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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How many ancilla qubits to use with Multiple-Control Toffoli (mct) gate in Qiskit?

The Multiple-Control Toffoli (mct) gate takes as input: 1. a register containing the control qubits, 2. the target qubits and 3. a register containing ancilla qubits. I don't know how many ...
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'ERROR: QasmSimulator: Circuit cannot be run using available methods.'

I used the following code. Can anyone say what that error is about? ...
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Code for implementing MCT in qiskit [duplicate]

I am trying to implement 7 control toffoli gate in qiskit .
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When I load a saved account, I get a license-agreement error (links to old website)

I cobbled together a few programs with Qiskit several months back which worked fine on both the BasicAer simulators and the actual IBMQ computers. However, when I tried to revisit them recently, ...
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Is there a way to develop a multiple controlled X or Z gate on Qiskit without using ancillary qubits?

I know for instance I can derive a cccX gate using 2 Toffoli gates on 5 qubit wire or ccccX with 3 Toffoli gates and 7 qubits and so on. you will notice the depth is increasing as the number of ...
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Exploring quantum computing with Qiskit [closed]

I'm prepared to explore quantum computing which is completely new to me. Searching for a while on the Internet, I found IBM Qiskit which is an Open Source software necessitated for Quantum Computing. ...
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1answer
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What is a “barrier” in Qiskit circuits?

I just started studying IBM Qiskit, and cannot find details about the barrier method on the QuantumCircuit class. It is shown in the circuit drawing, but I never heard about it after reading quantum ...
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1answer
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n-qubit circuit run with > n qubits?

I was reading the Qiskit tutorial on circuit properties and there is a section (Unitary Factors) which states that even though an example circuit is made of 12 qubits, it may not need 12 qubits to run....
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1answer
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What is ''524 Server Error''?

When running my code, sometimes I find this 524 Server Error: Origin Time-out for url and then my code stop. The error is in ...
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1answer
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Quantum Circuit Properties typo (documentation bug?)

Just to report that the notebook "Quantum Circuit Properties" under the Tutorial uses a circuit named qc2 but afterwards the sample code still uses the ...
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3answers
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How to plot custom gate labels in Qiskit?

How can I create a custom gate in qiskit that is plotted using latex formatting (or another type of formatting)? For example the following code generates a circuit diagram ...
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Is it possible to run a general implementation Shor's algorithm on a real IBM quantum computer at least for N = 15?

I need to make a general implementation of Shor's algorithm that factors, at least, N = 15. I have been able to perform an implementation that works in simulators, with ProjectQ, but when running it ...
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1answer
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QAOA Maxcut for larger qubits

I am using QAOA to solve maxcut problem. It takes a very long time to simulate 10 qubits and I never get the results. Is there a way to simulate faster for larger qubit? Here is my code ...
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How many classical registers are there on (IBM) quantum computers?

I have a circuit where I only use 3 qubits but need to utilize hundreds of classical registers. My questions are: what is the maximum number of classical bits on the current IBM Qs? What is the ...
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How to unpickle a Result object returned by an IBMQ experiment?

I have executed an experiment using IBMQ and receive a Result object. I am writing the ASCII repr of the result with f.write(res)...
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1answer
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How can we construct a square root of NOT gate in Qiskit and IBMQ circuit composer using universal gates?

I have tried it with decomposing controlled S then conjugating with H gate. But I want to construct it using a minimum number of gates.
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In Qiskit, when creating multi-bit quantum and classical registers, what is the ordering of MSB to LSB?

When creating multi-bit quantum and classical registers, what is the ordering of MSB to LSB? For instance, I created a quantum register via ...
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Is it possible to simulate or replicate a cryptographic algorithm using Qiskit?

I would like to know if it is possible to recreate or simulate a cryptographic encryption algorithm like DES or AES using the quantum computing platform Qiskit from IBM?
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Running HHL tutorial on real backend

I tried to follow the HHL tutorial. Since the 8x8 problem is not realistically simulable (I stopped after a few minutes), I tried to make it run on another backend, starting on the easiest example: <...
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1answer
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Backend Warning: The skip Qobj validation does not work for IBMQ provider. Disable it

I am using QAOA to solve the max-cut problem. On my machine, 10 qubits already takes a minute or two to simulate. I'm hoping that the ibmq-qasm-simulator could simulate 32 qubits faster than my laptop ...
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1answer
36 views

Question on using the Collect2qBlocks() and ConsolidateBlocks() optimizations

I'd like to run the optimizations from Qiskit's level 3 transpiler pass on some example programs for benchmarking, but when I try to include the Collect2qBlocks() and ConsolidateBlocks() passes I get ...
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Big Endian vs. Little Endian in Qiskit

I've noticed that Q# favors Little Endian. Meaning that most operations are designed for this type of encoding. Is is it the same with Qiskit?
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Cirq, qiskit, q#, ibmq(circuit board), other [closed]

Which platform is the best for programming quantum computers? Which one is your personal favourite? If other mention which one it is and if possible few resources for it.
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3answers
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AttributeError: 'AerJob' object has no attribute 'get_counts'

result = execute(circuit, backend=simulator) plot_histogram(result.get_counts(circuit)) I used the above code to plot a histogram for a simple entanglement ...
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1answer
45 views

How to understand run_algorithm() inputs in qiskit

I'd like to better understand the Max-Cut algorithm from the qiskit tutorials. Particularly, the run_algorithm function inputs. The inputs are two dictionaries, but I can't find any documentation or ...
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1answer
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IBMQ.load_account from stored ACCOUNT is failing on Qiskit 0.9.0

The following statement is causing an error in Qiskit Version 0.9.0: provider = IBMQ.load_account() Error Message: ...
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How to get amplitudes only for chosen qubits?

For computation, I use N working qubits and M ancilla qubits. ...
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In Grover's Algorithm, does the exact solution need to be given to the oracle?

From my understanding, the oracle function in Grover's algorithm is used as a way to check for the desired outcome. I have looked at this example which implements the Exactly-1 3-SAT problem and the ...
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1answer
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Qiskit plot_histogram and count not working

im trying to plot a histogram of my code but when i run plot_histogram(results.get_counts(circuit)) it gives me a traceback error This is what i had before calling ...
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1answer
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How to obtain qubit's amplitude in qiskit

For example, I have some circuit circuit = QuantumCircuit(2) After operations: circuit.h(0) circuit.cx(0, 1) probability ...
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Why qiskit changed the order of gated applied to a circuit

Below I created a circuit and applied several gates to it: ...
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1answer
41 views

Qiskit - Renormalize the qubit after measurement

I have a 2 qubits system, maximally entangled, and I performed measurement on one of the qubit. ...
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2answers
48 views

Access results from an experiment without having to run the script again

I have ran an experiment in one of the IBM processors and the work has finished. However, I can not obtain the data as histograms or counts in the qiskit notebook because the experiment was concluded ...
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1answer
54 views

Loading Qiskit account in the Jupyter notebook gives RequestsApiError error

I successfully installed qiskit, yet am unable to load my account in the Jupyter notebook. Each time I load my account in Jupyter notebook here is the response I get RequestsApiError: 401 Client ...
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Error ERROR_TRANSPILING_JOB when trying to simulate the circuit

I'm trying to implement an algorithm (https://dl.acm.org/citation.cfm?id=1128034, basically a simple Grover Algorithm in which the oracle is made of a Fitness operator- some CNOT gates- and 2 adders) ...
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2answers
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Using Qiskit with Blender

I want to use Blender and Blender Python Scripts working with Qiskit. (want to make 3D creations) (www.blender.org) How can I do this ? (because when I try to install Qiskit inside Blender Python, it ...
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1answer
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qiskit - measure only 1 of the register out of n registers

I have created a 9 qubit register: q = QuantumRegister(9) c = ClassicalRegister(9) qc = QuantumCircuit(q, c) I want to measure only 1 of the register(let's ...
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1answer
57 views

Expected value of a product of the Pauli matrices in different bases

I'm trying to reproduce the results of this article https://arxiv.org/abs/1801.03897, using Qiskit and Xanadu PennyLane. Particularly, this part with expected values of the Pauli operators: For ...
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1answer
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How to do subplots when plot_histogram etc. closes the figure

I would like to display two histograms next to each other, using something like matplotlib's subplot function. This doesn't seem to work because plot_histogram() closes the figure. It is possible to ...
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Job execution issue while using IBMQ Experience

I am trying to run QSVM algorithm on the IBMQ backend devices using the API_TOKEN. Below is the snippet of the code that I am running. The code fails the validation test and throws an exception after ...
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1answer
121 views

How do I interpret the readout error for a quantum computer?

For example, the ibmqx2 computer has the most recent readout error of $4.40 \cdot 10^{-2}$. Does this mean per 1000 measurements, 44 faulty results exist?
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Why does Qiskit swap gate accept registers, but cswap doesn't?

In Qiskit, I am trying to perform controlled-Swap (cswap) of two registers, but an error occurs: ...
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2answers
242 views

How to calculate an Expected Value of some operator acting on qubits?

I'm trying to implement the Variational Quantum Eigensolver in Qiskit. Suppose, I have an operator $A = \sigma_1^z\sigma_2^z$ acting on some two-qubit state $|\psi\rangle$. After a measurement I get ...
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1answer
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Chose how to map virtual qubits to physical qubits

I'm currently trying to specify an initial_layout for a circuit on a IBM Q device. Looking at the device's topology I would like to use the less noisy qubits in order to have the best performance. ...
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1answer
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How is it possible to perform a c-not on 4 qubits using the same control qubits on IBM Q computers?

I was wondering after seeing ibmq_16_melbourne layout how it is possible to perform this circuit : It seems when looking at ibm q computers that a qubits can at max target 3 qubits because the arrow ...
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Hybrid classical-quantum linear solver based on the Neumann-Ulam method

I read this article on quantum linear solver based on the Neumann-Ulam method (here is a lesson about it). But the article has not a lot of details. Therefore I don't understand what is the algorithm ...
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1answer
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OpenPulse: Modifying pulse sequence for basic gates

I'm trying to familiarise myself with OpenPulse but I'm confused about a few things. Mainly, I would like to be able to take the pulse sequences that comprise standard gates on an IBMQ device and ...
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Please help: get_statevector gives wrong result in qiskit

I simulated the circuit below in qiskit and used the statevector simulator to extract the statevector: The resulting statevector that it gave me was: array([ 0.5+0.j, -0.5+0.j, 0.5+0.j, 0.5+0.j]) ...
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2answers
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How to initialize classical register in Qiskit?

I'm working on a Hybrid classical-quantum linear solver. For this, they make a loop on a quantum circuit (ie. below), and each time they change the value of the classical register and apply a X gate ...