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Questions tagged [ibm-q-experience]

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).

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22 votes
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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 ...
czwang's user avatar
  • 859
20 votes
3 answers
1k views

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 ...
Didix's user avatar
  • 785
19 votes
1 answer
9k views

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 ...
Van Peer's user avatar
  • 577
18 votes
1 answer
4k views

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 ...
Felipe Rojo Amadeo's user avatar
18 votes
2 answers
10k views

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 ...
JanVdA's user avatar
  • 1,148
12 votes
4 answers
5k views

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^{...
Sanchayan Dutta's user avatar
12 votes
2 answers
5k views

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's user avatar
11 votes
2 answers
3k views

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: ...
alexhak's user avatar
  • 471
11 votes
1 answer
568 views

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. ...
James Wootton's user avatar
11 votes
3 answers
2k views

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 ...
Bick's user avatar
  • 842
11 votes
1 answer
2k 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 ...
WaSon's user avatar
  • 111
10 votes
2 answers
2k 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, ...
Sanchayan Dutta's user avatar
9 votes
1 answer
4k views

Phase-Shift Gate in Qiskit

How to implement the phase shift gate in qiskit or ibmq? Phase Shift Gate : $$\begin{pmatrix}e^{ia} && 0 \\ 0 && e^{ia}\end{pmatrix} = e^{ia}I$$
Debarghya Kundu's user avatar
9 votes
3 answers
4k views

How to implement the "Square root of Swap gate" on the IBM Q (composer)?

I would like to simulate a quantum algorithm where one of the steps is "Square root of Swap gate" between 2 qubits. How can I implement this step using the IBM composer?
JanVdA's user avatar
  • 1,148
9 votes
2 answers
848 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 ...
Mathist's user avatar
  • 495
8 votes
2 answers
1k views

Changing one qubit causes changes in another independent qubit on ibmqx2 in IBM Q Experience

When I run this program on ibmqx2 (the backend matters) in IBM Q Experience, the results are interesting. Essentially, the program measures the error rate on $|q_0\rangle$ after fiddling with $|q_1\...
balios's user avatar
  • 137
8 votes
3 answers
194 views

What are the differences between the IBM machines?

I'm quite new to this field, and have started sending jobs to IBM's quantum computers. I have access to around 11 locations. I can see that these have different numbers of qubits within them, and then ...
Andrew's user avatar
  • 333
8 votes
3 answers
3k 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 ...
Henao's user avatar
  • 113
8 votes
2 answers
498 views

Apply readout error mitigation to mid-circuit measurement

I'm trying to construct a quantum circuit with 3 mid-circuit measurements, here's an example: ...
ZR-'s user avatar
  • 2,398
8 votes
1 answer
1k views

What are the differences between the different transpiler optimization levels in qiskit

I am currently running a simple algorithm using Qiskit and I am running it for various transpiler optimization levels (0-3). I wish to know what exactly occurs differently when for example I run the ...
Generic_dp's user avatar
8 votes
1 answer
2k views

Depolarizing channel implementation on IBM Q

Given a single qubit in the computational basis, $|\psi\rangle =\alpha |0\rangle + \beta|1\rangle$, the density matrix is $\rho=|\psi\rangle\langle\psi|=\begin{pmatrix} \alpha^2 & \alpha \beta^*\\ ...
Mathist's user avatar
  • 495
8 votes
1 answer
308 views

$T_2>2T_1$ qubits on the ibm_washington quantum processor

I have been checking out the parameters of the new ibm_washington processor and I have the following doubt about the calibration data provided by them. Checking out the relaxation and dephasing times ...
Josu Etxezarreta Martinez's user avatar
8 votes
2 answers
562 views

Practical Implementations of QECCs in IBM Q Experience

I am learning how to program the IBM Q Experience quantum computers in order to learn more about how does it work and in order to perform some experiments in it. By doing so I was wondering what are ...
Josu Etxezarreta Martinez's user avatar
8 votes
1 answer
1k 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 ...
brzepkowski's user avatar
  • 1,049
8 votes
1 answer
2k views

Physical implementation of gates on IBM Q

There is a lot of quantum gates in IBM Q Composer, however, only few are implemented physically while others can be composed of them. When one looks at description of a quantum processor in IBM Q ...
Martin Vesely's user avatar
8 votes
1 answer
521 views

How does measurement calibration work?

One of the possible ways to improve the results of an experiment on the IBM machine using the Qiskit language is to use the measurement calibration methods. This is the link to the documentation. I ...
Marco Ballarin's user avatar
7 votes
3 answers
3k views

How are IBM's 127 qubits more potent than the 5760 qubits D-Wave - Advantage_system6.1?

Hi I'm a newbie in quantum computing recently I had a look at the AWS braket and I've seen they had a machine called D-Wave - Advantage_system6.1 that has 5760 qubits but when I googled the highest ...
Zakaria Halloumi's user avatar
7 votes
1 answer
2k views

Why use U2 and U1 gate in IBM quantum computers?

I was wondering why IBM's computer were using U1 and U2 gates as part of there basis gates since as I understood, they are particular cases of the U3 gate. Why not just use U3 gate instead ? Thanks ...
Samuel Beaussant's user avatar
7 votes
2 answers
3k views

How do I get the names of all currently available IBMQ devices?

How do I get the names of all currently available IBMQ devices?
Holger's user avatar
  • 161
7 votes
2 answers
2k views

What is maximum circuit depth and size IBM Q5 and Q16 could handle?

I'm trying to implement a couple of algorithms on ibmq_16_melbourne, so I need to know if this device is able to handle with depth and size of my current circuit or ...
C-Roux's user avatar
  • 888
7 votes
3 answers
3k views

How to run a qasm file on IBMQ device?

I can find many qasm examples. How can I run them on different IBMQ devices?
peachnuts's user avatar
  • 1,393
7 votes
1 answer
1k 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.
Theodore Lewitt's user avatar
7 votes
1 answer
334 views

How are Rigetti and IBM QX device parameters related to Kraus operators?

Rigetti reports the following parameters: (https://www.rigetti.com/qpu) T1, T2* times 1-qubit gate fidelity (F1q) 2-qubit gate fidelity (F2q) and, read-out fidelity (Fro) IBM QX reports the ...
Edifice's user avatar
  • 429
7 votes
2 answers
851 views

How can I get access to IBM Q 20 Tokyo and IBM Q 20 Austin?

How can I get access to IBM Q 20 Tokyo and IBM Q 20 Austin? In the Q- experience site there is written that the access is for IBM clients only and in the profile there is a "promotional code" that ...
Daniel Vainshtein's user avatar
7 votes
1 answer
276 views

Publicly available samples for quantum circuits and/or simulators

With Yosi Rinott and Tomer Shoham we studied various statistical aspects of samples coming from NISQ computers. My question is about available data consisting of samples from NISQ computers We would ...
Gil Kalai's user avatar
  • 201
7 votes
1 answer
626 views

Why is a different convention used for the $Rz$ implementation on IBM Q?

A $z$ rotation gate is defined as $$ Rz(\theta)=\mathrm{e}^{-i\frac{\theta}{2}Z}= \begin{pmatrix} \mathrm{e}^{-i\frac{\theta}{2}} & 0 \\ 0 & \mathrm{e}^{i\frac{\theta}{2}} \end{pmatrix}, $$ ...
Martin Vesely's user avatar
7 votes
1 answer
851 views

How can I run a VQE on one of IBMQ's Quantum Computers

I have implemented a VQE based on Qiskit's VQE function and want to run that on an actual quantum computer. My understanding was, that an IBMQ backend can be passed into the function as a Quantum ...
Tom's user avatar
  • 71
6 votes
3 answers
8k views

How can I obtain transformation matrix of a quantum circuit in the Qiskit?

I need to draw a quantum circuit in Clifford+T library and obtain automatically its transformation matrix. Is there any feature on Qiskit in this case?
Moein sarvaghad's user avatar
6 votes
1 answer
2k views

What does the error rate on the IBMQ website mean?

How is the error rate pointed by the arrow defined? How did you get it? thanks!
wei zi's user avatar
  • 325
6 votes
2 answers
945 views

What are examples of quantum computing platforms availble for free (other than IBM Q)?

IBM Q is (maybe first) quantum computing platform allowing users to register for free and run algorithm on real quantum processors. There are several processors with usually 5 qubits, however, it is ...
Martin Vesely's user avatar
6 votes
3 answers
118 views

How to create the state $\vert 0 \rangle+i \vert 1 \rangle$ using elementary gates?

I am trying to write $|0\rangle+i|1\rangle$ in terms of elementary gates like H, CNOT, Pauli Y, using the IBM QE circuit composer. I was thinking some kind of combination of H and Y since $Y|0\rangle=...
Natasha's user avatar
  • 121
6 votes
2 answers
438 views

How to implement the CCH gate in quantum computers available in clouds?

How to implement CCH gate in quantum computers available in clouds? If there is not any gate directly available for it, what are the possible ways to represent CCH?
Ankit Raj's user avatar
6 votes
2 answers
915 views

Custom gates on IBM Q

I realized that QASM supports custom gates. However, when I tried to create the gate, transpiling error appeared both on simulator and real quantum processor. I suspect that IBM has not implemented ...
Martin Vesely's user avatar
6 votes
3 answers
930 views

Why can I not apply a control gate/function to a gate like T, S, S dagger, ... (using IBM Quantum Experience)? Is there another option?

I am trying to use the circuit composer of the IBM QE. I am doing the inverse QFT on 3 qubits and therefore need a control on T and S dagger gates, but it won't let me. Does anyone know why or know a ...
Natasha's user avatar
  • 121
6 votes
1 answer
5k views

How to make circuit for n-control Z gate( i.e $C^3Z$ )?

I am trying to make circuit for $C^3Z$ gate I have seen a circuit for $C^2Z$ or $CCZ$ gate made by using $CCX$ gate so is there any way to make circuit for $C^3Z$ in this similar manner( i.e by using $...
zircon's user avatar
  • 439
6 votes
1 answer
676 views

What is the basic hardware gate library in the IBM & google?

I need to know what is the basic hardware gate library in hardware IBM and Google? I mean, which one of the gates can be implemented directly in the hardware. I would be very grateful if everyone ...
Moein sarvaghad's user avatar
6 votes
1 answer
562 views

How to parallelly run a quantum circuit on IBMQ?

I am trying to implement the following circuit and my code is The above circuit has size 5 and depth 3. My question is, how can I run the circuit parallelly. I mean, the gate ...
wei zi's user avatar
  • 325
6 votes
1 answer
892 views

IBM Q devices scheduling of gates with different durations

I was trying to figure out how scheduling works in IBM devices. The thing that's bugging me is that in the quantum computer implementations I had seen before, the cycle concept is used. Say, for ...
Kelthar's user avatar
  • 149
6 votes
2 answers
629 views

Simple Hadamard Circuit gives incorrect results?

I am running the simplest Hadamard circuit possible - one qubit, initialised to 0, apply H gate, measure in Z basis. When I run the circuit on the simulator I obtain the expected result (50% in 0, 50% ...
Catherine's user avatar
6 votes
1 answer
2k views

What is the difference between Qiskit execute and the IBMQJobManager?

I was researching how to submit multiple pulse schedules/circuits in the same job and came across 2 methods: Executing Experiments with qiskit.execute and ...
MShakeG's user avatar
  • 411

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