A few months ago I wrote this line down, but it does not seem to follow any more. Am I mistaking a mistake now or when I first wrote it down? thanks(adsbygoogle = window.adsbygoogle || []).push({});

[tex] ( | 0 \rangle \langle 0 | + | 1 \rangle \langle 1 |) \rho ( | 0 \rangle \langle 0 | + | 1 \rangle \langle 1 |) [/tex]

[tex]= | 0 \rangle \langle 0 | \rho | 0 \rangle \langle 0 | + | 1 \rangle \langle 1 | \rho | 1 \rangle \langle 1 | [/tex]

where [tex]\rho[/tex] is an arbitrary mixed state.

(It is not letting me preview my latex so fingers crossed this works as expected)

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# Projector Question

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