  Semiconductor quantum-dot spin qubits are a promising platform for quantum
computation, because they are scalable and possess long coherence times. In
order to realize this full potential, however, high-fidelity information
transfer mechanisms are required for quantum error correction and efficient
algorithms. Here, we present evidence of adiabatic quantum-state transfer in a
chain of semiconductor quantum-dot electron spins. By adiabatically modifying
exchange couplings, we transfer single- and two-spin states between distant
electrons in less than 127 ns. We also show that this method can be cascaded
for spin-state transfer in long spin chains. Based on simulations, we estimate
that the probability to correctly transfer single-spin eigenstates and two-spin
singlet states can exceed 0.95 for the experimental parameters studied here. In
the future, state and process tomography will be required to verify the
transfer of arbitrary single qubit states with a fidelity exceeding the
classical bound. Adiabatic quantum-state transfer is robust to noise and
pulse-timing errors. This method will be useful for initialization, state
distribution, and readout in large spin-qubit arrays for gate-based quantum
computing. It also opens up the possibility of universal adiabatic quantum
computing in semiconductor quantum-dot spin qubits.
