A fundamental requirement in the circuit model of quantum information processing is the realization of fault-tolerant multi-qubit quantum gates with entangling capabilities. A key step towards this end is to achieve control of qubit states through geometric phases at very small spatial scales in an effective and feasible way. A spin-electric coupling present in antiferromagnetic triangular single-molecule magnets (SMMs) allows for manipulation of the spin (qubit) states with a great flexibility. Here, we establish an all-electrical two-qubit geometric phase shift gate acting on the four-fold ground state manifold of a triangular SMM, which represents an effective two-qubit state space. We show that a two-qubit quantum gate with arbitrary entangling power can be achieved through the Berry phase effect, induced by adiabatically varying an external electric field in the plane of the molecule.
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