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10 videos · 3 h 13 min
Explainer · YouTube
Sabine Hossenfelder
A compact statement of the measurement problem from the theoretical physicist Sabine Hossenfelder, who explains why the measurement update cannot simply be derived from the Schrödinger equation. Her conclusion, that quantum mechanics therefore needs to be completed, is one position among several; chapter 22 lays out the others.
Demo · YouTube
Orion Lawlor
A 90-second tabletop demo: two crossed polarizers block the light, and a third at a diagonal angle lets light through again, but only when it sits between them, not before or after. Watch it right after this section's three-filter paragraph and narrate each filter as a measurement in a new basis; the uploader's notes also point to Dirac, who opened his 1930 textbook with the polarization of single photons.
Demo · YouTube
Looking Glass Universe
Looking Glass Universe uses a laser pointer, a calcite crystal and polarizing film to make a polarization measurement at home, then works through rotating the measurement (4:15), orthogonal states (5:47), equivalent measurements (6:41) and the quantum versus classical view (7:47). It makes 'ask sideways' tangible: watch how rotating the measurement changes which question is being put to the light.
Explainer · YouTube
PBS Space Time
PBS Space Time starts from Zeno's arrow paradox and builds the quantum Zeno effect out of superposition and collapse (2:24), with chapters on stopping the quantum arrow (3:33), its experimental verification (5:03) and the debate over what counts as a measurement (8:16). Compare its account with the 1990 NIST beryllium-ion experiment in this section, and with the point that scattered photons, not detected ones, do the freezing.
Explainer · YouTube
Looking Glass Universe
Starts at 2:37, just after the sponsor segment; YouTube's chapter markers then run from quantum determinism to the measurement contradiction (5:23), testing the measurement rule (8:02), the Heisenberg cut (10:41) and alternatives to Copenhagen (13:10), the same arc as this section. Set its Schrödinger equation against Rule A and its measurement rule against Rule B, and pair the Heisenberg-cut chapter with this section's 'sliding cut' callout.
Explainer · YouTube
Arvin Ash
A beginner-level account of how the quantum world turns into the definite classical one, starting at 'Switch from quantum to classical' (5:03) and 'Quantum decoherence explained' (6:06), then asking whether decoherence is really irreversible (8:52) and whether there is a point of no return (11:26). Read any talk of 'looking' as interacting and leaving a record, keep this section's caveat in mind (decoherence explains why interference vanishes, not by itself which outcome occurs), and treat the closing link to the arrow of time (12:18) as speculation.
Lecture · MIT
MIT OpenCourseWare · Allan Adams · 2013
The opening lecture of MIT's 8.04 Quantum Physics I (Spring 2013), in which Allan Adams uses thought experiments with measuring boxes to build superposition and uncertainty from scratch. Skip the first ten minutes of course logistics, then watch how a few simple box experiments force exactly the rules of this session: repeat a measurement and the answer stays put; measure an incompatible property and it is scrambled.
Lecture · MIT
MIT OpenCourseWare · Barton Zwiebach
Zwiebach contrasts classical superposition of fields with the quantum kind using single photons in a Mach-Zehnder interferometer, then states the rule this section builds on: measure a property on αA + βB and you never get anything in between, only a or b, with odds set by |α|² and |β|², after which the state is the one you found. When he says a photon is 'in both beams at the same time', translate it into this section's language (one definite state written as a sum of two path states), and catch his point at about 7:30 that the same vector can be written as a sum in many different ways.
Lecture · IBM Quantum
Qiskit
An IBM Quantum classroom lesson that tries to understand superposition by comparing measurements on a qubit in superposition with a classical coin flip, and explores how the 'quantum coin' and the classical coin behave differently. That is this section's coin-under-the-cup question; keep its test in mind as you watch: asked only 'zero or one?', |+⟩ and a fair coin give identical statistics, so the difference has to come from asking a different question.
Lecture · MIT
MIT OpenCourseWare · Barton Zwiebach
Starts at 7:55, where Zwiebach states the measurement postulate as this section does: the result is always an eigenvalue, its probability is |αᵢ|², the squared overlap with the eigenstate, and the state collapses to that eigenstate, so an immediate repeat gives the same value; rewind to the beginning to see how any state is expanded in eigenfunctions and why the |αᵢ|² add up to 1. Stay for 15:10, where he calls it 'a very strange postulate' that splits quantum mechanics into the realm of the Schrödinger equation and the realm of measurement, a preview of section 6.