USING QUBITS TO LEARN ABOUT IT

JUAN PABLO PAZ

SCIENCE AND ULTIMATE REALITY

CAMBRIDGE UNIVERSITY PRESS

Lugar: CAMBRIDGE; Año: 2004; p. 300 - 320

Almost a century after its birth, quantum theory remains odd and counterintuitive. As Richard Feynman wrote, it seems that nobody really understands it. This is indeed true if by understanding we mean being able to explain it using our common sense and everyday experience. The developement of some kind of ``quantum common sense´´ has been very slow even though our everyday life is being continuously influenced by technologies whose deep roots lay in quantum laws. In recent years the growing field of quantum information and quantum computation became a fruitful playground for physicists, matematicians, computer scientists and researchers from other fields that developed new interesting ways of storing, transmitting and processing information using quantum mechanics at its best. Thus, both theoretical and experimental research on multiparticle entanglement, on the manipulation of individual quantum systems, on decoherence and the transition from quantum to classical are subjects of interest not only for their basic relevance but also by their potential practical significance as they might be of help for the development of a real quantum computer. Even if this technology may be far away in our future, it is interesting to speculate which lessons on quantum reality could be learned about from quantum computation (eg., if one could operate a quantum computer). From a physicist perspective this is much more interesting than, for example, being able to efficiently factor large numbers or rapidly search a giant database (two of the most important killer applications known today). In this paper I will give a simple presentation of current research on the area of physics simulations on quantum computers. Among the applications discussed, that would enable us to learn about quantum properties of natural systems I will mention both the simulation of spectroscopy and state tomography (which can be viewed as dual forms of quantum computation). Lessons learned from these studies will hopefully help us develop our quantum intuition and, maybe, enable us to finally understand the quantum.