  The next generation of space-based networks will contain optical clocks
embedded within satellites. To fully realize the capabilities of such clocks,
high-precision clock synchronization across the networks will be necessary.
Current experiments have shown the potential for classical frequency combs to
synchronize remote optical clocks over free-space. However, these classical
combs are restricted in precision to the standard quantum limit. Quantum
frequency combs, however, which exhibit quantum properties such as squeezing
and entanglement, provide pathways for going beyond the standard quantum limit.
Here, we present our perspective on the prospects for practical clock
synchronization in space using both classical and quantum frequency combs. We
detail the current outcomes achievable with a classical frequency comb approach
to synchronization, before quantifying the potential outcomes offered by
quantum frequency combs. Challenges to be overcome in deploying frequency combs
in space are presented, and the implications of almost-perfect synchronization
for future space-based applications and experiments discussed.
