Nanowerk April 5, 2024 An international team of researchers (Portugal, Brazil) analysed nonclassical resources in interference phenomena using generalized noncontextuality inequalities and basis-independent coherence witnesses. They used inequalities that witness both resources within the same framework. In view of the previous contextual advantage results, they proposed a systematic way of applying these tools to characterize advantage provided by coherence and contextuality in quantum information protocols. They used this methodology as an example for the task of quantum interrogation, introduced by the paradigmatic bomb-testing interferometric experiment, showing contextual quantum advantage for such a task… read more. Open Access TECHNICAL ARTICLE
Category Archives: Quantum science
New research area promotes both quantum computing and cognitive science
Phys.org March 26, 2024 Quantum biology applies quantum mechanics to biological systems at the molecular scale. Molecular quantum computing explores the degrees of freedom of molecules that can be used to produce quantum coherence. Cognitive science focuses on understanding how learning processes are realized, particularly within the human brain. An international team of researchers (US, USA – New Jersey Institute of Technology, Morgan State University) reviewed progress in quantum biology, molecular quantum computing, and quantum theory in cognitive science. Based on their analysis and review, they highlighted that molecular quantum computing could be an important bridging research area between quantum […]
Making quantum bits fly
Nanowerk March 6, 2024 Matter qubit to traveling photonic qubit conversion is the cornerstone of numerous quantum technologies such as distributed quantum computing, as well as several quantum internet and networking protocols. Researchers in Germany formulated a theory for stimulated Raman emission which is applicable to a wide range of physical systems, including quantum dots, solid-state defects, and trapped ions, and various parameter regimes. They found the upper bound for the photonic pulse emission efficiency of arbitrary matter qubit states for imperfect emitters and showed a path forward to optimizing the fidelity. Based on these results, they proposed a paradigm […]
Deciphering quantum enigmas: The role of nonlocal boxes in defining the boundaries of physical feasibility
Phys.org February 14, 2024 Nonsignaling boxes (NS) are theoretical resources defined by the principle of no-faster-than-light communication. They generalize quantum correlations and some of them are known to collapse communication complexity (CC). However, this collapse is strongly believed to be unachievable in nature. An international team of researchers (France, Canada) provided intuition on which theories are unrealistic. They found a better sufficient condition for a nonlocal box to collapse CC, thus extended the known collapsing region. In some slices of NS, they showed that this condition coincides with an area outside of an ellipse… read more. TECHNICAL ARTICLE Full […]
Physicists discover new quantum phases in low-dimensional polar systems
Phys.org December 13, 2023 Quantum fluctuations (QFs) caused by zero-point phonon vibrations (ZPPVs) are known to prevent the occurrence of polar phases in bulk incipient ferroelectrics down to 0 K. On the other hand, little is known about the effects of QFs on the recently discovered topological patterns in ferroelectric nanostructures. A team of researchers in the US (University of Arkansas, Fayetteville, Lonestar College, Texas) has shown how QFs affect the topology of several dipolar phases in ultrathin Pb(Zr0.4Ti0.6)O3 (PZT) films. They showed that the ZPPVs do not suppress polar patterns but rather stabilize the labyrinth, bimeron and bubble phases within […]
Solving quantum mysteries: New insights into 2D semiconductor physics
Nanowerk October 16, 2023 An international team of researchers (Australia, Spain) has introduced a novel approach ‘quantum virial expansion,’ to uncover the complex quantum interactions in two-dimensional semiconductors. They showed that this constituted a perturbatively exact theory in the high-temperature or low-doping regime, where the electrons’ thermal wavelength was smaller than their interparticle spacing. They obtained exact analytic expressions for the photoluminescence and predicted new features such as a nontrivial shape of the attractive branch peak related to universal resonant exciton-electron scattering and an associated energy shift from the trion energy. The theory allowed them to formally unify the two […]
How quantum light sees quantum sound
Nanowerk October 3, 2023 Researchers in the UK have proposed a new way of using quantum light to ‘see’ quantum sound. They showed that the second-order, two-time correlation functions for phonons and photons emitted from a vibronic molecule in a thermal bath resulted in bunching and antibunching (a purely quantum effect), respectively. Signatures relating to phonon exchange with the environment were revealed in photon-photon correlations. They demonstrated that cross-correlation functions have a strong dependence on the order of detection giving insight into how phonon dynamics influences the emission of light. It is hoped that the discovery may help scientists better […]
‘Quantum avalanche’ explains how nonconductors turn into conductors
Phys.org July 24, 2023 The significant discrepancy observed between the predicted and experimental switching fields in correlated insulators under a DC electric field far-from-equilibrium necessitates a reevaluation of current microscopic understanding. An international team of researchers (USA – SUNY Buffalo, France, South Korea) has shown that an electron avalanche can occur in the bulk limit of such insulators at arbitrarily small electric field by introducing a generic model of electrons coupled to an inelastic medium of phonons. The quantum avalanche arose because of the generation of a ladder of in-gap states, created by a multi-phonon emission process. Hot-phonons in the […]
For experimental physicists, quantum frustration leads to fundamental discovery
Phys.org June 14, 2023 A typical frustrated system is correlated bosons on moat bands, which could host topological orders with long-range quantum entanglement. However, the realization of moat-band physics is still challenging. Researchers at UMass, Amherst explored moat-band phenomena in shallowly inverted InAs/GaSb quantum wells, where they observed an unconventional time-reversal-symmetry breaking excitonic ground state under imbalanced electron and hole densities. They found a large bulk gap encompassing a broad range of density imbalances at zero magnetic field (B), accompanied by edge channels that resemble helical transport. Under an increasing perpendicular B, the bulk gap persisted, and an anomalous plateau […]
Using nanofaceting to manipulate quantum dots into nanocrystals
Phys.org May 17, 2023 Colloidal nanocrystals (NCs) have shown remarkable promise for optoelectronics, energy harvesting, photonics, and biomedical imaging. In addition to optimizing quantum confinement, the current challenge is to obtain a better understanding of the critical processing steps and their influence on the evolution of structural motifs. Through computational simulations and electron microscopy an international team of researchers (UK, France, South Korea, China) has shown that nanofaceting can occur during nanocrystal synthesis from a Pb-poor environment in a polar solvent. This could explain the curved interfaces and the olivelike-shaped NCs observed experimentally when these conditions were employed. Furthermore, the […]