arXiv subjects

Marcelo de Almeida

Publications and source records attributed to Marcelo de Almeida.

3 recordsLinked to original sources

arXiv2022

A note on continuity of strongly singular Calderón-Zygmund operators in Hardy-Morrey spaces

In this note we address the continuity of strongly singular Calderón-Zygmund operators on Hardy-Morrey spaces $\mathcal{HM}_{q}^λ(\mathbb{R}^n)$, assuming weaker integral conditions on the associated kernel. Important examples that falls into this scope are pseudodifferential operators on the Hörmander classes $OpS^{m}_{σ,μ}(\mathbb{R}^n)$ with $0<σ\leq 1$, $0 \leq μ<1$, $μ\leq σ$ and $m\leq -n(1-σ)/2$.

math.AP↗

arXiv2013

Entanglement-free certification of entangling gates

Not all quantum protocols require entanglement to outperform their classical alternatives. The nonclassical correlations that lead to this quantum advantage are conjectured to be captured by quantum discord. Here we demonstrate that discord can be explicitly used as a resource: certifying untrusted entangling gates without generating entanglement at any stage. We implement our protocol in the single-photon regime, and show its success in the presence of high levels of noise and imperfect gate operations. Our technique offers a practical method for benchmarking entangling gates in physical architectures in which only highly-mixed states are available.

quant-ph↗

arXiv2012

Conclusive quantum steering with superconducting transition edge sensors

Quantum steering allows two parties to verify shared entanglement even if one measurement device is untrusted. A conclusive demonstration of steering through the violation of a steering inequality is of considerable fundamental interest and opens up applications in quantum communication. To date all experimental tests with single photon states have relied on post-selection, allowing untrusted devices to cheat by hiding unfavourable events in losses. Here we close this "detection loophole" by combining a highly efficient source of entangled photon pairs with superconducting transition edge sensors. We achieve an unprecedented ~62% conditional detection efficiency of entangled photons and violate a steering inequality with the minimal number of measurement settings by 48 standard deviations. Our results provide a clear path to practical applications of steering and to a photonic loophole-free Bell test.

quant-ph↗