Uncomputation: Difference between revisions

Revision as of 15:26, 15 October 2022

Revision as of 15:28, 15 October 2022

Line 5:

Uncomputation is a fundamental step in [[quantum computing]] algorithms. Whether or not intermediate effects have been uncomputed affects how states interfere with each other when measuring results.<ref>{{Cite journal|arxiv=quant-ph/0209060|last1=Aaronson|first1=Scott|title=Quantum Lower Bound for Recursive Fourier Sampling|journal=Quantum Information and Computation ():, 00|volume=3|issue=2|pages=165–174|year=2002|doi=10.26421/QIC3.2-7 |bibcode=2002quant.ph..9060A}}</ref>

The process is primarily motivated by the principle of implicit measurement.<ref>Nielsen, Michael; Chuang, Isaac. "Quantum Computation and Quantum Information"</ref>, which states that ignoringdiscarding a register during computation is physically equivalent to measuring it. Failure to uncompute garbage registers can have unintentional consequences during computation, such as wave-function collapse. For example, if we take the state <math></math> <math>

\frac{1}{\sqrt 2}(|0\rangle|g_0\rangle + |1\rangle|g_1\rangle)

</math> where <math>g_0</math> and <math>g_1</math> are garbage registers. Then, if we do not apply any further operations to those registers, then according to the principle of implicit measurement, the entangled state can be taken tohas bebeen measured, resulting in a collapse to either <math>|0\rangle|g_0\rangle</math> or <math>|1\rangle|g_1\rangle</math> with probability <math>\frac{1}{2}</math>. What makes this undesirable is that wave-function collapse occurs before the program terminates, and thus may not yield the expected result.

==References==