96 research outputs found
On the practicality of time-optimal two-qubit Hamiltonian simulation
What is the time-optimal way of using a set of control Hamiltonians to obtain
a desired interaction? Vidal, Hammerer and Cirac [Phys. Rev. Lett. 88 (2002)
237902] have obtained a set of powerful results characterizing the time-optimal
simulation of a two-qubit quantum gate using a fixed interaction Hamiltonian
and fast local control over the individual qubits. How practically useful are
these results? We prove that there are two-qubit Hamiltonians such that
time-optimal simulation requires infinitely many steps of evolution, each
infinitesimally small, and thus is physically impractical. A procedure is given
to determine which two-qubit Hamiltonians have this property, and we show that
almost all Hamiltonians do. Finally, we determine some bounds on the penalty
that must be paid in the simulation time if the number of steps is fixed at a
finite number, and show that the cost in simulation time is not too great.Comment: 9 pages, 2 figure
Calibration of cardy-ion meters to measure nutrient concentrations in soil solution an in plant sap
Hidrólise da uréia em latossolos: efeito da concentração de uréia, temperatura, pH, armazenamento e tempo de incubação
Teores foliares e esclerofilia de Calophyllum brasiliense Cambess. (Clusiaceae) e suas relações edáficas no litoral do Estado do Paraná, Brasil
Soil carbon and nitrogen stocks in traditional agricultural and agroforestry systems in the semiarid region of Brazil
Nutrient composition of mature and litter leaves and nutrient mobilization in leaves of tree species from secondary rainforests in the South of Brazil
Estoques de carbono e nitrogênio e frações orgânicas de Latossolo submetido a diferentes sistemas de uso e manejo
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