# Tag Info

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### Is 216 qumodes photonic quantum processor equivalent to 216 qubits superconducting quantum processor, in terms of computational power?

My name is Isaac and I work at Xanadu. That’s a really good question! Generally speaking, you can argue that 216 qumodes are more powerful than 216 superconducting (SC) qubits since qumodes encode ...

### Is there a quantum gate that can turn any superposition $|\varphi \rangle$ into a unit column vector $|00\cdots 1\cdots 0\rangle$

It depends on what you mean. For a given state $|\varphi\rangle$, it is always possible to find a gate $U_\varphi$ such that $U_\varphi|\varphi\rangle=|i\rangle_{10}$ for some given $i$. However, it ...
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### Visualize representation of a qubit

One certainly can give examples of the form you're asking for. Here's one: $$\frac{1}{\sqrt{2}}(e^{i\pi/3}|0\rangle+e^{-i\pi/3}|1\rangle).$$ However, note that you will essentially never see an ...

### what does it mean to "measure a qubit" if measurement is defined on operators

I'm not sure if your question is about "what is a measurement", or what does "measuring a qubit" mean if we don't specify the operator or basis. For the first answer, a generic ...
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### What is the difference between "maximally entangled" and "entangled" states?

A maximally entangled state is a state that maximises some entanglement measure. In the case of bipartite states, this generally means a state that maximises the entanglement entropy, that is, the von ...
1 vote

### How to tell if a state is entangled?

$\alpha\gamma|00\rangle + \alpha\lambda|01\rangle +\beta\gamma|10\rangle+\beta\lambda|11\rangle = (\alpha|0\rangle+\beta|1\rangle)\otimes(\gamma|0\rangle+\lambda|1\rangle)$ is a separable state, so it'...
1 vote

### How to write a code to separate two qubits?

Maybe it should be useful tu use qutip to better understand what you desire (if you are familiar with python) by visualizing exactly the 2 qubits and its state vectors (which I believe is what you ...
1 vote

### Is there a gate sending $|0\rangle^{\otimes n}$ to a state where some amplitudes are zero?

you can check out qiskit textbook, https://qiskit.org/textbook/ch-gates/phase-kickback.html https://qiskit.org/textbook/ch-quantum-hardware/density-matrix.html#5.-Mixed-States-in-the-Bloch-Sphere-- ...
1 vote

### When starting from Qubit State |0>, which operations when applied (from right to left) will result in the qubit state |->

To answer your question, the correct answer is option $(i)ZH$. This is because mathematically, the gates are applied in the right-to-left order and hence you apply the $H$ gate first taking us from ...
1 vote
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### What is the difference between $|+\rangle$ and $|-\rangle$?

States with different complex amplitudes are simply different states with different observable consequences. They are not the same. We need them because they describe the outcomes of measurements. To ...

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