Frequency Division Multiplexing Readout and Simultaneous Manipulation of   an Array of Flux Qubits
  An important desired ingredient of superconducting quantum circuits is a readout scheme whose complexity does not increase with the number of qubits involved in the measurement. Here, we present a readout scheme employing a single microwave line, which enables simultaneous readout of multiple qubits. Consequently, scaling up superconducting qubit circuits is no longer limited by the readout apparatus. Parallel readout of 6 flux qubits using a frequency division multiplexing technique is demonstrated, as well as simultaneous manipulation and time resolved measurement of 3 qubits. We discuss how this technique can be scaled up to read out hundreds of qubits on a chip. 
Markus Jerger, Stefano Poletto, Pascal Macha, Uwe H\"ubner, Evgeni   Il'ichev and Alexey V. Ustinov
quant-ph cond-mat.mes-hall cond-mat.supr-con