arXiv subjects

B. J. Alexander

Publications and source records attributed to B. J. Alexander.

3 recordsLinked to original sources

arXiv2026

Weighted hypergraph states as a resource for quantum metrology

Quantum correlations can be used to improve sensing precision beyond classical limits, yet the correlated resource states needed can be challenging to prepare and preserve. Here, we study the family of weighted hypergraph states and identify subclasses characterized by their underlying graph topology that exhibit enhanced metrological performance. Using the quantum Fisher information and a novel Dicke state basis representation, we show that these subclasses outperform both separable and standard weighted graph state benchmarks over broad ranges of edge weights corresponding to weak controlled operations between qubits representing the vertices of the graph. We provide analytical formulas for an arbitrary number $N$ of qubits, supplemented by a general study, while focusing a detailed analysis on the example case of $N=4$. By identifying the critical probabilities for local dephasing, we show that adding higher-order weighted hyperedges for $N$ qubits can enhance metrological robustness, allowing the resulting states to retain a quantum advantage at higher noise levels. These probe states exhibit favorable scaling, enhanced precision, and noise tolerance. Our findings establish weighted hypergraph states as viable, structurally tunable and robust resources for quantum-enhanced metrology.

quant-ph↗

arXiv2026

Weighted graph states as a resource for quantum metrology

Quantum metrology exploits quantum mechanical effects to increase the precision of measurements of physical quantities. A wide variety of applications are currently being developed for scientific and technological purposes, however, most research relies on the use of highly entangled resource states that are challenging to generate and control in a given physical system. Here, we study the use of weighted graph states as more accessible resources for quantum metrology, which yield a favorable precision beyond the classical limit, approaching the Heisenberg limit. We find a notable robustness to variation in weights and less challenging weight requirements compared to standard graph states, which require a maximal weight at all edges. Both of these aspects reduce the practical demands in a physical setup, with the latter implying significantly less entanglement is required to gain a quantum advantage in metrology. We study the quantum Fisher information and optimized estimator variance of two identified sub classes of weighted graph states for an arbitrary number of N qubits, providing analytical forms and investigating their scaling. Our work opens up opportunities for using weakly entangled states in quantum-enhanced metrology.

quant-ph↗

arXiv2024

Robustness of the projected squeezed state protocol

Projected squeezed (PS) states are multipartite entangled states generated by unitary spin squeezing, followed by a collective quantum measurement and post-selection. They can lead to an appreciable decrease in the state preparation time of the maximally entangled N-qubit Greenberger-Horne-Zeilinger (GHZ) state when compared to deterministic preparation by unitary transformations in physical systems where spin squeezing can be realized, such as ion, neutral atom, and superconducting qubits. Here we simulate the generation of PS states in non-ideal experimental conditions with relevant decoherence channels. By employing the Kraus operator method, and quantum trajectory method to reduce the computational complexity, we assess the quantum Fisher information and overlap fidelity with an ideal GHZ state. Our findings highlight PS states as useful metrological resources, demonstrating a robustness against environmental effects with increasing qubit number N.

quant-ph↗