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Video URL

http://youtu.be/I7oZAo8hJnU

Video Description

Is it possible to detect the presence of an object without interacting with it? For instance, can we take a photograph of an object without bouncing off photons from it? In a classical world such a feat is impossible: to see, you need to reflect photons from the observed object and collect them in your eye. However, in a quantum mechanical world it is a piece of cake. In this short thriller, Vlatko Vedral, a professor of quantum physics, explains how it is possible.

Video Creator Bio

Dagomir Kaszlikowski is a quantum physicist who spends his spare time making short movies.

Fun idea to base a short film on! I appreciate the cinematography that went into this video as well as the physics explanation that went into it at the end. One of my critiques would be that I thought the initial short was a little bit drawn out. I found myself losing focus during certain parts of the film. Otherwise, I thought it was well made and interesting!

    20 days later
    8 days later

    This is one of my favorite videos. Well made and very informative. The set up is a bit different from the Elitzur-Vaidman bomb tester which is mentioned above by Cristinel Stoica and this leads me to my one question: if the bomb is inside a suitcase would not the photon detect if there is a suitcase in the path, but unless the photon can (in principle) penetrate the suitcase wouldn't the result be that one could tell if the suitcase was in the path or not, but not whether there is a bomb inside? In the explanation given at the end of the video I think this is taken into account since in the drawing on the "clear" board a hole is drawn in the green suitcase which would allow the photon to enter. Or are we missing something? Anyway even if a tiny hole would need to be made in the suitcase this is a very minor plot point, but the video really sparked us to discuss this and also do a bit of homework on this (although the above question was something we did not reach agreement on).

    Best of luck,

    Mike, Max, Dan, Simon, Doug

      Dear Mike, Max, Dan, Simon and Doug,

      Thank you very much for your kind comments about our video. It's encouraging and exciting that through our short movie we managed to spark your interest in the Elitzur-Vaidman bomb tester. This is reward enough for us!

      You are very observant. Yes, Vlatko would have to somehow bore a hole in the suitcase in order to obstruct the photon's way with a potential bomb inside it. Any stray photons would detonate the bomb and all our protagonists would "kiss the night goodbye":-) We skipped this detail in the movie to make it simpler and to keep a reasonable dramatic pace.

      I remember my surprise when I heard about the Elitzur-Vaidman bomb for the first time. It was truly mind-boggling for me in spite of the fact that I had been working as a quantum physicist for at least ten years at the time. Many years later I had the pleasure to meet Prof. Vaidman and had a very pleasant dinner with him during which I realised that he is one of the coolest quantum physicists around!

      Quantum mechanics is cool!

      Thank you very much for your kind words and Wikipedia's link. Initially we planned to create a webpage with a detailed written explanation but it seems that old good Wikipedia does the job!

      Dagomir,

      Congratulations for a very imaginative video! You nicely recreated a retro film noir ambiance in the intro movie, and Vlatko's explanation at the end was very clear --- clever use of a clear board makes it even cooler! That said, the intro movie was perhaps a bit long (as already mentioned by another reviewer), and it would have been nice if the defusing of the bomb in the intro movie had been a little bit more explicit: perhaps Vlatko could have brought the suitcase to a dark room and drilled holes in it, to eliminate the risk that photons from the streetlights would trigger it. Also, at the very end of the video, during Vlatko's explanation, it would have been a nice plus if a schematic of the 5 beam splitter / 10 mirrors setup could have been shown... But of course these are little details: overall, yours is a very strong entry. You nicely illustrated the fun and coolness of quantum mechanics, and I predict your video will do very well in this contest! Good luck!

      Marc

      P.S. Compared to the regular FQXi essay contests, the video creators seem to be reluctant to rate each other's videos, and, as you may have noticed, it looks like very few videos will get to the 10 community votes threshold needed to be even considered for the final round (if you are not already a FQXi member). If you have the time to take a look at my trilogy of videos "This Is Physics", where I try to convey the "fun of physics" by focusing on some of the greatest moments of its history, it would be quite appreciated!

        Hi. Brilliantly executed and very entertaining to watch. I agree with some of the comments above that the intro movie is perhaps a little long, and perhaps a bit hard to follow at times. But that aside, this is undoubtedly one of the most ingeniously done and fun-to-watch videos in the contest.

        Best wishes,

        Tejinder

          Dear Marc,

          Thank you very much for your kind words and a constructive criticism of our short film. Such a critical look by other filmmakers is invaluable to evolve in the art of movie making.

          Many thanks!

          Dag

          Dear Tejinder,

          Many thanks for your kind words! We are grateful for your comments as they will allow us to grow as filmmakers.

          Thank you very, very much!

          Best

          Dag

          Dear Mr. Fisher,

          Thank you very much for your comments on our short film.

          I did watch your video and I must admit that I do not understand your theory so I am unable to make any insightful comments. However, I would like to point out that your statement about uniqueness of drips of water seems to be invalid. Water, like everything else, is made of elementary particles and those are identical.

          Best

          Dag

          Hello,

          I came to say that I truly enjoyed your idea of dressing a quantum mechanical problem as a thriller subject.

          I must say it took me a while to open the video since it was a bit long, but that is due to the really nice theatrical introduction. I assume you hold a position as faculty, in which case you might benefit from a slightly shorter intro, one that presents the set up concisely before the explanation. Either that or my students have shorter attention spans... =)

          Feel free to look at our video, in which we discuss what is quantum gravity, present an existing solution and give examples of applications and future directions:

          http://fqxi.org/community/forum/topic/2221

          Good job!

          ---Pedro.

          Dear dagomir

          i too am blown away by your video ,wonderful making sense of holograghy,just voted for you .Kindly take your time to view and vote for my simple video here-

          http://fqxi.org/community/forum/topic/2223.

          It details how the universe requires only one quantum operator on a dirac to completely unravel what einstein thought of as Dice.its not so drab i couldnt afford to make it better but i tried to my best.all the best.

          7 days later

          I was wondering why this video was at the top of the list... now I know. One of the most professional entries I've seen, and the first to actually teach me something that, even with a master's in physics, I'd never seen before! (Well, not the interferometer, obviously, but an arbitrarily accurate bomb-detector?? Sweet!)

          I liked the style of the movie, although as stated by some of the other people, I felt like there was quite a bit more build-up than was really needed, and it could have maybe been better spent on actually dramatizing for us how you detected the bomb in the end. But you know what they say... everyone's a critic. I have absolutely no complaints about the physics; it was spot-on.

          If you feel like watching/rating my videos, they're the A Capella Science ones. Hope to be sharing a prize with you!

          Cheers,

          -Tim

          3 months later
          8 years later
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