Questions tagged [qiskit]
Quantum Software Development Kit for writing quantum computing experiments, programs, and applications. If appropriate, also use the [programming] tag.
742
questions
2
votes
1answer
507 views
Module BasicAer not found
After installing qiskit-terra via git (pip install qiskit), all python programs involving the line ...
15
votes
5answers
5k views
How do I build a gate from a matrix on Qiskit?
I'm creating a gate for a project and need to test if it has the same results as the original circuit in a simulator, how do I build this gate on Qiskit? It's a 3 qubit gate, 8x8 matrix:
$$
\frac{1}{...
2
votes
1answer
236 views
Print circuit compiled on hardware?
I would like to see the compiled circuit as executed on a hardware.
Nominally, this sequence of commands should return the QASM circuit in the variable ran_qc, but ...
3
votes
2answers
712 views
How to fix? 'E1101:Instance of 'QuantumCircuit' has no 'h' member' and 'E1101:Instance of 'QuantumCircuit' has no 'cx' member'
I'm using this simple code to test my Qiskit and learn how to use it but it keeps giving this problems, how do I fix it (Using VS Code and Anaconda Python 3.7)
...
2
votes
1answer
679 views
qiskit - Is there any way to discard the results of a measurement?
I have a circuit composed by n qubits, plus a single one which is an ancilla. I'm making multiple measurements on the ancilla at different stages of the circuit, ...
3
votes
1answer
606 views
Is it possible to expand/merge different circuits?
Suppose I have created a circuit composed of some registers with the usual
qc = QuantumCircuit(qr, cr)
where qr and ...
3
votes
1answer
372 views
How to set up Qconfig.py and where is the file?
How to set up Qconfig.py and where is the file? I mean under which folder? Like /anaconda/lib/python3.6/site-packages/qiskit/.
3
votes
2answers
309 views
Implementing gate with two parameters using Qiskit in Python
I am trying to implement the HHL algorithm (for solving $Ax=b$). I am assuming $A$ to be unitary and Hermitian so that I can find the Hamiltonian simulation for it easily.
For any $A$ to be Hermitian ...
8
votes
2answers
646 views
Qubits specification on IBMQ devices
As it is shown here, CNOT gates between different qubits have different error rates. I have the following questions:
1) While defining a circuit on QISkit, does ...
2
votes
2answers
173 views
How can the state $\lvert0\rangle+M^{-1/2}\sum_{j=1}^M\lvert j\rangle$ be generated?
I was wondering if anybody to help me to generate the following state.
It would be preferable if you use only Hadamard, CNOT and T-gates, on $\lceil\log_2(M+1)\rceil$ qubits:
$$|\psi\rangle = \frac{1}{...
3
votes
3answers
514 views
How to run algorithms on IBMQ via Qiskit-Aqua?
I am trying to run an optimization problem on IBMQ. Running the same code on QASM simulator works fine. However, changing only the backend name to IBMQX takes long time. I am aware of the queues ...
3
votes
0answers
519 views
Qiskit SDK problem [closed]
So I am getting this error when I fire the command on Ipython or Jupyter Notebook
...
4
votes
0answers
516 views
Qiskit Python program cannot connect to QE API
I am just getting started with Qiskit and IBM Quantum Experience, so please forgive my newby question.
I have a IBM Quantum Experience account and I generated an API token.
I used the generated ...
5
votes
1answer
304 views
Entanglement state preparation by using amplitude values
I have an algorithm that uses QRAM, after accessing the given QRAM that store M d-dimensional classical vectors, the state of the index register and the data register become entangled. But for now I ...
3
votes
1answer
172 views
How can I resolve the error QISkit Error: The same provider has already been registered!
I am writing a small algorithm to multiply two numbers using IBM's QISkit. The code is below:
times_shell.py
...
4
votes
1answer
155 views
How can I get the qiskit module
I have successfully installed qiskit. However, when I try to run a simulation I get the error "No module named 'qiskit'
...
7
votes
1answer
1k views
How would one implement a quantum equivalent of a while loop in IBM QISkit?
I'm writing a simple multiplication algorithm that uses the Quantum Fourier Transform to repetitively add a number (the multiplicand) to itself and decrements another number (the multiplier). The ...
5
votes
2answers
1k views
How to create a condition on only one classical bit when we have a total of 2 classic bits in the system
I am trying to make a quantum circuit with one qubit and 2 classical bits for each measurment in the system below:
I want to make condition on the first bit: if the first collapse to zero so x ...
5
votes
1answer
200 views
How to deal with -LookupError: backend “ibmqx4” is not found?
I am using Jupyter notebook to write and running my qiskit codes (python 3.6)
and every time I encounter the message: LookupError: backend "ibmqx4" is not found, right now the ibmqx4 computer is not ...
5
votes
1answer
672 views
How to install qiskit in spyder editor?
I am working in Anaconda using spyder editor.
Can anyone tell me how to install qiskit in spyder?
7
votes
2answers
413 views
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 ...
5
votes
2answers
1k views
9
votes
3answers
527 views
Does conditional gate collapse controller's superposition?
I've created a simple circuit in Q-Kit to understand conditional gates and outputted states on each step:
In the beginning there is clear 00 state, which is the input
The first qubit is passed ...
7
votes
1answer
548 views
What is the purpose of the TDG gate in QISKit?
The QISKIT documentation doesn't explain what a TDG gate does and I can't find it anywhere else online.
5
votes
1answer
310 views
Quantum SVM Algorithm Error on import
I am experimenting with some Qiskit ACQUA AI algorithms which require the following import statement:
from datasets import *
However, ...
7
votes
1answer
416 views
SWAP gate(s) in the $R(\lambda^{-1})$ step of the HHL circuit for $4\times 4$ systems
Context:
On the 5th page of the paper Quantum circuit design for solving linear systems of equations (Cao et al, 2012) there's this circuit:
Schematic:
A brief schematic of what's actually ...
6
votes
1answer
430 views
Is there a common set of modules for user-defining-quantum-gate for QISKit
I am wondering if there exists a common library or a set of modules for user-defining-quantum-gate for QISKit.
If it does, could you tell me?
By referring to Define Quantum Gates and How to define ...
7
votes
1answer
2k views
What are theta, phi and lambda in cu1(theta, ctl, tgt) and cu3(theta, phi, lam, ctl, tgt)? What are the rotation matrices being used?
I was reading the documentation for qiskit.QuantumCircuit and came across the functions cu1(theta, ctl, tgt) and ...
5
votes
2answers
363 views
Checking value of variable using quantum approach
A beginner question after watching few videos.
Say, var=a; var can be either of two values, ...
8
votes
1answer
2k views
Phase-Shift Gate in Qiskit
How to implement the phase shift gate in qiskit or ibmq?
Phase Shift Gate : $$\begin{pmatrix}e^{ia} && 0 \\ 0 && e^{ia}\end{pmatrix} = e^{ia}I$$
8
votes
2answers
237 views
Construct Controlled-$G^{\dagger}$ from known Controlled-$G$
Let there be a known a scheme (quantum circuit) of Controlled-G, where unitary gate G has G$^ā $ such that Gā G$^ā $ and GG$^ā $=I (for example S and S$^ā $, T and T$^ā $, V and V$^ā $, but not Pauli and H ...
8
votes
1answer
418 views
One-qubit gate results in QISKit
I found it odd that the result of the action of identity gate (namely a $2\times2$ identity matrix) on a pure state $|0\rangle$ (namely the vector corresponding to the $2\times1$ matrix $\begin{...
9
votes
2answers
1k views
Quantum algorithm for linear systems of equations (HHL09): Step 2 - Preparation of the initial states $|\Psi_0\rangle$ and $|b\rangle$
This is a continuation of Quantum algorithm for linear systems of equations (HHL09): Step 2 - What is $|\Psi_0\rangle$?
In the paper: Quantum algorithm for linear systems of equations (Harrow, ...
8
votes
1answer
513 views
Changing indices of qubits in QISKit
I was wondering if something like this is possible in QISKit: let's say we have two registers containing target and ancilla qubits:
$a_0$ -------------------
$a_1$--------------------
$\vdots$
$...
12
votes
2answers
1k views
Composing multiple quantum circuits in single quantum program in QISKit
I was wondering if there is a way to compose a program with multiple quantum circuits without having the register reinitialized at $0$ for each circuit.
Specifically, I would like run a second ...
9
votes
1answer
2k views
Visualization of Quantum Circuits when using IBM QISKit
I have followed the installation steps, regarding QISKit working environment. For circuit visualization, I've installed latex as in addition to poppler to convert from PDF to images. Afterwards, I ...
22
votes
3answers
6k views
How can I implement an n-bit Toffoli gate?
I want to create a Toffoli gate controlled by n qubits, and implement it in QISKit. Can this be done? If so, how?
9
votes
1answer
770 views
How to delete pending jobs on IBM Quantum Computer to retrieve units?
I am trying to run some code using qiskit, but I get the error message, that I have run out of necessary Experiment Units. I ...
5
votes
1answer
959 views
What is Qconfig in QISKit and how do I set it up?
To use certain things in QISKIt, such as acessing the real quantum processors, it seems that there is a file 'Qconfig.py'. That needs to be set up.
How do I do this?
7
votes
1answer
133 views
Why does job.running in QISKit output False, even if the job is still running?
I submitted a job in the 0.5.0 version of QISKit using
job = execute(qc, 'ibmqx5', shots=shots)
This just submits the job, and does not wait for a result.
I ...
8
votes
1answer
4k views
How to create an arbitrary state in QISKit for a local_qasm_simulator?
I would like to play with a quantum circuit local_qasm_simulator in QISKit, but I do not want to implement a separate quantum circuit that would prepare an initial ...
9
votes
2answers
618 views
There was an error in the circuit!. Error = 'QISkit Time Out'
I've got the following quantum code using QISKit (based on hello_quantum.py):
...
