Parity Measurement in Ultrastrong Coupling Regime
  The measurement of the parity of two qubits is a primitive of quantum computing that allows creating deterministic entanglement. In the field of circuit quantum electrodynamics, a scheme to achieve parity measurement of two superconducting qubits has been proposed and analyzed under the usual rotating-wave approximation (RWA). We show that the same scheme can be carried over beyond this approximation, to the regime of ultrastrong coupling, with an improvement in the fidelity. 
Jing Yan Haw, Yimin Wang, Valerio Scarani
quant-ph