  Besides the superior efficiency compared to their classical counterparts,
quantum algorithms known so far are basically task-dependent, and scarcely any
common features are shared between them. In this work, however, we show that
the depletion of quantum coherence turns out to be a common phenomenon in these
algorithms. For all the quantum algorithms that we investigated including
Grover's algorithm, Deutsch-Jozsa algorithm and Shor's algorithm, quantum
coherence of the system states reduces to the minimum along with the successful
execution of the respective processes. Notably, a similar conclusion cannot be
drawn using other quantitative measures such as quantum entanglement. Thus, we
expect that coherence depletion as a common feature can be useful for devising
new quantum algorithms in the future.
