Experimental demonstration of two-photon magnetic resonances in a single-spin-system of a solid

While the manipulation of quantum systems is significantly developed so far, achieving a single-source multi-use system for quantum-information processing and networks is still challenging. A virtual state, a so-called ``dressed state," is a potential host for quantum hybridizations of quantum physical systems with various operational ranges. We present an experimental demonstration of a dressed state generated by two-photon magnetic resonances using a single spin in a single nitrogen-vacancy center in diamond. The two-photon magnetic resonances occur under the application of microwave and radio-frequency fields, with different operational ranges. The experimental results reveal the behavior of two-photon magnetic transitions in a single defect spin in a solid, thus presenting new potential quantum and semi-classical hybrid systems with different operational ranges using superconductivity and spintronics devices.Comment: 9 pages, 7 figures, Revised manuscript and figure

Arithmetic topology in Ihara theory

Ihara initiated to study a certain Galois representation which may be seen as an arithmetic analogue of the Artin representation of a pure braid group. We pursue the analogies in Ihara theory further, following after some issues and their inter-relations in the theory of braids and links such as Milnor invariants, Johnson homomorphisms, Magnus-Gassner cocycles and Alexander invariants, and study relations with arithmetic in Ihara theory.Comment: 66pages, to appear in Publ. Res. Inst. Math. Sci., corrected typo