  There are many different types of time keeping devices. We use the phrase
ticking clock to describe those which -- simply put -- "tick" at approximately
regular intervals. Various important results have been derived for ticking
clocks, and more are in the pipeline. It is thus important to understand the
underlying models on which these results are founded. The aim of this paper is
to introduce a new ticking clock model from axiomatic principles that overcomes
concerns in the community about the physicality of the assumptions made in
previous models. The ticking clock model in [arXiv:1806.00491] achieves high
accuracy, yet lacks the autonomy of the less accurate model in
[10.1103/PhysRevX.7.031022]. Importantly, the model we introduce here achieves
the best of both models: it retains the autonomy of [10.1103/PhysRevX.7.031022]
while allowing for the high accuracies of [arXiv:1806.00491]. What is more,
[10.1103/PhysRevX.7.031022] is revealed to be a special case of the new ticking
clock model.

Quantum Physics