Phys.org February 19, 2020
Researchers in Japan placed a millimeter-sized sphere of yttrium iron garnet in the same resonant cavity as a superconducting Josephson junction qubit, which acted as the sensor. Because of the coupling of the sphere to resonant cavity, and, in turn, between the cavity to the qubit, the qubit could only be excited by an electromagnetic pulse if no magnetic excitations were present in the sphere. Reading the state of the qubit then reveals the state of the sphere. By using single-shot detection instead of averaging, they were able to make the device both highly sensitive and very fast. This research could open the way for sensors powerful enough to help with the search for theoretical dark-matter particles called axions…read more. TECHNICAL ARTICLE
Schematic of modes of interest in the single-magnon detector. Credit: ©Dany Lachance-Quirion