Linear-optical simulation of the cooling of a cluster-state Hamiltonian system

摘要

A measurement-based quantum computer could consist of a local-gappedHamiltonian system, whose thermal states --at sufficiently low temperature--are universal resources for the computation. Initialization of the computerwould correspond to cooling the system. We perform an experimental quantumsimulation of such cooling process with entangled photons. We preparethree-qubit thermal cluster states exploiting the equivalence between localdephasing and thermalisation for these states. This allows us to tune thesystem's temperature by changing the dephasing strength. We monitor theentanglement as the system cools down and observe the transitions fromseparability to bound entanglement, and then to free entanglement. We alsoanalyze the performance of the system for measurement-based single-qubit statepreparation. These studies constitute a basic characterisation of experimentalcluster-state computation under imperfect conditions.