@article{oai:ynu.repo.nii.ac.jp:00009296,
 author = {Sekiguchi, Yuhei and Komura, Yusuke and Mishima, Shota and Tanaka, Touta and Niikura, Kaeko and Kosaka, Hideo},
 journal = {Nature Communications},
 month = {May},
 note = {Spin echo is a fundamental tool for quantum registers and biomedical imaging. It is believed that a strong magnetic field is needed for the spin echo to provide long memory and high resolution, since a degenerate spin cannot be controlled or addressed under a zero magnetic field. While a degenerate spin is never subject to dynamic control, it is still subject to geometric control. Here we show the spin echo of a degenerate spin subsystem, which is geometrically controlled via a mediating state split by the crystal field, in a nitrogen vacancy centre in diamond. The demonstration reveals that the degenerate spin is protected by inherent symmetry breaking called zero-field splitting. The geometric spin echo under zero field provides an ideal way to maintain the coherence without any dynamics, thus opening the way to pseudo-static quantum random access memory and non-invasive biosensors.},
 title = {Geometric spin echo under zero field},
 volume = {7},
 year = {2016}
}