Quantum simulator accessible to the world

Experimental physicists have put a lot of effort in isolating sensitive measurements from the disruptive influences of the environment. In an international first, Innsbruck quantum physicists have realized a toolbox of elementary building blocks for an open-system quantum simulator, where a controlled coupling to an environment is used in a beneficial way.
An ion interacts with the quantum system and, at the same time, establishes a controlled contact to the environment. (Graphics: Harald Ritsch)

Many phenomena in our world are based on the nature of quantum physics: the structure of atoms and molecules, chemical reactions, material properties, magnetism and possibly also certain biological processes. Since the complexity of phenomena increases exponentially with more quantum particles involved, a detailed study of these complex systems reaches its limits quickly; and conventional computers fail when calculating these problems. To overcome these difficulties, physicists have been developing quantum simulators on various platforms, such as neutral atoms, ions or solid-state systems, which, similar to quantum computers, utilize the particular nature of quantum physics to control this complexity. In a special issue at the end of 2010, the scientific journal Science chose the progress made in this field as one of the scientific breakthroughs of the year 2010.

Using controlled dissipation

The physicists use a natural phenomenon In their experiments that they usually try to minimize as much as possible: environmental disturbances. Such disturbances usually cause information loss in quantum systems and destroy fragile quantum effects such as entanglement or interference. In physics this deleterious process is called dissipation. Innsbruck researchers, led by experimental physicists Julio Barreiro and Philipp Schindler as well as the theorist Markus Müller, have now been first in using dissipation in a quantum simulator with trapped ions in a beneficial way and engineered system-environment coupling experimentally. “We not only control all internal states of the quantum system consisting of up to four ions but also the coupling to the environment,” explains Julio Barreiro. “In our experiment we use an additional ion that interacts with the quantum system and, at the same time, establishes a controlled contact to the environment,“ explains Philipp Schindler. The surprising result is that by using dissipation, the researchers are able to generate and intensify quantum effects, such as entanglement, in the system. “We achieved this by controlling the disruptive environment,“ says an excited Markus Müller.

Putting the quantum world into order

