Lumped-Element Filters for Protecting Qubits from Control and Readout Ports

It is essential to isolate qubits from their environment, which includes all control and readout ports. Each port can open up the qubit system to noise and dissipation. "Purcell filters" have typically described filters that isolate the qubit from the cavity readout port, decoupling qubit relaxation from cavity decay. In this talk, we describe our efforts to decouple the qubits from both the readout and the parametric control ports. We have designed and tested custom band-stop and band-pass filters using microstrip, coplanar waveguide, and lumped-element technologies. These modular designs provide flexibility to implement the filtering in an external package or directly on the qubit chip. In this talk, we will discuss the design methodology, fabrication, and cryogenic characterization of these filters.