[ot]

1) One time pads require a secure channel to transmit the key, which must be the same length of the message. It is not a feasible cryptography scheme, more of a theoretical framework.

2) Integer factorization is trivially in NP (the decision problem "n has a factor < x" has a certificate: the factor)

[jbri]

A quantum channel provides protection against eavesdropping for random data, but does not provide security for specific data. A shared quantum channel can be used to easily produce a shared one-time key that only the two parties involved know, which can then be used to encrypt specific data over an unsecured channel.

[smallblacksun]

One time pads are not useful in many cases, but they have been used:

http://en.wikipedia.org/wiki/One-time_pad#Historical_uses