Depending on how involved your circuit is you could use Quantikz (written by @DaftWullie I believe) or Q-circuit by Bryan Eastin and Steve Flammia. These are tools to make circuit diagrams in ...

is the decomposition (I took this from google images, originally on this website.) In order to understand how to decompose it, we can look at it's base structure. The idea is that we combine gates ...

I think the closest thing to a "while loop" in a quantum algorithm is something like the Variational Quantum Eigensolver (VQE) or other classical-quantum hybrid algorithms. In these, a ...

So any universal gate set can replicate any other, since both are universal, but different architectures generally have different physical gates. While Clifford+T is a universal gate set that is very ...

So Alice sends Bob a qubit with the density matrix $$\rho = \frac{1}{2}|0\rangle\langle 0| + \frac{1}{2}|1\rangle\langle 1| = \begin{bmatrix} .5 & 0 \\ 0 & .5 \end{bmatrix}$$ as you said. (I'...

Here's a paper comparing Trapped Ion and Superconducting (the main competitors right now) from the group at UMD which compares their trapped ion system with IBM's transmon (superconducting) system. If ...

It's not that both the qubits are independently picking up a phase, it's that the two qubit state itself is picking up that phase. $$\mathbf{CZ}|1\rangle\otimes |1\rangle = |1\rangle\otimes(-1\times |... View answer Accepted answer 5 votes If \tilde{\lambda_{k}} < C, the controlled rotation becomes non-physical since you have coeffecient greater than 1 on your |1\rangle state. As a result C < \lambda_{min} is a safer choice,... View answer Accepted answer 4 votes There are three major levels of simulation difficulty (broadly, there are a bunch of others, but these are the main levels.) Clifford simulators can simulate circuits composed of only Clifford ... View answer Accepted answer 4 votes A density matrix \rho on two qubits has 16 complex amplitudes (although not all are free variables due to constraints from normalization and Hermeticity), so the City plot is showing those ... View answer Accepted answer 4 votes What do you mean by "Quantum Mechanical Simulations" ? One of the primary motivations in the early history of quantum computing was a statement from Richard Feynman that a quantum computer would be ... View answer Accepted answer 4 votes This explanation of Surface Codes has a lot of detail and starts from the basics. It should hopefully help out, as well as looking at some of the initial Toric Code papers by Alexei Kitaev. My ... View answer Accepted answer 4 votes Your intuition is correct for a single qubit, in that if I measure$$\alpha\vert 0 \rangle + \beta\vert 1 \rangle$$I would get either \vert 0 \rangle or \vert 1 \rangle. But since the qubits are ... View answer 3 votes So the general definition of pseudothreshold is when the logical qubit outperforms a physical qubit. If your error model is idling error, for example, you want to find the physical value of T1 and T2 ... View answer 3 votes Phase is really one of the things that makes quantum computing what it is! In fact, I think there is a quote by Aaronson like how quantum is "probability theory with negative numbers." The ... View answer 3 votes I think that most people would understand what you mean, although maybe mentioning they are the eigenstates of Y wouldn't go amiss depending on your target audience. View answer Accepted answer 3 votes Are you looking for algorithms to look through, or programs for an actual quantum computer? If the former the IBM Q Experience user guide has good explanations of some of them, and other questions ... View answer 2 votes So there are two major advantages qubits have over classical bits: superposition and entanglement. Superposition is the one more often discussed, and is the "0 or 1" phrase you always hear. ... View answer 2 votes This is a good list made by Prof. Rod Van Meter. Maybe you could look at the papers you based your work off of and see where they were published? That should give you a sense of which journals are ... View answer Accepted answer 2 votes Ok, so starting with Trace Preserving, since it's easier:$$Tr(I/2) = 1Tr(\rho) = 1Tr((1-\lambda)I/2 + \lambda\rho) = (1-\lambda)Tr(I/2) + \lambda Tr(\rho) = 1$$Now for a map to be ... View answer 2 votes A rolling n-sided die would be a good analogy that follows the coin example very closely. Until the die settles you can think of it as having not "collapsed", and die can come in whatever side number ... View answer 2 votes The only commercially available quantum machines are from a company called D-Wave however there is debate on exactly how "quantum" their machines are. True quantum computers in the way most of the ... View answer 2 votes EDIT: I completely misunderstood your question and thought that you were confused about what a negative amplitude means, and not about physical mechanisms. I'm leaving this up in case that actually ... View answer Accepted answer 1 votes So the biggest number used when comparing families of QECCs is the threshold, which is the error rate (generally depolarizing noise or XZ noise, depends on the paper) for which increasing the size (... View answer 1 votes So the no cloning theorem doesn't preclude you from creating the state$$\alpha|0\rangle + \beta|1\rangle \rightarrow \alpha|00\rangle + \beta|11\rangle,$$it just says you cant create$$\alpha|0\...

The author in that paper allows himself arbitrary angle single and two qubit gates. With this set it is generally pretty easy to exactly match a given unitary, since the two qubit gates can give you ...

For quantum circuits: So the main answer is that far-term quantum computers will implement Quantum Error Correction, where each logical qubit is composed out of a number of physical qubits and the ...

1) So $|\psi_1\rangle \neq |\psi_2\rangle$, but it effectively is since they give the exact same distributions for any measurement in any basis. 2) Same discussion as above. 3) True 4) States in ...