Wigner has many friends, and they can disagree: **Daniela Frauchiger and Renato Renner**: *Quantum Theory Cannot Consistently Describe the Use of Itself*. **Lidia del Rio**: *Journal club: Frauchiger-Renner No-Go theorem for Single-World Interpretations of Quantum Theory*: "In this talk I will go over the recent paper by Daniela Frauchiger and Renato Renner, "Single-World Interpretations of Quantum Theory Cannot Be Self-Consistent" (arXiv:1604.07422)...

...The paper introduces an extended Wigner's friend thought experiment, which makes use of Hardy's paradox to show that agents will necessarily reach contradictory conclusions-unless they take into account that they themselves may be in a superposition, and that their subjective experience of observing an outcome is not the whole story. Frauchiger and Renner then put this experiment in context within a general framework to analyse physical theories. This leads to a theorem saying that a theory cannot be simultaneously (1) compliant with quantum theory, including at the macroscopic level, (2) single-world, and (3) self-consistent across different agents. In this talk I will (1) describe the experiment and its immediate consequences, (2) quickly review how different interpretations react to it, (3) explain the framework and theorem in more detail...

**Scott Aaronson**: *It’s Hard to Think When Someone Hadamards Your Brain*: "So: a bunch of people asked for my reaction to the new Nature Communications paper by Daniela Frauchiger and Renato Renner, provocatively titled 'Quantum Theory Cannot Consistently Describe the Use of Itself'...