Reversible computation as a model for the quantum measurement process∗

The connection between information and physical entropy, in particular the entropy increase during computational steps corresponding to an irreversible loss of information—deletion or other many-to-one operations—has raised considerable attention in the physics community [1]. Figure 1 [2] depicts a flow diagram, illustrating the difference between one-toone, many-to-one and one-to-many computation. Classical reversible computation [2–6] is characterized by a single-valued invertible (i.e., bijective or one-to-one) evolution function. In such cases it is always possible to “reverse the gear” of the evolution, and compute the input from the output, the initial state from the final state.