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In this question on Quora: What is meant by "the photon is its own antiparticle"?, an answer is given which states:

In quantum theory, we have a procedure for transforming the wave function of a particle into that of an antiparticle. It is called the "CP" operation.

Unfortunately, the author of the answer does not explain what the "CP" operation is.

What is the "CP" Operation in the context of anti-particles?

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C = charge conjugation
P = parity

CP symmetry is often mentioned in the context of particle physics.

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This is the context of Particle Physics and Field Theory where CP as pointed out above very precisely, are the fundamental symmetries which conserve various quantities. This has no direct significance with Quantum Information/Computation.

In the context of the term "CP", in Quantum Information Theory, we have what is called "Completely Positive" maps or more restrictively "CPTP - Completely Positively Trace Preserving Maps" which are transformations (called Quantum Channels) on a qudit state from one Hilbert space to another. There are certain axioms that the channels satisfy.

Just for the literature of the subject, this is a very hot topic of research in QI, you may find some information in https://en.wikipedia.org/wiki/Quantum_channel Or, Nielsen and Chuang, Chapter 8 titled "Quantum noise and quantum operations."

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    $\begingroup$ This does not answer the question. The question is about the meaning of CP in the quoted context. $\endgroup$ – Norbert Schuch Nov 4 '18 at 17:01
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    $\begingroup$ This information was posted because the person asking the question was confused with the abbreviation "CP" in Quantum Computing terminology. $\endgroup$ – Siddhant Singh Nov 4 '18 at 17:03
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    $\begingroup$ It is one of those cases where title and the actual question don't match. The actual question is clearly about the meaning of "CP" in the quoted context. $\endgroup$ – Norbert Schuch Nov 4 '18 at 17:25

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