Adriano Barenco

CONDITIONAL QUANTUM DYNAMICS AND LOGIC GATES

Quantum logic gates provide fundamental examples of conditional quantum dynamics. They could form the building blocks of general quantum information processing systems which have recently been shown to have many interesting nonclassical properties. We describe a simple quantum logic gate, the quantum controlled-NOT, and analyze some of its applications. We discuss two possible physical realizations of the gate, one based on Ramsey atomic interferometry and the other on the selective driving of optical resonances of two subsystems undergoing a dipole-dipole interaction.

Quantum networks for elementary arithmetic operations

Quantum computers require quantum arithmetic. We provide an explicit construction of quantum networks effecting basic arithmetic operations: from addition to modular exponentiation. Quantum modular exponentiation seems to be the most difficult (time and space consuming) part of Shors quantum factorizing algorithm. We show that the auxiliary memory required to perform this operation in a reversible way grows linearly with the size of the number to be factorized. \textcopyright{} 1996 The American Physical Society.

Universality in Quantum Computation

We show that in quantum computation almost every gate that operates on two or more bits is a universal gate. We discuss various physical considerations bearing on the proper definition of universality for computational components such as logic gates.

A Universal Two-Bit Gate for Quantum Computation

We prove the existence of a class of two-input, two-output gates any one of which is universal for quantum computation. This is done by explicitly constructing the three-bit gate introduced by Deutsch ( Proc. R. Soc. Lond. A 425, 73 (1989)) as a network consisting of replicas of a single two-bit gate.

Stabilization of Quantum Computations by Symmetrization

We propose a method for the stabilization of quantum computations (including quantum state storage). The method is based on the operation of projection into

Approximate Quantum Fourier Transform and Decoherence

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Dense Coding Based on Quantum Entanglement

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Effects of noise on quantum error correction algorithms

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Stabilisation of Quantum Computations by Symmetrisation

redundant copies of the computer. We describe an efficient algorithm and quantum network effecting

Un salto de escala para los calculadores

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