  We introduce an adiabatic transfer protocol for spin states in large quantum
dot arrays that is based on time-dependent modulation of the Heisenberg
exchange interaction in the presence of a magnetic field gradient. We refer to
this protocol as spin-CTAP (coherent transport by adiabatic passage) in analogy
to a related protocol developed for charge state transfer in quantum dot
arrays. The insensitivity of this adiabatic protocol to pulse imperfections has
potential advantages for reading out extended spin qubit arrays. When the
static exchange interaction varies across the array, a quantum-controlled
version of spin-CTAP is possible, where the transfer process is conditional on
the spin states in the middle of the array. This conditional operation can be
used to generate N-qubit entangled GHZ states. Using a realistic noise model,
we analyze the robustness of the spin-CTAP operations and find that
high-fidelity (>95%) spin eigenstate transfer and GHZ state preparation is
feasible in current devices.
