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Events that could have happened but didn't, so called counterfactual events, are but a mind-game in our reality. In quantum reality, however, they are quite real indeed. In this video I explain how this can be used to do a computation without actually running the computer. This is called "counterfactual computation" (or "counterfactual quantum computation" more specifically).

The key papers which I mention are:

Counterfactual Computation
Graeme Mitchison and Richard Jozsa
https://royalsocietypublishing.org/do...

Counterfactual Quantum Computation through Quantum Interrogation
Hosten et al
https://www.nature.com/articles/natur...

The two papers I mention as further developments at the end are:

Counterfactual Quantum Cryptography
Tae-Gon Noh
https://journals.aps.org/prl/abstract...

Counterfactual universal quantum computation
Zhu Cao
https://journals.aps.org/pra/abstract...

The specific setup that I use is discussed in more detail here:

The Impossibility of the Counterfactual Computation for all Possible Outcomes
Lev Vaidman
https://arxiv.org/abs/quant-ph/0610174

00:00 Intro
00:38 Quantum Mechanics is Simple
02:00 Lasers, Beam Splitters, and Photons
05:47 Interferometers
07:09 Counterfactual Computation
10:23 What Does It Mean?
13:07 Quantum Mechanics with Sabine on Brilliant

#physics #quantum #science