Use this tag for questions about IBM's Quantum Service - Circuit Composer & Quantum Lab. DO NOT use this for questions about general Qiskit issues (use [qiskit] for that).
Questions tagged [ibm-q-experience]
673 questions
24
votes
2 answers
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 computing text books. Is it a unitary gate? If so,…
czwang
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21
votes
3 answers
What would a very simple quantum program look like?
After reading the "first programmable quantum photonic chip". I was wondering just what software for a computer that uses quantum entanglement would be like.
Is there any example of code for specific quantum programming? Like pseudocode or…
Didix
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20
votes
1 answer
What's meant by the depth of a quantum circuit?
I'm using Qiskit to create quantum circuits wherein I've this attribute called depth. The documentation states it is the length of the critical path here. What does it represent and how to find it out manually?
Van Peer
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18
votes
2 answers
How to implement the 4 Bell states on the IBM Q (composer)?
I would like to simulate the 4 "Bell States" on the IBM composer?
How can I best implement those 4 Bell states using the existing set of gates ?
Here below you see the definition of the 4 Bell states.
The first bell state can be easily implemented…
JanVdA
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18
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1 answer
Which subatomic particle does each company use in quantum computing?
Probably each company (Google, Amazon, Intel, IBM, Microsoft, D-Wave and so on) uses a mix of subatomic particles and technologies. I would like to know which particles/technologies are used by each company.
Are there specific reasons to choose a…
Felipe Rojo Amadeo
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13
votes
2 answers
How can a controlled-Ry be made from CNOTs and rotations?
I want to be able to applied controlled versions of the $R_y$ gate (rotation around the Y axis) for real devices on the IBM Q Experience. Can this be done? If so, how?
James Wootton
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12
votes
4 answers
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^{i\lambda} \sin\left(\frac{\theta}{2}\right) \\
e^{i\phi}…
Sanchayan Dutta
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12
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2 answers
Characteristics of the IBM quantum computer
On the IBM Quantum Composer website, there are characteristics of qubit computers. For example, ibmq_16_melbourne.
But there is no description anywhere of what:
T1(us),
T2(us),
Frequency (GHz),
Readout assignment error,
Prob meas0 prep1,
Prob meas1…
alexhak
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11
votes
1 answer
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 on a real quantum computer.
I have decided to try…
WaSon
- 111
- 4
11
votes
2 answers
Submitting jobs to IBMQ backend via HTTP API Requests
Qiskit can be used to submit jobs to IBM devices using Python (or Swift and JavaScript). But what if I want to use a different language?
For example, suppose I have a specific circuit I want to run. Assume I've already created it in Python Qiskit,…
James Wootton
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11
votes
3 answers
Implementation of the oracle of Grover's algorithm on IBM Q using three qubits
I am trying to get used to IBM Q by implementing three qubits Grover's algorithm but having difficulty to implement the oracle.
Could you show how to do that or suggest some good resources to get used to IBM Q circuit programming?
What I want to do…
Bick
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10
votes
2 answers
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, Hassidim & Lloyd, 2009), the details of the actual…
Sanchayan Dutta
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9
votes
3 answers
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 while I was logged off and therefore now I would…
Henao
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9
votes
2 answers
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 q[0] always correspond to the same qubit on a device (e.g. the qubit labeled q0 on the…
Mathist
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9
votes
1 answer
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$$
Debarghya Kundu
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