Simple Explanation of the Most Notorious Experiment | Double Slit and Delayed Choice Quantum Eraser

Simple Explanation of the Most Notorious Experiment | Double Slit and Delayed Choice Quantum Eraser

This is not science fiction. This is real experimental physics.

In this video, we break down the most mind-bending experiment ever done in science — the Delayed Choice Quantum Eraser — in simple, clear language. No complex equations. No intimidating jargon. Just pure, mind-blowing reality.

We begin with the famous Double Slit Experiment, trace its evolution through single-particle interference, and finally dive into the baffling world of quantum entanglement, coincidence counting, and the experiment that some believe… broke time.

Did this experiment really prove retrocausality? Or is the truth even stranger?

Even Einstein struggled with these ideas. He called it “spooky action at a distance.” But the experiments that followed seem to confirm exactly what he couldn’t accept.

0:00 – Intro
02:22 – History Of Light
03:25 – Double Slit Experiment
05:44 – Explanation Of Double Slit Experiment
08:47 – History Of Light Continues
10:49 – Double Slit Experiment with Electron
11:31 – Single Particle Double Slit Experiment
13:36 – Which Way Experiment
15:40 – Using Entangled Photons and New Experiment Setup
17:56 – Delayed Choice Experiment
19:53 – The Delayed Choice Quantum Eraser Experiment.

🎥 If you’ve ever wondered why scientists say reality itself is weird, this video is your gateway.
🎯 By the end, you’ll never look at the world — or time — the same way again.

🧠 No knowledge is small. And some knowledge might just break your understanding of reality.

👇 WATCH TILL THE END to witness the experiment that still shocks physicists today.

⚠️ UPDATE October 2025:
Recently, PBS Space Time released a new video discussing the same experiment, featuring quantum physicist Mithuna Yoganathan.
In my video, I had clearly mentioned that even though this setup may appear to show retro causality — where the future seems to affect the past — it should not be treated as proof of it, and retro causality should be ruled out.
The new PBS Space Time explanation explores in more depth why retro causality should be ruled out.
Both videos complement each other and together help viewers understand the ongoing debate around the quantum eraser interpretation in modern quantum mechanics.
Watch their perspective here:    • We Were WRONG About the Quantum Eraser! ft...  

This video explores whether future measurements can influence past events through the quantum eraser setup. We examine which-way information, causal ordering, and the role of post-processing in understanding these results. The debate continues: Does Alice's measurement choice affect Bob's earlier photon behavior, or does quantum superposition explain everything without backwards causation?


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You are welcome to my science channel Science Simplified 4 All. My name is Anoop. I am a science enthusiast. My science talk videos are an attempt to simplify complicated science topics so that everyone can understand. My videos will include topics like Physics, Astrophysics, Astronomy, Blackholes, Special Theory of relativity, General Theory of relativity, Spacetime, stars, quantum mechanics, science experiments, science projects, biology, aliens, science facts, science documentry etc. I will try to explain science in simple ways without too much equations, formulas and graphs. Some of my videos may be useful for the science students, science class, science master, and competitive exam students like UPSC etc.