# Tag Info

## Hot answers tagged terminology

45 votes
Accepted

### What is meant by "Noisy Intermediate-Scale Quantum" (NISQ) technology?

When we talk about quantum computers, we usually mean fault-tolerant devices. These will be able to run Shor's algorithm for factoring, as well as all the other algorithms that have been developed ...
• 10.5k
34 votes
Accepted

### What exactly is an oracle?

An oracle (at least in this context) is simply an operation that has some property that you don't know, and are trying to find out. The term "black box" is used equivalently, to convey the idea that ...
• 46.2k
24 votes
Accepted

### What is postselection in quantum computing?

"Postselection" refers to the process of conditioning on the outcome of a measurement on some other qubit. (This is something that you can think of for classical probability distributions and ...
• 10.8k
23 votes
Accepted

### Significance of The Church of the Higher Hilbert space

The church of the larger (or higher, or greater) Hilbert space is just a trick that some people like (myself included) for rewriting some operations. The most general operations that you can write ...
• 46.2k
21 votes

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

The terminology of 'surface code' is a little bit variable. It might refer to a whole class of things, variants of the Toric code on different lattices, or it might refer to the Planar code, the ...
• 46.2k
18 votes
Accepted

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

The surface codes are a family of quantum error correcting codes defined on a 2D lattice of qubits. Each code within this family has stabilizers that are defined equivalently in the bulk, but differ ...
• 10.5k
14 votes
Accepted

• 359
7 votes
Accepted

### When was the first use of the word Entanglement?

I managed to get access to the paper mentioned in the question. Schrödinger in 1935 (the same year the original EPR paper was published) wrote in English: "By the interaction the two representatives (...
• 11.9k
7 votes

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

There is no standard name for a qudit for $d>3$. The community has mostly settled on the term qudit (but you will still find qunit or quNit, for example, using $n$ or $N$ instead of $d$ in some ...
• 46.2k
7 votes

### What is quantum computing vs. what is not quantum computing

The difficulty with explaining quantum computing is that quantum objects and processes have no direct classical analogue; they're an entirely new ontological category. For example, you might have ...
• 3,888
7 votes
Accepted

### What does fidelity mean?

It might be worth mentioning the physical motivation for these definitions and the concept of fidelity itself. Unlike the classical computers we all know and love, quantum computers are ...
• 186
7 votes
Accepted

### Significance of the term "diffusion" in Grover's diffusion operator

I had forwarded this question to Dr. Lov Grover and received the following response. I guess inversion about average is a better name for the $\mathrm{W}\mathbb I_0\mathrm{W}$ transformation. When I ...
7 votes
Accepted

### How is a promise gap related to a spectral gap?

The spectral gap is pretty much independent of the promise gap. (First off, my feeling is that "promise gap" is a little bit misleading, though formally correct: What it really refers to, in ...
• 4,988
6 votes

### 'Rectilinear' and 'Diagonal' Basis in BB84 Protocol

Talking about bases such as $\left|0\rangle\langle0\right|$ and $\left|1\rangle\langle1\right|$ (or the equivalent vector notation $\left|0\right>$ and $\left|1\right>$, which I'll use in this ...
• 3,397
6 votes

### Is qsphere an actual term representing 5 qubits?

Is qsphere an actual term representing 5 qubits? If it is, it is not widely used. I claim this because I looked around in arXiv, a repository of electronic preprints of research articles, and found ...
• 1,785

Only top scored, non community-wiki answers of a minimum length are eligible