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Dive into the research topics where Nicolás Quesada is active.

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Featured researches published by Nicolás Quesada.


Journal of Modern Optics | 2012

Quantum properties and dynamics of X states

Nicolás Quesada; Asma Al-Qasimi; Daniel F. V. James

X states are a broad class of two-qubit density matrices that generalize many states of interest in the literature. In this work, we give a comprehensive account of various quantum properties of these states, such as entanglement, negativity, quantum discord and other related quantities. Moreover, we discuss the transformations that preserve their structure both in terms of continuous time evolution and discrete quantum processes.


Physical Review A | 2014

Effects of time ordering in quantum nonlinear optics

Nicolás Quesada; J. E. Sipe

We study time ordering corrections to the description of spontaneous parametric down-conversion (SPDC), four wave mixing (SFWM) and frequency conversion (FC) using the Magnus expansion. Analytic approximations to the evolution operator that are unitary are obtained. They are Gaussian preserving, and allow us to understand order-by-order the effects of time ordering. We show that the corrections due to time ordering vanish exactly if the phase matching function is sufficiently broad. The calculation of the effects of time ordering on the joint spectral amplitude of the photons generated in spontaneous SPDC and SFWM are reduced to quadrature.


Journal of Physics B | 2013

Bound entanglement in the Jaynes–Cummings model

Nicolás Quesada; A. Sanpera

We study in detail entanglement properties of the Jaynes–Cummings model assuming a two-level atom (qubit) interacting with the first N levels of an electromagnetic field mode (qudit) in a cavity. In the Jaynes–Cummings model, the number operator is the conserved quantity that allows for the exact diagonalization of the Hamiltonian and thus we study states that commute with this conserved quantity and whose structure is preserved under the Jaynes–Cummings dynamics. Contrary to the common belief, we show that there are bound entangled states that satisfy the symmetries imposed by the conservation of the number of excitations when N > 3. Furthermore we show that the Jaynes–Cummings interaction can be used to generate bound entanglement between the atom and the mode.


Physical Review A | 2013

Self-calibrating tomography for multidimensional systems

Nicolás Quesada; Agata M. Brańczyk; Daniel F. V. James

We present a formalism for self-calibrating tomography of arbitrary dimensional systems. Self-calibrating quantum state tomography was first introduced in the context of qubits, and allows the reconstruction of the density matrix of an unknown quantum state despite incomplete knowledge of the unitary operations used to change the measurement basis. We show how this can be generalized to qudits, i.e. d-level systems, and provide a specific example for a V-type three-level atomic system whose transition dipole moments are not known. We show that it is always possible to retrieve the unknown state and process parameters, except for a set of zero measure in the state-parameter space.


Physical Review A | 2012

Strong coupling of two quantum emitters to a single light mode: The dissipative Tavis-Cummings ladder

Nicolás Quesada

A criterion for strong coupling between two quantum emitters and a single resonant light mode in a cavity is presented. The criterion takes into account the escape of cavity photons and the spontaneous emission of the emitters, which are modeled as two-level systems. By using such a criterion, the dissipative Tavis-Cummings ladder of states is constructed, and it is shown that the inclusion of one more emitter with respect to the Jaynes-Cummings (single emitter) case increases the effective parameter region in which


Journal of Physics: Condensed Matter | 2011

Strong coupling of two interacting excitons confined in a nanocavity–quantum dot system

Paulo Cárdenas; Nicolás Quesada; Herbert Vinck-Posada; Boris A. Rodriguez

n\text{th}


conference on lasers and electro optics | 2015

Particle vs. mode entanglement in optical quantum metrology

Nicolás Quesada; Jaspreet Sahota

-order Rabi splitting is observed.


Physical Review A | 2015

Quantum correlations in optical metrology: Heisenberg-limited phase estimation without mode entanglement

Jaspreet Sahota; Nicolás Quesada

We present a study of the strong coupling between radiation and matter, considering a system of two quantum dots, which are in mutual interaction and interact with a single mode of light confined in a semiconductor nanocavity. We take into account dissipative mechanisms such as the escape of the cavity photons, decay of the quantum dot excitons by spontaneous emission, and independent exciton pumping. It is shown that the mutual interaction between the dots can be measured off-resonance only if the strong coupling condition is reached. Using the quantum regression theorem, a reasonable definition of the dynamical coupling regimes is introduced in terms of the complex Rabi frequency. Finally, the emission spectrum for relevant conditions is presented and compared with the above definition, demonstrating that the interaction between the excitons does not affect the strong coupling.


Optics Letters | 2016

High efficiency in mode-selective frequency conversion

Nicolás Quesada; J. E. Sipe

We present a constructive proof of the fact that mode entanglement is not necessary for optical quantum enhanced metrology (QEM) but particle entanglement is. We provide a particle entanglement witness that detects all path symmetric states useful for QEM in a Mach-Zender interferometer.


arXiv: Quantum Physics | 2018

Gaussian Boson Sampling using threshold detectors.

Nicolás Quesada; Juan Miguel Arrazola; Nathan Killoran

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Herbert Vinck-Posada

National University of Colombia

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A. Sanpera

Autonomous University of Barcelona

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