Universal coherence protection in a solid-state spin qubit

Unlike their classical counterparts, qubits exhibit quantum phase coherence. All physical realizations of qubits, however, suffer from decoherence channels that eventually destroy the phase information encoded within the qubit. Mitigating these unwanted interactions is of paramount importance in quantum science. Here, we demonstrate a significant advance in protecting a solid-state spin qubit from decoherence channels caused by impurities and fluctuations in its host crystal. By hybridizing an applied microwave drive with the ground state electron spin of a silicon carbide divacancy defect, we construct a robust qubit and prepare it in a decoherence-protected subspace. Once embedded in this subspace, the qubit becomes largely insensitive to magnetic, electric, and temperature fluctuations, which account for nearly all relevant decoherence channels in the solid state. This culminates in an increase of the qubit’s inhomogeneous dephasing time by over four orders of magnitude (to>22 milliseconds), while its Hahn-echo coherence time approaches 64 milliseconds. This readily translatable result indicates that substantial coherence improvements can be achieved in a wide selection of quantum architectures, and charts a path forward for many facets of quantum engineering, including the creation of robust hybrid quantum systems interfacing with otherwise weakly interacting quantum subsystems