But what is quantum computing? (Grover's Algorithm) | Leonard Susskind

Most people have heard the summary.

"Quantum computers try every answer at once."

It sounds clean. It's also wrong. And that wrong summary makes it basically
impossible to understand what quantum computers can and can't actually do.

In this video, we think through quantum computing the way Leonard Susskind
actually explains it — from the state vector up. No analogies that break
down under pressure. The real picture.

We build from scratch to a complete walkthrough of Grover's Algorithm —
the quantum search algorithm that proves a square root speedup is possible,
and that no quantum computer can ever do better than that on this class
of problem.

What we cover:
→ Why the "parallel processing" summary leads you completely wrong
→ What a qubit actually is (not the pop-sci version)
→ The state vector — what it is, why it matters, why you can't see it
→ Why quantum programs produce probability distributions, not fixed outputs
→ Sign flips — why they don't change probability but change everything
→ The geometry behind Grover's Algorithm
→ Where the square root of n actually comes from (it's Pythagoras)
→ Why the speedup is NOT parallelism
→ What quantum computers are genuinely good at vs. wildly overhyped

This channel doesn't rush through physics. We sit with it.

———

📌 Susskind's free Stanford lectures on quantum mechanics:
https://www.youtube.com/channel/UCV5cyrPoB5zRkDvZ4mxDcIg/

📌 The Theoretical Minimum — Susskind's book:
https://...https://www.penguin.co.uk/authors/78685/leonard-susskind
———

CHAPTERS:
0:00 — The summary everyone gives (and why it's wrong)
2:30 — The puzzle that breaks the popular story
5:10 — What a qubit actually is
7:45 — The state vector explained
08:00 — Sign flips and why they matter
09:20 — Setting up Grover's Algorithm geometrically
11:40 — Two reflections make a rotation
13:00 — Where square root of n comes from
15:30 — The honest answer on where the speedup comes from
17:00 — What this means for quantum computing overall

———

Physics Unrushed is a channel for people who want to actually understand
physics — not just feel like they do.

New videos every [your schedule].

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#physics #qubits #statevector #quantumalgorithms #computerscience
#physicseducation
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This video clarifies a common misconception about quantum computing, moving beyond the oversimplified idea that it merely processes all combinations simultaneously. We explore the true nature of quantum computing, focusing on how "qubits" and specific "algorithm" applications truly operate. Understanding the nuances of "quantum technology" and its underlying "quantum mechanics" is crucial for grasping its potential.

We break down how "quantum information" is managed and what sets "ibm quantum" apart, providing a more accurate perspective on this complex field.

Join Membership:
https://www.youtube.com/channel/UCV5cyrPoB5zRkDvZ4mxDcIg/join

Видео But what is quantum computing? (Grover's Algorithm) | Leonard Susskind канала Physics Unrushed