A Are Quantum Measurements Truly Special Cases of Unitary Operators?

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Quantum measurements are considered special cases of quantum channels, specifically CPTP maps, according to Stinespring dilation, which states that any quantum channel can be represented by a unitary operator on a larger Hilbert space. The discussion raises the question of whether a specific example of such a unitary operator exists, suggesting that the evolution process may be random. The original poster expresses uncertainty about the relevance of another forum post related to Stinespring dilation to their inquiry. Clarification on the connection between unitary operators and quantum measurements is sought. Understanding this relationship is crucial for deeper insights into quantum mechanics.
Heidi
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Hi Pfs

I read this answer in
https://quantumcomputing.stackexcha...-gates-must-be-unitary-what-about-measurement

Quantum measurements are special cases of quantum channels (CPTP cards). Stinespring dilation states that any quantum channel is realized by partially tracing a unitary operator acting on a possibly larger Hilbert space.

I wonder if it is true. and in this case is it possible to give an example of such unitary operator? i suppose that the evolution process is random.

[I translated the French part. Please use English only.]
 
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