When considering the production of an electron hole via photoionization (few-photon or strong-field ionization), a key question for the field of attosecond science is: Under what conditions will the state of the hole be nonstationary? An implicit assumption often made is that such states can always be represented in terms of a wave function (a Schroedinger ket); the significance of electronic density matrices, which are required in order to be able to capture effects that limit the coherence of the hole state, is sometimes underestimated. In this presentation, I will show that the electronic degree of coherence is not only limited by the duration of the ionizing pulse, but also by electron-hole interaction (an electron correlation effect causing entanglement between the photoelectron and the parent ion). In addition, in polyatomic systems, nuclear (zero-point) motion can cause surprisingly rapid electronic decoherence. I will also describe efforts to employ quantum optimal control theory to maximize electronic coherence in attosecond photoionization. Particularly, I will address some of the challenges to identify ionizing light pulses that give rise to hole density matrices with tailored properties.