Questions tagged [ibm-q-experience]

Use this tag for questions about IBM's quantum processors which are accessible online. DO NOT use this for questions about general Qiskit issues. As of July 2018, there are five processors on the IBM Q Experience: two 5-qubit processors, one 16-qubit processor and two 20-qubit processors (only available to hubs, partners, and members of the IBM Q network).

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75 views

Why does my code run a long time?

I want to run code on ibm qx, and I choose the backend "simulator", I also use the monitor to check the queue, but I have this problem. "Job is actively running" still a long time, how can I solve ...
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Software for Quantum Computing

From what I read classical computing evolved so quickly because of the funding-applications cycle. Even though the cost to make denser IC's was increasing rapidly, the applications were also getting ...
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What is the IBM Q credits?

I find in this link that "A User has a maximum of 15 credits, and these credits are replenished upon the greater of 24 hours or when your execution has run off the queue." But what is credit? Is ...
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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 ...
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76 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?
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Gate error in IBM-Q simulator vs real backend

Does the simulator of the IBM-Q supercomputer involves a CNOT gate error rate ? What are the main differences reasons in outcome between simulators and real backends in IBM-Q ? Best,
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58 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. ...
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1answer
47 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 ...
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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]) ...
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ERROR_RUNNING_JOB with 32 qubit circuit running on ibmq_qasm_simulator backend

I recently made a quantum circuit that uses 32 qubits and try to run it on IBM Q Experience qasm_simulator backend. But it always ends with ERROR_RUNNING_JOB. ...
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Measuring the effect of energy relaxation with IBMQ Experience

I want to investigate the effect of the decoherence time on a qubit, and I followed the tutorial here. https://quantumexperience.ng.bluemix.net/proxy/tutorial/full-user-guide/002-...
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1answer
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How call from IBM Q Experience (Jupyter Notebook) cplex

I have the latest version of cplex (12.9) installed on my computer. I use it very well with Jupyter notebook, but in IBM Q Experience, I did not get way to call it. IBM Q Experience warns me that the ...
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edit a program on IBM Q experience

Can I edit a program with python numpy and scipy and of course qiskit in the IBM Q experience, using code? (I am not interested in drugging gates) and I can't find the way to edit my own program
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Problem with initial_layout on Qiskit/IBMQ: 'Not enough qubits in CouplingGraph'

I am trying to run an execution on IBMQx2 where I can specify the physical qubits to which I apply gates. The execution without the initial_layout runs fine, but ...
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165 views

How do I check my remaining IBM Q credits?

I've already tried the approach in this answer, but I'm getting this error: ...
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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. ...
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Number of Shots always 1024/or nothing (IBM q experience)

I have been running some simple "Hello Quantum World" code and every time I try to run it on 4096 shots or 8192 shots, the results always show as if I ran the code on 1024 shots (or in the most recent ...
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1answer
79 views

How to upload .py file to new online Qiskit Notebook

I'm trying to run a program in the Qiskit Notebook on the IBMQ Experience. I need to import some .py files that I've done in order to run my main program but the notebook won't accept .py files. I've ...
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Measuring Coherence Length for T1 and T2 values with IBMQ Experience

So I'm currently working on a little program to measure how long the coherence time of a qubit is. Basically the idea is to initialise a qubit with a X or H gate then stick in a varying amount of ...
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73 views

What does a quantum circuit look like after qiskit.compile() has been applied?

IBM-Q states that the real devices available for public use have a set of "basis" gates consisting of u1,u2,u3 and CNOT. However in Qiskit the circuit can be built with many gates which are not ...
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Having trouble communicating with the IBM Q Experience REST API

I have started using IBM's Q Experience and I am trying to obtain an access token in order to communicate with the REST API. I understand that I can use my API token to obtain authorization by sending ...
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Bug report bug report? [duplicate]

The full user guide here states "If you find any bugs, please report them with our bug tracker, accessible via the little bug icon in the lower right-hand corner of each page." However, I was unable ...
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1answer
54 views

Bug in IBM backend?

I was trying to see what IBM would do under the hood with a CCNOT gate. Something appears to be erroneous with the run. The circuit above should produce state 11100 with 100% probability, as ...
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Bell State 11 not working for parity curve

I am currently writing a script to automate the creation of parity curves for a 2 qubit bell state and then calculate fidelity and proving entanglement from that (inspired by this paper). It was going ...
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1answer
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IBM Slack links broken

Does anyone know where I can find working Slack invite links to any of IBM's Slack pages? The Slack links on this support page are all broken. Thank you.
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1answer
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Experiments stuck on VALIDATING ibmq_16_melbourne

Since yesterday I'm trying to run on the new composer (quantum-computing.ibm.com) both new experiments (never run before) and older experiments (that have been successfully run and completed some ago) ...
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1answer
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Back End for Reset Gate

IBM's simulator allows the use of a reset gate ($|0\rangle$ gate) however when I try to run a circuit using this gate on the hardware it fails to execute. Is there a plan to physically realize this ...
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1answer
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Weeding out qubit states with leftmost qubit as 1

Need help! I was working on a project when I required to use a projection operator. For an example case, I have the Bell state, $$|\psi\rangle = \frac1{\sqrt2}\left(\color{blue}{|0}0\rangle+|11\rangle\...
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Visualizer error in IBM Q Experience Beta

I am noticing some erroneous behavior coming from the visualizer in some circuits I was running. I am not sure how widespread the issue is, but see the attached image for some strange behavior with ...
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Results from looped experiments on IBM Q different than individual experiments

I'm experiencing an issue while using Qiskit where the counts from a job return vastly different values when ran in a loop or as an array of circuits as opposed to single experiments when run by ...
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1answer
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How to implement the XY Heisenberg interaction using IBMQ and Qiskit?

A possible way to implement the 2 qubit Heisenberg XYZ model using a Quantum computer is to decompose the Hamiltonian as follows: $$H_{XYZ} = H_{XY} + H_{YZ} + H_{XZ}$$. In this case, these operators ...
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1answer
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2-qubit QFT in IBMQ: controlled phase rotation

I've started getting into quantum computing in the last few days. As part of the learning, I've figured it would be fun to implement some circuits on IBMQ Experience as I learn. So now I'm stuck with ...
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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 ...
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1answer
51 views

How to define custom controlled unitaries in OPENQASM 2.0?

According to the OPENQASM 2.0 documentation, it's possible to define custom unitary gates using the format: gate name(params) qargs { body } where the optional ...
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Implementing Deutsch's problem on IBM Q composer

I tried to implement the Deutsch's problem on IBM Q but didn't get the results as expected. So here is the circuit for the Deutsch algorithm and this is my implementation on the composer: so let me ...
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How to run quantum SVM algorithm from Qiskit in real IBM Quantum Computer using IBMQ?

I'm trying to run QSVM algorithm in IBMQ experience, want to run in one of those real quantum computers. ...
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IBM Q devices' hardware/resource constraints

I tried to look for the resource constraints but so far haven't been able to find them. They are not present in the GitHub repository that usually provides the hardware information for the different ...
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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^{...
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2answers
257 views

How do the credit points work in IBM quantum experience?

I am using Qiskit language, and I am working with IBM devices via Quantum Experience beta. How can I find how many credit points I have used and how much there are left till they fill back 24 hour's ...
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2answers
216 views

IBM QISKit: creating a variational algorithm from zero

I would like to implement a variational algorithm (similar to VQE but with another cost function, no expectation of a Hamiltonian involved) from zero. Is there any tutorial explaining how to implement ...
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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 ...
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How to measure a Bell inequality violation in IBM Q?

Note: Cross-posted on Physics SE. I made some circuit to prepare a 2 qubit state, but I am having trouble understanding how to measure Bell's inequality. I know the inequality is of the form $$|E(a,...
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1answer
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Interpreting results from IBM's processor vs. simulator

I am working with a circuit where I use 4 cables, and perform measurements in all of them. Nevertheless, I am only interested in the results from two cables since the other two are ancillas. When I ...
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What interesting properties can I measure with a 1 qubit state?

I am playing with the IBM Q and I would like to know what interesting properties I can measure with only a 1 qubit state. This is because things like Bell's inequalities, concurrence, PPT criterion, ...
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1answer
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Making a maximally mixed 2-qubit state in the IBM Q

I am trying to make a 2-qubit maximally mixed state $\mathbb{I}/4$ where $\mathbb{I}$ is the identity $4\times 4$ matrix. I know that, for a maximally mixed 1-qubit state I can use a Hadamard gate, ...
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Implementing a depolarizing channel for 2 qubits on IBM Q

I am trying to use IBM Q to perform the following depolarizing channel on a state of 2 qubits $\rho=|\psi \rangle \langle \psi |$: $$\rho \to (1-\lambda)\rho + \frac{\lambda}{4}I$$ This is within ...
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1answer
125 views

Experiment runtime on IBMQ

I have been trying to get the runtime of my experiment on IBM's quantum computer. I am using the classic stuff, i.e ...
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1answer
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How many physical qubits are used when I run a program on a IBM Q computer?

How do I find out how many physical-qubits I'm using when I run my program in an IBM Q backend quantum computing system?
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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 ...
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1answer
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How much variation is there in the results between each quantum computer on the IBMQ Quantum Experience system?

For example, if you ran the same program on the 'ibmqx2' and 'ibmqx4' computers, how much variance would there be between the results from both systems? There is the inherent presence of noise in each ...