  Supernova remnants (SNRs) are thought to be one of the major acceleration
sites of galactic cosmic rays (CRs) and an important class of objects for
high-energy astrophysics. SNRs produce multi-wavelength, non-thermal emission
via accelerated particles at collisionless shocks generated by the interactions
between the SN ejecta and the circumstellar medium (CSM). Although it is
expected that the rich diversities observed in supernovae (SNe) and their CSM
can result in distinct very-high-energy (VHE) electromagnetic signals in the
SNR phase, there are only a handful of SNRs observed in both GeV and TeV
gamma-rays so far. A systematic understanding of particle acceleration at SNRs
in different ambient environments is therefore limited. Here, we explore
non-thermal emission from SNRs in various circumstellar environments up to 5000
yrs from explosion using hydrodynamical simulations coupled with efficient
particle acceleration. We find that time-evolution of emission characteristics
in the VHE regime is mainly dictated by two factors; the number density of the
target particles and the amplified magnetic field in the shocked medium. We
also predict that Cherenkov Telescope Array (CTA) will have a sufficient
sensitivity to detect VHE gamma-rays from most young SNRs at distances <~ 5.0
kpc. Future SNR observations with CTA will thus be promising for probing the
CSM environment of SNe and hence their progenitor properties, including the
mass loss history of massive stars.
