Questions tagged [qiskit]

Quantum Software Development Kit for writing quantum computing experiments, programs, and applications. If appropriate, also use the [programming] tag.

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1answer
231 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 ...
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1answer
160 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 ...
3
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1answer
143 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' ...
6
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1answer
896 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 ...
4
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2answers
656 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 ...
4
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1answer
171 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 ...
4
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1answer
510 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
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2answers
334 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 ...
3
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2answers
907 views

Comparing run times on IBM Quantum Experience

I have run this program - ...
9
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3answers
425 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 ...
6
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1answer
312 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.
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1answer
282 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
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1answer
326 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 ...
5
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1answer
323 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 ...
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1answer
1k 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
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2answers
299 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
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1answer
960 views

Phase-Shift Gate in Qiskit

How to implement the phase shift gate in qiskit or ibmq? Phase Shift Gate : $$\begin{pmatrix}e^{ia} && 0 \\ 0 && e^{ia}\end{pmatrix} = e^{ia}I$$
6
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2answers
177 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$^†$ such that G≠G$^†$ and GG$^†$=I (for example S and S$^†$, T and T$^†$, V and V$^†$, but not Pauli and H ...
7
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1answer
350 views

One-qubit gates 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
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2answers
972 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, ...
7
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1answer
435 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: $a_0$ ------------------- $a_1$-------------------- $\vdots$ $...
9
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2answers
487 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 ...
8
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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 ...
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3answers
4k 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?
8
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1answer
639 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
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1answer
835 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?
6
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1answer
113 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 ...
5
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1answer
2k 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 ...
8
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2answers
513 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): ...

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