Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session S26: Quantum Resource Theories IFocus
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Sponsoring Units: DQI Chair: Barbara Kraus, Universitat Innsbruck Room: LACC 404A |
Thursday, March 8, 2018 11:15AM - 11:51AM |
S26.00001: Quantum Resource Theories Invited Speaker: Iman Marvian If one looks at the scientific history of the theory of entanglement, the turning point is easily seen to occur in the mid-nineties, at the point when researchers in quantum information theory began to consider entanglement as "a resource as real as energy". It gradually became clear that the entanglement theory should be understood as a framework to study questions about manipulating resource states for performing certain tasks, similar to the theory of thermodynamics. From this point on, entangled states and entangling operations were defined as those states and operations that cannot be implemented when one only has access to Local Operations and Classical Communication. Researchers then began to systematically answer questions such as: under this kind of restriction when is it possible to convert one resource state into another? How do we quantify the resource? What is the resource cost of simulating an operation? Subsequently, motivated by the success of the resource theory approach to entanglement, many researchers started applying this approach to understand other properties of quantum systems, such as coherence, asymmetry and athermality in quantum thermodynamics. In this talk, I give an introduction to quantum resource theories, with more emphasis on the resource theories of entanglement, coherence and asymmetry. |
Thursday, March 8, 2018 11:51AM - 12:27PM |
S26.00002: Mathematical structures and features of quantum resource theories Invited Speaker: Gilad Gour A common theme in Chemistry, Thermodynamics, and Information Theory is how one type of resource -- be it chemicals, heat baths, or communication channels -- can be used to produce another. These processes of conversion and their applications are studied under the general heading of "resource theories". While resource theories use a wide range of sophisticated and apparently unrelated mathematical techniques, there is also an emerging general mathematical framework which seems to underpin all of them. In this talk, I will give an overview on the |
Thursday, March 8, 2018 12:27PM - 12:39PM |
S26.00003: Quantifying nonlocality: a resource theory of nonclassicality of common-cause processes David Schmid, Ravi Kunjwal, Ana Sainz, Robert Spekkens, Elie Wolfe We introduce a resource theory of non-signalling black-box correlations in nonlocality scenarios. We imagine a number of parties under a physical restriction: they cannot signal each other, and the common causes they share are classical. The parties are able to freely perform local processings of classical inputs and outputs, potentially conditioned on their shared classical randomness. These free operations impose a partial order on the black-box correlations—the resources—in the theory. Correlations that are higher in the order are more nonclassical than those that are lower in the order. We discuss various monotones and conversion witnesses, and we show that standard Bell inequalities do not form a complete set of monotones. That is, we find that one correlation can be more nonclassical than another, even if the two differ only in their marginals. Additionally, we provide an algorithm for deducing, for any pair of correlations in this setting, which is more nonclassical (if either). |
Thursday, March 8, 2018 12:39PM - 12:51PM |
S26.00004: The resource theory of incompatibility Gilad Gour, Teiko Heinosaari, Robert Spekkens We conceptualize quantum incompatibility as an intrinsically quantum relation between different ways of refining one's information about a system. This notion of incompatibility applies not only to sets of measurements (multi-meters), but to sets of sources of quantum states (multi-sources), to sets of quantum instruments (multi-instruments), and various generalizations of these (multi-devices). Specifically, we define the resource theory as follows: (i) a multi-device is deemed to be a free resource (having no incompatibility) if all of the devices in the set over which it ranges can be jointly simulated by a single device; (ii) one multi-device is above another in the partial order of all such resources---and therefore has more incompatibility---if the first can be processed to the second using only free multi-devices. We identify many monotones and conversion witnesses. In particular, we demonstrate how no-go conversion witnesses can be obtained as infeasibility certificates in a semi-definite programming feasibility problem. We also identify a low-level partial order over the resources based on the compatibility hypergraph of each mutli-device, where the hypergraph for a set of devices specifies which subsets are compatible. |
Thursday, March 8, 2018 12:51PM - 1:03PM |
S26.00005: Coherence Generating Power of Quantum Dephasing Processes Georgios Styliaris, Lorenzo Campos Venuti, Paolo Zanardi We provide a quantification of the capability of various quantum dephasing processes to generate coherence out of incoherent states. The measures defined, admitting computable expressions for any finite Hilbert space dimension, are based on probabilistic averages and arise naturally from the viewpoint of coherence as a resource. We investigate how the capability of a dephasing process (e.g., a non-selective orthogonal measurement) to generate coherence depends on the relevant bases of the Hilbert space over which coherence is quantified and the dephasing process occurs, respectively. We extend our analysis to include those Lindblad time evolutions which, in the infinite time limit, dephase the system under consideration and calculate their coherence generating power as a function of time. We further identify specific families of such time evolutions that, although dephasing, have optimal (over all quantum processes) coherence generating power for some intermediate time. Finally, we investigate the coherence generating capability of random dephasing channels. |
Thursday, March 8, 2018 1:03PM - 1:15PM |
S26.00006: Characterization of the non-classical correlations from the dynamical susceptibilities Fernando Rojas, J. A. Maytorena Quantum correlations are a central feature in Quantum Information and Quantum Computation. Specifically the Quantum Fisher Information (QFI) is known to be a good indicator of non classical correlation and quantum entanglement in multipartite systems[I]. |
Thursday, March 8, 2018 1:15PM - 1:27PM |
S26.00007: Information Scrambling in Chaotic Systems with Dissipation Yong-Liang Zhang, Yichen Huang, Xie Chen Chaotic dynamics in closed local quantum systems scrambles quantum information, which is manifested quantitatively in the decay of the out-of-time-ordered correlators (OTOC) of local operators. How is information scrambling affected when the system is coupled to the environment and suffers from dissipation? We address this question by defining a dissipative version of OTOC and numerically study its behavior in a prototypical chaotic quantum chain in the presence of dissipation. We find that dissipation leads to not only the overall decay of quantum information due to leaking, but also structural changes in the scrambled information so that the `information light cone' can only reach a finite distance even when the effect of overall decay is removed. Based on this observation we conjecture a modified version of the Lieb-Robinson bound in dissipative systems. |
Thursday, March 8, 2018 1:27PM - 1:39PM |
S26.00008: Optimal Crossing of a Quantum Critical Point with a Noisy Control Field Armin Rahmani Quantum evolution is widely used for state transformation, e.g., through adiabatic annealing. Crossing quantum phase transitions is of particular interest as it allows for the preparation of nontrivial correlated states. However, this scheme is challenging due to the closure of the energy gap and unavoidable Kibble-Zurek excitations. In the presence of noise, the problem is even more severe due to the recently discovered anti-Kibble-Zurek behavior, where slower driving results in the accumulation of more noise-induced excitations. Focusing on the canonical example of the transverse-filed Ising model, we show that optimal control provides fast shortcuts to the adiabatic evolution, which, in the absence of noise, can exactly prepare many-body ground states on the other side of a quantum critical point in a finite time. It also provides remarkable advantages in the presence of a noisy control field. We demonstrate that the optimal protocols contain both bang-bang and singular oscillatory segments in agreement with Pontryagin's minimum principle. |
Thursday, March 8, 2018 1:39PM - 1:51PM |
S26.00009: An optimistic protocol for entanglement distribution Siddhartha Santra, Liang Jiang, Vladimir Malinovsky Shared remote entanglement is a resource for distributed quantum information processing tasks such as cryptography, networked clocks, high resolution interferometry and other applications of quantum technology. To establish remote entanglement one can start from smaller distances by directly charging a pair of quantum memories with an entangled state and then performing entanglement swapping between previously non-interacting memories. The effective rate of remote entanglement generation using this approach depends on probability that pairs of memories are successfully charged per attempt, the swapping success probability, lifetime of the quantum memories and cycle-time which is required for the classical control to check if two pairs of quantum memories are successfully charged. We propose a protocol for the classical controls that resets the quantum memories after a finite waiting-time window to mitigate the decoherence in imperfect quantum memories. We show that this protocol can yield up to a three-fold increase of distillable entanglement rates and determine the optimal size of the time window depending on the operating point in parameter space. |
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