Coherent transfer of singlet-triplet qubit states in an architecture of triple quantum dots

We propose two schemes to coherently transfer arbitrary quantum states of the two-electron singlet-triplet qubit across a chain of 3 quantum dots. The schemes are based on electrical control over the detuning energy of the quantum dots. The first is a pulse-gated scheme, requiring dc pulses and engineering of inter- and intra-dot Coulomb energies. The second scheme is based on the adiabatic theorem, requiring time-dependent control of the detuning energy through avoided crossings at a rate that the system remains in the ground state. We simulate the transfer fidelity using typical experimental parameters for silicon quantum dots. Our results give state transfer fidelities between $94.3\% < \mathcal{F} < 99.5\%$ at sub-ns gate times for the pulse-gated scheme and between $75.4\% < \mathcal{F} < 99.0 \%$ at tens of ns for the adiabatic scheme. Taking into account dephasing from charge noise, we obtain state transfer fidelities between $94.0\% < \mathcal{F} < 99.2\%$ for the pulse-gated scheme and between $64.9\% < \mathcal{F} < 93.6\%$ for the adiabatic scheme.