Sensor Uses Quantum Entanglement to Detect Magnetic Excitation

Using the principle of quantum entanglement, scientists at the University of Tokyo’s Research Center for Advanced Science and Technology (RCAST) demonstrated the coupling of a millimeter-size magnetic sphere with a sensor and showed that the sensor could determine if a single magnetic excitation was present in the sphere. A millimeter-size 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 the resonant cavity, and in turn, the coupling of the cavity to the qubit, the qubit could only be excited by an electromagnetic pulse if no magnetic excitations were present in the sphere. Using the...