Long-range universal quantum computation in a large-size coupled cavity array independent of cavity number

We present a new approach for implementing a universal √(swap) gate between two spatially far apart sites connected by a large-size coupled cavity array as a quantum bus. The duration is only related to the parity of cavity number but independent of a specific number of cavities, thus it is possible to process quantum information in an arbitrary long distance in principle without time variation. Referring to the recent experimental progress on coupled cavity array, we also make an assessment of the scalability and take the cavity number N = 5 as an example to illustrate the robustness of our proposal via quantum process tomography. (letter)