A spookily good sensor using quantum entanglement

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.

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.

The work is published in the journal Science. (Japan Science and Technology Agency)

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