Back to the Future on a Quantum Computer: Demystifying Time Loops

Back to the Future on a Quantum Computer: Demystifying Time Loops | Paradoxes Ep. 09

Рет қаралды 8,475

Күн бұрын

Imagine you could go back in time and meet your past self. Time-travel can lead to all kinds of paradoxes - but what happens when we try and model time-travel using quantum mechanics?
In this video, Oxford PhD researcher Maria Violaris, together with her past self, explain how to resolve the famous Grandfather Paradox in quantum mechanics, by simulating a time-loop with a quantum computer. Maria shows how these "closed-timelike-curves", if they exist, would give quantum computers a huge boost in computational power. She also explains some open problems with time-loops that are yet to be resolved.
Learn more at the Qiskit Blog: Blog post coming soon to / qiskit !
Find all the code in this Jupyter Notebook: github.com/maria-violaris/qua...
Relevant papers to find out more:
-"Quantum mechanics near closed-timelike-lines", David Deutsch, web.archive.org/web/201604010....
-"Localized Closed Timelike Curves Can Perfectly Distinguish Quantum States", Todd A. Brun, Jim Harrington, Mark M. Wilde, arxiv.org/abs/0811.1209.
-"Closed Timelike Curves Make Quantum and Classical Computing Equivalent", Scott Aaronson and
John Watrous, arxiv.org/abs/0808.2669.
Watch the previous video which explains how quantum teleportation really works:
• Quantum Teleportation ...
Watch the other videos in the Quantum Paradoxes series:
• Quantum Paradoxes
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New to qubits and quantum circuits? Check out the Understanding Quantum Information and Computation lecture series: • Understanding Quantum ...
#qiskit #ibmquantum #learnquantum

Пікірлер: 21

@diemilio 5 ай бұрын

Cool video! During Xanadu's QHack 2023 challenges, there was a problem where you had to code an quantum algorithm to solve a SAT problem using qubits that could travel backwards in time. I thought this concept was extremely interesting; I even have a video explaining how this works.

@maria_violaris 5 ай бұрын

Thanks! That sounds like a fun coding activity, it's cool that people are exploring how time-loops could in theory enable computing and very nice that you have video tutorials on the problems! 😄

@rin_4659 5 ай бұрын

Wow this channel just popped up on my recommendations, awesome to see you Maria after qotc last year :)

@maria_violaris 5 ай бұрын

Hey! Yes I first started making this series of Quantum Paradoxes videos a while ago and it's part of what inspired me to create QotC! Hope everything's going well 😄 In case anyone sees this - QotC is "Quantum on the Clock", a competition I ran with the IOP QQQ group in 2022 for High School students to create 3-minute videos about quantum science and technology. The winning videos are available to watch on the IOP KZfaq channel: kzfaq.info/sun/PLnpAhkiu3jSbicIhAm1gWS21EY_9fq3Hb&si=CX8gfLRbCVeDc7pN.

@cwc137 5 ай бұрын

Delightful!

@chandruv9537 5 ай бұрын

Informative😊

@JavSusLar 5 ай бұрын

1:14 future Maria: "I said all the exact things you are saying, and here..." Past Maria: "stop there, say a random number, but different from the one your future you said". TAKE THAT, TIMELINE.

@maria_violaris 5 ай бұрын

Future Maria: “Haha, I tried that trick too! But my future self didn’t tell me a random number!” 😄 That being said - my conversation between past and future selves did brush over the interesting detail of free choice as an observer in a time-loop. It’s a problem for classical CTCs that it seems the time-travellers are extra restricted in what actions they can do in the time-loop. Quantum CTCs in the many-worlds theory resolve this problem, because if your actions in the time-loop change the future, they will correspond to a different future quantum branch compared to the future branch you came from. The consistency condition ensures that the branches line up so everything makes sense. This is the sense in which the quantum consistency condition really resolves the grandfather paradox, in a way that the classical version of it wouldn’t :)

@lucadepaoli4790 5 ай бұрын

Great video Maria!!!! I have a question: if I change the state of the CTC after the measurement in the end of the circuit and than i measure the state of the CTC in the beginning of the circuit It changes?????

@maria_violaris 5 ай бұрын

Glad you liked the video! After the measurement in the end of the circuit, the CTC qubit must go back into the time-loop. According to the consistency condition I show at 6:33, the state of the CTC qubit going into the time-loop must be the same as that coming out of the time-loop at the beginning of the circuit. For a particular |Ψ_in> and U, the CTC qubit's state is fixed. It cannot be "changed" in any way after the measurement, or the time-loop won't be self-consistent anymore so it will give a contradiction. Hope that helps!

@lucadepaoli4790 5 ай бұрын

@@maria_violaris thank you so much for the very clear answer!!!!👍👍👍

@PetraKann 5 ай бұрын

How is Quantum Mechanics interpreted?

@maria_violaris 5 ай бұрын

See my videos on Schrödinger's cat (kzfaq.info/get/bejne/qaikdMhpp9mzmHU.htmlsi=4OpHO9jSSnjcabM3) and a test for the many-worlds interpretation against the Copenhagen interpretation (kzfaq.info/get/bejne/Y791oLWZ1M3Fg4U.htmlsi=xUfxfZO2wbSZixva) to find out more about the implications of interpretations of quantum mechanics on quantum computing.