Questions tagged [qiskit]
Quantum Software Development Kit for writing quantum computing experiments, programs, and applications. If appropriate, also use the [programming] tag.
3
votes
0answers
27 views
Bell State 11 not working for parity curve
I am currently writing a script to automate the creation of parity curves for a 2 qubit bell state and then calculate fidelity and proving entanglement from that (inspired by this paper). It was going ...
3
votes
1answer
47 views
Implementing a complex circuit for a Szegedy quantum walk in qiskit
Problem definition
I'm implementing a quantum circuit in qiskit for a Szegedy quantum walk, (reference, Fig 21.). It uses two registers of dimension $N$ ($N=3$) each one. The challenges I'm facing ...
5
votes
1answer
39 views
Get result measurement into a circuit with Qiskit
I'm trying to implement the three qubit bit flip code in Qiskit.
Therefore, I need to get the result of a measure of two ancilla qubits, to deduce which gate I need to use do recover my logical qubit....
7
votes
2answers
118 views
How to program a controlled Hadamard-Hadamard gate?
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?
3
votes
1answer
47 views
About the Qiskit draw function
Where does Qiskit put the rendered figure created by circuit.draw(output='mpl')?
3
votes
0answers
73 views
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:
...
3
votes
1answer
64 views
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.
...
4
votes
0answers
54 views
Results from looped experiments on IBM Q different than individual experiments
I'm experiencing an issue while using Qiskit where the counts from a job return vastly different values when ran in a loop or as an array of circuits as opposed to single experiments when run by ...
2
votes
0answers
39 views
How can I express controlled unitary operation in QPE of this implementation of HHL?
I have found this implementation of HHL, and I don't understand why the controlled unitary operation is expressed in the form of $\exp(i t_0 A/2)$ and $\exp(i t_0 A/4)$.
The rotation of $\pi$ and $\...
3
votes
1answer
48 views
How to implement the XY Heisenberg interaction using IBMQ and Qiskit?
A possible way to implement the 2 qubit Heisenberg XYZ model using a Quantum computer is to decompose the Hamiltonian as follows: $$H_{XYZ} = H_{XY} + H_{YZ} + H_{XZ}$$. In this case, these operators ...
5
votes
1answer
64 views
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 ...
6
votes
1answer
240 views
Defining qubit operator from scratch
I'm a beginner with Qiskit and the Python language at all.
Here is my question:
One of the VQE function arguments is qubit operator (qubitOp).
I saw some examples ...
1
vote
0answers
66 views
How to run quantum SVM algorithm from Qiskit in real IBM Quantum Computer using IBMQ?
I'm trying to run QSVM algorithm in IBMQ experience, want to run in one of those real quantum computers.
...
2
votes
1answer
88 views
How to construct a CCY gate in Qiskit
How can one construct a CCY gate using gates which are native to Qiskit (CCX and single qubit gates). I was able to find the answer for CCZ gates, however guessing and testing until I can figure out ...
3
votes
3answers
152 views
How to quickly calculate the custom U3 gate parameters $\theta, \phi$ and $\lambda$ for any unitary?
In IBM Qiskit and Quantum Experience, the custom U3 gate is defined as
$$
U(\theta, \phi, \lambda) =
\begin{pmatrix}
\cos\left(\frac{\theta}{2}\right) & -e^{...
5
votes
2answers
126 views
Transform matrix into a combination of simple quantum gates
I am trying to transform this matrix into a combination of quantum gates but I cannot find any such functionality on Qiskit or anywhere else. I have tried to use Quirk but I do not understand it.
$$\...
2
votes
2answers
109 views
IBM QISKit: creating a variational algorithm from zero
I would like to implement a variational algorithm (similar to VQE but with another cost function, no expectation of a Hamiltonian involved) from zero. Is there any tutorial explaining how to implement ...
5
votes
1answer
64 views
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 ...
1
vote
1answer
57 views
Order of controls and targets of cnx gates in Qiskit (Python)
In the following piece of code:
cnx(qwc, q[0], q[1],q[2],q[3])
in what order control qubits and target qubit are? Which qubit is inverted for which values of ...
3
votes
1answer
97 views
How does the cnx gate work in Qiskit (Python)?
Could somebody explain the cnx operator, and how it operates on its qubit parameters to flip the target qubit in Qiskit (Python)?
1
vote
1answer
48 views
Default value for a state created by QuantumRegister
What's the default value for a state created by QuantumRegister(1,'name_of_the_register')? Is it a $|0\rangle$ or a $|1\rangle$?
2
votes
1answer
107 views
Grover's algorithm returns skewed probability distribution
I wrote an implementation of Grover's algorithm that looks like this:
...
4
votes
1answer
114 views
Controlled unitary from the HHL algorithm – practical implementation using Qiskit
I have a question about the implementation of the controlled unitary $e^{iAt}$, from the paper Demonstration of a Quantum Circuit Design Methodology for Multiple Regression, using the Qiskit framework....
5
votes
0answers
56 views
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 ...
1
vote
0answers
54 views
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 ...
1
vote
1answer
75 views
(name of gate) is not in the list of basis operations
I'm trying to define a custom gate for my computations. I decided to copy the structure in one of the files in qiskit.extensions.standard package. Here is the code ...
2
votes
1answer
70 views
Qiskit DAG circuit - print information about individual gate/node by number
I created a DAG circuit in Qiskit and don't really understand how to see which gate is which.
I want to call a function like dag_circuit.gate_info(gate_number), ...
1
vote
1answer
51 views
Using latest (GitHub) version of Qiskit as Python library
I just started working in Qiskit and want to use some of the new functions available to Qiskit on Github. Unfortunately, I don't know how to implement the latest GitHub version into my Anaconda ...
1
vote
1answer
120 views
Import from qiskit-aqua error
I try to use Quantum SVM kernel algorithm: multiclass classifier extension. This is my code section with imports
...
3
votes
2answers
113 views
Problems with qiskit-terra: missing members of instance QuantumCircuit
I have installed a Python 3.7.2, download anaconda and visual studio code. Install Qiskit SDK 0.5.3. But when I launch my first test program from https://github.com/Qiskit/qiskit-terra I received a ...
7
votes
3answers
318 views
How is the Grover-Algorithm applied to a database?
Question
I want to use the Grover-Algorithm to search an unsorted database for an element $x$. Now the question arises, how do I initialize index and value of the database with the qubits?
Example
...
2
votes
1answer
46 views
Qiskit predecessor and successor map of DAG circuits
I am trying to figure out how to use the functions "_make_pred_succ_maps". Here is a description of the function from Github:
...
3
votes
2answers
124 views
Finding the second smallest number. Is it achievable in QC?
I have a set of numbers in a superposition state (example: 3,8,1,5) in a quantum register (of 3 qubits).
So I try to find the $n^{\text{th}}$ smallest number (...
3
votes
0answers
46 views
What are reasonable noise/dephasing parameters for QuEST to emulate state-of-the-art quantum computers?
The QuEST code allows for simulation of quantum computers taking dephasing and depolarizing noise into account via one and two qubit dephasing and depolarization. What are realistic parameters for ...
4
votes
1answer
172 views
Quantum algorithm for linear system of equations (HHL) - Final Step: How can I find my vector of solution $|x\rangle$?
I'm working on solving a linear system with the quantum algorithm HHL. I don't understand how I can recover my vector $|x\rangle$ of real solution of the system starting from the states measured with ...
3
votes
1answer
81 views
For CNOT gate with control qubit set to 1, the measured state of the second qubit unexpectedly depends on the measurement
I have the following circuit in qiskit. It is a simple CNOT operation with the control qubit set to 1, by running the control qubit through an X-gate.
However, when I measure the 2nd qubit, I get the ...
2
votes
1answer
121 views
Building an N-qubit Controlled S Gate
I've been beating my head against this problem for three days now and I just can't seem to crack it. To construct an N-qubit controlled Unitary gate, I can do something like this (note I'm using ...
3
votes
1answer
66 views
“Wait” gate throws an error “NotImplementedError: ('No decomposition rules defined for ', 'wait')”
My Quantum circuit contains "Wait" Gate. When I try to execute it (qasm_simulator or unitary-simulator), it throws an error . ...
1
vote
1answer
108 views
Cannot load account with Qiskit
I just got started with Qiskit. When I tried to save my account with the API token from IBMQ website, I got the error: ...
1
vote
0answers
37 views
Qiskit gates in LaTeX representation: notation meaning [duplicate]
I started working in Qiskit, and here is an example of how gates of a circuit are represented graphically in LaTeX format:
Obviously, $R_y(\theta)$, is a y rotation by a certain angle. But all the ...
3
votes
1answer
81 views
Consistent QISkit error: “All devices are currently unavailable”
I am attempting to run the following on a remote backend through QISkit:
...
3
votes
1answer
108 views
Is it possible to create a superposition in IBMQ QISkit which has probability amplitudes $|a|\neq |b|$?
For example, we can create a single qubit state with a polar angle of $\pi/2$ with the Hadamard gate. But, can we create a state such as this,
$$\Psi = \cos(\pi/8)|0\rangle + \sin(\pi/8)|1\rangle$$
...
1
vote
1answer
120 views
QISKit warrning on marshmallow
I have updated qiskit module but unfortunately, it doesn't work it says
...
4
votes
1answer
197 views
Qiskit - How do we measure the same single qubit system multiple times while also getting the counts/results after each measurement?
I am able to apply multiple measurements (2) to the same qubit system. However, I would like to get the counts right after each measurement is executed. I realize that the counts should be the same ...
3
votes
1answer
72 views
LaTeX error when drawing circuits with Qiskit
I am currently running the following document from this Qiskit documentation.
This notebook is running in Jupyter, and I started Jupyter from the Mac terminal within a Conda environment. Normally, ...
2
votes
1answer
88 views
Qiskit: 'per shot' result
Is there a way to access the results of measurements 'per shot' performed on a backend such as one of the real IBM machines?
I know it can generate a histogram from the cumulative data, but I was ...
4
votes
1answer
636 views
ImportError: cannot import name 'QuantumProgram' from 'qiskit'
I get below error when I run a code on spyder environment:
File C:/MYPYTHON Programs/My Quantum Programs/Shor algo.py, line 4, in from ...
4
votes
1answer
191 views
Deprecation warnings in Qiskit (circuit drawing)
I am just starting to get around Qiskit, I'm going at baby steps, so I tried to run the code below and I noticed three things:
I tried using ...
3
votes
1answer
201 views
Path to learn Qiskit as a tool for the future
I am an undergraduate in Engineering physics, yet to take classes on Quantum mechanics, but none (if I'm not mistaken) on quantum information and quantum algorithms, and I am curious about the subject ...
3
votes
2answers
197 views
Why won't Qiskit ccx gate accept registers?
In Qiskit, they have the concept of a Toffoli gate (ccx). However, the following code throws an error:
...
