Quantum Levitation and Superconductors

quantum levitation

I was mesmerized the first time I saw the quantum levitation (also known as quantum locking) experiment, in which a disk containing a superconductor hovers above some magnets. The superconductor can even glide freely over a track of magnets – even upside down (VIDEO 1).

I was so impressed by this experiment that I just had to try it out for myself. I was able to receive some grant funds1 to purchase a quantum levitation system.2 Since acquiring one of these systems, I have spent a lot of time experimenting with superconductors and reading about how they work.3-7 Specifically, I wanted to understand how it could be that superconductors could levitate near a track of magnets – especially when the track of magnets was turned upside down. Although I am very far from an expert on superconductors, I do think I have developed a rudimentary understanding of how they behave. The video below (Video 1) is a presentation of some quantum locking and quantum levitation experiments, along with some explanations for how this curious behavior occurs.

Video 1: Superconductivity and Quantum Locking Explained, , May 2021


There is a lot of dense information contained in the video, so I thought I’d expand upon some of these ideas below. As I stated before I am not an expert in superconductivity, so please do let me know in the comments how my explanations and understandings might be improved.

Superconductors are materials that are made of ordinary ceramics – and yet they are remarkable materials. A common superconducting material is comprised of a mixed metal oxide that contains the elements yttrium, barium, copper, and oxygen. (YBa2Cu3O7, or YBCO). When superconductors are cooled beneath a certain temperature called the critical temperature, they take on magnetic and electric properties that behave in very curious ways. The critical temperature for a YBCO superconductor is 93 K.3-7

When a magnet is placed near a superconductor cooled to below its critical temperature, the superconductor appears to repel the magnet. However, it is actually the superconductor that repels the magnet’s field. The fact that superconductors repel magnetic fields is known as the Meissner Effect.3-7 A magnet placed above a superconductor falls due to gravity. However, for the magnet to fall onto the superconductor, the superconductor must be pushed directly against the surface of the magnet so that the two are touching. But if this were to happen, the magnetic field from the magnetic would penetrate the superconductor – but superconductors repel magnetic fields! Because of this, the superconductor is repelled by the magnetic field given off by the magnet. This repulsion causes a force upwards on the superconductor – enough force is generated that the superconductor becomes suspended in the air!

Because of the Meissner Effect, the electric field, e, inside a superconductor is zero. To see this, imagine electrons flowing in a superconducting wire fashioned into a closed loop (Figure 1). The electric current density, j, in such a wire can found to be:4

j = se,                         Equation 1

Interestingly, the conductivity, s, is infinite for superconductors! According to j = se, if s is infinite, then the current density must also be infinite – and this is impossible! The solution to this problem lies in the fact that e  = 0 inside all superconductors. This scenario makes it possible to have infinite conductivity but finite current density.

Figure 1: Current flowing in a superconducting ring. The red arrow indicates electric current. Blue arrows represent magnetic field lines flowing through the ring.


The important point here is that e = 0 inside a superconductor. This fact has interesting applications for “locking” a superconductor in a magnetic field. To see this, we’ll start with Faraday’s Law:4

                            Equation 2

Where dφdt is the change in the magnetic flux through the ring. Certainly, this equation looks a bit daunting. However, recognizing that e  = 0 inside the superconductor, we see that the left-hand side is zero:4

                                 Equation 3

Ah, this is much simpler now! Equation 3 assures us that the magnetic flux through a superconductor cannot change with time. So according to Equations 2 and 3, current flowing in a superconducting ring produces magnetic flux that cannot change with time. Now notice that if the current stops, the magnetic flux will as well. Because of this, the electric current must continue forever (superconduction) to keep the magnetic flux constant!  

When a Type 2 superconductor (Figure 2) is placed in a magnetic field, the magnetic field penetrates at microscopic impurities embedded in the superconductor (Video 1, 2:34–5:50).3-4,7 Ring currents like those described above get set up around the impurities located in the superconductor. The term flux tube is used to describe the system of ring current, impurity, and penetrating magnetic field.3-4,7 The magnetic field penetrating the flux tubes locks the superconductor in place, because changes to the magnetic field through all the flux tubes is resisted.

Figure 2: A Type 2 superconductor (grey rectangular solid) in a magnetic field (blue arrows). The magnetic field penetrates impurities (white rings) in the superconductor. The flow of field lines through the impurities must stay constant, which locks the superconductor in place.


Flux tubes that are penetrated by constant magnetic field explain why a Type 2 superconductor can hover undisturbed above or below a magnetic field. Once locked in place, the magnetic flux through the flux tubes cannot change. Movement of the superconductor closer to – or away from – the magnets changes the strength of the magnetic field. Changing the field naturally changes the flux through the tubes, which can’t happen. Thus, the superconductor remains locked in place (Video 1, 9:03 – 9:30).

On the other hand, the superconductor can freely move over a constant magnetic field, such as near a circular magnet or a circular magnetic track (Video 1, 9:30 – 10:10). However, it will resist but moving into regions where the field is different, such as off the track.

As stated previously, I welcome comments for improvements to my understanding of superconductivity and quantum levitation that I have described here. Also, I would love to hear if any suggestions you might have for experiments to try that involve superconductors and quantum levitation.

Happy experimenting!


1.  Thanks to the Hurst and Bauervic Foundations for their generous support of this work.

2. Magnet, track, and superconductors were purchased at:

3. Quantum Levitation Booklet:

4. James F. Annett, Superconductivity, Superfluids and Condensates. Oxford University Press, 2004.

5. Stephen Blundell, Superconductivity: A very short introduction. Oxford University Press, 2009.

6. Gianfranco Vida, Superconductivity: The Next Revolution? Cambridge University Press, 1993.

7. Tank, H. et. al Study of Quantum Levitation and Locking in High Temperature Superconductors and Ways of Cooling IJESJ, 2018, 8 (4), 17186-17190.



Students who demonstrate understanding can plan and conduct an investigation to provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current. 

*More information about all DCI for HS-PS2 can be found at .


Students who demonstrate understanding can plan and conduct an investigation to provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current. 

Assessment Boundary:

Assessment is limited to designing and conducting investigations with provided materials and tools.