2022 Developer Survey is open! Take survey.

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).

Filter by
Sorted by
Tagged with
19 votes
1 answer
6k 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 ...
user avatar
  • 749
18 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 ...
user avatar
  • 765
17 votes
1 answer
3k 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 ...
user avatar
15 votes
2 answers
7k 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 ...
user avatar
  • 1,098
12 votes
1 answer
3k 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 ...
user avatar
  • 385
11 votes
1 answer
467 views

Submitting jobs to IBM devices without Python

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. ...
user avatar
11 votes
1 answer
3k 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?
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 ...
user avatar
  • 842
9 votes
1 answer
2k views

Phase-Shift Gate in Qiskit

How to implement the phase shift gate in qiskit or ibmq? Phase Shift Gate : $$\begin{pmatrix}e^{ia} && 0 \\ 0 && e^{ia}\end{pmatrix} = e^{ia}I$$
user avatar
9 votes
3 answers
3k 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?
user avatar
  • 1,098
9 votes
2 answers
2k 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: ...
user avatar
  • 431
9 votes
2 answers
741 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 ...
user avatar
  • 485
9 votes
3 answers
4k 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^{...
user avatar
9 votes
1 answer
1k 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 ...
user avatar
  • 91
9 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, ...
user avatar
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\...
user avatar
  • 137
8 votes
3 answers
2k 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 ...
user avatar
  • 113
8 votes
1 answer
690 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^*\\ ...
user avatar
  • 485
8 votes
2 answers
532 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 ...
user avatar
8 votes
1 answer
924 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 ...
user avatar
8 votes
1 answer
453 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 ...
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 ...
user avatar
7 votes
3 answers
135 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 ...
user avatar
  • 293
7 votes
3 answers
1k 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?
user avatar
  • 1,223
7 votes
2 answers
323 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: ...
user avatar
  • 2,158
7 votes
1 answer
940 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.
user avatar
7 votes
1 answer
121 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 ...
user avatar
7 votes
1 answer
876 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 ...
user avatar
7 votes
1 answer
282 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 ...
user avatar
7 votes
2 answers
777 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 ...
user avatar
6 votes
2 answers
1k 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 ...
user avatar
  • 728
6 votes
2 answers
820 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 ...
user avatar
6 votes
3 answers
109 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=...
user avatar
  • 121
6 votes
2 answers
577 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 ...
user avatar
6 votes
3 answers
571 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 ...
user avatar
  • 121
6 votes
1 answer
274 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 ...
user avatar
6 votes
1 answer
420 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 ...
user avatar
6 votes
2 answers
418 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% ...
user avatar
6 votes
1 answer
748 views

What is the state of the art on Quantum Random Access Memories? [duplicate]

I realized that Quantum Random Access Memory (qRAM) was proposed to make quantum computers more similar to classical one. Currently quantum computers have very constrained memory, given only quantum ...
user avatar
6 votes
1 answer
375 views

How to implement a Square root of Swap gate that swaps 2n-qubits on the IBM Q (composer)?

I am looking for an implementation using the quantum gates provided by the IBM composer of the following quantum function: input $2n$ qubits output $2n$ qubits wherein $50\%$ of the cases the state ...
user avatar
  • 1,098
6 votes
1 answer
359 views

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

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

Do individual qubits on IBM quantum processors share the same control unit?

I want to investigate the maximum possible parallelism of quantum operations on a specific IBM device (such as the latest heavy-hex architecture), which requires a basic knowledge of their control ...
user avatar
  • 71
6 votes
1 answer
991 views

My IBM quantum account has been disabled [closed]

As shown in the picture above, my IBMQ account is unavailable, and I found that my friend's account is also unavailable, but I have not received any email or message notification. what happened?
user avatar
  • 179
5 votes
3 answers
1k 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 ...
user avatar
5 votes
2 answers
946 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?
user avatar
  • 131
5 votes
2 answers
974 views

Trying to build a circuit for quantum teleportation on IBMQ I get ERROR_RUNNING_JOB error

I am trying to build a circuit for quantum teleportation. On the simulator, everything runs fine and according to expectations, however, I am not able to run the algorithm on the real quantum ...
user avatar
5 votes
1 answer
1k 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!
user avatar
  • 179
5 votes
2 answers
873 views

Given a state $|\phi\rangle=\frac{1}{\sqrt{2}}(|0\rangle+e^{i\theta}|1\rangle)$, how do I know the angle $\theta$?

Question1. If there is a state $|\phi\rangle=\frac{1}{\sqrt{2}}(|0\rangle+e^{i\theta}|1\rangle)$, and I want to know the angle $\theta$. What kind of measurement should I do? Could somebody give me ...
user avatar
5 votes
2 answers
309 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?
user avatar
5 votes
2 answers
501 views

Can I initialize only one qubit in a 4-qubit circuit?

I wonder if there's a way we can initialize the quantum state only for part of the qubits in a quantum circuit. Say if I have a quantum circuit defined as ...
user avatar
  • 2,158

1
2 3 4 5
12