New paper: Sampling generalized cat states with linear optics is probably hard

Full paper here.

Boson-sampling has been presented as a simplified model for linear optics quantum computing. In the boson-sampling model, Fock states are passed through a linear optics network and sampled via number-resolved photodetection. It has been shown that this sampling problem likely cannot be efficiently classically simulated. This raises the question as to whether there are other quantum states of light for which the equivalent sampling problem is also computationally hard. We present evidence that a very broad class of quantum states of light - arbitrary superpositions of two or more coherent states - when evolved via passive linear optics and sampled with number-resolved photodetection, likely implements a classically hard sampling problem.

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  1. the wave function was eptsmeiic I’ll admit that even amongst this audience, there is a great deal of confusion about what the word Copenhagen means. Some mistake it for the orthodox interpretation and some for shut up and calculate . It is possible that this accounts for the discrepancy with the eptsmeiic wavefunction question. However, it seems unlikely to me that many of the respondents meant the orthodox interpretation, as people attending such a conference would be very familiar with the fact that the measurement problem is a flat out contradiction for this view. Therefore, foundationally inclined people who think that orthodox=Copenhagen are likely to view the measurement problem as ruling out Copenhagen, so they are unlikely to pick it as their favourite option. It also seems unlikely that many people at a foundations conference would favour shut up and calculate.There is also another possible resolution of the discrepancy, which is that perhaps some people object to ever using the term eptsmeiic for a state in the context of physics. It does presuppose a broadly Bayesian account of probability theory in which probabilities represent knowledge, information or belief. Frequentists may prefer the term statistical , which is equivalent as far as most of the implications of the eptsmeiic/ontic distinction go. Whether you say that the wavefunction is eptsmeiic or statistical you are still saying that it is not an intrinsic property of an individual system. It makes a difference if you are someone who believes that taking the correct foundation for probability theory is important for understanding quantum foundations, as the Quantum Bayesians do for example, but not if you think that the two problems are independent. However, the fact that 0% of people picked the statistical interpretation lends some doubt to this view.It is probably useless to speculate upon what people actually meant in their responses to this survey. If I were being cynical, I would say that the whole excercise was an attempt to undermine Max Tegmark’s frequent rhetorical use of his earlier poll, which came out in support of Everett. You can see that in the way the questions are phrased. For example, respondents were allowed to pick multiple responses and were given multiple oppportunities to say that they agreed with Copenhagen-type ideas, but only one opportunity to say that they like Everett. I guess what we have learned from this survey is that if you conduct a survey about favourite interpretations at a conference organized by Tegmark then Everett will come out top whereas if you conduct one at a conference organized by Zeilinger then Copenhagen-type ideas will come out top. Is this really a surprise to anyone?

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