Novel schemes for measurement-based quantum computation
Prof. Jens Eisert (Imperial College, London)

We establish a framework which allows one to construct novel schemes for measurement-based quantum computation. In such schemes, one fully abandons the need for exact unitary control: Quantum computation then amounts to merely performing local measurements at single sites of a quantum lattice system, so to "reading out the system'.
Candidates for such physical systems are architectures based on cold atoms in optical lattices. Our technique further develops tools from many-body physics to go beyond the cluster-state based one-way computer. It hence constitutes an instance where ideas of many-body theory are used in quantum information processing, and not vice versa. We identify resource states that are radically different from the cluster state, in that they exhibit non-vanishing correlation functions, can partly be prepared using gates with non-maximal entangling power, or have very different local entanglement properties. In the computational models, the randomness is compensated in a different manner. It is shown that there exist resource states which are locally arbitrarily close to a pure state. We remark on the idea of tailoring the computational model to actual physical systems at hand. Throughout the talk, we will address the question of implementations using ultracold atoms in optical lattices.