def _eig_rightvec_add_mps(rv, lt1, lt2):
    """Add one column to the right vector (MPS version)"""
    # rv axes: 0: mps1 bond, 1: mps2 bond
    rv = np.tensordot(rv, lt1.conj(), axes=(0, 2))
    # rv axes: 0: mps2 bond, 1: mps1 bond, 2: physical leg