# Questions tagged [programming]

For questions relating to the process of assembling quantum programs that can be executed on a quantum computer. For questions using or about a specific programming language, consider using a more specific tag

172 questions
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### How to find a common eigenstate of commuting operators?

I have multiple different operators in matrix form and I need to find their common eigenstates. The challenge is that the common eigenstate is in a superposition of multiple states and isn't just a ...
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### Eliminating a term of a superposition state

Is there a way of eliminating a term of a superposition state? Let's say I have the state $$\frac{1}{\sqrt 2}|00\rangle + \frac{1}{2}|01\rangle + \frac{1}{2}|10\rangle$$ What operation would I do to ...
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I'm trying to program a controlled gate as the figure below in Qiskit. Should it be sufficient to separate and control individually the Hadamard gates?
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### Quantum counting in Q#

I cannot seem to get an estimate for the number of solutions using the quantum counting algorithm described in Nielsen and Chuang, i.e. phase estimation with the Grover iteration acting as $U$. I try ...
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### Counting in Q#: number of solutions

I have this program derived from Microsoft Quantum Katas for counting (see here): ...
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### Grover search for basis states with complex coefficents and multiple marked states

I tried to run Grover's search for basis states with complex coefficients, including the marked basis (complex coefficients because the states are obtained from inverse QFT), but it could not amplify ...
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### Perform quantum gate operations using state vectors and matrices

I am getting confused as to how to perform gate operations using matrices and am hoping someone will help me walk through this example. Say I want to perform a Pauli-X gate on the 3rd qubit in a 3-...
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### Plotting Bloch sphere in QuTiP

Is there anyone who reproduced the Bloch sphere given in the paper QuTiP: An open-source Python framework for the dynamics of open quantum systems by J. R. Johansson, P. D. Nation, Franco Nori? I am ...
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### Can't draw figures with Qiskit in Visual Studio

I'm using Qiskit in Visual Studio 2019. I want to draw quantum circuits, but it only shows their sizes with text instead of figures. The output on the interactive window is like this. ...
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### About the Qiskit draw function

Where does Qiskit put the rendered figure created by circuit.draw(output='mpl')?
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### Measurement inconsistency in Qiskit

I am using Qiskit in an algorithm. In the end, I am measuring exactly a register of 4 qubits but the histograms show states with 5 qubits. This is the code I used: ...
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### How to calculate the fidelity of a certain gate of a IBMQ device in Qiskit using randomized benchmarking/tomography?

For example, I want to calculate the fidelity of a 1-qubit and 2-qubit gates (similar to the result shown in figure 2 in this paper). Is there any way to do that in Qiskit? I've gone through the ...
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### How to define custom controlled unitaries in OPENQASM 2.0?

According to the OPENQASM 2.0 documentation, it's possible to define custom unitary gates using the format: gate name(params) qargs { body } where the optional ...
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### How to see the QASM code corresponding to compiled Q# function?

I'm learning Q#. Is there any way to see the QASM code of a Q# function I write, the same way I can see the disassembly of a C# function?
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### How does measurement calibration work?

One of the possible ways to improve the results of an experiment on the IBM machine using the Qiskit language is to use the measurement calibration methods. This is the link to the documentation. I ...
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### How to draw a multiple qubit controlled NOT gate using qasm2circ?

In Example 6, the case of multiple qubit controlled custom $U$ gate is covered, but I want to reuse the standard NOT symbol i.e. $\bigoplus$. Say I want to draw this circuit, but with a $\bigoplus$ ...
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### Automatic compilation of quantum circuits

A recent question here asked how to compile the 4-qubit gate CCCZ (controlled-controlled-controlled-Z) into simple 1-qubit and 2-qubit gates, and the only answer given so far requires 63 gates! The ...
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### Drawing tangent vectors to the Bloch sphere with qutip

I need to plot drawings of qubit dynamics on the Bloch sphere. I know QuTip allows to do such drawings but I specifically need to represent evolution velocities on the Bloch sphere so I need to draw ...
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### How to build a quantum circuit representing the Ising Model?

Can someone explain to me how to build a quantum circuit representing the Ising Model? I just want to understand how to represent the Ising Model for the purposes of quantum state label classification....
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### Experiment runtime on IBMQ

I have been trying to get the runtime of my experiment on IBM's quantum computer. I am using the classic stuff, i.e ...
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### How to create the oracle matrix in Grover's algorithm?

I'm trying to implement Grover's algorithm in pyQuil, but I'm having trouble creating the oracle matrix given the function $f$, where $f(x)=1$ if $x=w$ and $f(x)=0$ otherwise. In most of the ...
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### Does a complete list of open quantum software projects exist?

An answer to Is there any source which tabulates quantum computing algorithms for simulating physical systems? mentions the Quantum Algorithm Zoo, a list of quantum algorithms. Several answers to ...
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### How do you start a simulation with a random initial state in Cirq?

How do you create a random initial state by modifying the $2^{n}$ vector amplitudes instead of starting every simulation at $|0000...000\rangle$?
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### Graphing the decoherence of qubits being used to perform an algorithm

How would I be able to graph the decoherence of qubits being used to perform an algorithm? I'm working with the IBMQ Qiskit framework and I'm trying to write a program that allows me to find the ...
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### Exception encountered while running quantum-enhanced support vector machines

I am trying to run the code of the notebook example aqua/artificial_intelligence/qsvm_kernel_classification.ipynb. I save it in a python file and I have an exception at runtime the display of ...