But how is it possible to combine two theories that, despite both describing the physical processes in their domains very accurately, differ so greatly? One possibility is to conduct quantum physics experiments with increasingly larger objects in the hope that discrepancies will eventually appear that point to possible solutions. But physicists must work within tight constraints. The famous double-slit experiment, for instance, which can be used to show that solid particles simultaneously behave like waves, can't be performed with everyday objects.
Thought experiments, on the other hand, can be used to transcend the boundaries of the macroscopic world. That's exactly what Renato Renner, Professor for Theoretical Physics, and his former doctoral student Daniela Frauchiger have now done in a publication that appears in Nature Communications magazine today. Roughly speaking, in their thought experiment, the two consider a hypothetical physicist examining a quantum mechanical object and then use quantum mechanics to calculate what that physicist will observe. According to our current worldview, this indirect observation should yield the same result as direct observation, yet the pair's calculations show that precisely this is not the case. The prediction as to what the physicist will observe is exactly the opposite of what would be measured directly, creating a paradoxical situation.
Experiment - Journal - Topic - Discussion - Experts
Although the thought experiment is only now being officially published in a scientific journal, it has already become a topic of discussion among experts. As the publication process was repeatedly delayed, various other publications are already addressing the findings -- itself a paradoxical situation, Renner notes.
The most common initial reaction of his colleagues in the field is to question the calculations, Renner says, but so far, no one has managed to disprove them. One reviewer conceded that he had meanwhile made five attempts to find an error in the calculations...
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