are ‘enough’: from 100 today to millions for RSA-scale tasks

   The host compares billions of transistors to ~100-qubit quantum chips and asks what scale is required for meaningful advantage. Prof. Mandayam clarifies that advantage is usually in time/steps, but practical factoring at scale requires large numbers of error-corrected qubits.

10. 10

    Quantum error correction: redundancy without copying + the no-cloning theorem

    Classical error correction uses redundancy by copying bits, but quantum states can’t be duplicated arbitrarily due to the no-cloning theorem. The episode explains why quantum error correction must encode information differently—protecting an entire state space, not just 0/1.

11. 11

    Entanglement as the workaround: encoding information into the whole system

    Entanglement is introduced as the key ingredient enabling quantum error correction. By spreading information across multiple qubits in a way that can’t be decomposed into independent parts, systems can detect/correct errors while respecting quantum constraints.

12. 12

    Will quantum computers be personal devices? Likely ‘facilities’ first

    The conversation explores whether quantum computers could become handheld like smartphones. Prof. Mandayam predicts specialized shared facilities in the near term—similar to early mainframe access—before any consumer-scale transformation becomes plausible.

13. 13

    What to learn + programming the stack: linear algebra, VQAs, and Qiskit

    The episode becomes a practical guide for learners: linear algebra is the core language of quantum computing, with probability theory as support. It also touches on variational quantum algorithms for chemistry/biology use cases and how people can program real devices via platforms like IBM Qiskit.

14. 14

    Quantum research in India: National Quantum Mission, hubs, and milestones

    Prof. Mandayam outlines India’s position in the global race and argues India can still catch up, especially in hardware. She explains the National Quantum Mission structure (four hubs) and gives concrete deliverables for communication and computing targets.

15. 15

    Prof. Mandayam’s journey into quantum + women in the field + closing advice

    The episode closes with Prof. Mandayam’s personal path—from Chennai to IITM to Caltech—and her emphasis on following curiosity rather than trends. She discusses gender representation challenges and encourages students to enter quantum now as skills will remain valuable regardless of how the field evolves.