Questions tagged [qiskit]
Quantum Software Development Kit for writing quantum computing experiments, programs, and applications. If appropriate, also use the [programming] tag.
185
questions
2
votes
1answer
37 views
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 ...
1
vote
0answers
31 views
'ERROR: QasmSimulator: Circuit cannot be run using available methods.'
I used the following code. Can anyone say what that error is about?
...
-3
votes
0answers
24 views
Code for implementing MCT in qiskit [duplicate]
I am trying to implement 7 control toffoli gate in qiskit .
2
votes
1answer
54 views
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, ...
3
votes
0answers
38 views
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 ...
-3
votes
1answer
91 views
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. ...
3
votes
1answer
67 views
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 ...
2
votes
1answer
40 views
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....
-1
votes
1answer
56 views
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 ...
0
votes
1answer
31 views
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 ...
3
votes
3answers
77 views
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
...
3
votes
0answers
103 views
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 ...
2
votes
1answer
58 views
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
...
1
vote
3answers
88 views
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 ...
2
votes
2answers
98 views
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)...
1
vote
1answer
44 views
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.
-2
votes
1answer
73 views
2
votes
1answer
48 views
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
...
2
votes
0answers
43 views
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?
2
votes
0answers
46 views
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:
<...
1
vote
1answer
47 views
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 ...
1
vote
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 ...
3
votes
2answers
105 views
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?
1
vote
3answers
105 views
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.
2
votes
3answers
43 views
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 ...
1
vote
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 ...
2
votes
1answer
37 views
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:
...
1
vote
2answers
114 views
How to get amplitudes only for chosen qubits?
For computation, I use N working qubits and M ancilla qubits.
...
2
votes
2answers
66 views
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 ...
0
votes
1answer
62 views
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 ...
0
votes
1answer
66 views
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 ...
1
vote
2answers
50 views
Why qiskit changed the order of gated applied to a circuit
Below I created a circuit and applied several gates to it:
...
0
votes
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.
...
2
votes
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 ...
1
vote
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 ...
2
votes
0answers
63 views
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) ...
2
votes
2answers
67 views
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 ...
1
vote
1answer
46 views
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 ...
2
votes
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 ...
1
vote
1answer
45 views
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 ...
1
vote
0answers
98 views
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 ...
1
vote
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?
0
votes
0answers
70 views
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:
...
2
votes
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 ...
3
votes
1answer
84 views
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.
...
1
vote
1answer
69 views
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 ...
2
votes
0answers
43 views
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 ...
1
vote
1answer
93 views
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 ...
1
vote
0answers
79 views
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])
...
1
vote
2answers
133 views
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 ...
