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Quantum Computing

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Required fields*

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    $\begingroup$ The qubit is entangled with the environment, and the information leaks into the environment. Since we do not control the environment, the information is lost. You can read Chapter 3 of Preskill's lectures for details. theory.caltech.edu/~preskill/ph229 $\endgroup$ Commented Sep 6, 2023 at 10:30
  • $\begingroup$ Imagine for example that the qubit is a particle being kept in a vacuum, but not a perfect vacuum. Then it will be "measured" at a very low rate by the occasional interactions with gas molecules, even if we don't measure it on purpose. (I think in reality we can pull a good enough vacuum that other factors will decohere it first, but this happens to be an easy example to visualize.) $\endgroup$ Commented Sep 6, 2023 at 18:05
  • $\begingroup$ In a trapped ion quantum computer, the ion which is in a superposition state is kept in an electric field under vacuum. The claim is that the decoherence time is long (about 50 seconds) as the ion is kept in vacuum and has little chance of interacting with the environment. But I wonder, doesn't interaction with the electric field constitute a "measurement" and lead to decoherence? $\endgroup$ Commented Sep 6, 2023 at 21:52
  • $\begingroup$ This is a fundamental question in quantum theory, the interpretation of quantum wave function with respect to collapse/measurement: There are several different interpretations: en.wikipedia.org/wiki/… for a summary. $\endgroup$ Commented Sep 7, 2023 at 0:24