Most Popular
1500 questions
8
votes
1 answer
How does the conditional min-entropy $H_{\rm min}(A|B)_\rho$ relate to the conditional entropy $H(X|Y)_\rho$?
Suppose we have a classical quantum state $\sum_x |x\rangle \langle x|\otimes \rho_x$, one can define the smooth-min entropy $H_\min(A|B)_\rho$ as the best probability of guessing outcome $x$ given $\rho_x$. How does this quantity relate to…
john_smith
- 81
- 1
8
votes
1 answer
Depolarizing channel implementation on IBM Q
Given a single qubit in the computational basis, $|\psi\rangle =\alpha |0\rangle + \beta|1\rangle$, the density matrix is $\rho=|\psi\rangle\langle\psi|=\begin{pmatrix} \alpha^2 & \alpha \beta^*\\
\alpha^*\beta & \beta ^2\end{pmatrix}$.…
Mathist
- 495
- 3
- 11
8
votes
2 answers
What's a Qubit on D-Wave 2000Q?
From D-Wave flyer:
The D-Wave 2000Q system has up to 2048 qubits and 5600 couplers. To reach this scale, it uses 128,000
Josephson junctions, which makes the D-Wave 2000Q QPU by far the most complex superconducting
integrated circuit ever…
0x90
- 263
- 1
- 6
8
votes
1 answer
Rotationally invariant maximally entangled states in higher dimensions
Is there a straightforward generalization of the $\mathbb{C}^2$ Bell basis to $N$ dimensions? Is there a rotational invariant Bell state in higher dimensions? If yes, then what is the form of that state (how does it look like)? And, by rotational…
Vijeth Aradhya
- 361
- 1
- 7
8
votes
0 answers
In D-Wave's universal quantum computer, why does the YY term have to be driven along with the linear X term?
D-Wave has a new prototype annealer that uses a Hamiltonian which, if there was enough qubits and sufficient control, would be able to simulate any universal circuit-based quantum computer with at most polynomial overhead. It was presented at the…
user1271772 No more free time
- 13,847
- 2
- 25
- 71
8
votes
1 answer
How to say "apply CNOT on qubit 1 controlled by qubit 2"?
Say you have $2$ qubits, namely $q_1, q_2$. What's the right language for saying apply CNOT on $q_1$ and $q_2$ where $q_1$ is the control qubit and $q_2$ is the target?
For instance, can I say "apply CNOT on $q_2$ controlled by $q_1$"? What's the…
R. Chopin
- 1,199
- 6
- 17
8
votes
1 answer
Compact way of describing the set of all stabilizer groups for fixed number of physical qubits and encoded logical qubits
Fix $n$, the number of qubits and $k$, the number of encoded logical qubits. We can find a set of $(n-k)$ operators that all mutually commute and moreover form a group $S$. Let's assume that the group $S$ is a subgroup of the Pauli group. We can use…
Amara
- 411
- 2
- 5
8
votes
2 answers
How does one obtain amplitude information in Q#?
Is it possible to obtain amplitude information (in lexicographic ordering) for a particular qubit register in Q#?
For example, in the following code:
operation GetProbabilityAmplitude() : Double[]
{
body
{
mutable result = new…
jman
- 443
- 2
- 8
8
votes
2 answers
Physical meaning of twirling in Randomized Benchmarking
I was reading papers on Randomized Benchmarking, such as this and this.
(more specifically, equation 30 in the second paper)
It appears to be some kind of averaging but I would like to have a more intuitive and physical picture of what it actually…
Blackwidow
- 599
- 2
- 8
8
votes
1 answer
Does a Wigner function uniquely determine a quantum state?
We know that the Wigner function of a Gaussian quantum state is (up to a constant) a Gaussian distribution. The first moment and the covariance of this distribution uniquely specify a quantum state. Therefore a Wigner function uniquely determines a…
taper
- 203
- 1
- 6
8
votes
1 answer
Can two states with the same entanglement be transformed into each other using local unitaries?
Take two pure bi-partite states $\psi$ and $\phi$ that have the same amount of entanglement in them as quantified by concurrence (does the measure make a difference?). Can any such states be transformed into each other using local unitaries?
user120404
- 407
- 2
- 5
8
votes
2 answers
Why do we need a Classical Register for carrying out Quantum Computations?
I've just started to mess about with QISKit on Python and one thing is confusing me a fair bit.
Given that we are building Quantum Circuits what is the need for a classical register ?
Is it because the collapsed state must be classical ?
Jake Xuereb
- 466
- 2
- 7
8
votes
2 answers
What about BosonSampling can be publicly verified?
Boson Sampling, sometimes stylized as BosonSampling, is an attractive candidate problem to establish quantum supremacy; the engineering problems appear more surmountable than those associated with a Turing-complete quantum computer.
However, Boson…
Mark Spinelli
- 11,947
- 2
- 19
- 65
8
votes
2 answers
What exactly is "matrix sparsity" $s$?
In many sources (like on Page 30 here), I found that the complexity of the original Harrow Hassidim Lloyd is stated as $\mathcal{O}(\log (N) s^2 \kappa^2/\epsilon)$ where $s$ is said to be the "matrix sparsity". What is a precise definition of the…
Sanchayan Dutta
- 17,497
- 7
- 48
- 110
8
votes
1 answer
Resources for quantum biology
Are there any books, courses, tutorials, etc. for studying quantum biology?
Preferably they provide some introduction/primer on the relevant quantum aspects of the quantum biological systems being described.
TanMath
- 275
- 3
- 11