Thermal States as Universal Resources for Quantum Computation with   Always-on Interactions
  Measurement-based quantum computation utilizes an initial entangled resource state and proceeds with subsequent single-qubit measurements. It is implicitly assumed that the interactions between qubits can be switched off so that the dynamics of the measured qubits do not affect the computation. By proposing a model spin Hamiltonian, we demonstrate that measurement-based quantum computation can be achieved on a thermal state with always-on interactions. Moreover, computational errors induced by thermal fluctuations can be corrected and thus the computation can be executed fault-tolerantly if the temperature is below a threshold value. 
Ying Li, Daniel E. Browne, Leong Chuan Kwek, Robert Raussendorf,   Tzu-Chieh Wei
quant-ph