title: Molecular nanomagnets with switchable coupling for quantum simulation.
abstract: Molecular nanomagnets are attractive candidate qubits because of their wide inter- and intra-molecular tunability. Uniform magnetic pulses could be exploited to implement one- and two-qubit gates in presence of a properly engineered pattern of interactions, but the synthesis of suitable and potentially scalable supramolecular complexes has proven a very hard task. Indeed, no quantum algorithms have ever been implemented, not even a proof-of-principle two-qubit gate. Here we show that the magnetic couplings in two supramolecular {Cr7Ni}-Ni-{Cr7Ni} assemblies can be chemically engineered to fit the above requisites for conditional gates with no need of local control. Microscopic parameters are determined by a recently developed many-body ab-initio approach and used to simulate quantum gates. We find that these systems are optimal for proof-of-principle two-qubit experiments and can be exploited as building blocks of scalable architectures for quantum simulation.
authors.affiliation: 1] Dipartimento di Fisica e Scienze della Terra, Università di Parma, Parco Area delle Scienze 7/a, 43124 Parma, Italy [2] Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Chiesa
authors.affiliation: School of Chemistry and Photon Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: George F S
authors.initials: GF
authors.lastname: Whitehead
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, Parco Area delle Scienze 7/a, 43124 Parma, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Carretta
authors.affiliation: School of Chemistry and Photon Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Laura
authors.initials: L
authors.lastname: Carthy
authors.affiliation: School of Chemistry and Photon Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Grigore A
authors.initials: GA
authors.lastname: Timco
authors.affiliation: Advanced Light Source, Lawrence Berkeley Laboratory, MS2-400 Berkeley, California 94720, USA.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Teat
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, Parco Area delle Scienze 7/a, 43124 Parma, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Amoretti
authors.affiliation: 1] Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany [2] JARA High-Performance Computing.
authors.forename: Eva
authors.initials: E
authors.lastname: Pavarini
authors.affiliation: School of Chemistry and Photon Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Richard E P
authors.initials: RE
authors.lastname: Winpenny
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, Parco Area delle Scienze 7/a, 43124 Parma, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Santini