Hamiltonian exceptional points (HEPs) are spectral degeneracies of
non-Hermitian Hamiltonians describing classical and semiclassical open systems
with gain and/or loss. However, this definition overlooks the occurrence of
quantum jumps in the evolution of open quantum systems. These quantum effects
are properly accounted for by considering Liouvillians and their exceptional
points (LEPs) [Minganti et al., Phys. Rev. A {\bf 100}, 062131 (2019)]. Here,
we explicitly describe how standard quantum process tomography, which reveals
the dynamics of a quantum system, can be readily applied to reveal and
characterize LEPs of non-Hermitian systems. We conducted experiments on an IBM
quantum processor to implement a prototype model simulating the decay of a
single qubit through three competing channels. Subsequently, we performed
tomographic reconstruction of the corresponding experimental Liouvillians and
their LEPs using both single- and two-qubit operations. This example
underscores the efficacy of process tomography in tuning and observing LEPs,
despite the absence of HEPs in the model.Comment: 9+17 pages, 2+4 figure
