arXiv subjects

Jesús Liñares

Publications and source records attributed to Jesús Liñares.

8 recordsLinked to original sources

arXiv2026

Multichannel Hybrid Quantum Cryptography for Submarine Optical Communications

We present a multichannel hybrid quantum cryptography approach intended for submarine quantum optical communications between Alice and Bob separated a distance beyond the current QKD possibilities, each located on a coastline. It is based on the difficult of a simultaneous access to $M$ optical submarine channels. The optical lines from the coastline and ideally to the end of the continental platform are governed by the quantum properties of the light under an autocompensating high-dimensional discrete-modulation continuous variable QKD protocol. The hybrid approach consists of combining several secret keys of the $M$ channels and introducing extra layers of security, passive and/or active, on the non quantum optical lines located beyond the continental platform.

physics.optics↗

arXiv2025

High-dimensional autocompensating discrete modulation CV-QKD protocol in optical fibers

In this work we present a high-dimensional discrete modulated CV-QKD protocol, with dimension 2N , in optical fibers, where N is the number of optical modes. We use N-dimensional product states of weak coherent states that undergo perturbations along optical fibers and that are cancelled in a passive way (autocompensation) and then measured by a standard balanced homodyne detection. We analyze the security of this high-dimensional protocol when an intercept and resend attack is implemented with simultaneous homodyne measurement in both quadratures and the resulting secure key gains are calculated showing a significative increase with dimension.

quant-ph↗

arXiv2021

Quantum projectors implemented with optical directional couplers fabricated by Na/K ion-exchange in soda-lime glass

We present a preliminary theoretical and experimental study of quantum projectors implemented by integrated optical directional couplers fabricated by ion-exchange Na/K processes in soda-lime glass. Theoretical considerations about devices formed by concatenated 2x2 directional couplers are presented in order to show their capabilities for implementing N-dimensional quantum projective measurements, and concomitantly the production of 1-qudit states. Since the fundamental unit of these devices are 2x2 directional couplers, we present an experimental study for obtaining, by an optical characterization, empiric relationships between fabrication and optical parameters of such couplers. Likewise, a two-dimensional quantum projector is demonstrated in such a way that projective measurements are obtained for the states of X (diagonal) and Y (circular) bases.

quant-ph↗

arXiv2020

Fully autocompensating high-dimensional quantum cryptography by optical phase conjugation

We present a bidirectional quantum communication system based on optical phase conjugation for achieving fully autocompensating high-dimensional quantum cryptography. We prove that random phase shifts and couplings among 2N spatial and polarization optical modes described by SU(2N) transformations due to perturbations are autocompensated after a single round trip between Alice and Bob. Bob can use a source of single photons or, alternatively, coherent states and then Alice attenuates them up to a single photon level, and thus non-perturbated 1-qudit states are generated for high-dimensional QKD protocols, as the BB84 one, of a higher security.

quant-ph↗

arXiv2020

Engineering continuous and discrete variable quantum vortex states by nonlocal photon subtraction in a reconfigurable photonic chip

We study the production of entangled two- and N-mode quantum states of light in optical waveguides. To this end, we propose a quantum photonic circuit that produces a reconfigurable superposition of photon subtraction on two single-mode squeezed states. Under postselection, continuous variable or discrete variable entangled states with possibilities in quantum information processing are obtained. Likewise, nesting leads to higher-dimension entanglement with a similar design, enabling the generation of non-Gaussian continuous variable cluster states. Additionally, we show the operation of the device through the generation of quantum vortex states of light and propose an integrated device that measures their order and handedness. Finally, we study the non-Gaussianity, nonclassicality, and entanglement of the quantum states generated with this scheme by means of the optical field-strength distribution, Wigner function, and logarithmic negativity.

quant-ph↗

arXiv2020

Detection of two-mode spatial quantum states of light by electro-optic integrated directional couplers

We study both manipulation and detection of two-mode spatial quantum states of light by means of a reconfigurable integrated device built in an electro-optical material in a Kolgelnik-Schmidt configuration, which provides higher error tolerance to fabrication defects and larger integration density than other current schemes. SU(2) transformations are implemented on guided spatial modes in such a way that reconstruction of both the optical field-strength quantum probability distribution, via spatial two-mode homodyne detection, and the full optical field-strength wavefunction, by means of weak values, are carried out. This approach can easily be extended to spatial N-mode input quantum states. Apart from its usefulness to characterize optical quantum states, it is also emphasized its application to the measurement of the so-called generalized quantum polarization.

quant-ph↗

arXiv2017

Comment on "Generating a perfect quantum optical vortex"

In a recent article, Banerji et al. introduced a novel quantum state of light, coined as the perfect quantum optical vortex state [Phys. Rev. A 94, 053838 (2016)] due to its mathematical similarity with the classical perfect vortex beam. This state is obtained by means of the Fourier transform of a Bessel-Gaussian vortex state, and the authors claim that this can be accomplished by means of a simple lens. Here, we will show that this statement is wrong since a lens cannot modify the quantum noise distribution related to the input optical quantum state and this has to be exchanged by an "effective lens".

quant-ph↗

arXiv2015

Quantum light propagation in longitudinally inhomogeneous media as a spatial Lewis-Ermakov physical invariance

We study the propagation of quantum states of light in separable longitudinally inhomogeneous media. By means of the usual quantization approach this kind of media would lead to the unphysical result of quantum noise squeezing. This problem is solved by means of generalized canonical transformations in a comoving frame. Under these transformations the generator of propagation is a physical Lewis-Ermakov invariant in space which is quantized and, accordingly, a propagator consistent with experiments is obtained. Finally, we show that the net effect produced by propagation in these media is a quantum Gouy's phase with application in quantum interferometry.

quant-ph↗