Geometric spin echo under zero field

TL;DR

This paper demonstrates a geometric spin echo technique in a nitrogen vacancy center in diamond that operates under zero magnetic field, leveraging symmetry breaking to preserve coherence without dynamic control.

Contribution

It introduces a novel geometric control method for degenerate spins at zero magnetic field, enabling long coherence times without dynamic manipulation.

Findings

Successful demonstration of geometric spin echo at zero field

Protection of degenerate spins via zero-field splitting

Potential applications in quantum memory and biosensing

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 center 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.