Fig. 5: Experimental wiring setup and false colored optical image of the qubit device.

There are five adjacent qubits used in this experiment. To perform the state manipulation and detection, five sets of qubit control and one set of readout units are used. For the control of each qubit, there are one microwave (XY) control and one flux bias. We use two digital-analog converter (DAC) channels and one microwave source to modulate the control signal via an IQ mixer. The XY signal is then wire-bonded to the XY control line, which is capacitively coupled to the qubit. The low speed and high-speed bias (Z) signal is generated by a DC source and a DAC channel, and then combined together at the mixing chamber (MXC) plate via a bias-Tee. The Z signal is also wire-bonded to the Z control line, which is inductively coupled to the qubit. For state detection, the readout signal is modulated by two DAC channels and one microwave source via an IQ mixer. The signal is attenuated for 60 dB and then connected to the transmission line of the device. Then, the readout signal goes to the array of circulators. On the second circulator, the signal is amplified by the Josephson parametric amplifier (JPA), which is biased by the DC source and driven by the microwave source. The readout signal is then amplified by a HEMT at the 4K plate and a low-noise amplifier at room temperature, and finally demodulated by an IQ mixer and captured by the analog-digital converter (ADC). We use frequency multiplexing method to simultaneously readout the states of all qubits. All room temperature electronic instruments are controlled by a computer via 1Gb Ethernet.