[MCM 2/3] How-to: Dynamic circuits with mid-circuit measurements

[dwierichs]

Title: How to create dynamic circuits with mid-circuit measurements

Summary: This how-to is a walkthrough of creating a QNode that contains mid-circuit measurements, logical processing of the measured values, and conditioning functions on these processed measurements. As a warmup task, we implement a T-gadget, which showcases a single MCM without processing that conditions a single follow-up gate. This serves the purpose to have a minimal example of a dynamic circuit, in addition to the more contrived QNode example.

Relevant references:

Possible Drawbacks:

Related GitHub Issues:

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If you are writing a demonstration, please answer these questions to facilitate the marketing process.

• GOALS — Why are we working on this now?

  This how-to promotes mid-circuit measurement functionality in PennyLane, which has been extended in recent releases. In addition, this how-to is part of the broader goal of emphasizing MCMs and dynamic circuits in our contents.

• AUDIENCE — Who is this for?

  Typical how-to audience: Fundamental concepts of measurements and quantum computing are known, but the audience may not yet be familiar with PennyLane's syntax for MCMs and conditioning circuit parts on their outcomes, or they may want to consult this how-to as a reference of how to realize their dynamic circuit with MCMs. Anyone really with the goal of coding up a circuit that uses MCM values and feedforward can be in the audience.

• KEYWORDS — What words should be included in the marketing post?

  • Dynamic circuit
  • Mid-circuit measurements
  • Feedforward control
  • [optional] Measurement value processing

• Which of the following types of documentation is most similar to your file? (more details here)

• [ ] Tutorial

• [ ] Demo

• [x] How-to

[sc-60837]

[github-actions[bot]]

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[KetpuntoG]

(Even if It doesn't use new features, I will target dev to ensure that there are no unexpected problems on Monday)

[KetpuntoG]

Thanks for that last change @dwierichs ! Once It pass the CI, if there is not issues, I will do the merge. Is it ok for you? or anything else I should keep in mind?

[KetpuntoG]

Thanks for that last change @dwierichs ! Once It pass the CI, if there is not issues, I will do the merge. Is it ok for you? or anything else I should keep in mind?

Oh I see the auto-merge, I'll consider it as a yes 😄