by gill1109 » Tue Oct 01, 2019 2:36 pm
Dirkman wrote:Well yeah , but my question is serious.
They are thinking of quantum systems built out of qubits - quantum systems with a two dimensional Hilbert space. Their remark shows that they have no idea at all of what they are talking about since the Tsirelson bound is the best that QM can do with two parties, binary setting choices, and binary measurement outcomes, but he actually optimises over all possible quantum systems (of any dimension whatsoever) and all possible binary measurements on those systems, and not just the rather special class of projective measurements corresponding to measurement of "observables" according to the Neumann-von Lüders projection postulate. It is just that the bound happens to be attained on with two dimensional Hilbert spaces, and the famous spin measurements of Bell, Aspect etc. [well ... Aspect moved from spin of spin half particles to polarization of photons but the abstract math is the same once you have figured out the mapping]
Anyway, it is a silly paper. Experimentally they are clever, their engineering is good and novel. They need to raise money to pay for their expensive experiments with many research assistants and PhD students, and they need to gain prestige within the academic world, so they write the kind of nonsense in Science or Nature which especially appeals to science journalists and the public. Academic publication is based on in-crowds and cliques promoting the work of their friends so as to promote their own work, keeping the science funding flowing and the scientific prestige and hence power and hence funding...
[quote="Dirkman"]Well yeah , but my question is serious.[/quote]
They are thinking of quantum systems built out of qubits - quantum systems with a two dimensional Hilbert space. Their remark shows that they have no idea at all of what they are talking about since the Tsirelson bound is the best that QM can do with two parties, binary setting choices, and binary measurement outcomes, but he actually optimises over all possible quantum systems (of any dimension whatsoever) and all possible binary measurements on those systems, and not just the rather special class of projective measurements corresponding to measurement of "observables" according to the Neumann-von Lüders projection postulate. It is just that the bound happens to be attained on with two dimensional Hilbert spaces, and the famous spin measurements of Bell, Aspect etc. [well ... Aspect moved from spin of spin half particles to polarization of photons but the abstract math is the same once you have figured out the mapping]
Anyway, it is a silly paper. Experimentally they are clever, their engineering is good and novel. They need to raise money to pay for their expensive experiments with many research assistants and PhD students, and they need to gain prestige within the academic world, so they write the kind of nonsense in Science or Nature which especially appeals to science journalists and the public. Academic publication is based on in-crowds and cliques promoting the work of their friends so as to promote their own work, keeping the science funding flowing and the scientific prestige and hence power and hence funding...
