In the real world, computers don't start with blank tapes. Whether you can reversibly compress a noisy tape, then, is a question of the tape's entropy. If you c

In the real world, computers don't start with blank tapes. Whether you can reversibly compress a noisy tape, then, is a question of the tape's entropy. If you can't create blank tape on which to work, you can't do any computing, reversible or otherwise.