  In TCSS (Threshold Changeable Secret Sharing) scheme, the threshold can be
changed to deal with share leakage in the long term. But in classical TCSS,
there is no guarantee that old shares are deleted even if the participated
parties are honest. So, the changed threshold may not prevent an adversary from
reconstructing the secret by the old shares and old threshold number of
parties. We show how to tackle this problem quantum mechanically. I.e., quantum
mechanically we can make the changed threshold mandatory. So, there is quantum
advantage of quantum TCSS over classical TCSS.
