Fix instruction duration unit in estimated success probability calculation

[Shaobo-Zhou]

Description

Fixes instruction duration unit in estimated success probability calculation in src/mqt/predictor/reward.py, as the default unit is "dt" instead of "s": https://github.com/Qiskit/qiskit/blob/stable/2.1/qiskit/transpiler/target.py#L415-L430

Checklist:

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Corrected instruction duration unit handling in success probability estimates for Qiskit 2.0.0+ devices, improving accuracy of idle-time decoherence calculations.

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Walkthrough

For Qiskit >= 2.0.0, the estimated_success_probability function now multiplies the decay exponent for single-qubit delay instructions by the device dt (instruction-duration scaling) when computing idle-time decoherence. A changelog entry documenting the fix was added.

Changes

Cohort / File(s)	Summary
Decoherence decay update src/mqt/predictor/reward.py	estimated_success_probability retrieves device.dt for Qiskit >= 2.0.0 and multiplies the exponential decay exponent for single-qubit delay gates by this scaling factor when computing idle-time decoherence.
Changelog CHANGELOG.md	Added Unreleased entry: "Fix instruction duration unit in estimated success probability calculation" (PR #445, Shaobo-Zhou).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• Verify correct use and units of device.dt in src/mqt/predictor/reward.py.
• Confirm Qiskit version check is correct and preserves behavior for older versions.
• Ensure change applies only to single-qubit delay handling and doesn't affect other gate error calculations.

Poem

🐰 I tiptoe on the circuit's beat,
dt whispers time beneath my feet,
Decay now counts the proper pace,
Small hops of code, a steadier trace,
I munch a carrot, errors meet.

Pre-merge checks and finishing touches

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	The description identifies the bug fix and includes a relevant code reference, but the checklist items are largely unchecked and the description lacks detail on testing, documentation updates, and migration needs.	Provide more context about testing coverage, documentation updates, and whether this fix requires any migration guidance or breaking changes for users.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and concisely summarizes the main change: fixing the instruction duration unit in the estimated success probability calculation.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing touches

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📥 Commits

Reviewing files that changed from the base of the PR and between c0af637 and b9b5991.

📒 Files selected for processing (1)

• CHANGELOG.md (3 hunks)

🧰 Additional context used

🧠 Learnings (1)

📚 Learning: 2025-10-14T14:37:38.047Z

Learnt from: burgholzer
Repo: munich-quantum-toolkit/yaqs PR: 212
File: CHANGELOG.md:12-15
Timestamp: 2025-10-14T14:37:38.047Z
Learning: In the munich-quantum-toolkit/yaqs project, changelog entries follow the template: "- $TITLE ([#$NUMBER]($URL)) ([**AUTHOR**](https://github.com/$AUTHOR))". Issue references should not be included in changelog entries; the PR number is sufficient for traceability.

Applied to files:

• CHANGELOG.md

⏰ Context from checks skipped due to timeout of 900000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (3)

• GitHub Check: 🐍 Test (windows-2022) / 🐍 windows-2022
• GitHub Check: 🐍 Test (macos-14) / 🐍 macos-14
• GitHub Check: 🐍 Test (ubuntu-24.04) / 🐍 ubuntu-24.04

🔇 Additional comments (1)

CHANGELOG.md (1)

14-14: Changelog entry formatting and links corrected.

All issues from the previous review have been properly addressed:

• Line 14: Entry now has correct spacing and properly closed author markup
• Line 48: PR link [Fix instruction duration unit in estimated success probability calculation #445] is now defined with the correct URL
• Line 66: Contributor link is defined and correctly positioned in alphabetical order

Also applies to: 48-48, 66-66

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[flowerthrower]

@Shaobo-Zhou, could you please add a brief update to the changelog? You can merge this once all tests have succeeded. Thanks for fixing!

[coderabbitai]

Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI

Review profile: ASSERTIVE

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 57e58ec and c0af637.

📒 Files selected for processing (1)

• CHANGELOG.md (1 hunks)

🧰 Additional context used

🧠 Learnings (1)

📚 Learning: 2025-10-14T14:37:38.047Z

Learnt from: burgholzer
Repo: munich-quantum-toolkit/yaqs PR: 212
File: CHANGELOG.md:12-15
Timestamp: 2025-10-14T14:37:38.047Z
Learning: In the munich-quantum-toolkit/yaqs project, changelog entries follow the template: "- $TITLE ([#$NUMBER]($URL)) ([**AUTHOR**](https://github.com/$AUTHOR))". Issue references should not be included in changelog entries; the PR number is sufficient for traceability.

Applied to files:

• CHANGELOG.md

⏰ Context from checks skipped due to timeout of 900000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (3)

• GitHub Check: 🐍 Test (macos-14) / 🐍 macos-14
• GitHub Check: 🐍 Test (ubuntu-24.04) / 🐍 ubuntu-24.04
• GitHub Check: 🐍 Test (windows-2022) / 🐍 windows-2022

[Shaobo-Zhou]

@Shaobo-Zhou, could you please add a brief update to the changelog? You can merge this once all tests have succeeded. Thanks for fixing!

I don't seem to have write access for merging. Can you do it as all checks have passed now?