# Questions tagged [qudit]

For questions mainly related to qudits, the unit of quantum information in d-level quantum systems.

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### How to show that an n-level system is entangled?

"How do I show that a two-qubit state is an entangled state?" includes an answer which references the Peres–Horodecki criterion. This works for $2\times 2$ and $2\times3$ dimensional cases; however, ...
533 views

### Is quantum computing limited to a superposition of only two states?

From Wikipedia: A qubit is a two-state quantum system [...] There are two possible outcomes for the measurement of a qubit — usually $0$ and $1$, like a bit. The difference is that whereas the state ...
2k views

### What is the difference between a qudit system with d=4 and a two-qubit system?

I understand that a qudit is a quantum $d$-state system. If $d=4$, is this exactly the same as a two-qubit system, which also presents $4$ quantum states? The Hilbert space is the same, right? Are ...
134 views

### In qubit/qudit terms, where is the experimental limit between 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: ...
209 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 ...
816 views

### Difference between 3 qubits, 2 qutrits & 1 six level qunit

What is the difference between 3 qubits, 2 qutrits and a 6th level qunit? Are they equivalent? Why / why not? Can 6 classical bits be super-densely coded into each?
118 views

### Are qudit graph states well-defined for non-prime dimension?

Qudit graph states are $d$-dimension generalisations of qubit graph states such that each state is represented by a weighted graph $G$ (with no self-loops) such that each edge $(i, j)$ is assigned a ...