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Questions tagged [terminology]

For questions about the meaning and usage of vocabulary specific to quantum computing or quantum information

11
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1answer
2k views

What exactly is an oracle?

What exactly is an "oracle"? Wikipedia says that an oracle is a "blackbox", but I'm not sure what that means. For example, in the Deutsch–Jozsa algorithm,$\hspace{85px}$,is the oracle just the box ...
6
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3answers
133 views

What is quantum computing vs. what is not quantum computing

That is to say, what are some common or popular misconceptions about what constitutes quantum computing? and how are those things misconceptions? It could help in explaining to frame this ...
16
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2answers
778 views

What is 'Surface Code'? (Quantum Error Correction)

I am studying Quantum Computing and Information. I have crossed with the 'Surface Code' phrase but I can't find a brief explanation of what it is and how it works. Hopefully you guys can help me with ...
7
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2answers
138 views

Do any specific types of qudits other than qubits and qutrits have a name?

For example, has anyone seen something like: "quqrit" for a 4-level system[1], or "qupit" for a 5-level system[2] ? 1 From "quad" or "quart" since "tetra" would be qutrit, which is already a 3-level ...
10
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3answers
131 views

When was the first use of the word Entanglement?

Schrödinger wrote a letter to Einstein after the 1935 EPR paper, and in that letter Schrödinger used the German word "Verschränkung" which translates into "entanglement", but when was the word first ...
4
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2answers
127 views

What does it mean for a result of a measurement to be known/unknown?

Let me start the question with two examples. First, I am reading Nielsen & Chuang section "8.3.3 Bit flip and phase flip channels". There is a description of a quantum operation $\rho \to \...
9
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1answer
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What is the difference between a qubit and a quantum state?

In general, a qubit is mathematically represented as a quantum state of the form $\lvert \psi\rangle = \alpha \lvert 0\rangle + \beta \lvert 1\rangle$, using the basis $\{ \lvert 0\rangle, \lvert 1\...
14
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1answer
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What is meant by “Noisy Intermediate-Scale Quantum” (NISQ) technology?

Preskill introduced recently this term, see for example Quantum Computing in the NISQ era and beyond (arXiv). I think the term (and the concept behind it) is of sufficient importance that it deserves ...
8
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2answers
131 views

Use of the term “dimension” in this description of Simon's algorithm?

In Kaye, Laflamme and Mosca (2007) pg106 they write the following (in the context of Simon's algorithm): ...where $S=\{\mathbf{0},\mathbf{s}\}$ is a $2$-dimensional vector space spanned by $\mathbf{...
6
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2answers
144 views

What do we mean by parity of qubits?

I am currently reading "Quantum Computation and Quantum Information" by Nielsen and Chuang. In the section about Quantum Simulation, they give an illustrative example (section 4.7.3), which I don't ...
13
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3answers
681 views

What does “measurement in a certain basis” mean?

In the Wikipedia article about Bell states it is written: Independent measurements made on two qubits that are entangled in Bell states positively correlate perfectly, if each qubit is measured in ...
6
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1answer
88 views

Is qubit/qudit terms, where is the experimental limit between an S=3/2 and 2·S=1/2?

This question is inspired by "What is the difference between a qudit system with d=4 and a two-qubit system?", as an experimental follow-up. Consider for illustration these two particular cases: ...
7
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2answers
802 views

What counts as an “ancilla” qubit?

I am getting confused about the meaning of the term "ancilla" qubit. It's use seems to vary a lot in different situations. I have read (in numerous places) that an ancilla is a constant input - but in ...
7
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3answers
361 views

What is the difference between “code space”, “code word” and “stabilizer code”?

I keep reading (e.g. Nielsen and Chuang, 2010; pg456 and 465) the following three phases; "code space", "code word" and "stabilizer code" - but am having a difficult time finding definitions of them ...
13
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2answers
2k views

Significance of The Church of the Higher Hilbert space

The term "Church of the Higher Hilbert Space" is used in quantum information frequently when analysing quantum channels and quantum states. What does this term mean (or, alternately, what does the ...
9
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2answers
239 views

Is qsphere an actual term representing 5 qubits?

I'm a total beginner, I've been brought here by the featured stackoverflow blog post so I started studying. Watching this youtube video (A Beginner’s Guide To Quantum Computing (3:58), I saw this ...
10
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2answers
186 views

What is postselection in quantum computing?

A quantum computer can efficiently solve problems lying in the complexity class BQP. I have seen a claim the one can (potentially, because we don't know whether BQP is a proper subset or equal to PP) ...