  Superconducting circuits offer a scalable platform for the construction of
large-scale quantum networks where information can be encoded in multiple
temporal modes of propagating microwaves. Characterization of such microwave
signals with a method extendable to an arbitrary number of temporal modes with
a single detector and demonstration of their phase-robust nature are of great
interest. Here we show the on-demand generation and Wigner tomography of a
microwave time-bin qubit with superconducting circuit quantum electrodynamics
architecture. We perform the tomography with a single heterodyne detector by
dynamically changing the measurement quadrature with a phase-sensitive
amplifier independently for the two temporal modes. By generating and measuring
the qubits with hardware lacking a shared phase reference, we demonstrate
conservation of phase information in each time-bin qubit generated.
