How the Quantum Eraser Rewrites the Past | Space Time | PBS Digital Studios

Causality is meant to move in one direction: forward. But the Quantum Eraser experiment seems to reverse causality. How and why can this happen and what are the implications of this experiment on how we understand Quantum Mechanics and our greater universe?

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A Delayed Choice Quantum Eraser
Kim, Yu, Kulik, Shih & Scully, 2000, Physical Review Letters v.84 p.1

Previous Episode on Can We Survive the Destruction of the Earth? ft. Neal Stephenson

Previous Episode on The Quantum Experiment that Broke Reality

Gamma Ray Bursts by In a Nutshell

Episode written and hosted by Matt O’Dowd

Comments answered by Matt

MirceaKitsune

tsjoencinema

Weapon Valhalla

Narigone

TimmacTR

kaleb tandberg

The deathless face of the unborn mind

Error 404: Hodor Not Found

[parakmi]

When you are not looking at it, this comment describes the answer to the quantum eraser problem.

[lazergurka-smerlin]

Dammit i told you the universe wasn't ready for offical release yet.

[dgafbrapman]

I remember opening and closing a fridge and every time wondering if the light was always on..then i found the button switch and the magic died forever.

[paolocannizzaro]

This is the most absurd thing I've ever tried to wrap my head around in my entire life. Thank you

[EGarrett]

...yeah. I'll be watching this one a few more times.

[physicside]

Proof that universe has a parental control, " You're are not that evolved to take this yet".

[MarkFredrickGravesJr]

Sabine made a video debunking the quantum eraser experiment, and I saw your comment on her video saying you would make a retraction video... has that already been released? What's the title of the video?

[theunironicpeasant]

"Physicists hate being outsmarted by the universe." 😂

[AnaseSkyrider]

I swear: Quantum physics is just a giant middle finger to anyone who wants this shit to make any kind of sense.

[capisenior]

Damn programmers, trying to make performance optimizations that end up being noticed.

[sock]

I really like the transactional interpretation for explaining this. In it particles only appear after a three part process where an emitter sends out an offer wave (psi), then receives confirmation waves (psi*) from every possible future absorber and non deterministically "chooses" a single confirmation wave, which then creates something almost like a standing wave in spacetime that transfers energy, spin, momentum, etc from emitter to absorber. Which we perceive as a particle at a timelike interval. The mutual atemporal interaction between both emitter and detector is required for a particle to exist in the first place.

So when you have entangled wave packets moving through the delayed choice experiment, as a single offer wave, the potential properties of "future" particles stemming from that offer wave are basically doled out to suitable absorbers in the system as you measure. Which explains all the seemingly retrocausal weirdness.

Which is also why when you measure the spin of an entangled particle the spin of the other instantly changes. The possibility of it being one or the other became finalized as soon as it was measured since measuring itself is what caused potential properties to manifest from possible ones into actual events at timelike intervals.

[Laff]

You kinda represented the data in the study wrong. The pattern that is created by the double slit experiment doesn't change when you turn any of the detectors on or off. The reason why they talked about the pattern changing was they used the detectors to create a list of which photons went through which slit. They were able to get an interference pattern when they only looked at the data of photons which went through one slit. When the data from both slits is put together the pattern disappears.

[Madridy]

Quantum physics: the science that makes no sense at all and gives you the middle finger saying deal with it

[odairfernandes]

"Sabine, this is amazing. You are, as usual, 100% right. The delayed choice quantum eraser is a prime example of over-mystification of quantum mechanics, even WITHIN the field of quantum mechanics! I (Matt) was guilty of embracing the quantum woo in that episode 5 years ago. Since then I've obsessed over this family of experiments and my thinking shifted quite a bit. And then I procrastinated on filming the retraction! Thanks for laying it out more clearly than I could have. I have some thoughts to share that might add one more nail to the coffin ... coming to a video real soon!"

The comment above was posted by PBS on the video...

Was the "retraction video" posted by PBS Space Time already?
If so, could you provide me a link? (I couldn't find it).
If not, can you tell when you will post it?

[thatonekid]

Its like the universe is preventing the existence of a paradox

[zac]

“An entangled pair...”
I had surgery for that in 9th grade...

[HM-rcnn]

Hello simulation runners. Just a humble request to fix the bug before it gets wider attention.

[serveandprotect]

You are 100% right about that one - quote: "Physicists DO LOVE a good MYSTERY!" ...even more than answers!
PS. ...maybe that's why each answer they provide us with discloses a 100 new questions...

[keeganlacroix]

Last time I was this early the universe was still orange

[wellplayed]

Even the universe gets stuck with spaghetti code