Operational relevance of resource theories of quantum measurements

For any resource theory it is essential to identify tasks for which resource objects offer advantage over free objects. We show that this identification can always be accomplished for resource theories of quantum measurements in which free objects form a convex subset of measurements on a given Hilbert space. To this aim we prove that every resource measurement offers advantage for some quantum state discrimination task. Moreover, we give an operational interpretation of robustness, which quantifies the minimal amount of noise that must be added to a measurement to make it free. Specifically, we show that this geometric quantity is related to the maximal relative advantage that a resource measurement offers in a class of minimal-error state discrimination problems. Finally, we apply our results to two classes of free measurements: incoherent measurements (measurements that are diagonal in the fixed basis) and separable measurements (measurements whose effects are separable operators). For both of these scenarios we find, in the asymptotic setting in which the dimension or the number of particles increase to infinity, the maximal relative advantage that resource measurements offer for state discrimination tasks.Comment: 6.5 + 4.5 pages, 1 Figure, comments and suggestions are welcome, v3: version accepted in Quantum: slight change in the format, updated reference

Networks of coupled oscillators: From phase to amplitude chimeras

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Chaos 28, 113124 (2018) and may be found at https://doi.org/10.1063/1.5054181.We show that amplitude-mediated phase chimeras and amplitude chimeras can occur in the same network of nonlocally coupled identical oscillators. These are two different partial synchronization patterns, where spatially coherent domains coexist with incoherent domains and coherence/incoherence referring to both amplitude and phase or only the amplitude of the oscillators, respectively. By changing the coupling strength, the two types of chimera patterns can be induced. We find numerically that the amplitude chimeras are not short-living transients but can have a long lifetime. Also, we observe variants of the amplitude chimeras with quasiperiodic temporal oscillations. We provide a qualitative explanation of the observed phenomena in the light of symmetry breaking bifurcation scenarios. We believe that this study will shed light on the connection between two disparate chimera states having different symmetry-breaking properties. Chimera states are emergent dynamical patterns in networks of coupled oscillators where coherent and incoherent domains coexist due to spontaneous symmetry-breaking. In oscillators that exhibit both phase and amplitude dynamics, two types of distinct chimera patterns exist, namely, amplitude-mediated phase chimeras (AMCs) and amplitude chimeras (ACs). In the AMC state coherent and incoherent regions are distinguished by different mean phase velocities: all coherent oscillators have the same phase velocity, however, the incoherent oscillators have disparate phase velocities. In contrast to AMC, in the AC state, all the oscillators have the same phase velocity, however, the oscillators in the incoherent domain show periodic oscillations with randomly shifted center of mass. Surprisingly, in all the previous studies on chimeras, a given network of continuous-time dynamical systems seems to show either AMC or AC: they never occur in the same network. In this paper, for the first time, we identify a network of coupled oscillators where both AMC and AC are observed in the same system, and we also provide a qualitative explanation of the observation based on symmetry-breaking bifurcations.DFG, 163436311, SFB 910: Kontrolle selbstorganisierender nichtlinearer Systeme: Theoretische Methoden und Anwendungskonzept

Transition from homogeneous to inhomogeneous limit cycles : Effect of local filtering in coupled oscillators

10 pages, 8 FigsPeer reviewedPublisher PD

Control of birhythmicity through conjugate self-feedback : Theory and experiment

ACKNOWLEDGMENTS D.B. acknowledges the financial support from CSIR, New Delhi, India, T.B. acknowledges the financial support from SERB, Department of Science and Technol- ogy (DST), India [Project Grant No.: SB/FTP/PS-005/2013]Peer reviewedPublisher PD

Optimal allocation of quantum resources

The optimal allocation of resources is a crucial task for their efficient use in a wide range of practical applications in the fields of science and engineering. This paper investigates the optimal allocation of resources in multipartite quantum systems. In particular, we show the relevance of two optimality criteria for the application of quantum resources. Moreover, we present optimal allocation solutions for an arbitrary number of qudits in a particular resource theory. In addition, we study a third optimality criterion and demonstrate its application to scenarios involving several resource theories. Finally, we highlight the potential consequences of our results in the context of quantum networks

Efficacy and safety of a centrally acting analgesic flupirtine in primary knee osteoarthritis in comparison to tramadol: a randomized controlled trial

Background: Osteoarthritis (OA) is a chronic, degenerative joint disorder responsible for considerable morbidity, particularly in old age. Flupirtine, a new centrally acting analgesic, is devoid of the adverse effects of NSAIDs and opioid analgesics. In this study author compared the effectiveness and safety of flupirtine with tramadol in knee OA.Methods: An open label, randomized, controlled trial was done with patients of primary knee OA of both sexes, age >50 years. Patients were recruited from Rheumatology OPD of SSKM Hospital. A minimum WOMAC score of 35 was essential for recruitment. Patients with serious comorbidities were excluded. They were treated orally with either flupirtine (100mg thrice daily) or tramadol (50mg thrice daily) for 12 weeks.Results: Ninety patients were recruited and data of 42 on flupirtine and 41 on tramadol were analysed. There was significant improvement in pain, stiffness and physical function compared to baseline in both the groups. However, there was no significant difference between groups at 4, 8 and 12 weeks. Responder rate (50% reduction in pain score from baseline) was 66.67% with flupirtine and 48.78% with tramadol (p = 0.122). Flupirtine caused 4 adverse events compared to 16 with tramadol. However, both the drugs were well-tolerated.Conclusions: The effectiveness of flupirtine in knee OA is comparable to tramadol, while causing minimal adverse effects. Long-term benefits need to be explored