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Pedro Chamorro-Posada

Publications and source records attributed to Pedro Chamorro-Posada.

At least 19 recordsLinked to original sources
arXiv2024

Corner Reflector Plasmonic Nanoantennas for Enhanced Single-Photon Emission

The emission rate of atom-like photon sources can be significantly improved by coupling them to plasmonic resonant nanostructures. These arrangements function as nanoantennas, serving the dual purpose of enhancing light--matter interactions and decoupling the emitted photons. However, there is a contradiction between the requirements for these two tasks. A small resonator volume is necessary for maximizing interaction efficiency, while a large antenna mode volume is essential to achieve high emission directivity. In this work, we analyze a hybrid structure composed of a noble metal plasmonic resonant nanoparticle coupled to the atom-like emitter, which is designed to enhance the emission rate, alongside a corner reflector aimed at optimizing the angular distribution of the emitted photons. A comprehensive numerical study of silver and gold corner reflector nanoantennas, employing the finite difference time domain method, is presented. The results demonstrate that a well-designed corner reflector can significantly enhance photon emission directivity while also substantially boosting the emission rate.

physics.optics↗
arXiv2024

Silicon nitride bent asymmetric coupled waveguides with partial Euler bends

Waveguide geometries combining bent asymmetric coupled structures and adiabatic transitions shaped as partial Euler bends are put forward and theoretically analyzed in this work. Designs aiming to reduce the radiation loss, with application in curved waveguide sections and Q-enhanced microresonators, and polarization selection geometries, both for the silicon nitride platform, are studied using highly accurate numerical techniques.

physics.optics↗
arXiv2023

Corner reflectors: fractal analysis and integrated single-photon sources

In this work, the properties of the radiation emitted by a corner reflector with an electric dipole feeder are analyzed in the optical domain where the distance between the dipole and the corner apex can be large in terms of the optical wavelength. A comprehensive study of the fractal properties of the radiated intensity patterns is presented. The use of this setup for the realization of single-photon sources in photonic integrated circuits is also put forward and a detailed study of the emission properties of the device and its optimal configurations is presented.

physics.optics↗
arXiv2023

The SWITCH test for discriminating quantum evolutions

We propose a quantum circuit to discriminate between two arbitrary quantum evolution operators. It permits to test the equality of two quantum operators and to estimate a fidelity measure of them. The relation of the proposal to the SWAP test for discriminating two quantum states is analyzed. We also discuss potential applications for the discrimination of quantum communication channels and possible laboratory implementations with light along the same lines of recent experimental realizations of quantum superpositions of causal orders exploiting the different degrees of freedom of photons. We also discuss hardware efficient realizations for noisy intermediate scale quantum computers.

quant-ph↗
arXiv2020

Design and Characterization of Q-enhanced Silicon Nitride Racetrack Micro-Resonators

Q-enhanced racetrack micro-resonators for the silicon nitride photonics integration platform have been designed, fabricated and characterized. The proposed geometries permit to mitigate the impact of radiation loss at curved waveguides, one of the major limitations of silicon nitride circuits, therefore providing an increase of the intrinsic Q factor of micro-resonators when compared with the conventional structures with the same bent radii. The schemes put forward in this work permit a reduction of the size of the devices that has a direct impact on the integration scale in this platform. When used in the curved sections of waveguides routing optical signals within an integrated photonic circuit, these geometries provide a reduction of the radiation loss and permit the use of smaller bent radii and to increase the circuit integration density.

physics.optics↗
arXiv2018

Radiation in Bent Asymmetric Coupled Waveguides

A numerical study of the radiation in coupled bent waveguides is presented. Such arrangements of curved waveguides in reduced radiation-loss configurations can be used to enhance the quality factor of integrated micro-resonators. 3D full vector computations of the complex modal fields (and propagation constants) and the transient propagation effects have been performed. The results obtained agree qualitatively with former 2D FDTD analyses. At the same time, the calculations presented meet the accuracy requirements for the design of practical implementations that are unattainable with 2D approaches.

physics.optics↗
arXiv2017

Hidden probe attacks on ultralong fiber laser key distribution systems

In ultralong fiber laser key distribution, two sides use standard optical equipment to create kilometer long fiber lasers in a communication link to establish a secret key. Its security rests on the assumption that any attacker would need much more sophisticated equipment and techniques than those of the legitimate user in order to discover the generated key. We present a challenge to that assumption with a hidden probe attack in which the eavesdropper hides a weak signal in the unavoidable noise floor that appears in the laser during amplification and probes with it the configuration of one or both communication parties. We comment how this attack can compromise different proposals for ultralong laser key distribution and propose possible countermeasures.

physics.app-ph↗
arXiv2016

Q-enhanced racetrack micro-resonators

A $Q$-enhancement strategy for racetrack microresonators is put forward. The design is based on the modification of the resonator geometry in order to mitigate the two main sources of radiation loss in the presence of curved waveguides: the discontinuities at the junctions between straight waveguides and the bent sections, and the continuous loss at the curved waveguide sectors. At the same time, the modifications of the geometry do not affect the versatility of coupling of racetrack resonators in integrated optical circuits, which is their main advantage over ring microresonators. The proposal is applied to the design of high-$Q$ racetrack resonators for the silicon nitride CMOS-compatible platform having bent radii amenable for large-scale photonic integration. Numerical calculations show over $100\%$ improvement of the $Q$ factor in $\text{Si}_3\text{N}_4/\text{SiO}_2$ resonators.

physics.optics↗
arXiv2015

On the asymptotic evolution of finite energy Airy wavefunctions

In general, there is an inverse relation between the degree of localization of a wavefunction of a certain class and its transform representation dictated by the scaling property of the Fourier transform. We report that in the case of finite energy Airy wavepackets a simultaneous increase in their localization in the direct and transform domains can be obtained as the apodization parameter is varied. One consequence of this is that the far field diffraction rate of a finite energy Airy beam decreases as the beam localization at the launch plane increases. We analyse the asymptotic properties of finite energy Airy wavefunctions using the stationary phase method. We obtain one dominant contribution to the long term evolution that admits a Gaussian-like approximation, which displays the expected reduction of its broadening rate as the input localization is increased.

physics.optics↗
arXiv2015

Gap solitons and symmetry breaking in parity-time symmetric microring CROWs

The propagation properties of optical fields in linear and nonlinear parity-time symmetric microring coupled resonator optical waveguides are studied. The effects described include the existence of symmetry breaking thresholds, the propagation of gap solitons in nonlinear transmission lines and the existence of quasi stable propagation regimes outside the broken symmetry regions.

physics.optics↗
arXiv2014

Quantum spread spectrum multiple access

We describe a quantum multiple access scheme that can take separate single photon channels and combine them in the same path. We propose an add-drop multiplexer that can insert or extract a single photon into an optical fibre carrying the qubits of all the other users. The system follows the principle of code division multiple access, a spread spectrum technique widely used in cellular networks.

quant-ph↗
arXiv2013

Intermittent Giant Goos-Hanchen shifts from Airy beams at nonlinear interfaces

We study the giant Goos-Hanchen shift obtained from an Airy beam impinging on a nonlinear interface. To avoid any angular restriction associated with the paraxial approximation, the analysis is based on the numerical solution of the nonlinear Helmholtz equation. We report the existence of non-standard intermittent and oscillatory regimes for the nonlinear Goos-Hanchen shifts which can be explained in terms of the competition between the critical coupling to a surface mode of the reflected component of the Airy beam and the soliton emission from the refracted beam component.

physics.optics↗
arXiv2013

A SWAP gate for qudits

We present a quantum SWAP gate valid for quantum systems of an arbitrary dimension. The gate generalizes the CNOT implementation of the SWAP gate for qubits and keeps its most important properties, like symmetry and simplicity. We only use three copies of the same controlled qudit gate. This gate can be built with two standard higher-dimensional operations, the Quantum Fourier Transform and the d-dimensional version of the CZ gate.

quant-ph↗
arXiv2013

The SWAP test and the Hong-Ou-Mandel effect are equivalent

We show that the Hong-Ou-Mandel effect from quantum optics is equivalent to the SWAP test, a quantum information primitive which compares two arbitrary states. We first derive a destructive SWAP test that doesn't need the ancillary qubit that appears in the usual quantum circuit. Then, we study the Hong-Ou-Mandel effect for two photons meeting at a beam splitter and prove it is, in fact, an optical implementation of the destructive SWAP test. This result offers both an interesting simple realization of a powerful quantum information primitive and an alternative way to understand and analyse the Hong-Ou-Mandel effect.

quant-ph↗
arXiv2012

Quantum computer networks with the orbital angular momentum of light

Inside computer networks, different information processing tasks are necessary to deliver the user data efficiently. This processing can also be done in the quantum domain. We present simple optical quantum networks where the orbital angular momentum of a single photon is used as an ancillary degree of freedom which controls decisions at the network level. Linear optical elements are enough to provide important network primitives like multiplexing and routing. First we show how to build a simple multiplexer and demultiplexer which combine photonic qubits and separate them again at the receiver. We also give two different self-routing networks where the OAM of an input photon is enough to make it find its desired destination.

quant-ph↗
arXiv2012

Scouting the spectrum for interstellar travellers

Advanced civilizations capable of interstellar travel, if they exist, are likely to have advanced propulsion methods. Spaceships moving at high speeds would leave a particular signature which could be detected from Earth. We propose a search based on the properties of light reflecting from objects travelling at relativistic speeds. Based on the same principles, we also propose a simple interstellar beacon with a solar sail.

physics.pop-ph↗
arXiv2011

A counterfactual Rydberg gate for photons

Quantum computation with photons requires efficient two photon gates. We put forward a two photon entangling gate which uses an intermediate atomic system. The system includes a single Rydberg atom which can switch on and off photon absorption in an ensemble using the dipole blockade. The gate is based in a counterfactual protocol. The mere possibility of an absorption that can only occur with a vanishing probability steers the photons to the desired final state.

quant-ph↗