Real-world Quantum Hall Circulators
Work started in the Aachen University group continues under the umbrella of PGI-11, in an effort to take the basic idea of the Hall circulator and adapt it further to real-world conditions. A problem with the original proposal is that it would produce a very high impedance device, i.e., one that would not match well to the 50-ohm microwave world.
While conventional impedance matching is possible, current work shows that resonant behaviour intrinsic to the capacitively-coupled Hall device itself can cause the device to self-impedance match, which could result in a profoundly reduced size of the on-chip circulating device. The group currently has a cooperation with a group at the University of Sydney that is carrying out experiments on these concepts.