Nature - USA (2019-07-18)

reSeArCH Letter

4K

1K

50mK

Dir.

Cplr.

50pF

1μH 500Ω

Bias Te e

-20dB

Bias Te e

1.2nF

2kΩ

DC block

-6dB

300kHz low pass

-10dB

1:501:51:51:51:5

0.38pF

258.3MHz

-9dB

-10dB -3dB

Bias Te e

Computer

RF source

Var. Atten.

IQ De-

modulator

SIM 965

Filter

NI DAQ NI6363

Output

SIM 928 Input Output

Voltage Source

1:501:50

AWG70001A

Master

Out1 Sync Sync Out2

AWG70001A

Slave

Sync module

Trig

Amplifier

CMT

CITLF-3

Amplifier

SET gate

Left gate

Source

Middle gate

Right gate

Drain

Extended Data Fig. 2 | Experimental set-up for the two-qubit gate in
a millikelvin dilution refrigerator. The schematic shows the electrical
connections from the device to the control computer at the different
temperature stages of the dilution refrigerator from the top to bottom.
An STM image of the device attached to the cold finger of the refrigerator
at 50 mK is shown in the lower orange pane. The RF-reflectormetry
circuit attached to the device employs a variable attenuator (‘Var. Atten.’)
to control the power coupled through a directional coupler (‘Dir. Cplr.’)
and sent to the source contact of the SET (red lines). The blue line is for
d.c. current/voltage measurements of the SET. The slow signals (black
components) and fast signals (green components) are combined using bias
tees at 50  mK before being sent to the left and right gate electrodes.