  Alice has made a decision in her mind. While she does not want to reveal it
to Bob at this moment, she would like to convince Bob that she is committed to
this particular decision and that she cannot change it at a later time. Is
there a way for Alice to get Bob's trust? Until recently, researchers had
believed that the above task can be performed with the help of quantum
mechanics. And the security of the quantum scheme lies on the uncertainty
principle. Nevertheless, such optimism was recently shattered by Mayers and by
us, who found that Alice can always change her mind if she has a quantum
computer. Here, we survey this dramatic development and its implications on the
security of other quantum cryptographic schemes.
