Qubit readout pump suppression method
A qubit readout device that suppresses an unwanted pump leakage signal using an absorptive notch filter. The notch filter allows for two distinct ranges of passing frequencies above and below a notch frequency.
1 . An apparatus comprising:
a qubit providing an output;
a parametric amplifier configured to amplify the output of the qubit upon receiving a pump signal having a pump frequency; and
a notch filter configured to suppress transmission at the pump frequency and configured to pass frequencies in two ranges above and below the pump frequency.
2 . The apparatus of claim 1 , wherein the notch filter is absorptive at the notch frequency.
3 . The apparatus of claim 2 wherein the notch filter further comprises coupled resonators.
4 . The apparatus of claim 2 wherein the notch filter further comprises one or more coupled resonators, wherein one or more of the coupled resonators are lossy.
5 . The apparatus of claim 3 , wherein one or more of the coupled resonators are lossy resonators composed of nichrome (NiCr) material.
6 . The apparatus of claim 1 , additionally comprising:
a coupler, coupled to provide the pump signal to the parametric amplifier; and
wherein the notch filter is disposed between the qubit and the coupler.
7 . The apparatus of claim 1 , wherein the notch filter is disposed at an output of the parametric amplifier.