|Image: Graphic Harald Ritsch|
The properties of the quantum physics underlying many phenomena of our world: the structure of atoms and molecules, chemical reactions, material properties, magnetism, and possibly some biological processes. Detailed understanding comes quickly but are limited because the complexity of the phenomena involved with the growing number of quantum particles rises rapidly. Conventional computers fail very quickly in the calculation of such problems. Physicists are thus developing for several years on various platforms such as neutral atoms, ions or solid state quantum systems, simulators, which use similar quantum computer, the special properties of quantum physics to manage this complexity. At the turn of the journal Science has named the progress in this area one of the scientific breakthroughs of 2010. A team of young researchers from the groups of Rainer Blatt and Peter Zoller at the Institute of Experimental Physics and Theoretical Physics, University of Innsbruck and the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences (AAS), these efforts brings now an essential step further. They have first developed a comprehensive toolkit for an open quantum computer, designed with the future in larger quantum simulators to study complex problems can be.
Controlled disturbances desired
The scientists use to a property that is usually minimized in experiments as possible: interference from the environment. Quantum systems lose information and disturbances are usually fragile quantum effects like entanglement or superposition be destroyed. The physics of this process is called dissipation. The Innsbruck researchers around the experimental physicist Julio Barreiro and Philipp Schindler and use the theorist Mark Muller, the dissipation of their quantum simulator of trapped ions for the first time profitably by constructing the coupling to the environment artificially. "We are not only the quantum system from up to four ions control in all its internal states, but also its connection to the environment," said Julio Barreiro. "In our experiment, we use to an additional ion, which interacts with the quantum system, while producing a controlled contact with the outside world," explains Philipp Schindler. The surprising result: dissipation can be quantum effects within the system, produce such as entanglement, targeted and strengthen. "We achieved this through the strategic use of the disturbing environmental factor in itself," said Markus Mueller.
Dissipation creates order in the quantum world
In one experiment, the researchers demonstrate the successful use of dissipation, by fully using the immersion environment entangled four ions. "In contrast to the usual procedures for this to work regardless of the initial states of the individual particles," said Mueller. "Through a collective cooling process, the particles are pushed into a common state." In this way, many-body states can be generated, which otherwise can be produced and observed only in the environment very well isolated quantum systems. This profitable use of the environment allows it to realize new types of quantum dynamics and to explore systems that were previously difficult to access experimentally. In theory, in recent years used a reflection of how dissipation no longer relate only suppressed, but also actively used as a resource for the construction of quantum computers and quantum memory can. In close cooperation between theorists and experimental physicists in Innsbruck, it is successfully able to implement these basic effects successfully in a quantum simulator.
The Innsbruck researchers were supported among others by the Austrian Science Fund FWF, the European Commission and the Tyrolean industry.
Julio T. Barreiro, Markus Muller, Philipp Schindler, Daniel Nigg, Thomas Monz, Michael Chwalla, Markus Hennrich, Christian F. Roos, Rainer Blatt and Peter Zoller: An Open-system quantum simulator with Trapped Ions. Nature 470, 486-491 (24 February 2011).