Josephson Parametric Devices Having Same-Frequency Ports

A readout system for a quantum computing device, comprising:

• a plurality of resonators configured for coupling to a respective plurality of qubits;
• a filter coupled to the plurality of resonators and configured to produce a bandpass response for readout signals received by the plurality of resonators;
• a first Josephson parametric device configured to receive an output from the filter as an input signal and to generate a first output signal, the first Josephson parametric device comprising:
• first, second, and third resonant modes, the first resonant mode and the third resonant mode both configured to operate at a first resonant frequency and the second resonant mode configured to operate at a second resonant frequency that is different than the first resonant frequency;
• and
• a plurality of couplings including a passive coupling between the first resonant mode and the third resonant mode, a first parametric coupling between the first resonant mode and the second resonant mode, and a second parametric coupling between the second resonant mode and the third resonant mode.

A quantum computing system, comprising:

• quantum hardware comprising a plurality of qubits;
• a readout system coupled to the plurality of qubits for receiving a readout response of the plurality of qubits, the readout system comprising one or more Josephson parametric devices, each Josephson parametric device comprising:
• first, second, and third resonant modes, the first resonant mode and the third resonant mode both configured to operate at a first resonant frequency and the second resonant mode configured to operate at a second resonant frequency that is different than the first resonant frequency;
• and
• a plurality of couplings including a passive coupling between the first resonant mode and the third resonant mode, a first parametric coupling between the first resonant mode and the second resonant mode, and a second parametric coupling between the second resonant mode and the third resonant mode.