# Tag Info

### Why is the Qiskit transpiler not resolving the equivalence $I = R_y(-\theta) R_y(\theta)$?

It was a bug, now fixed in release 0.40.0. In the release notes, you can read: Fixed an issue with the transpile() function when run with optimization_level=3 and no backend, basis_gates, or target ...
• 1,189
1 vote

### Problem with qiskit only accepting ${\rm tr}(\rho^2)=1.$ while performing state tomography

You can convert the density matrix to a StateVector using to_statevector() method and set a suitable value for ...
• 6,471
1 vote
Accepted

### Bernstein-Vazirani algorithm to find whether the secret has a one at a specific location

You have to separate out the implementation of the black box from the rest of the circuit. If we implement this ourselves when we're not actually given a black box, we have to create the circuit for ...
• 50.3k
1 vote

### How to get the density matrix from a stabilizer table in qiskit

If your input state is $|000\rangle$, then you can easily get the output as a Statevector as follows: ...
• 6,471
1 vote
Accepted

### How to get the density matrix from a stabilizer table in qiskit

EDIT: you can build the desired DensityMatrix starting from an empty $n$-qubits circuit (in the state $| \psi \rangle = | 0 \rangle^{\otimes n}$) and then use the <...
1 vote

### hhl algorithm output

Interesting! It appears your (mapped to integer) eigenvalues are $\{1.0, 2.0, 4.0, 4.0\}$. We know that for the rotations controlled by the clock register $c$, this relationship must hold:  \theta(...
• 543
1 vote

### How to get exact measurement probabilities when having intermediate measurements with Qiskit?

To do what you want in Qiskit, you could replace each measurement operation in your circuit by a simple call to the Statevector.probabilities(qargs) method, where ...
1 vote

### How to get exact measurement probabilities when having intermediate measurements with Qiskit?

You can use save_probabilities() function to save the measurement outcome probabilities anywhere in your quantum circuit when using ...
• 6,471
1 vote

### How to get exact measurement probabilities when having intermediate measurements with Qiskit?

Alternatively, you can use Quirk for small circuits. Especially it's chance and amplitude displays are useful for visualizing measurement probabilities.
• 445

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