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The complexity of the selection procedure of a genetic algorithm that requires reordering, if we restrict the class of the possible fitness functions to non–local or time–dependent fitness functions, is O (N log N) where N is the size of the population. Quantum Genetic Algorithm (QGA) exploits the power of quantum computation in order to speed up genetic… (More)

- Simone Montangero, Tommaso Calarco, Rosario Fazio
- Physical review letters
- 2007

Quantum optimal control theory allows us to design accurate quantum gates. We employ it to design high-fidelity two-bit gates for Josephson charge qubits in the presence of both leakage and noise. Our protocol considerably increases the fidelity of the gate and, more important, it is quite robust in the disruptive presence of 1/f noise. The improvement in… (More)

- Tommaso Caneva, Tommaso Calarco, Simone Montangero
- 2011

In this work, we describe in detail the chopped random basis (CRAB) optimal control technique recently introduced to optimize time-dependent density matrix renormalization group simulations Here, we study the efficiency of this control technique in optimizing different quantum processes and we show that in the considered cases we obtain results equivalent… (More)

- Patrick Doria, Tommaso Calarco, Simone Montangero
- Physical review letters
- 2011

We present an efficient strategy for controlling a vast range of nonintegrable quantum many-body one-dimensional systems that can be merged with state-of-the-art tensor network simulation methods such as the density matrix renormalization group. To demonstrate its potential, we employ it to solve a major issue in current optical-lattice physics with… (More)

- Zbigniew Idziaszek, Tommaso Calarco, Peter Zoller
- 2007

We consider a system composed of a trapped atom and a trapped ion. The ion charge induces in the atom an electric dipole moment, which attracts it with an r −4 dependence at large distances. In the regime considered here, the characteristic range of the atom-ion interaction is comparable or larger than the characteristic size of the trapping potential,… (More)

We apply theoretically open-loop quantum optimal control techniques to provide methods for the verification of various quantum coherent transport mechanisms in natural and artificial light-harvesting complexes under realistic experimental constraints. We demonstrate that optimally shaped laser pulses allow to faithfully prepare the photosystem in specified… (More)

- Alexey V Gorshkov, Tommaso Calarco, Mikhail D Lukin, Anders S Sørensen
- 2008

We use the numerical gradient ascent method from optimal control theory to extend efficient photon storage in ⌳-type media to previously inaccessible regimes and to provide simple intuitive explanations for our optimization techniques. In particular, by using gradient ascent to shape classical control pulses used to mediate photon storage, we open up the… (More)

- S. van Frank, A. Negretti, T. Berrada, R. Bücker, S. Montangero, J.-F. Schaff +3 others
- Nature communications
- 2014

The Ramsey interferometer is a prime example of precise control at the quantum level. It is usually implemented using internal states of atoms, molecules or ions, for which powerful manipulation procedures are now available. Whether it is possible to control external degrees of freedom of more complex, interacting many-body systems at this level remained an… (More)

- Tommaso Caneva, Tommaso Calarco, Rosario Fazio, Giuseppe E Santoro, Simone Montangero
- 2011

The number of defects which are generated upon crossing a quantum phase transition can be minimized by choosing properly designed time-dependent pulses. In this work we determine what are the ultimate limits of this optimization. We discuss under which conditions the production of defects across the phase transition is vanishing small. Furthermore we show… (More)

- Shmuel Fishman, Gabriele De Chiara, Tommaso Calarco, Giovanna Morigi
- 2008

A chain of singly charged particles, confined by a harmonic potential, exhibits a sudden transition to a zigzag configuration when the radial potential reaches a critical value, depending on the particle number. This structural change is a phase transition of second order, whose order parameter is the crystal displacement from the chain axis. We study… (More)