title: Universal quantum computation with the exchange interaction.
abstract: Various physical implementations of quantum computers are being investigated, although the requirements that must be met to make such devices a reality in the laboratory at present involve capabilities well beyond the state of the art. Recent solid-state approaches have used quantum dots, donor-atom nuclear spins or electron spins; in these architectures, the basic two-qubit quantum gate is generated by a tunable exchange interaction between spins (a Heisenberg interaction), whereas the one-qubit gates require control over a local magnetic field. Compared to the Heisenberg operation, the one-qubit operations are significantly slower, requiring substantially greater materials and device complexity--potentially contributing to a detrimental increase in the decoherence rate. Here we introduced an explicit scheme in which the Heisenberg interaction alone suffices to implement exactly any quantum computer circuit. This capability comes at a price of a factor of three in additional qubits, and about a factor of ten in additional two-qubit operations. Even at this cost, the ability to eliminate the complexity of one-qubit operations should accelerate progress towards solid-state implementations of quantum computation.
authors: IBM Research Division, T. J. Watson Research Center, Yorktown Heights, New York 10598, USA. divince@watson.ibm.com
authors: D P
authors: DP
authors: DiVincenzo
authors: D
authors: D
authors: Bacon
authors: J
authors: J
authors: Kempe
authors: G
authors: G
authors: Burkard
authors: K B
authors: KB
authors: Whaley