The "principle of deferred measurement" refers to the idea that in almost all cases measurement may be performed as a last step in a quantum computation. This tag is dedicated to questions that explore the concept and/or potential exceptions to the concept.
Questions tagged [deferred-measurement]
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Are there any algorithms that take measurements in an intermediate step?
As a beginner in quantum computation, I noticed that all quantum algorithms take various gates followed by measuring the qubits in the last step. Is it always the case? Are there any algorithms that take measurements in an intermediate step?
John Wong
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What is a proof for the principle of deferred measurement?
Does anyone know of a proof for the 'principle of deferred measurement'?
Quantum Guy 123
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Using principle of deferred measurement to replace gates conditional on classical bits (c_if)
I am trying to implement the Iterative Phase Estimation algorithm on one of Qiskit's labs. I can do it for a 'nice' phase, such as 1/4 :
But if I want to implement the algo generally (as a subroutine for other algorithms, etc), the R_z gates will…
Mykolas Sveistrys
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is there a measurement free decoder for $[[5,1,3]]$ and $[[8,3,3]]$ codes
Inspired by this post, is there a measurement free decoder for these two codes.
A concrete circuit to illustrate the process would be very helpful to understand the concept.
unknown
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Can I postpone a Pauli gate $X$ over a conditioned measurement $Y$ or $X$?
The above circuit shows a first measurement, which is $\langle X \rangle$ or $\langle Y \rangle$, depending on the outcome of a second measurement.
Assuming now that a third measurement decides whether applying a Pauli $X$ as in the above picture.…
Daniele Cuomo
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what does it mean to "measure a qubit" if measurement is defined on operators
As far as I know "measurement" depends on the two variables : state and operator.
So what exactly does measuring a qubit mean? is it implied that the operator is
the $Z$ operator on that qubit? In that case does the "deferred measurement…
unknown
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Show that the effect of a Controlled Unitary on qubits followed by a measurement is unchanged depending on when measurement is taken
I understand that a Controlled Unitary is just a generalization of a control gate, such as CNOT etc, and that it is given in state representation as $$\hat C_U = |0\rangle\langle0|\otimes\mathbb{I} + |1\rangle\langle1|\otimes \hat U $$or matrix…
Dwye
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Does principle of deferred measurement imply information can travel faster than light?
I have been reading the book by Michael A Nielsen and Isaac Chuang and came across the principle of deferred measurement. They showed using this principle how the circuit for quantum teleportation can be changed and measurements taken at last. But…
Rishabh Kothary
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Can transformations of qubits in quantum computing be carried out instead by transformations of the measurement instrument?
As far as I understand, transforming and maintaining states of qubit devices in quantum computers is associated with all sort of problems such as transformation errors and decoherence. At the same time, quantum mechanics describes states of a…
QC student
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What is the mathematical intuition behind deferred measurement?
Please give a complete proof of the principle of Deferred Measurement Principle, including careful notation (preferably explaining the meaning of each symbol) and rigorous mathematical reasoning (preferably giving the rationale or references for…
Ren-Xin Zhao
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