We identify precision limits for the simultaneous estimation of multiple parameters in multimode interferometers. Quantum strategies to enhance the multiparameter sensitivity are based on entanglement among particles, modes, or combining both. The maximum attainable sensitivity of particle-separable states defines the multiparameter shot-noise limit, which can be surpassed without mode entanglement. Further enhancements up to the multiparameter Heisenberg limit are possible by adding mode entanglement. Optimal strategies that saturate the precision bounds are provided.
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http://dx.doi.org/10.1103/PhysRevLett.121.130503 | DOI Listing |
Nature
January 2025
Xanadu Quantum Technologies Inc., Toronto, Ontario, Canada.
Photonics offers a promising platform for quantum computing, owing to the availability of chip integration for mass-manufacturable modules, fibre optics for networking and room-temperature operation of most components. However, experimental demonstrations are needed of complete integrated systems comprising all basic functionalities for universal and fault-tolerant operation. Here we construct a (sub-performant) scale model of a quantum computer using 35 photonic chips to demonstrate its functionality and feasibility.
View Article and Find Full Text PDFNat Nanotechnol
January 2025
Department of Chemistry, Columbia University, New York, NY, USA.
Van der Waals (vdW) semiconductors have emerged as promising platforms for efficient nonlinear optical conversion, including harmonic and entangled photon generation. Although major efforts are devoted to integrating vdW materials in nanoscale waveguides for miniaturization, the realization of efficient, phase-matched conversion in these platforms remains challenging. Here, to address this challenge, we report a far-field ultrafast imaging method to track the propagation of both fundamental and harmonic waves within vdW waveguides with femtosecond and sub-50 nanometre spatiotemporal precision.
View Article and Find Full Text PDFAm J Physiol Lung Cell Mol Physiol
January 2025
Department of Mechanical Engineering, University of California, Riverside CA, USA.
Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide and the progressive nature heightens the calamity of the disease. Despite countless existing COPD studies, lung mechanics are often reported under positive-pressure ventilation (PPV) and implications and extrapolations made from these studies pose serious restrictions as recent works have divulged disparate elastic and energetic results between PPV and more physiological negative-pressure counterparts (NPV). This non-equivalence of PPV and NPV needs to be investigated under diseased states to augment our understanding of disease mechanics.
View Article and Find Full Text PDFEntropy (Basel)
December 2024
Joint Laboratory of Optics of Palacký University and Institute of Physics of AS CR, Faculty of Science, Palacký University, 17. listopadu 12, 779 00 Olomouc, Czech Republic.
We discuss a family of W-class states describing three-qubit systems. For such systems, we analyze the relations between the entanglement measures and the nonlocality parameter for a two-mode mixed state related to the two-qubit subsystem. We find the conditions determining the boundary values of the negativity, parameterized by concurrence, for violating the Bell-CHSH inequality.
View Article and Find Full Text PDFSoc Sci Med
December 2024
School of Social Sciences, University of Westminster, London, United Kingdom.
Structural violence - related to 'isms' like racism, sexism, and ableism - pertains to the ways in which social institutions harm certain groups. Such violence is critical to institutional indifference to the plight of ethnic minority people living with long-term health conditions. With only emergent literature on the lived experiences of ethnic minorities with Long Covid, we sought to investigate experiences around the interplay of illness and structural vulnerabilities.
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