# Timeline for The effect of available information on random quantum channels

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Jun 12 '20 at 13:31 comment Maybe the following case helps to sharpen understanding... Consider two boxes. One contains 500 qubits in $|0\rangle$ state and 500 in $|1\rangle$. A second box contains 500 qubits in $|+\rangle$ and 500 in $|-\rangle$. You remove one photon and can perform any measurements you want on it. Is there any way that you can distinguish the two boxes using that single photon? (If I can remove more than one photon, does that change?)
Jun 12 '20 at 13:27 comment Turn it the other way around. Does knowing that meta information alter, in any way, how you predict the outcomes of experiments that you perform on your state? In this case, it doesn't, so it shouldn't impact the description of the state that we hold. That might even be how you define the information to be "meta"
Jun 12 '20 at 13:24 comment I am curious if there is more to it, and am wondering about your view on the following: I believe I understand your statement "if we don't know the outcome, then our best description of the system is the same in both cases". Here however, besides possibly knowing the outcome of the coin flip, we have in fact other meta information also available: that is, we know the second device operates according to a classical coin flip. Nothing is known about the internals of the first device. Generally, should we and/or can we express availability of meta information in our quantum mechanical models?
Jun 12 '20 at 10:53 history answered