Brian R. La Cour
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What makes quantum computations different from randomized classical computations?
Accepted answer
13 votes

The question is, how did you get to your final state? The magic is in the gate operations that transformed your initial state to your final state. If we knew the final state to begin with, we wouldn'...

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What is the mathematical justification for the "universality" of the universal set of quantum gates (CNOT, H, Z, X and π/8)?
Accepted answer
12 votes

The answer you mention references Michael Nielsen and Isaac Chuang's book, Quantum Computation and Quantum Information (Cambridge University Press), which does contain a proof of the universality of ...

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Who was the first to call the phase gates $P(\pi/2)$ and $P(\pi/4)$ the $S$ and $T$ gates, and were they motivated by generators of the modular group?
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3 votes

I believe Neilsen and Chuang were the first to use this particular notation. Previous work had referred to $S$ and $T$ as $\sigma_z^{1/2}$ and $\sigma_z^{1/4}$, respectively (Boykin et al. 1999). ...

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How is a single qubit fundamentally different from a classical coin spinning in the air?
3 votes

The analogy between qubits and coin flips is popular but can be misleading. (See, for example, this video: https://www.youtube.com/watch?v=lypnkNm0B4A) A coin spinning in the air and landing on the ...

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Implementation of quantum adder
2 votes

I'm assuming an initial state of the form $|a\rangle|b\rangle = |1\rangle|0\rangle$ for your simple case. You first perform a QFT on the right qubit, obtaining $|1\rangle(\frac{|0\rangle+|1\rangle}{\...

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