November 2019 - ITP-quantumseminare

tomorrow's group meeting HIT H42 @ 13:45
by Joe Renes 25 Nov '19

25 Nov '19

Hi all, Tomorrow Raban will tell us about "Efficient template matching in quantum circuits", which appears in arXiv:1909.05270 <http://arxiv.org/abs/1909.05270>. The abstract appears below. Best, -joe Abstract: In this talk, I will introduce an efficient algorithm to search for maximal matches of a small quantum circuit, called template, in a large circuit under consideration of pairwise commutation relations between quantum gates. Our algorithm provably finds all maximal matches with a running time that is polynomial in the number of gates and the number of qubits of the circuit for a fixed template size. Such an algorithm finds direct applications in quantum circuit optimization. Given a template circuit for which a lower-cost implementation is known, we may search for all instances of the template in a large circuit and replace them with their optimized version.

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tomorrow's group meeting, HIT H42 @ 13:45
by Joe Renes 18 Nov '19

18 Nov '19

Hi all, Tomorrow Nicholas Meinhardt will present the results of his master thesis, entitled "Quantum Hopfield Neural Networks: A New Approach and Its Storage Capacity". Best, -joe

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tomorrow's group meeting H42 @13:45
by Joe Renes 11 Nov '19

11 Nov '19

Hi all, Tomorrow we have a visitor from downtown, Jansen Zhao Zhikuan from the CS department, who will tell us about Causal limits on quantum communication. See below for the abstract. Best, -joe Title: Causal limit on quantum communication Abstract: The capacity of a channel is known to be equivalent to the highest rate at which it can generate entanglement. Analogous to entanglement, the notion of a causality measure characterizes the temporal aspect of quantum correlations. Despite holding an equally fundamental role in physics, temporal quantum correlations have yet to find their operational significance in quantum communication. Here we uncover a connection between quantum causality and channel capacity. We show the amount of temporal correlations between two ends of the noisy quantum channel, as quantified by a causality measure, implies a general upper bound on its channel capacity. The expression of this new bound is simpler to evaluate than most previously known bounds. We demonstrate the utility of this bound by applying it to a class of shifted depolarizing channels, which results in improvement over previously known bounds for this class of channels.

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tomorrow's group meeting H42 @ 13:45
by Joe Renes 04 Nov '19

04 Nov '19

Hi all, Tomorrow we have just one student talk, from Romain Moyard, who will tell us about his semester project entitled "Path integral formalism and quantum foundations". The abstract is below. Best, -joe Abstract: During the 60s R. Feynman developed the path integral formalism, a version of quantum mechanics involving Lagrangians. The probabilities obtained within this formalism are the same as in the canonical one, their prediction power is equivalent. Since that time, path integral formalism has been widely used to compute probabilities and extended research was done to develop mathematical tools to facilitate the computation. However, there have been few attempts to use this framework in quantum foundations. In this talk I will present how it is possible to describe a spin-measurement process using path integrals. I will also elaborate on what dichotomy exists between canonical quantum mechanics and path integral formalism when it comes to questions about quantum foundations like the measurement problem and the lack of realism.

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