A. Stepanenko

K. S. Chernova

M. A. Gorlach

We use the quantum brachistochrone method to design an optimal control strategy for the fastest quantum state transfer in long qubit chains.

Large-scale qubit arrays promise to deliver powerful quantum processors but demand fast, high-fidelity state transfer. Using a modified quantum brachistochrone method, we find the time-optimal protocol for moving a single excitation across a tunable nearest-neighbor chain. The scheme achieves the quantum speed limit with transfer time scaling linearly with length, surpassing stepwise and perfect-transfer strategies.

Recent technological advances have allowed the fabrication of large arrays of coupled qubits serving as prototypes of quantum processors. However, the optimal control of such systems is notoriously hard, which limits the potential of large-scale quantum systems. Here, we investigate a model problem of quantum state transfer in a large nearest-neighbor-coupled qubit array and derive an optimal control that simultaneously enables maximal fidelity and minimal time of the transfer.

Optimal transfer

Time-optimal transfer of the quantum state in long qubit arrays