Quantum Zeno subspaces by repeated multi-spin projections

TL;DR

This paper demonstrates that repeated multi-spin projections create quantum Zeno subspaces, enhancing coherence times and controlling multi-qubit states, with implications for quantum information processing.

Contribution

It experimentally shows that repeated joint measurements form Zeno subspaces in multi-qubit systems, suppressing dephasing and enabling logical qubit encoding.

Findings

Dephasing time scales with the number of projections independently of spin count.

Repeated projections create coherent Zeno subspaces in multi-spin systems.

Enhanced coherence times observed through repeated joint measurements.

Abstract

Repeated observations inhibit the coherent evolution of quantum states through the quantum Zeno effect. In multi-qubit systems this effect provides new opportunities to control complex quantum states. Here, we experimentally demonstrate that repeatedly projecting joint observables of multiple spins creates coherent quantum Zeno subspaces and simultaneously suppresses dephasing caused by the environment. We encode up to two logical qubits in these subspaces and show that the enhancement of the dephasing time with increasing number of projections follows a scaling law that is independent of the number of spins involved. These results provide new insights into the interplay between frequent multi-spin measurements and non-Markovian noise and pave the way for tailoring the dynamics of multi-qubit systems through repeated projections.