Quantum locking

Matthew Cobb sent me this YouTube video, which is described as follows:

Tel-Aviv University demos quantum superconductors locked in a magnetic field.

The explanation is above my pay grade, but the video is cool. I’m counting on some physics-friendly readers to explain it.


  1. Posted October 18, 2011 at 4:02 am | Permalink

    That was very entertaining! I look forward to someone explaining it 🙂

    • Orlando
      Posted October 18, 2011 at 6:37 am | Permalink

      Deepak Chopra hears you and is preparing an explanation, which naturally boils down to consciousness creating reality.

      That is, human consciousness. Other animal consciousness apparently does not affect reality as they do not have quantum souls.

      • Orlando
        Posted October 18, 2011 at 7:48 am | Permalink

        Pardon moi for replying to my own post, but Deepak and his ilk might do well to read mystery writer Rex Stout, whose quirky Nero Wolfe proclaims: “I cannot remake the universe, and must therefore put up with this one.”

    • Parag Dixit
      Posted October 18, 2011 at 11:12 am | Permalink

      It’s only a guess based on what I remember from Physics :
      It can be explained on the basis of Lenz’s law – whenever magnetic field changes, it produces closed loops of electric field in a direction such that the resulting current (if any conductor is present) would oppose the change in magnetic field. Suppose a superconductor is kept next to a magnet, any change of it’s distance from magnet will produce electric field-loops which will produce huge amount of current opposing the change in magnetic field (and hence the motion). So, in simple terms, if you try to move it away from north-pole of a magnet, the superconductor will behave like a south pole and get attracted towards it, and if you try to move it closer to N-pole, it’ll behave as a North-pole and will get repelled.
      On a circularly symmetric magnet, it can rotate in circle without change in magnetic field through it.
      I don’t know why they called it quantum locking, and if there are quantum mechanical theory that explains the same behavior.. Of course the amount of energy spent in super-cooling the conductor will be much greater in the amount that is saved because of ‘lack-of-friction’ , otherwise this thing would have been implemented like crazy at all places in all moving parts of machines…

      • Justin
        Posted October 18, 2011 at 11:47 am | Permalink

        I’m sure there are applications where supercooling a part of an object would be worth frictionless movement, but I wonder how it could be made useful. Suppose you attach a weight to the superconductor to use it like a train. How much weight could be carried, and what parameters is that based on? The strength of the magnet? How difficult would it be to insulate the cargo from the superconductor?

        I wonder, can the superconductor be completely shrouded, so that it’s not exposed to the air? In that case you could just encase a massive superconductor in a refrigeration unit, stick it over a magnetic track, and it would be able to work without any exposure to the air. Some pretty interesting devices could be imagined…

  2. Posted October 18, 2011 at 4:03 am | Permalink

    I want one of those contraptions; my oldest just turned 16. I have a plan involving her, this quantum locking bit, and a permanent configuration / rotation rate for our pet pitbull.

    • Dominic
      Posted October 18, 2011 at 5:42 am | Permalink

      Let us hope she does not read this page!

    • Grey
      Posted October 19, 2011 at 1:47 pm | Permalink

      Perfect example of when the cost to cool is worth the benefit gained from lack of friction.

      Well played, sir.

  3. Tom Phoenix
    Posted October 18, 2011 at 4:14 am | Permalink

    I believe it’s the Meissner effect you’re seeing. Magnetic fields cannot freely pass through a superconductor. Once the superconductor is pushed onto a “track” of magnetic fields, it cannot easily escape.


    • Posted October 18, 2011 at 5:47 am | Permalink

      I am not so sure. That wouldn’t explain the upside-down locking.

      • Tom Phoenix
        Posted October 18, 2011 at 10:31 am | Permalink

        Why not upside down?

        A superconductor resists letting a magnetic field move through it. When the superconducting disk is forced into the field, the so-called magnetic field lines become pinned within the body of the disk or on either side of it. The disk is now like a bead on a string; it can still move freely along the lines, but not across them, even if the track is upside down.

        Repositioning the disk requires another force (such as that provided by the experimenter’s hand) to force the magnetic field to pass through or around the superconductor.

    • Posted October 18, 2011 at 5:54 am | Permalink

      I’m not so sure. From what I understand of the Meisner effect is that it is a diamagnetic effect – meaning that it creates a repulsing force to the magnetic field. Therefore the Meisner effect can explain the levitation, but not why it also keeps the disk in place when holding the magnet or the track upside down. No doubt this new effect is somehow related to the Meisner effect though.

    • Posted October 18, 2011 at 6:14 am | Permalink

      According to this site that may have been made by the people that made the youtube video, it is the Meissner effect, but with the special feature of the target being a thin crystal, so the magnetic field does penetrate, but in a curved way on both sides of the crystal. By the looks of it, the crystal is “pinched” in place by the magnetic field.

      As a bonus, they show how they made it here 8)

      • Torbjorn Larsson, OM
        Posted October 18, 2011 at 1:17 pm | Permalink

        It is adding a bit gee whiz to catch the watcher.

        – Many superconductors fails gracefully because they will admit quantized flux tubes (vortex lines, fluxons) at higher fields and/or temperatures. So they behave like this too.

        – Using a new-fangled “we-don’t-know-the-physics-yet” high temperature superconductor, hence the convenient sufficiency of liquid nitrogen, would perhaps necessitate a thin film to have defects such as grain boundaries admit flux tubes, but …

        – These HTSC are only (?, or mostly) made as thin films anyway.

        But it is all within the permissible stretch of a video maker. Or book writer… =D

      • Torbjorn Larsson, OM
        Posted October 18, 2011 at 1:22 pm | Permalink

        Oops, I forgot: you also have to tune the flux tube effect to appear with the chosen field (and temperature), so again thin films helps with relatively weak permanent magnets.

  4. Marella
    Posted October 18, 2011 at 4:45 am | Permalink

    Why does anyone need fairies when reality is this weird?

    • Stackpole
      Posted October 18, 2011 at 4:58 am | Permalink

      Come on, now. Just what or who do you think IS holding the little ice cube in place?

      • Posted October 18, 2011 at 5:19 am | Permalink


      • Posted October 18, 2011 at 7:37 am | Permalink

        It’s quantum angels, heathen.

      • Ian
        Posted October 18, 2011 at 11:41 am | Permalink

        An invisible turtle?

        • Posted October 18, 2011 at 4:53 pm | Permalink

          But what is the invisible turtle standing on? HA! Gotcha!

          • JBS
            Posted October 18, 2011 at 8:56 pm | Permalink

            Turtles all the way down, of course.

          • Rocco
            Posted October 18, 2011 at 9:01 pm | Permalink

            He isn’t standing at all. He’s a supercooled superconductor floating on a magnet.

          • Alan Macphail
            Posted October 19, 2011 at 12:39 am | Permalink

            Ha! Its turtles all the way down!

    • Graham Martin-Royle
      Posted October 18, 2011 at 5:38 am | Permalink


    • Grey
      Posted October 19, 2011 at 1:53 pm | Permalink

      I read an intriguing thing on the webs somewhere discussing the fact that we have more evidence for the existence of fairies than we do for electrons.

      Just thought I’d throw that out there, since you brought it up. lol


  5. Posted October 18, 2011 at 4:46 am | Permalink

    Looks fascinating. I wonder how it scales up though.

  6. heleen
    Posted October 18, 2011 at 5:08 am | Permalink

    Here’s a levitating frog:

  7. Rod
    Posted October 18, 2011 at 5:21 am | Permalink

    Dawkins is right….. reality is magic, and someone, somewhere understands it and can explain it.

    • Posted October 18, 2011 at 6:18 am | Permalink

      Reading his new book to my 8 year old daughter now. It’s wonderful.

      I’ll be passing it on to my mother next (she found his Greatest Show and Jerry’s WEIT too “boring”). Her religious views make it hard for her to concentrate!

      • Michael Fisher
        Posted October 18, 2011 at 10:46 am | Permalink

        “Her religious views make it hard for her to concentrate!”

        I’ve noticed this with my Christian friends. I can’t decide if the reason is as you describe it or
        The sort of people who are drawn to Christian belief are non-analytical & therefore struggle to follow the thread of a reasoned argument. In other words…

        Theists are soundbite people

        • PB
          Posted October 18, 2011 at 6:20 pm | Permalink

          “Theists are soundbite people”

          How true.

  8. NewEnglandBob
    Posted October 18, 2011 at 6:16 am | Permalink

    (subscribing to hear the explanation).

  9. Posted October 18, 2011 at 6:19 am | Permalink

    “Fascinating”, in my best Spock impression.
    Here is a good explanation.


    These maglev trains should be Cris-crossing the Americas, but superstition keeps dragging us backward.

    • Adam M.
      Posted October 18, 2011 at 10:08 am | Permalink

      Great video!

    • Tim
      Posted October 19, 2011 at 10:30 am | Permalink

      Unless the ‘superstition we’re talking about is the belief that whatever the fossil fuel lobby says is ‘holy’ becasue it has to do with some mythical ‘free market’, I’m not clear why it is superstition that is holding us back.

      You’re right, of course – that we should be building these things, I mean. But let’s be honest, the fact that the superconductor contains yttrium and the tracks contain neodymium and the world is already feeling the pinch from rare earth shortages also is holding us back. It is worth mentioning that demand for neodymium in Nd₂Fe₁₄B is also being driven by their use in high-efficiency motors in wind turbines and lots of other places. The squeeze on rare earths is a big and very real deal.

  10. 3cat
    Posted October 18, 2011 at 6:36 am | Permalink

    A longer video with explanation. Includes a speed bump and double levitation.

    • Posted October 18, 2011 at 9:15 am | Permalink

      Superconductors expel magnetic fields. Giving the Meissner effect a different name and then getting the physics wrong is a crappy thing to do.

      • Posted October 24, 2011 at 8:33 pm | Permalink

        Turns out I got the physics wrong: The superconductor is Type II, so some lines of magnetic flux do penetrate the superconducting sample (“flux tubes”).

        The traditional name is “flux pinning.”

  11. Sigmund
    Posted October 18, 2011 at 7:00 am | Permalink

    So it’s basically a flying beer mat that can keep your drink cold?
    Isn’t science wonderful!

    • wilzard
      Posted October 19, 2011 at 12:12 am | Permalink


  12. Posted October 18, 2011 at 8:22 am | Permalink

    Yea, we love the Israeli University podcasts as well.

    Let’s not for Deepak Chopra can explain all things quantum as well.

  13. Still learning
    Posted October 18, 2011 at 9:07 am | Permalink

    Wow! We’re one step closer to personal jet packs, right?

  14. Posted October 18, 2011 at 9:08 am | Permalink

    Another vote for the Meissner effect.

  15. Dr. I. Needtob Athe
    Posted October 18, 2011 at 9:18 am | Permalink

    That was NOT an appropriate usage of the expression “above my pay grade.” You’re not necessarily above or below the people who understand how that thing works, you only happened to choose a different branch of science.

  16. Posted October 18, 2011 at 9:34 am | Permalink

    That is a fantastic video, I saw it on Twitter yesterday. The comment by Rixaeton is exactly what I would have written.

    In particular, that page


    that they link to gives a pretty decent explanation. Things floating because they expel magnetic fields is old news, but the trick here is that the expulsion is imperfect; there are some lines of magnetic flux that penetrate the very thin superconductor. Those act kind of like guide wires, locking the thing in place.

    Note that the earlier levitating frog came from the lab of Andre Geim, and his work won him the coveted Ig Nobel Prize. Later that same lab discovered graphene, and he won the equally-coveted Nobel Prize.


  17. Still learning
    Posted October 18, 2011 at 5:18 pm | Permalink

    Heck, you know cats can do the same thing, only in a more rudimentary form…

  18. PB
    Posted October 18, 2011 at 6:31 pm | Permalink

    #16 explanation in the website is clear.http://www.quantumlevitation.com/levitation/The_physics.html

    Meissner effects on thin superconductor, so that there is quantum effects on the flux-tubes that hold the disc in space.

    Amazing! Theoretical physics and technological savvy! Wonder of nature and human mind..

    The explanation from website is clear and compact.

    –from website–
    We start with a single crystal sapphire wafer and coat it with a thin (~1µm thick) ceramic material called yttrium barium copper oxide (YBa2Cu3O7-x ). The ceramic layer has no interesting magnetic or electrical properties at room temperature. However, when cooled below -185ºC (-301ºF) the material becomes a superconductor. It conducts electricity without resistance, with no energy loss. Zero.

    Superconductivity and magnetic field do not like each other. When possible, the superconductor will expel all the magnetic field from inside. This is the Meissner effect. In our case, since the superconductor is extremely thin, the magnetic field DOES penetrates. However, it does that in discrete quantities (this is quantum physics after all! ) called flux tubes.

    Inside each magnetic flux tube superconductivity is locally destroyed. The superconductor will try to keep the magnetic tubes pinned in weak areas (e.g. grain boundaries). Any spatial movement of the superconductor will cause the flux tubes to move. In order to prevent that the superconductor remains “trapped” in midair.

    • PB
      Posted October 18, 2011 at 6:43 pm | Permalink

      Sorry for self reply, I cannot stop wondering, this is “magic at its highest” (as Dumbledore might say).

      Read “Any spatial movement of the superconductor will cause the flux tubes to move”, and because of this the superconductor is “not allowed to move in space” or trapped in space (huh?)

      A theoretical construct, an abstract one at that, tested using high precision materials (technology), and found validated! Against common sense of laymen.

      And repeated, again and again (will we have a hovercraft later? personal?).

      This is, verily, magic at its highest form…. and wonderfully, this magic is open to everyone who are willing to learn, much easier if done from those specialists who are willing to popularize their special knowledge.

      As in the above website. And for biology, by Coyne, Dawkins et al. Thanks!!

    • PB
      Posted October 18, 2011 at 7:03 pm | Permalink

      What if you use room temperature superconductor? On a flexible lattice.

      Can we then have a personal levitating suit? Plus a small motor, personal hovercraft? heh heh heh … (wolfish grin..)

  19. Mohan Malhotra
    Posted October 18, 2011 at 9:46 pm | Permalink

    Truely amazing video-‘GOD works in mysterious way!’ quipped my religious friend, as scientific explanations just pass over his brain without making any impact.

  20. Jan
    Posted October 19, 2011 at 3:24 am | Permalink

    Cant we build a very large version of this and use the magnetic field of earth to fly around?

    Posted October 19, 2011 at 5:43 am | Permalink

    Sounds just like Jeff Goldblum (esp. at 1:00).

  22. Colin
    Posted October 19, 2011 at 1:00 pm | Permalink

    All very cool and everything, but just how much of a force (like the demonstrators hand) is required to un-quantum lock it? A gust of wind, gravity, a curious fly?

    • PB
      Posted October 19, 2011 at 9:07 pm | Permalink

      This is a very technologically important question, have they quantized it? How big a disk and magnet could support how much load?

      Seems feasible, but we need numbers.

  23. Posted October 19, 2011 at 3:03 pm | Permalink

    Great video! o__o

  24. Posted October 24, 2011 at 8:46 pm | Permalink

    I talked with some of my friends about this video today and had to come over to this comment thread and correct myself, on record. I’m glad that Ethan Siegel wrote this post (linked in an above comment by Tom Phoenix).

%d bloggers like this: