Extended Ground-Rydberg Qubit T1 in a Cryogenic Atom Array

We report the realization of a 133Cs optical tweezer array operated in a cryogenic blackbody radiation (BBR) environment and present progress toward achieving high-fidelity two-qubit gates under such conditions. By enclosing the atoms within a 4K radiation shield and employing single-photon Rydberg excitation, we measure extended ground–Rydberg qubit relaxation times T1, reaching up to 406(36) μs for the 55P3/2 Rydberg state. This represents an improvement by a factor of 3.3(3) compared to measurements at room temperature and corresponds to an effective BBR temperature of 10 K(+13 K/-10 K), indicating more than an order-of-magnitude suppression of BBR-induced transitions.

These results establish a pathway toward advancing neutral-atom two-qubit gate fidelities as error budgets increasingly become dominated by the fundamental limit imposed by the ground–Rydberg T1. In addition, we demonstrate the technical components required for implementing two-qubit gates with ground state Cs qubits in this regime and provide an analysis of the expected error budgets.