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by randomsearch 2895 days ago
Great comment. Circuits are particularly unhelpful in describing quantum algorithms because they usually indicate a fixed problem size, and they do not provide an insight into entanglement, one of the fundamental “resources” of QC.

We need new representations and much better abstractions to get away from the low-level thinking we are currently promoting.
1 comments
throwaway37585 2895 days ago
> [Quantum circuits] do not provide an insight into entanglement

What do you mean? Entanglement occurs whenever the state of a system cannot be factored into a product of the states of its components. Quantum circuits can definitely do that. Just take a qubit, apply the Hadamard gate to it, then CNOT it with a second qubit to get an entangled Bell state. You can see it in action here: http://demonstrations.wolfram.com/GeneratingEntangledQubits/.

Quantum circuits are also used to describe all kinds of quantum algorithms (quantum Fourier transform, Grover’s algorithm, quantum teleportation, etc).

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antpls 2895 days ago
I'm not sure about the actual intent of the grand-parent, but I think it was referring to insight that a larger audience can understand.

I have a CS degree, and I don't know what is "Hadamard", "Bell state", etc. Also your link doesn't load on Firefox Mobile Android, so it didn't help :-)

Proposing a Python library about Quantum Computing is an attempt at explaining mechanisms to a larger audience (surely it is not an easy task)

Edit : the link finally loaded on another tab while writing the comment, but you have to pay for a license of Wolf.A. to run it, I guess. That can't be arguably considered "accessible" knowledge.

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randomsearch 2895 days ago
I mean, they do not illustrate when qubits have become entangled. You can't see that. I'm sure we can do better.
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throwaway37585 2895 days ago
I’m not sure what you mean by “illustrate when qubits have become entangled”. Can you explain?
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randomsearch 2894 days ago
Entanglement is fundamental to QC, right? So in order to be a useful visualisation of an algorithm, a pictorial representation like a circuit should give some intuition to aid understanding such as: which qubits can potentially be entangled at a given stage in the circuit, etc.
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throwaway37585 2893 days ago
Why is this (or the demo I linked to earlier) not a satisfactory representation?

https://qph.fs.quoracdn.net/main-qimg-1ab704621d3c845630ab6f....

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