Generalized Hahn echo for neutral atom qutrits

Scaling qubit-based quantum systems requires effective strategies to suppress and mitigate errors arising from unwanted couplings to the environment, such as magnetic-field gradients, differential light shifts, and laser-beam inhomogeneities. For qubits, commonly used techniques include the Hahn echo, which employs an intermediate Pauli-X operation to refocus inhomogeneous dephasing, as well as multi-pulse dynamical decoupling sequences.

Extending such error-suppression methods to higher-dimensional systems is of significant interest, as qudits promise notable advantages for quantum simulation, quantum information processing and multiparameter quantum sensing. In this work, we experimentally demonstrate the creation of qutrit states encoded in atomic ground states and extend their coherence time by more than an order of magnitude using a generalized Hahn-echo protocol. The protocol is implemented using all-optical, single-step SU(3) operations designed via optimal control.

Our results open the door to realizing more sophisticated dynamical decoupling sequences for qudits based on single-step SU(d) operations, which may offer more favorable error scaling compared to implementations relying on decompositions into multiple SU(2) operations.