  Quantum walks are central to a wide range of applications such as quantum
search, quantum information processing, and entanglement transport. Gaining
control over the duration and the direction of quantum walks (QWs) is crucial
to implementing dedicated processing. However, in current systems, it is
cumbersome to achieve in a scalable format. High-dimensional quantum states,
encoded in the photons' frequency degree of freedom in on-chip devices are
great assets for the scalable generation and reliable manipulation of
large-scale complex quantum systems. These states, viz. quantum frequency combs
(QFCs) accommodating huge information in a single spatial mode, are
intrinsically noise tolerant, and suitable for transmission through optical
fibers, thereby promising to revolutionize quantum technologies. Existing
literature aimed to generate maximally entangled QFCs excited from
continuous-wave lasers either from nonlinear microcavities or from waveguides
with the help of filter arrays. QWs with flexible depth/duration have been
lately demonstrated from such QFCs. Here, instead of maximally-entangled QFCs,
we generate high-dimensional quantum photonic states with tunable entropies
from periodically poled lithium niobate waveguides by exploiting a novel pulsed
excitation and filtering scheme. We confirm the generation of QFCs with
normalized entropies from $\sim 0.35$ to $1$ by performing quantum tomography
with high fidelities. These states can be an excellent testbed for several
quantum computation and communication protocols in nonideal scenarios and
enable artificial neural networks to classify unknown quantum states. Further,
we experimentally demonstrate the steering and coherent control of the
directionality of QWs initiated from such QFCs with tunable entropies. Our
findings offer a new control mechanism for QWs as well as novel modification
means for joint probability distributions.
