Fig. 1: Device layout with integrated on-chip filters.
From: Decay-protected superconducting qubit with fast control enabled by integrated on-chip filters
a, b Schematic representation of qubits (white crosses) strongly coupled to a transmission line (turquoise) implemented as (a) λ/4 and (b) λ/2 filters at the qubit frequency fq which corresponds to the full wavelength λq. c, d Voltage amplitude of the transmission line mode as a function of position x along the transmission line for the (c) λ/4 and (d) λ/2 filters. At the resonance frequency f = fq (red line), both on-chip filters effectively decouple from the qubit due to net zero voltage at the qubit, whereas at the subharmonic frequency f = fq/3 (blue line), the on-chip filters couple strongly to the qubit. The pink shading highlights the region where the modes couple to the qubit. e False-color optical-microscope image of the device. The device consists of three flux-tunable transmon qubits (violet) labeled Q1, Q2, and Q3. Each qubit is individually coupled to its own readout resonator (red) and flux lines (magenta). The readout resonators are further coupled to a common Purcell filter (yellow) for qubit readout. Additionally, qubits Q2 and Q3 are coupled to λ/4 and λ/2 filters respectively, whereas qubit Q1 is weakly coupled to a standard transmission line for control (turquoise).
