- #1

antonantal

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The usual justification for this is that in QM the time evolution of a system is a unitary operator which, by linear algebra, is reversible (invertible).

But I am trying to get a better intuition of this, so I came up with the following explanation:

In order to maintain the superposition state, information must be conserved during quantum computation (note that this isn't the case at measurement, when we lose the superposition and we lose information). So a quantum gate must conserve information.

If information is conserved, then entropy must remain constant. The 2nd law of thermodynamics says that entropy remains constant only if the process is reversible. So, the process performed by a quantum gate must be reversible.

Is my reasoning correct?