Catálogo de publicaciones - libros

This year marks the tenth anniversary of the algorithms Peter Shor wrote for factoring and computing discrete logarithms on a quantum computer. It is no understatement to say that those algorithms have revolutionized our thinking about information processing and computability. By showing that there are certain, meaningful problems that are better solved on a quantum computer than on a classical computer, they inspired us to try to tame the weird world of quantum phenomena in order to reap these revolutionary benefits. Spurred by the importance and promise of this fundamentally new form of information processing, worldwide interest in research related to quantum information processing has skyrocketed in the intervening years. One measure of the remarkable impact of Shor’s algorithms is seen in the United States’ investment in quantum information, which rose from under $5M in 1994 to more than $100M in 2004.

We discuss the progress (or lack of it) that has been made in discovering algorithms for computation on a quantum computer. Some possible reasons are given for the paucity of quantum algorithms so far discovered, and a short survey is given of the state of the field.

Nuclear magnetic resonance (NMR) has provided a valuable experimental test-bed for quantum information processing (QIP). Here, we briefly review the use of nuclear spins as qubits, and discuss the current status of NMR-QIP Advances in the techniques available for control are described along with the various implementations of quantum algorithms and quantum simulations that have been performed using NMR. The recent application of NMR control techniques to other quantum computing systems are reviewed before concluding with a description of the efforts currently underway to transition to solid state NMR systems that hold promise for scalable architectures.

We discuss the basic aspects of quantum information processing with trapped ions, including the principles of ion trapping, preparation and detection of hyper-fine qubits, single-qubit operations and multi-qubit entanglement protocols. Recent experimental advances and future research directions are outlined.

The scheme of an ion trap quantum computer is described and the implementation of quantum gate operations with trapped Ca ions is discussed. Quantum information processing with Ca ions is exemplified with several recent experiments investigating entanglement of ions.

We give a brief overview of cavity-QED and its roles in quantum information science. In particular, we discuss setups in optical cavity-QED, where either atoms serve as stationary qubits, or photons serve as flying qubits.

Quantum information can be processed using large ensembles of ultracold and trapped neutral atoms, building naturally on the techniques developed for high-precision spectroscopy and metrology. This article reviews some of the most important protocols for universal quantum logic with trapped neutrals, as well as the history and state-of-the-art of experimental work to implement these in the laboratory. Some general observations are made concerning the different strategies for qubit encoding, transport and interaction, including trade-offs between decoherence rates and the likelihood of two-qubit gate errors. These trade-offs must be addressed through further refinements of logic protocols and trapping technologies before one can undertake the design of a general-purpose neutral-atom quantum processor.

We discuss prospects for building a silicon-based quantum computer with phosphorous donor qubits. A specific architecture is proposed for initial demonstrations; and the advantages and difficulties of this approach are described along with a plan for systematic development and calibration of the individual components.

We review progress on the spintronics proposal for quantum computing where the quantum bits (qubits) are implemented with electron spins. We calculate the exchange interaction of coupled quantum dots and present experiments, where the exchange coupling is measured via transport. Then, experiments on single spins on dots are described, where long spin relaxation times, on the order of a millisecond, are observed. We consider spin-orbit interaction as sources of spin de-coherence and find theoretically that also long de-coherence times are expected. Further, we describe the concept of spin filtering using quantum dots and show data of successful experiments. We also show an implementation of a read out scheme for spin qubits and define how qubits can be measured with high precision. Then, we propose new experiments, where the spin decoherence time and the Rabi oscillations of single electrons can be measured via charge transport through quantum dots. Finally, all these achievements have promising applications both in conventional and quantum information processing.

The spins of localized electrons in silicon are strong candidates for quantum information processing because of their extremely long coherence times and the integrability of Si within the present microelectronics infrastructure. This paper reviews a strategy for fabricating single electron spin qubits in gated quantum dots in Si/SiGe heterostructures. We discuss the pros and cons of using silicon, present recent advances, and outline challenges.