Quantum Computing Stack Exchange
Quantum Computing Stack Exchange

Questions tagged [bloch-sphere]

For questions related to the Bloch sphere. In quantum mechanics, the Bloch sphere is a geometrical representation of the pure state space of a two-level quantum mechanical system (qubit), named after the physicist Felix Bloch. (Wikipedia)

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Why is the Bloch sphere three-dimensional?

I can understand the intuition behind a two dimensional bloch circle, as it represents the probability distribution of a certain state vector. However, I fail to grasp what the third dimension adds to the visualization when it comes to…
Sinestro 38
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Can I draw platonic solid inside a Bloch sphere?

I wonder if there's a tool available to draw platonic solids or other 3-D shapes inside a Bloch sphere. Here's an example I found on a research paper: In my previous visualizations, I used the kaleidoscope package in Python to simulate…
ZR-
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What utility is provided by the Bloch sphere visualization?

The Bloch sphere is a mainstay of introductions to quantum computing, but what utility does it actually provide? It can't usefully represent multiple qbits because of entanglement and requires a weird transformation to map to & from a state vector.…
ahelwer
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How to represent an entangle state on Bloch Sphere

If states are not entangle, both bloch sphere represent the state of qubit but if they are entangle, why bloch sphere show nothing??
Quantum_society
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when we specify quantum states in $\mathbb C^2$, why do we only have $2$ basis states?

I am just starting to get up to speed with quantum computing via the Quiskit learning path: online tutorial Here they explain the Dirac notation and use it to describe quantum states as elements in $\mathbb{C}^2$ (square could be for the initial…
Dan Ward
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Solving a Bloch sphere where alpha is imaginary

$$ \begin{array}{l} |\psi\rangle=\frac{\sqrt{3 i}}{2}|0\rangle-\frac{1}{2}|1\rangle \\ |\psi\rangle=0.924|0\rangle-0.382 i |1\rangle \end{array} $$ Basically I’m trying to convert these to a standard form/Bloch sphere. I thought the Bloch sphere was…
Max Rush
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Why do H and T gates generate rotations of an (irrational * pi)

My quantum information lecture notes state that neither $H$ nor $T$ is a rotation of (irrational * $\pi$). However it states that both $TH$ and $HT$ are. Could somebody explain why?
SVMteamsTool
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What does the notation $|+\rangle,|−\rangle,|±i \rangle$ mean in Bloch sphere?

The axis in a a 2D diagram like the following, usually represent 2 quantities. Eg in pic below, $x$ represents time and $y$ represents velocity What gets measured along each axis of a Bloch sphere? In other words what do the different axis of Bloch…
Manu Chadha
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time evolution around a 'reflective axis'

Here's a diagram illustrates my question: The pink and purple vectors are 'reflective' (just like a light ray hitting a surface, though the direction is not the same case). Two grey vectors are some initial states I prepared. My question is if the…
ZR-
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Does normalizing a mixed state give a pure state?

According to bloch sphere interpretation, any point on the surface of the sphere corresponds to a pure state and any point inside the sphere corresponds to a mixed state. Suppose you have a point inside the bloch sphere C corresponding to a mixed…
Eesh Starryn
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Can a many-qubit quantum state be represented on Bloch spheres?

Can a general multi-qubit quantum state be represented on Bloch spheres? If not, what is the maximal number? Are there any corresponding constraints? Thanks.
QubitTy
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why θ/2 in the Bloch sphere?

Describing the Restricted Qubit State is the best introduction I've seen on the Bloch sphere, but one thing still bugs me... Question: Why use $θ/2$ instead of $θ$ or $zθ$ for that matter (i.e. ANY non-zero real factor of $θ$ will do)? Once we…
DarkSky
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