Science – Page 33

Beyond Qubit Count: A Faster Path to Quantum Simulation

16.12.2025 by pricpr

New research reveals a fundamental limit on the time needed for digital-analog quantum computation, shifting the focus from the number of qubits to the complexity of interactions.

Picking the Right Basis: Neural Networks and the Quest for Quantum Ground States

15.12.2025 by pricpr

$The capacity of a restricted Boltzmann machine to accurately learn the ground state of a Hamiltonian is fundamentally determined by the system’s spectral gap-$E\Delta E$-relative to optimization parameters, specifically the ratio of the spectral gap to the learning rate multiplied by a factor $f\_k$, as described by the equation $E\Delta E / \eta f\_k$ [34].$

New research reveals that the effectiveness of neural networks in simulating quantum systems is heavily influenced by how the quantum state is represented, impacting the accuracy and efficiency of calculations.

Beyond Universality: Entanglement Reveals Quantum Criticality’s Hidden Depths

15.12.2025 by pricpr

$The quantum Grüneisen parameter, $ \Gamma^{\textmd{0K}}\_{q=q\_{special}}$, exhibits a strong dependence on the tuning parameter $ \lambda = J/B$ for a one-dimensional Mott transition, revealing a shift from a superposition of spin states at infinite $ \lambda$ to a quantum paramagnetic phase aligned with the external field at zero $ \lambda$, with the critical value $ \lambda_c$ being system-size dependent and characterized by a specific value of $ \Gamma^{\textmd{0K}}\_{q=q\_{special}}$ indicated for a system of eight spins and further corroborated in the thermodynamic limit for $S=1/2$ through analysis of nearest-neighbor interactions.$

New research leverages the Schmidt decomposition theorem and non-additive entropy to dissect the interplay between universal and non-universal behaviors in quantum phase transitions.

Twisting Security: The Promise of Orbital Angular Momentum QKD

15.12.2025 by pricpr

Orbital angular momentum (OAM)-encoded quantum key distribution (QKD) faces systemic challenges at various stages, demanding careful consideration of factors that influence secure key generation and distribution.

This review explores how encoding quantum keys on the ‘spin’ of light offers a path to faster, more secure communication networks.

Beyond the Wave Function: A Classical Path to Quantum Systems

15.12.2025 by pricpr

The study of a potential well with depth $V_0 = -0.5$ demonstrates how solutions to the Bohm and Schrödinger equations reveal a ground-state energy of $E = -0.36$ alongside a scattering solution characterized by a wave number $k = 1.5$ (corresponding to $E = 1.125$), illuminating the dynamics described by the underlying nonlinear Schrödinger equation detailed in Eq. (4).

New research explores a Bohmian mechanics-based approach to bridge the gap between classical statistical descriptions and quantum phenomena.

Beyond Equilibrium: Bridging Classical and Quantum System Dynamics

15.12.2025 by pricpr

$The dynamics of a quantum harmonic oscillator coupled to a thermal bath demonstrate how entropy-total, production, and flow-evolves over time, converging towards the expected thermal equilibrium of $\frac{1}{2}\hbar\omega+\hbar\omega/(e^{\frac{\hbar\omega}{k\_{B}T}}-1)$, with the specific trajectory influenced by the properties of the friction operator-Hermitian or non-Hermitian-and mirroring the established Caldeira-Leggett model under standardized parameters like $\hbar=1$, $k\_{B}=1$, and $T=1$.$

A new framework unifies the description of open systems, revealing a fundamental connection between classical Langevin equations and quantum master equations.

The Fuzzy Fabric of Space-Time

15.12.2025 by pricpr

A system’s ability to precisely measure both time and position exists in inverse proportion-a sharply defined clock reading inevitably introduces uncertainty in spatial localization, a consequence of the coupling between internal clock dynamics and the system’s external freedom as described by $Eq. (5)$.

New research reveals a fundamental limit to how precisely we can define space and time using quantum systems, demonstrating an inherent trade-off between coordinate precision and system dynamics.

Beyond Quantum Weirdness: Measuring the true Depth of Contextuality

15.12.2025 by pricpr

$For a spin-1 system, maximal contextuality of an observable $A_{\mathbf{k}}$ arises from states lying on a surface perpendicular to the direction $\mathbf{k}$ within the Majorana-stellar representation, a surface defined by the orientations of other contextually-related observables and intersecting to reveal the system’s inherent relational structure, mirroring the geometry of the KCBS pentagram.$

A new framework establishes a rigorous link between information theory and the operational power of quantum contextuality, revealing its limits and potential.

The Inevitable Collapse of Quantum Superpositions

15.12.2025 by pricpr

$The study demonstrates that maximizing the difference between the density matrices of the GHZ state and a mixed state-specifically, $tr[A(\rho_{GHZ} - \rho_{mix})]$ at time 0 and $tr[A(\overline{\rho_{GHZ}} - \overline{\rho_{mix}})]$ as time approaches infinity-yields consistent behavior across a range of parameters ($h_z = 0.6$, $h_x = 0.2$, $J_1 = 1.0$, $J_2 = 1.35$, $d = 0.5$, and $e = 0.1$), suggesting a robustness in the observed phenomenon despite variations in system configuration.$

New research demonstrates that even perfectly isolated macroscopic quantum states are destined to behave classically due to inherent dynamical processes.

Spotting the Shift: How Quantum Computing Can Detect Manipulated Video Content

15.12.2025 by pricpr

$The Quantum-BAR framework utilizes a quantum encoder to map normal videos into a hypersphere, where malicious mutations deviate from the center and align with a sensationalism axis, enabling detection through their altered quantum state-a process achieved by amplitude-encoding input features into a 12-qubit system and processing them with a variational quantum circuit parameterized by $\theta$.$

A new approach leverages quantum machine learning to identify subtle semantic changes in short videos by focusing on the unique style of individual creators.