Professor Yasunobu Nakamura and his colleagues at the Research Center for Advanced Science and Technology (RCAST) have succeeded in developing a new quantum sensor using superconducting qubits. They have developed a mechanism that detects a quantum entanglement between a superconducting qubit and a single energy quantum excited in a ferromagnet called a magnon, making it possible to detect even a single collectively excited energy quantum in a single trial measurement. This mechanism can be applied to the detection of axions, one of the candidates for dark matter in the universe, and is attracting attention as a new quantum sensor. The paper was published in the online edition of Science on 24 January.