  Josephson traveling wave parametric amplifiers enable the amplification of
weak microwave signals close to the quantum limit with large bandwidth, which
has a broad range of applications in superconducting quantum computing and in
the operation of single-photon detectors. While the large bandwidth allows for
their use in frequency-multiplexed detection architectures, an increased number
of readout tones per amplifier puts more stringent requirements on the dynamic
range to avoid saturation. Here, we characterize the undesired mixing processes
between the different frequency-multiplexed tones applied to a Josephson
traveling wave parametric amplifier, a phenomenon also known as intermodulation
distortion. The effect becomes particularly significant when the amplifier is
operated close to its saturation power. Furthermore, we demonstrate that
intermodulation distortion can lead to significant crosstalk and reduction of
fidelity for multiplexed readout of superconducting qubits. We suggest using
large detunings between the pump and signal frequencies to mitigate crosstalk.
Our work provides insights into the limitations of current Josephson traveling
wave parametric amplifiers and highlights the importance of performing further
research on these devices.
