Geometric spin echo under zero field.

Yuhei Sekiguchi,Shota Mishima,Yusuke Komura,Touta Tanaka,Hideo Kosaka,Naeko Niikura

doi:10.1038/ncomms11668

Yuhei Sekiguchi, Shota Mishima + Show 4 more

Open Access

https://doi.org/10.1038/ncomms11668

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Journal: Nature Communications	Publication Date: May 19, 2016
Citations: 46	License type: CC BY 4.0

Affiliation: Yokohama National University

Abstract

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.

Highlights

Spin echo is a fundamental tool for quantum registers and biomedical imaging
Those demonstrations introduced an energy gap to the qubit for controllability, here we show that it is possible to control a degenerate logical qubit, which we call a geometric spin qubit, by a purely geometric gate operation and that it can be protected by zero-field splitting with the help of a time-reversal operation, which we call geometric spin echo
Our experimental demonstration of geometric spin control is based on the application of resonant microwave to electron spin in a diamond Nitrogen vacancy (NV) centre under a zero magnetic field