Suppose it is known that a photon has diagonal polarisation (e.g. it has just passed through a diagonal slit), then Alice comes along and measures the photon using a horizontal/vertical polarisation basis. So, I believe there is a 50% chance she will get a horizontal result and 50% chance she will obtain a vertical result.(adsbygoogle = window.adsbygoogle || []).push({});

Now Bob comes along and also knows the particle has passed through the diagonal slit, but he is unaware that Alice has already made a measurement using a horizontal/vertical basis. Is there an experiment Bob can do to check if the particle's polarisation has been measured?

Thanks

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# Detection of a Quantum Measurement

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