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. As of August 2020, there are 20 processors on the IBM Q Experience ranging from 5 to 53-qubits. Note: Some systems are only available to hubs, partners, and members of the IBM Q network.

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16
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3answers
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 ...
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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 ...
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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?
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1answer
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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. ...
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2answers
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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 ...
9
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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 ...
9
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2answers
3k 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 ...
9
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3answers
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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?
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2answers
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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, ...
8
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2answers
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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 ...
8
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1answer
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Phase-Shift Gate in Qiskit

How to implement the phase shift gate in qiskit or ibmq? Phase Shift Gate : $$\begin{pmatrix}e^{ia} && 0 \\ 0 && e^{ia}\end{pmatrix} = e^{ia}I$$
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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^*\\ ...
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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 ...
8
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746 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 ...
7
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2answers
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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\...
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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 ...
7
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3answers
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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^{...
7
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2answers
702 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 ...
7
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1answer
737 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 ...
7
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1answer
335 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 ...
7
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1answer
225 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 ...
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708 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 ...
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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 ...
6
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1answer
474 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.
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1answer
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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 ...
6
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1answer
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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 ...
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335 views

How to run a qasm file on IBMQ device?

I can found many qasm examples. How can I run them on different IBMQ devices?
5
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2answers
201 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?
5
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1answer
371 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!
5
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1answer
129 views

How to not optimize the quantum gates in a qiskit circuit when running it in the real device?

I have been trying to run two circuits in the ibmq_london device, the one resulting of applying one X gate on qubit $0$ and the one that applies two X gates. I know that applying two X gates is the ...
5
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2answers
958 views

Controlled-U operation in IBMQ

Suppose we have any matrix in $\mathrm U(2)$ and we need to construct a Controlled-$U$ operation with the $H,T,S$ gates. Then I am aware of the construction given in N&C of decomposing $U$ into $e^...
5
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1answer
159 views

How to implement a random selection of one of the 3 qubits on the IBM Q (composer)?

I would like to implement a quantum program on the IBM Composer with following characteristics: The output is the observed value of 3 qubits Only one of the 3 qubits should be observed as $1$, the 2 ...
5
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1answer
129 views

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

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

Reversal of time arrow on IBM Q

It is well known that a quantum computer is reversible. This means that it is possible to derive an input quantum state $|\psi_0\rangle$ from an output $|\psi_1\rangle$ of an algorithm described by a ...
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317 views

Why is there a difference between the simulation results and the actual quantum computer results?

I ran the Grover's Algorithm for 3 Qubits on the IBM Q platform (ibmqx4) and the results of the simulation and the actual computer differ a lot. The screenshots of the circuit and the results are ...
4
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1answer
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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 ...
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4answers
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Implementing four oracles for the Deutsch Algorithm (preferably on IBM Q Experience)

I guess, I understood simple Deutsch Algorithm (if unary function is balanced or constant) as described here: Introduction to quantum computing: The Deutsch algorithm I need to test it. I was ...
4
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2answers
1k views

Comparing run times on IBM Quantum Experience

I have run this program - ...
4
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2answers
782 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 ...
4
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1answer
267 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 ...
4
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3answers
464 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 ...
4
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1answer
208 views

Moore's law for quantum computers

Moore's law states that performance of classical computers doubles every two years (later revised to 18 months) and a price for computing resources halves during same time period. Currently, it seems ...
4
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1answer
354 views

How can I get the entire histogram in a 5 qubit program done in IBM quantum experience machine?

I have run a program on an IBM quantum experience machine which involves 5 qubits. Obviously when I measure the whole system I have 32 results but the machine only represents 20 in the histogram. In ...
4
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1answer
213 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 ...
4
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2answers
104 views

How to create the logical $|0_L\rangle$ state for the Steane's 7-qubit code?

I don't know how to prepare using Qiskit the following state in order to implement a Steane's 7-qubit code circuit (I omit the normalization factor): \begin{align*} |0_L\rangle =&|0000000\rangle+|...
4
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1answer
214 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 $...
4
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1answer
283 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 ...
4
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1answer
98 views

Why are there such different UGate and U3Gate implementations in the Qiskit documentation?

The documentation for the new version Qiskit 0.20.0 states that: UGate is "Implemented using two X90 pulses on IBM Quantum systems: $U(θ,ϕ,λ)=RZ(ϕ−π/2)RX(π/2)RZ(π−θ)RX(π/2)RZ(λ−π/2)$" ...
4
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2answers
197 views

How do I get out 2 measurements from the same execution on Qiskit?

Here's my circuit, trying to checkout the effect of measurement on the IBM Q circuit. Here you can see I do 2 different measurement at different time, and I hope to be able to see both results. ...
4
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1answer
653 views

Qiskit - How do we measure the same single qubit system multiple times while also getting the counts/results after each measurement?

I am able to apply multiple measurements (2) to the same qubit system. However, I would like to get the counts right after each measurement is executed. I realize that the counts should be the same ...

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