Table 2 Parameters for the directional coupler.

From: Quantum efficiency, purity and stability of a tunable, narrowband microwave single-photon source

In ↔ ain

Cancel ↔ ain

In ↔ aout

ain ↔ aout

Cancel ↔ In

21.7 dB

50.6 dB

47.6 dB

0.4 dB

0.3 dB

  1. The values are measured in the room temperature at the maximal qubit frequency by the VNA with the fluctuations from the maximum to the minimum less than 1 dB in range of 4.8–5.6 GHz. Cancel and In present the cancellation port and the input port in Fig. 1a, respectively. The measured attenuation between ports Cancel ↔ aout is the same as that between ports In ↔ ain.
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