Scheduled maintenance

Maintenance of our systems is crucial. To give you the best performance we are doing extra maintenance, tuning and calibration of our systems and are preparing our systems for some hardware upgrades. This may lead to limited online availability and/or reduced performance of our systems. Meanwhile you can continue using our simulators, including a new fast system, QX-34-L, installed on Lisa, a powerful HPC system at Surf. You can now simulate up to 34 qubits on this back-end (QX-34-L). For the moment, this system is available to all users, even with a basic account!

Known issues and Frequently Asked Questions

reporting bugs or issues

I found a bug that is not listed below or I want to provide some feedback on QI. Who do I contact?

Your feedback, questions, bugs and comments can be sent to:


Please include where possible:

  • a detailed description of the error/bug, with step by step instructions how to reproduce the error
  • what exactly happened
  • what you were expecting to happen
  • a copy of your code that returns an error
  • a screenshot of your observations

Login and accounts

I forgot my password or want to change it

You can reset your password by clicking the 'Forgot password?' link on the log in screen or 'Change password' under My Account. Enter your email address and you will be sent a link to change your password.

I want to delete my account

You can delete your account clicking the 'Delete link' under my account. This will remove your account and all data related it to it such as projects and project results. If you accidentally remove your account we have no options to restore it.

I cannot login with my account

Your login name is the email address that you used for registration. If you keep having issues with logging in and resetting your password does not help please contact our support team at support@quantum-inspire.com.

I cannot change my username or email address

This functionality is not included. if you have issues with your account please contact our support team at support@quantum-inspire.com.

Password not accepted during registration or change of password.

When your password does not conform to the requirements, it is not accepted. Sometimes this happens silently (you don't get feedback that it failed or why). Please make sure you follow the following password requirements:

  • Should not be similar to your email address (or parts thereof)
  • Must be 8 characters at least
  • Cannot be too common (things like ‘secret’ are not allowed)
  • Cannot be just numbers

Password change does not work even when I use the rules above.

When you register your account you are requested to provide your email address.

  • Please check whether you filled in the correct email address.
  • We do not check for correctness of the email address to avoid database probing.

I did not get a confirmation email.

This may have the following causes:

  • We do not check for correctness of the email address to avoid database probing. Make sure you do not have a typing error in your email address (like myname@gmial.com instead of myname@gmail.com)
  • The confirmation email is regarded as spam. Please check your spam-box or contact your emial provider.
  • Some Chinese providers like NetEase (163.com) and Tencent (qq.com) show a high rate of email bounces (our confirmation mail does not reach the new user). If you experience these issues contact us directly at support@quantum-inspire.com so we can help ou activate your account.

Writing algorithms

No known issues

Executing algorithms

It takes many minutes/hours for my algorithm to be executed.

We have two quantum chip chips available. When many users submit jobs, your job will be put in the queue and executed when it reaches the front of the queue. You are not allowed to have more than 3 jobs in the queue for a hardware backend, in order to provide equal access opportunities for everybody. (Attempts of) abuse will lead to removal of your account.

  • The status of the execution is automatically refreshed in your web browser every 30 seconds. On most browsers clicking F5 will actively refresh your browser and results status.
  • Including overhead a typical job on a hardware backend takes 30 to 90 seconds. There may be other jobs before you in the queue which will add to the waiting time.
  • Hardware backends require regular tuning to maintain their optimum performance. The Spin-2 backend comes with an extensice automated tuning program that takes from a few seconds to 30 minutes long. When your job is scheduled while tuning is ongoing, this will add to your waiting time. In this version of the software we do not show when the system is actually calibrating. This will be updated in a next version.
  • When you run an algorithm on a emulator, it is usually NOT necessary to end it with a measurement instruction. This section of the knowledge base explains when it is better to omit the measurement (which DRASTICALLY improves execution time) and when it is needed to include a measurement statement at the end of the algorithm. Make sure you read this carefully because the correct implementation and details differ between WEB GUI and API access and whether you use the SDK with ProjectQ or Qiskit.
  • It could also be that you selected a large number of shots for a simulated algorithm. Try to start a new project with a smaller number of shots and copy the code and re-run. Please contact our support team at support@quantum-inspire.com if you think your algorithm stays in queue for a too long time.

Based on the reported fidelities I expect a higher probability for certain outcomes of experiments.

The reported fidelities for single- and two-qubit gates are based on standard benchmark methods like randomized benchmarking, which are independent of initialization and readout fidelity (sometimes reported as visibility), which are usually the dominant factor in current state-of-the-art devices. In research papers, the initialization and readout fidelities are often compensated by performaing normalization of the results. We do not normalize the outputs of our measurements, in order to show the actual measured outcomes, including all infidelities/errors of the system.

The histogram shows up empty and an error message is shown instead.

This usually indicates an error in the backend, e.g. due to a syntax error. Check the error output file for hints on what might be wrong.

A syntax error is returned, but my code is accepted by the parser (usually the histogram also shows up empty).

There are currently some differences in the support of cQASM 1.0 syntax by Quantum Inspire and QX-simulator. Please report any inconsistencies you discover, so we can resolve these issues.

I get a Oops. Something went wrong! (1589448436.5265803) error when running an algorithm on Spin-2.

Usually this is caused by an invalid cQASM code. Make sure that your code has a valid syntax and structure and check the allowed gate operations for the Spin-2 and Starmon-5 backends.

One example of invalid code:

  • You are not allowed to use quantum operations after a measurement in one sequence. As an example the following code will raise this error:

... measure_all h q[0] ...

  • .

I get a pthread_mutex_lock error when running an algorithm on the QX simulator.

The pthread error is an error which unfortunately we have not been able to solve yet. This communication error happens occasionaly. In most cases, a re-run of the circuit helps. If you do have an algorithm that always returns this error, please let us now.

I want to execute many algorithms without interruption. Is that possible?

The Spin-2 backend is automatically calibrated, approximately every 3 hours. When you create a new job in the web front-end for the Spin-2 backend you will see the latest calibration timestamp. When you want to run a variational algorithm for example, you can use the time stamp to estimate when the next calibration will take place. You can also start your first algorithms when the system is calibrating (the jobs will remain in the queue until the calibration is finished), however there are no guarantees that you execute your algorithms back to back:

  • The system can go offline, when the calibration fails or another fatal error occurs. This is very rare
  • You can have a maximum of 3 scheduled jobs in the queue. When you have reached the maximum, other users may also enter jobs in the queue, which will be treated first in first out.


I get a Qiskit import error ModuleNotFoundError: No module named 'qiskit.validation.base

After installing the quantuminspire SDK and the qiskit SDK and upon running a qiskit example I get the error:

ModuleNotFoundError: No module named 'qiskit.validation.base'.

This error is due to an backwards incompatible update of the Qiskit Terra package (as part of the Qiskit 0.20.0 package installed by the SDK). We are currently working on a solution and expect a new version of our SDK package on pypi soon. You can, in the meantime, try to install the previous version of Qiskit 0.19.6