  The questions we raise in this letter are as follows: What is the most
general representation of a quantum state at a single point in time? Can we
adapt the current formalisms to situations where the order of quantum
operations is coherently or incoherently superposed? If so, what are the
relations between the state at a given time and the uncertainty in the order of
events before and after it? Establishing the relationship between two-state
vector formalism and pseudo-density operators, we introduce the notion of a
single-time pseudo-state. The tomographic construction of single-time
pseudo-states is possible by ideal or weak measurements. We demonstrate that
the eigenspectrum obtained from weak measurements enables us to discriminate
between some coherent and incoherent superpositions of causal orders in pre-
and post-selected systems before the process is completed. Finally, we discuss
some possible experimental realizations in existing photonic setups.
