Dr. Boaz Almog is research physicist and member of the superconductivity group at Tel Aviv University in Israel. Dr. Almog spoke at this year’s The UP Experience to the topic, "The Future of Quantum Physics," by demonstrating and explaining the phenomenon of quantum levitation.
Quantum levitation occurs when an electrical superconductor interacts with external magnets. The magnetic field lines passing through the superconductor are constrained to behave like quantum particles (flux tubes), locking themselves (and the superconductor) in place.
Quantum levitation research comprises three generations of work to date. It forces new intuitions of physical behavior because it is quantum made visible. Practical applications, years away, include stronger magnets (allowing smaller MRI units for broader healthcare services), more powerful particle accelerators (for cost effective research), more powerful motors, mechanical energy storage for electrical grid buffering, and superconducting wires.
The demonstration – quantum made visible
Dr. Almog took a 3 inch disk, coated in superconductor, that had been sitting in liquid nitrogen. Using tweezers, Almog placed the disk over a strong magnet. The disk hovered in place over the magnet, not touching it. Although this looks like simple magnetic levitation, Almog explained, it is not. To prove it, he turned the magnet upside down. The disk hovered exactly in place without falling. There were gasps from the audience. Almog explained that the magnetic lines that are going through the superconductor are being pushed away by the superconductor. Since it can’t push them all away, it has to let some of the lines pass through. It does this grudgingly, and actually "locks" them in place. In whichever position you place the disk over or under the magnet, the superconductor will lock it in place. Almog demonstrated that the disk would hold firmly in position, even when placed at a 45° angle. It did not have to be flat relative to the magnet, as in simple levitation.
Almog gave the disk a spin, explaining that this was near frictionless rotation. Only air pressure could slow the disk’s spin. If placed in a vacuum, the disk could spin for weeks.
Dr. Almog moved to a 2 foot diameter circular railroad track made of magnets, and set the disk to slide along the track. Instead of sliding off the far end, the disk stayed perfectly lined up on the circle going around and around at speed. To remind us again that this is a new intuition, he moved the disk underneath the track where it slid at speed just as easily as before. Finally, Almog took two disks and slid them in opposite directions on the same side of the track, where they proceeded perfectly without ever bumping into each other.
A superconductor has zero electrical resistance. When a superconductor encounters an external magnetic field, it attempts to expel the external field by creating its own internal field via resistance-less electrical currents. The interaction between the fields creates the magnetic field "locking" at the quantum level. The disk is held suspended between upper and lower antagonists: quantum levitation. This is quantum made visible!
Practical applications are being investigated. Current superconductors typically require tremendously cold temperatures (e.g., liquid nitrogen). They also require special alloys (e.g., Yttrium) and substrates (sapphire).
Image courtesy: Ted.com
Video courtesy: Quantumlevitation.com
The UP Experience 2012 speaker announced – Dr. Boaz Almog
The UP Experience