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Questions tagged [terminology-and-notation]

For questions about the usage of, origin of or reasons for specific notation used in the context of quantum computing.

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Is there a convention in quantum circuit diagrams for specific quantum measurements?

Is there a convention in quantum circuit diagrams for specific quantum measurements? For example, how could one express the measurement $|0\rangle \langle 0|$ in a circuit diagram?
James Ellis's user avatar
4 votes
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What is the correct name of this quantum gate? Possibly state control gate

Let $\vec v \in \mathbb{C}^2 $ be the following quantum state: $$ \vec v = \frac{1}{\sqrt{2}}\begin{bmatrix} v_{1} \\ v_{2} \\ \end{bmatrix},\space \lvert v_1 \rvert = 1,...
misanek123's user avatar
4 votes
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What's a nice, intuitive notation for indicating that two operators can or should be run in parallel?

Suppose I have a unitary operator acting on a state $|\psi\rangle$, such as: $$\big (\sqrt A\sqrt B\sqrt C\sqrt D\big)|\psi\rangle.$$ Conventionally, $\sqrt D$ is performed first, then $\sqrt C$, then ...
Mark Spinelli's user avatar
4 votes
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Is there any standard notation for two states being "equivalent up to a global phase"?

Is there any standard notation for two states "equivalent up to a global phase"? Currently, I use just an equal sign but I'd like to use a different symbol to distinguish between two phases ...
Flipper's user avatar
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4 votes
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What does the term efficiency mean when talking about quantum memories?

Lots of papers about quantum memories talk about the efficiency generally or the storage/retrieval efficiency as a figure of merit. What exactly does this term mean? My intuition would be that it ...
Jason Pereira's user avatar
2 votes
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Quantum error correction terminology

I'm asking for help to clear up something, but instead of asking a question, I'm just writing my attempt of a definition below. I assume it's not this simple, and the below is not the correct ...
Tron's user avatar
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2 votes
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Why is the first register of $|x,y\oplus f(x)\rangle$ called "data" register?

When talking about quantum parallelism, in Nielsen and Chuang, it's said that: it is possible to transform this state into $|x, y \oplus f(x)\rangle$, where $\oplus$ indicates addition modulo 2; the ...
June-Barcarolle's user avatar
2 votes
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145 views

Writing the transformation matrix for the following in terms of Kronecker products of elementary 2-qubit gates

I have a set of transformations that transforms $|11001\rangle\to |10101\rangle$ which is basically keeping the leftmost qubit as it is and then it is just the CNOT between the successive qubits, I ...
Upstart's user avatar
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1 vote
0 answers
197 views

What is dual space, and why is it required?

I recently started QC/QM and came across something called dual space? How do we explain concept of dual space to a layman. why do we need dual space? I tried to read and watch some resources on dual ...
Vinay Sharma's user avatar
1 vote
0 answers
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Kronecker notation of an operator

Suppose I have the state $|A\rangle=|x\rangle^l\otimes |y\rangle^l \otimes |z\rangle^l \otimes |0\rangle_x^l\otimes |0\rangle_y^l\otimes |0\rangle_z^l$. I perform the transformation between the $|x\...
Upstart's user avatar
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1 vote
1 answer
128 views

Why is Dirac notation used for quantum states?

I am thinking that I am using Dirac notation to represent $|0\rangle$ and $|1\rangle$ and we are using column vector but why actually using column vector where first one is $(0 \,1)$ for $|1\rangle$ ...
Rayhan's user avatar
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