Abstract: 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.

Abstract: A cryogenic parametric amplifier control apparatus is disclosed. Methods of implementation and devices incorporated within the whole of the apparatus are disclosed. Methods of reducing the number of signal lines necessary to control a parametric amplifier are disclosed. Schema allowing for control of multiple parametric amplifiers with a single apparatus are disclosed.

Abstract: A rectangular waveguide circulator consists of multiple sections that meet at a common junction where a tapered ferrite portion is disposed. A ferrite portion is disposed within a hollow space adjacent the common junction. The ferrite portion has a shape that includes an upper portion, a middle portion, and a lower portion, such that a cross sectional area of the upper portion is greater than a cross-sectional area of the middle portion, and such that a cross sectional area of the lower portion is greater than the cross-sectional area of the middle portion.

Abstract: An adapter for coupling a coaxial transmission line to a waveguide, wherein the center conductor of the coaxial line passes via a back short of the waveguide through an iris and that terminates to the inside wall of the waveguide.