Low-error measurement-free PHASE gates for qubus computation

We discuss the desired criteria for a two-qubit PHASE gate and present a method for realizing such a gate for quantum computation that is measurement free and low error. The gate is implemented between qubits via an intermediate bus mode. We take a coherent state as the bus and use cross-Kerr-type interactions between the bus and the qubits. This new method is robust against parameter variations and is thus low error. It fundamentally improves on previous methods due to its deterministic nature and the lack of approximations used in the geometry of the phase rotations. This interaction is applicable both to solid-state and photonic qubit systems.