ICFO – The Institute of Photonic Sciences

About: ICFO – The Institute of Photonic Sciences is a facility organization based out in Barcelona, Spain. It is known for research contribution in the topics: Quantum & Quantum entanglement. The organization has 872 authors who have published 1965 publications receiving 56273 citations.

Advances in ultrafast optical parametric sources for the mid-infrared based on CdSiP_2

Abstract: We describe the evolution of ultrafast optical parametric sources for the mid-infrared (mid-IR) based on the new birefringent nonlinear crystal, cadmium silicon phosphide, CdSiP2, using well-established Nd-based solid-state and Yb-based fiber pump lasers near 1 μm. Optical parametric generators and optical parametric oscillators (OPOs) providing high-energy picosecond pulses, as well as high-repetition-rate femtosecond pulses, at high average powers across the 6–7 μm spectral range in the mid-IR are described in detail. Studies of viable pump laser technologies suitable for ultrafast femtosecond OPOs based on CdSiP2 are discussed, and the favorable linear and nonlinear optical properties, as well as unique phase-matching characteristics of CdSiP2, are presented using the most recent Sellmeier equations for the material. The described experimental results represent the highest output pulse energy and record average power in the ultrafast picosecond and femtosecond time scales across the 6–7 μm spectral range to date.

Ultimate Limit of Light Extinction by Nanophotonic Structures.

Abstract: Nanophotonic structures make it possible to precisely engineer the optical response at deep subwavelength scales. However, a fundamental understanding of the general performance limits remains a challenge. Here we use extensive electrodynamics simulations to demonstrate that the so-called f-sum rule sets a strict upper bound to the light extinction by nanostructures regardless their internal interactions and retardation effects. In particular, we show that the f-sum rule applies to arbitrarily complex plasmonic metal structures that exhibit an extraordinary spectral sensitivity to size, shape, near-field coupling effects, and incident polarization. The results may be used for benchmarking light scattering and absorption efficiencies, thus imposing fundamental limits on solar light harvesting, biomedical photonics, and optical communications.

Quantum Codes of Maximal Distance and Highly Entangled Subspaces

Abstract: We present new bounds on the existence of general quantum maximum distance separable codes (QMDS): the length $n$ of all QMDS codes with local dimension $D$ and distance $d \geq 3$ is bounded by $n \leq D^2 + d - 2$. We obtain their weight distribution and present additional bounds that arise from Rains' shadow inequalities. Our main result can be seen as a generalization of bounds that are known for the two special cases of stabilizer QMDS codes and absolutely maximally entangled states, and confirms the quantum MDS conjecture in the special case of distance-three codes. As the existence of QMDS codes is linked to that of highly entangled subspaces (in which every vector has uniform $r$-body marginals) of maximal dimension, our methods directly carry over to address questions in multipartite entanglement.

Quantum chaos and entanglement in ergodic and nonergodic systems.

Abstract: We study entanglement entropy (EE) as a signature of quantum chaos in ergodic and nonergodic systems. In particular we look at the quantum kicked top and kicked rotor as multispin systems and investigate the single-spin EE which characterizes bipartite entanglement of this spin with the rest of the system. We study the correspondence of the Kolmogorov-Sinai entropy of the classical kicked systems with the EE of their quantum counterparts. We find that EE is a signature of global chaos in ergodic systems and local chaos in nonergodic systems. In particular, we show that EE can be maximized even when systems are highly nonergodic, when the corresponding classical system is locally chaotic. In contrast, we find evidence that the quantum analog of Kolmogorov-Arnol'd-Moser (KAM) tori are tori of low entanglement entropy. We conjecture that entanglement should play an important role in any quantum KAM theory.

Noise-resistant optimal spin squeezing via quantum control

Abstract: Entangled atomic states, such as spin-squeezed states, represent a promising resource for a new generation of quantum sensors and atomic clocks. We demonstrate that optimal control techniques can be used to substantially enhance the degree of spin squeezing in strongly interacting many-body systems, even in the presence of noise and imperfections. Specifically, we present a protocol that is robust to noise and outperforms conventional methods. Potential experimental implementations are discussed.