# Tag Info

Accepted

### Does the symmetric logarithmic derivative operator have a geometric interpretation?

First, the classical correspondence, explaining why the SLD should be present. The Fisher information is the expectation value of the score, where the score is the logarithmic derivative of the ...
• 2,684
Accepted

### Why is the quantum Fisher information for pure states $F_Q[\rho,A]=4(\Delta A)^2$?

Suppose $\lambda_0 = 1$ and the rest are $0$.  F_Q [\rho,A] = 2 \sum_{k,l} \frac{(\lambda_k-\lambda_l)^2}{\lambda_k + \lambda_l} | \langle k |A| l \rangle |^2\\ = 2 \sum_{k=0,l \neq 0} \frac{(1-0)^...
• 3,593
Accepted

### Unit vanishes in the Quantum Cramer-Rao Bound?

You are correct: the units must indeed match. If we take a standard evolution with unitary $U=\exp(-i H \theta)$, then the units of $H$ and $\theta$ must match such that $H\theta$ is unitless. For a ...
• 2,684

### Are SIC-POVMs optimal for quantum state reconstruction?

First of all, here's a short disclaimer: I'm not an in-depth expert in this field, I'm just currently getting in contact with tomography more and more often :) So take the following with a grain of ...
• 3,942
Accepted

### Error in the Toth's 2012 paper: "Multipartite entanglement and high-precision metrology"?

Your conclusion appears correct to me. It seems that Eq.(23), modified with your proposed change to the RHS, can be verified by combining Eq.(3), for the upper bound on the $M$ unentangled particles, ...
• 3,282
Accepted

• 1,366
Accepted

• 2,684
1 vote

### Does the symmetric logarithmic derivative operator have a geometric interpretation?

Although, the Bures metric, the Fisher tensor and the symmetric logarithmic derivative appear mainly in quantum estimation theory, and even though the original discovery by Helstrom was in this ...
• 2,445

Only top scored, non community-wiki answers of a minimum length are eligible