The quantum Fisher information (QFI) is a fundamental quantity of interest in many areas from quantum metrology to quantum information theory. It can in particular be used as a witness to establish the degree of multiparticle entanglement in quantum many-body systems. In this work, we use polynomials of the density matrix to construct monotonically increasing lower bounds that converge to the QFI. Using randomized measurements we propose a protocol to accurately estimate these lower bounds in state-of-the-art quantum technological platforms. We estimate the number of measurements needed to achieve a given accuracy and confidence level in the bounds, and present two examples of applications of the method in quantum systems made of coupled qubits and collective spins.
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http://dx.doi.org/10.1103/PhysRevLett.127.260501 | DOI Listing |
Sci Rep
January 2025
Faculty of Physics, Semnan University, P.O.Box 35195-363, Semnan, Iran.
We derive the compact closed forms of local quantum uncertainty (LQU) and local quantum Fisher information (LQFI) for hybrid qubit-qutrit axially symmetric (AS) states. This allows us to study the quantum correlations in detail and present some essentially novel results for spin-(1/2, 1) systems, the Hamiltonian of which contains ten independent types of physically important parameters. As an application of the derived formulas, we study the behavior of these two quantum correlation measures at thermal equilibrium.
View Article and Find Full Text PDFACS Omega
December 2024
Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
Since the 1980s, pressure-sensitive paint (PSP) has been used as an optical pressure sensor for measuring surface pressure on aircraft models in wind tunnels. Typically, PSPs have utilized platinum(II)-5,10,15,20-tetrakis(2,3,4,5,6-pentafluorophenyl)-porphyrin due to its high pressure sensitivity, phosphorescence lifetime of ∼50 μs, reasonable quantum yield of emission, and resistance to photo-oxidation. This work investigates the photophysics and electronic structure of metal complexes of 5,10,15,20-tetrakis(2,3,4,5,6-pentafluorophenyl)-porphyrin, namely, Zn(II), Pd(II), and Ir(III), as potentially improved luminophores for polymer-based PSPs.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
School of Chemistry, University of New South Wales, Kensington, NSW 2052, Australia.
Hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs) are the leading synthetic replacements for compounds successively banned by the Montreal Protocol and amendments. HFOs and HCFOs readily decompose in the atmosphere to form fluorinated carbonyls, including CFCHO in yields of up to 100%, which are then photolyzed. A long-standing issue, critical for the transition to safe industrial gases, is whether atmospheric decomposition of CFCHO yields any quantity of CHF (HFC-23), which is one of the most environmentally hazardous greenhouse gases.
View Article and Find Full Text PDFSci Adv
December 2024
CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China.
Quantum systems, including superconducting circuits, trapped ions, quantum dots, solid-state defects, etc., have achieved considerable advancements in readout fidelity. However, the widely used threshold method disregards the importance of temporal characteristics of the signal during continuous measurements, leading to information loss.
View Article and Find Full Text PDFNanophotonics
May 2024
Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, VA, USA.
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