A single photon has many physical degrees of freedom (DOF) that can carry quantum information. Nevertheless, only one DOF is usually used.

We introduce a qubit-qudit information system, realized by two degrees of freedom in a single photon: polarization and time. The photon arrival time is divided into d time-bins representing a qudit, while its polarization state contains an additional qubit.

The time difference between the two time-bins is created without an interferometer at the picosecond scale, which is much smaller than the detector response time.

Full two-qubit and qubit-qutrit states encoded in single photons were reconstructed using quantum state tomography (QST), both when the two DOF were entangled and when they were not, with high fidelities.