# Timeline for In quantum process tomography, how does $\chi$ characterize a quantum process?

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May 6 '21 at 9:00 answer timeline score: 0
May 5 '21 at 18:24 comment also related: quantumcomputing.stackexchange.com/a/11814/55
May 5 '21 at 17:51 answer timeline score: 2
May 4 '21 at 7:40 comment Yes, I am considering only unitary transformations. I am trying to get a grasp of QPT for simple unitary transformations on one qubit.
May 4 '21 at 7:32 comment Do you mean with quantum operation a unitary (operation) that I perform on the qubit? The term quantum operation is somewhat more general in that it applies also to the more general quantum channels - of which unitary operations are a subset.
May 4 '21 at 1:06 comment I'm not familiar with Kraus operators unfortunately. Can the quantum operation itself be deduced from the chi matrix? I'm a beginner (clearly), so thanks for the patience with this!
May 3 '21 at 21:40 comment I'm afraid that I still don't fully understand the question. Are you familiar with Kraus operators? There is a very strong correlation between the eigen-values and -vectors of the $\chi$ matrix of a quantum channel, and a Kraus representation of the channel - and a particular nice representation. The eigenvectors are basically the coefficients of the Kraus operators decomposed into the basis used for the $\chi$ matrix. If this is something you are looking for in an answer, I can write one and elaborate a bit further?
May 3 '21 at 15:07 comment Thank you, I have read that Q&A previously, and the wikipedia page is references. I think my confusion is more fundamental. What I'm not clear on is this: given a chi matrix, what does it concretely tell me about a quantum process? For example, if I try to characterize a process on one qubit, how do I know my chi matrix is correct?
May 3 '21 at 8:36 comment See also the answer to How to perform Quantum Process Tomography for three qubit gates?. It describes in length the $\chi$ matrix; if you still have doubts, could you clarify what exactly you don't find clear about it?)
May 3 '21 at 8:35 history edited glS
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May 3 '21 at 4:00 history asked