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10 videos · 4 h 26 min

  • Lecture · MIT

    Lecture 1: Introduction to Superposition

    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

    The nature of superposition. Mach-Zehnder interferometer

    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 · MIT

    Completeness of eigenvectors and measurement postulate

    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.

  • Short · Washington University in St. Louis

    Zeno Effect

    Washington University in St. Louis

    A three-minute university video on Kater Murch's group, who probed the role of measurement in the Zeno effects with an artificial-atom qubit, including a 'quasimeasurement' interaction that only disturbs it; Murch calls the results the first observation of the two Zeno effects on a single quantum system. It sharpens this section's lesson that what freezes a quantum state is a physical interaction, not anybody looking.

  • Lecture · Yale

    22. Quantum mechanics IV: Measurement theory, states of definite energy

    YaleCourses · Ramamurti Shankar · 2010

    The lecture from Yale University PHYS 201 Fundamentals of Physics II (Ramamurti Shankar, 2010) that goes with Chapter 15. The whole course is in the Lecture Hall.

  • Lecture · Caltech

    Ph CS 219A Lecture 3A Measurement

    John Preskill · 2021

    The lecture from Caltech Ph/CS 219A Quantum Computation (John Preskill, 2021) that goes with Chapter 15. The whole course is in the Lecture Hall.

  • Course · Yale

    Fundamentals of Physics II

    YaleCourses · Ramamurti Shankar · 2010

    Ramamurti Shankar, author of a classic graduate textbook, gives one of the gentlest rigorous introductions anywhere: seven lectures from the double-slit experiment through measurement, the particle in a box, the time-dependent Schrödinger equation and the postulates.

  • Course · MIT

    Quantum Physics II

    MIT OpenCourseWare · Barton Zwiebach · 2013

    The sequel: vector spaces and Dirac notation, the uncertainty principle done properly, the Heisenberg picture, two-state systems, tensor products and the addition of angular momentum. The natural next step once Unit 3 of this course feels comfortable.

  • Explainer · YouTube

    Quantum Superposition, Explained Without Woo Woo

    The Science Asylum

    Nick Lucid of The Science Asylum takes superposition back to its roots in ordinary wave physics and strips away the mystical talk that usually surrounds it. As you watch, test what you hear against this session's central claim: a superposition is one perfectly definite state written as a sum, and whether a state counts as a superposition depends on which measurement you have in mind.

  • Explainer · YouTube

    The Problem with Quantum Measurement

    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.