Find appropriate initialization to make a measurement deterministic in Stim

Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Stack Overflow for Teams is now called Stack Internal. Bring the best of human thought and AI automation together at your work. Bring the best of human thought and AI automation together at your work. Learn more Stack InternalKnowledge at workBring the best of human thought and AI automation together at your work.Consider the following Stim circuit which is three rounds of a rotated surface code experiment initialized in the $\vert +\rangle$ logical state.A deterministic observable would be OBSERVABLE_INCLUDE(0) rec[-3] rec[-6] rec[-9] which I can add at the end of the circuit.Suppose I choose a different final measurement such as OBSERVABLE_INCLUDE(0) rec[-9]. I want to change some of the reset operations in my circuit such that this is deterministic. How can I do this with Stim?Mathematically, I have to evolve the Pauli string $S = ZIIIIIIII$ ($Z$ on qubit 1, identity on remaining data qubits) backwards through the circuit. Whenever it passes through a Clifford gate, I conjugate it to $CSC^{-1}$. If it hits a reset operation on some qubit, I must replace the existing reset it to the eigenstate of $P$, where $P$ is the Pauli on that register after the backpropagation and just before the reset.Since I have mid-circuit ancilla resets, some of those would also need to be fixed this way. Is there a tool to generate a new Stim circuit which is the same as the original except for the reset operations such that my arbitrarily chosen observable is deterministic?Thanks for contributing an answer to Quantum Computing Stack Exchange!But avoid …Use MathJax to format equations. MathJax reference.To learn more, see our tips on writing great answers.Required, but never shown By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy. Start asking to get answersFind the answer to your question by asking.Explore related questionsSee similar questions with these tags.To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Site design / logo © 2025 Stack Exchange Inc; user contributions licensed under CC BY-SA . rev 2025.11.24.37206