  This paper is a concise summary of the main ideas presented in the companion
paper `Quantum causal models via Quantum Bayesianism'[arXiv:1806.00895]. I
present the proposed definition of a quantum causal model with minimal
background and justification, focusing only on its essential physical
properties. The mathematical structure and definitions are provided as an
Appendix. I discuss the possible physical significance of the fact that the
model is symmetric under causal inversion.
