Storage of entangled logical states in decoherence-free subspaces for seconds
Phys. Rev. A 114, 012448 – Published 20 July, 2026
DOI: https://doi.org/10.1103/6xg5-8wx9
Abstract
The maintenance of quantum entanglement lays the elementary building block of quantum information processing, requiring an integration of long coherence time, sufficient storage capacity, and high-fidelity entangling gates. Here, we encode two-qubit entangled states into the decoherence-free subspaces (DFS) of four ions in a cryogenic Paul trap. We apply crosstalk-free sympathetic cooling under dual-type encoding and perform multistate detection that distinguishes the collision-induced leakage error from the qubit levels. By postselecting the leakage-free events, we achieve a storage lifetime of about 1 h for the entangled logical states. We further study the second-order DFS and show its advantage in suppressing the spatially nonuniform noise over the first-order DFS. Our work extends the storage capacity of a DFS quantum memory to support entangled logical states, with wide applications in quantum computing and precision measurement, as well as in each local node of a quantum network.
