The Innsbruck research group led by physicist Rainer Blatt suggests a fundamentally new architecture for quantum computation. In an international first, they have experimentally demonstrated quantum antennae, which enable the exchange of quantum information between two separate memory cells located on a computer chip. This offers new opportunities to build practical quantum computers. The researchers have published their work in the scientific journal Nature.

In an experiment carried out in 2009, our group has performed a quantum simulation of the Dirac equation using a single trapped ion and observed so called Zitterbewegung, a peculiar quivering motion of free relativistic quantum particles predicted by the Dirac equation. In a recent experiment we have implemented a more sophisticated quantum simulation, which made it possible to observe another counter-intuitive prediction of the Dirac equation: the Klein paradox.

The entanglement of quantum objects can take surprising forms. The quantum physicists at the University of Innsbruck, Prof. Rainer Blatt and Dr. Julio Barreiro, have investigated several facets of entanglement in four trapped ions and report their results in the journal Nature Physics. Their study promotes further developments towards quantum computing and a deeper understanding of the foundations of quantum mechanics.

In a recent experiment, our group has performed a quantum simulation of the Dirac equation using a single trapped ion and observed so called Zitterbewegung, a peculiar quivering motion of free relativistic quantum particles predicted by the Dirac equation.

Testing hidden-variable theories of quantum physics using trapped ions

A new important building block for a future quantum computer has been realised by physicists at the Institute for Experimental Physics in Innsbruck and the Institute for Quantum Optics and Quantum Information (IQOQI): a gate acting on three quantum bits, the so-called Toffoli gate, as has been reported in Physical Review Letters.

Entanglement—once only a subject of disputes about the foundation of quantum mechanics—has today become an essential issue in the emerging field of quantum information processing, promising a number of applications, including secure communication, teleportation and powerful quantum computation. Therefore, a focus of current experimental work in the field of quantum information is the creation and manipulation of entangled quantum systems. Here, we present our results on entangling two qubits in an ion-trap quantum processor not through a direct interaction of the ion qubits but instead through the action of a protocol known as entanglement swapping.

Choosing the rules of quantum physics as the physical basis for constructing models of computation allows for solving certain computational problems more efficiently as in models based on classical physics. In the quantum circuit model, information is encoded in quantum bits and manipulated by applying appropriate quantum operations acting on the joint state space of the qubits. Similar to what is done in classical computation, these quantum operations can be decomposed into a sequence of gate operations, consisting of single-qubit operations and entangling operations acting on pairs of qubits.