Deferred measurement principle
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The deferred measurement principle is a result in quantum computing which states that delaying measurements until the end of a quantum computation doesn't affect the probability distribution of outcomes.[1][2]
A consequence of the deferred measurement principle is that measuring commutes with conditioning. The choice of whether to measure a qubit before, after, or during an operation conditioned on that qubit will have no observable effect on a circuit's final expected results.
Thanks to the deferred measurement principle, measurements in a quantum circuit can often be shifted around so they happen at better times. For example, measuring qubits as early as possible can reduce the maximum number of simultaneously stored qubits; potentially enabling an algorithm to be run on a smaller quantum computer or to be simulated more efficiently. Alternatively, deferring all measurements until the end of circuits allows them to be analyzed using only pure states.
References
- ↑ Michael A. Nielsen; Isaac L. Chuang (9 December 2010). Quantum Computation and Quantum Information: 10th Anniversary Edition. Cambridge University Press. p. 186. ISBN 978-1-139-49548-6. https://books.google.com/books?id=-s4DEy7o-a0C.
- ↑ Odel A. Cross (5 November 2012). Topics in Quantum Computing. O. A. Cross. p. 348. ISBN 978-1-4800-2749-7. https://books.google.com/books?id=b_D9flK2h8QC&pg=PA348.
![]() | Original source: https://en.wikipedia.org/wiki/Deferred measurement principle.
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