The low temperature state when the magnitude of the spin (degree of freedom of the angular momentum of the electron) is an integer is called the Holden state.In this state, there is strong entanglement between spins (correlation effect between different quanta that appears by superposition of states), and two qubits (information unit of quantum calculation) are attached to two spins located at both ends of a one-dimensional chain. ) Equivalent to the degree of freedom.

　In addition, the development of quantum computers that actively utilize this state is expected from both aspects of basic science and engineering applications.On the other hand, the reproduction of the Holden state requires an integer spin, and the elements that realize this are very limited, so no active attempt has been made so far.

　K2Cu3O (SO4) 3 (mineral name: Fedotovite) is a mineral found at Tolbachik volcano on the Kamchatka Peninsula.The research group artificially synthesized this material under the name of "edge-shared tetrahedral quantum spin cluster chain" because of its structural characteristics, and experimentally and theoretically investigated the internal magnetism from around room temperature to 4K or less.As a result, it was found that the holding tetrahedral cluster (formed by 6 copper ions) has a one-dimensional interaction with sulfate ions, so that the Holden state is realized.Furthermore, it was found that the Holden state may appear as a low temperature state only when the number of side-shared tetrahedra is even.

　By generalizing this finding, we also provided a guideline for artificially reproducing the Holden state.In the future, it is expected that more flexible quantum computer design guidelines will be constructed.

Paper information:[Physical Review Letters] Cluster-Based Haldane State in an Edge-Shared Tetrahedral Spin-Cluster Chain: Fedotovite K2Cu3O (SO4) 3