(SciTechDaily) Scientists from the Research Center for Advanced Science and Technology (RCAST) at The University of Tokyo demonstrated a method for coupling a magnetic sphere with a sensor via the strange power of quantum entanglement. They showed that the existence of even a single magnetic excitation in the sphere could be detected with a one-shot measurement. This work represents a major advancement toward quantum systems that can interact with magnetic materials.
In the experiments conducted at RCAST, a millimeter-sized sphere of yttrium iron garnet was placed 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, we were able to make our device both highly sensitive and very fast,” Professor Yasunobu Nakamura explains. “This research could open the way for sensors powerful enough to help with the search for theoretical dark-matter particles called axions.”

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