backup_initial_state Subroutine

    subroutine backup_initial_state()
        character(*), parameter :: this_routine = "backup_initial_state"

        ! popsfile_dets is certainly large enough to house CurrentDets, so use it if available
        if (.not. allocated(popsfile_dets)) allocate(popsfile_dets(0:niftot, TotWalkers))
        popsfile_dets(:, 1:TotWalkers) = CurrentDets(:, 1:TotWalkers)
        ! number of initial walkers
        backup_size = int(TotWalkers)
    end subroutine backup_initial_state