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What do you mean by von Neumann architecture? I'll use the Wikipedia definition, and say that it's a computer which keeps its program and its data in the same random-access memory. This works well a …

The question of cloning the BB84 states was covered in the paper "Phase covariant quantum cloning" by Dagmar Bruß, Mirko Cinchetti, G. Mauro D'Ariano, and Chiara Macchiavello [Phys Rev. A, 62, 012302 …

From this we can find the convergents of the fraction $j/2^q$ , the convergents are possible values of the order $r.$ Here do we just try all the convergents $<N$ and if we don't find $r$ …

It's not clear to me whether you're asking about SU(3) or SU(3$^{n}$) acting on a tensor product of qudits. I'll assume you're asking about SU(3). It's not clear to me (despite what I said in a previo …

Now you've clarified your question, I can answer it. Assuming that the seminar was talking about universal quantum computational models (and there are universal computational models for all of these p …

For your question (1), the answer is yes. The 'hashing construction' for quantum encoding is independent of the quantum channel you use, so if you use this construction for encoding, you can send info …

Yes, they can. Recall that any reversible classical function can be computed in superposition. Now, generate the state $$ \frac{1}{\sqrt{n!}}\left(\sum_{i=1}^n |i \rangle \right) \left( \sum_{i=1}^{n …

Let $$P(0) = |a|^2 + |c|^2 + |e|^3 + |g|^2.$$ This is the probability of observing $0$. Then \begin{eqnarray*} w &=& a \big/ \sqrt{P(0)}, \\ x &=& c \big/ \sqrt{P(0)}, \\ y &=& e \big/ \sqrt{P(0)}, …

Look at John Preskill's Lecture Notes; particularly Section 3.2. As you noted, you can do a NAND gate by using a Toffoli gate and throwing away some of the output qubits. This results in decoherence, …

It's not unitary, so it's impossible because all quantum transformations have to be unitary. Consider the states $$ \frac{3}{5} |0\rangle + \frac{4}{5} |1\rangle \quad \mathrm{and} \quad \frac{3}{5} …

No, as far as I know, there are no models that use string theory. Given that quantum field theories seem to be simulatable in polynomial time by a quantum computer (Jordan, Lee, and Preskill, 2012), …

You seem to have the idea that a quantum gate is a physical thing rather than just a conceptual thing. It doesn't necessarily work that way. While CMOS gates are usually actual physical devices, qua …

I haven't looked at the paper carefully, but one thing I noticed is that their proof that BQP $\subsetneqq$ QMA works by their claiming that "bit commitment $\not \in$ BQP" but "bit commitment $\in$ Q …

To answer your question, a QRAM is a self-consistent and interesting model of quantum computation. It appears to be more powerful (up to a polynomial factor) than the usual circuit model of quantum co …

Since we don't know the ultimate physical laws of the universe, and we would need to know them (or at least know much more about them than we do now) to prove Feynman's conjecture, his conjecture is s …