Science – Page 62

Beyond the Limit: Smarter Quantum Parameter Estimation

11.11.2025 by pricpr

$The precision with which parameters $\phi$ and $\Delta$ can be estimated—as indicated by the sum of mean squared errors $V(\hat{\phi})+V(\hat{\Delta})$—improves with an increasing number of probe state copies, approaching the theoretical limit defined by the quantum Cramér–Rao bound in the asymptotic regime, while remaining fundamentally constrained by the Nagaoka–Cramér–Rao bound, given true values of $\phi=0$ and $\Delta=1/2$.$

Researchers demonstrate a new approach to estimating multiple quantum parameters, achieving optimal precision for key parameters without sacrificing information about others.

Beyond Bell: How Conservation Laws Could Explain Quantum Correlations

11.11.2025 by pricpr

Quantum mechanics and hidden-variable models—specifically those conserving angular momentum with varying degrees of permissible deviation (ΔL) for Bell singlet and triplet states—yield distinct correlation response functions, fundamentally differentiating their predictions regarding the nature of quantum entanglement.

A new model suggests that violations of Bell inequalities aren’t necessarily evidence of non-locality, but may arise from the fundamental physics of measurement itself.

How Fast Can Quantum Systems Change?

11.11.2025 by pricpr

Within the landscape of quantum evolution, any transition between states possesses a fundamental speed limit dictated not by the duration of change, but by the geometric length of the path taken through the space of all possible states—a principle illustrated by the distinction between a general evolution’s path and the shortest, geodesic connection between initial and final states.

New research establishes limits on the speed of quantum evolution based on a fundamental quantum property called ‘imaginarity.’

Beyond the Bloch Line: Seeing Spectral Distortion in Momentum Space

11.11.2025 by pricpr

Researchers directly observe how energy bands warp in complex momentum space within a non-Hermitian system, opening new avenues for manipulating light and matter.

Shielding Quantum Teleportation from Noise

11.11.2025 by pricpr

For a bipartite fidelity criterion, a weak measurement protocol demonstrably surpasses unprotected teleportation across a spectrum of parameter values—specifically for ratios of 0.5 and 0.9—indicating a pathway to enhance quantum state transfer reliability through refined measurement strategies.

Researchers demonstrate improved fidelity in quantum teleportation protocols using subtle measurements and error-correcting techniques.

Steering the Quantum Realm: A Guide to Gaussian Channels

11.11.2025 by pricpr

This review explores how different types of Gaussian quantum channels affect the transfer of quantum steering, a key resource for quantum communication.

Quantum Geometry’s Hidden Connections

10.11.2025 by pricpr

A new mathematical framework links mixed and pure quantum states through a unifying generating function.

Beyond Speed: The Energy Cost of Quantum Precision

10.11.2025 by pricpr

With parameters set at g=2.5, ξ=0.2, ω₀/ω=10⁴, and δ²=10⁻⁴, the total resource cost increases alongside implementation error—or decreasing m̄—due to the resultant need for more cooling rounds, a behavior consistent with observations in Figure 1(c), despite an optimal Ms of approximately 5 minimizing cost when state preparation is significantly less expensive than gate implementation.

Quantum phase estimation offers increased precision, but achieving it efficiently requires balancing computational complexity with energy expenditure.

Beyond Heisenberg: Linking Thermodynamics and Quantum Uncertainty

10.11.2025 by pricpr

A system of inequalities demonstrates a relationship where a tighter upper bound is geometrically derived from the lower bound and a conventional variance bound, establishing a constrained interplay between these values and revealing inherent dependencies within the system.

New research connects the fundamental limits of quantum precision with the laws governing energy and information flow.

Relativistic Revivals: When Particles Bounce Back

10.11.2025 by pricpr

Within the intermediate regime, a quantum particle—initially localized with a velocity of 1.2ℏ/L and a width of L/25—doesn’t trace a simple path, but instead generates blurred interference patterns resembling ridges and canals, which, upon closer inspection, resolve into the cumulative effect of numerous internal rebounds within the confining potential well.

New research explores the surprising phenomenon of wavepacket revivals within the framework of the relativistic Schrödinger equation.