Quantum measurement

Wigner's friend

Wigner's friend is a thought experiment in theoretical quantum physics, first conceived by the physicist Eugene Wigner in 1961, and further developed by David Deutsch in 1985. The scenario involves an indirect observation of a quantum measurement: An observer observes another observer who performs a quantum measurement on a physical system. The two observers then formulate a statement about the physical system's state after the measurement according to the laws of quantum theory. However, in most of the interpretations of quantum mechanics, the resulting statements of the two observers contradict each other. This reflects a seeming incompatibility of two laws in quantum theory: the deterministic and continuous time evolution of the state of a closed system and the nondeterministic, discontinuous collapse of the state of a system upon measurement. Wigner's friend is therefore directly linked to the measurement problem in quantum mechanics with its famous Schrödinger's cat paradox. Generalizations and extensions of Wigner's friend have been proposed. Two such scenarios involving multiple friends have been implemented in a laboratory, using photons to stand in for the friends. (Wikipedia).

Video thumbnail

Physics in the Days of Einstein and Feynman | Freeman Dyson | Big Think

Physics in the Days of Einstein and Feynman New videos DAILY: https://bigth.ink/youtube Join Big Think Edge for exclusive videos: https://bigth.ink/Edge ---------------------------------------------------------------------------------- Freeman Dyson never spoke to Einstein, but revered hi

From playlist Inside the mind of Albert Einstein | Big Think

Video thumbnail

Science Guy Steve Spangler's Halloween Tricks!

One of Ellen's favorite guests, Steve Spangler, brought another bunch of amazing -- and explosive -- science tricks.

From playlist Steve on Ellen

Video thumbnail

Gifting a Science Experience - Steve Spangler on 9NEWS

There’s a science to all of this Cyber Monday excitement and our science guy Steve Spangler is here to share some ideas on creating the perfect gift “experience” for that science enthusiast in your life. Contact Steve Spangler at steve@stevespangler.com Contact Steve’s business manager at

From playlist Science Mondays - 9NEWS with Steve Spangler

Video thumbnail

Does Consciousness Influence Quantum Mechanics?

PBS Member Stations rely on viewers like you. To support your local station, go to: http://to.pbs.org/DonateSPACE ↓ More info below ↓ Sign Up on Patreon to get access to the Space Time Discord! https://www.patreon.com/pbsspacetime Sign up for the mailing list to get episode notification

From playlist Space Time!

Video thumbnail

Steve Spangler - Making Science Fun!

Learn more about Steve at http://www.stevespanglerscience.com/ or http://www.stevespangler.com/ About Steve Spangler Science... Steve Spangler is a celebrity teacher, science toy designer, speaker, author and an Emmy award-winning television personality. Spangler is probably best kno

From playlist Don't try this at home!

Video thumbnail

The Spangler Effect - Steve Spangler Speaks with Rainn Wilson

The Spangler Effect series was created by Steve Spangler in partnership with YouTube’s Original Content Creator Project. © 2012 Steve Spangler, Inc. All Rights Reserved Steve Spangler is a bestselling author, STEM educator and Emmy award-winning television personality with more than 1,500

From playlist The Spangler Effect: Season 01

Video thumbnail

Understanding Quantum Mechanics: Schrödinger's Cat Experiments

Check out the physics courses that I mentioned (many of which are free!) and support this channel by going to https://brilliant.org/Sabine/ where you can create your Brilliant account. The first 200 will get 20% off the annual premium subscription. Schrödinger's cat is an old though-exper

From playlist Understanding Quantum Mechanics

Video thumbnail

William Shatner Explains the Importance of His Friendship with Leonard Nimoy | Big Think

William Shatner Explains the Importance of His Friendship with Leonard Nimoy Watch the newest video from Big Think: https://bigth.ink/NewVideo Join Big Think Edge for exclusive videos: https://bigth.ink/Edge ----------------------------------------------------------------------------------

From playlist Best Videos | Big Think

Video thumbnail

The Spangler Effect - Fun Science Pranks Season 02 Episode 04

The Spangler Effect series was created by Steve Spangler in partnership with YouTube’s Original Content Creator Project. © 2012 Steve Spangler, Inc. All Rights Reserved Steve Spangler is a bestselling author, STEM educator and Emmy award-winning television personality with more than 1,500

From playlist April Fool's Day Favorites

Video thumbnail

The Spangler Effect - EXTRAS - On the Set of The Spangler Effect

The Spangler Effect series was created by Steve Spangler in partnership with YouTube’s Original Content Creator Project. © 2012 Steve Spangler, Inc. All Rights Reserved Steve Spangler is a bestselling author, STEM educator and Emmy award-winning television personality with more than 1,500

From playlist The Spangler Effect: Season 02

Video thumbnail

Dyson Brownian motion, free fermions and connections to Random Matrix Theory by Gregory Schehr

PROGRAM : BANGALORE SCHOOL ON STATISTICAL PHYSICS - XII (ONLINE) ORGANIZERS : Abhishek Dhar (ICTS-TIFR, Bengaluru) and Sanjib Sabhapandit (RRI, Bengaluru) DATE : 28 June 2021 to 09 July 2021 VENUE : Online Due to the ongoing COVID-19 pandemic, the school will be conducted through online

From playlist Bangalore School on Statistical Physics - XII (ONLINE) 2021

Video thumbnail

Has quantum mechanics proved that reality does not exist?

Check out the math & physics courses that I mentioned (many of which are free!) and support this channel by going to https://brilliant.org/Sabine/ where you can create your Brilliant account. The first 200 will get 20% off the annual premium subscription. In the past years you may have se

From playlist Understanding Quantum Mechanics

Video thumbnail

Quantum chaos, random matrices and statistical physics (Lecture 03) by Arul Lakshminarayan

ORGANIZERS: Abhishek Dhar and Sanjib Sabhapandit DATE: 27 June 2018 to 13 July 2018 VENUE: Ramanujan Lecture Hall, ICTS Bangalore This advanced level school is the ninth in the series. This is a pedagogical school, aimed at bridging the gap between masters-level courses and topics in

From playlist Bangalore School on Statistical Physics - IX (2018)

Video thumbnail

The Spangler Effect - St Patrick's Day Science Season 02 Episode 01

The Spangler Effect series was created by Steve Spangler in partnership with YouTube’s Original Content Creator Project. © 2012 Steve Spangler, Inc. All Rights Reserved Steve Spangler is a bestselling author, STEM educator and Emmy award-winning television personality with more than 1,500

From playlist The Spangler Effect Episodes

Video thumbnail

Geometry and Topology in Quantum Mechanics - Mathematical Properties by N. Mukunda

DISCUSSION MEETING GEOMETRIC PHASES IN OPTICS AND TOPOLOGICAL MATTER ORGANIZERS: Subhro Bhattacharjee, Joseph Samuel and Supurna Sinha DATE: 21 January 2020 to 24 January 2020 VENUE: Madhava Lecture Hall, ICTS, Bangalore This is a joint ICTS-RRI Discussion Meeting on the geometric pha

From playlist Geometric Phases in Optics and Topological Matter 2020

Video thumbnail

Random Matrix Theory and its Applications by Satya Majumdar ( Lecture 2 )

PROGRAM BANGALORE SCHOOL ON STATISTICAL PHYSICS - X ORGANIZERS : Abhishek Dhar and Sanjib Sabhapandit DATE : 17 June 2019 to 28 June 2019 VENUE : Ramanujan Lecture Hall, ICTS Bangalore This advanced level school is the tenth in the series. This is a pedagogical school, aimed at bridgin

From playlist Bangalore School on Statistical Physics - X (2019)

Video thumbnail

Can We Observe the Quantum Origin of Primordial Perturbations? by Jerome Martin

PROGRAM: PHYSICS OF THE EARLY UNIVERSE - AN ONLINE PRECURSOR ORGANIZERS: Robert Brandenberger (McGill University, Montreal, Canada), Jerome Martin (Institut d'Astrophysique de Paris, France), Subodh Patil (Instituut-Lorentz for Theoretical Physics, Leiden, Netherlands) and L Sriramkumar (

From playlist Physics of The Early Universe - An Online Precursor

Video thumbnail

Entropy Growth during Free Expansion of an Ideal Fermi Gas by Saurav Pandey

ICTS In-house 2022 Organizers: Chandramouli, Omkar, Priyadarshi, Tuneer Date and Time: 20th to 22nd April, 2022 Venue: Ramanujan Hall inhouse@icts.res.in An exclusive three-day event to exchange ideas and research topics amongst members of ICTS.

From playlist ICTS In-house 2022

Video thumbnail

A Brief History of Stephen Hawking - with Len Mlodinow

Recalling his nearly two-decades as a friend and collaborator with Stephen Hawking, Leonard Mlodinow talks about the scientific discoveries as well as the personal stories of Hawking. Len's book "Stephen Hawking: A Memoir of Friendship and Physics" is available now: https://geni.us/yCBSEl

From playlist Livestreams

Video thumbnail

Implications | History and Philosophy of Astronomy 9.06

Learn about the history and philosophy of astronomy from Professor Impey, a University Distinguished Professor of Astronomy at the University of Arizona, with our Knowing the Universe: History and Philosophy of Astronomy course here on YouTube. This video is part of module 9, Quantum Theor

From playlist History and Philosophy Course Module 9: Quantum Theory

Related pages

Qubit | Schrödinger equation | Determinism | Hardy's paradox | Macroscopic scale | Schrödinger's cat | Measurement problem | Relational quantum mechanics | Spin (physics) | Many-worlds interpretation | No-go theorem | Information theory | Interpretations of quantum mechanics | Wave function collapse | Objective-collapse theory | Born rule | Bayesian probability | Quantum suicide and immortality | Basis (linear algebra) | Measurement in quantum mechanics