Nicolás Quesada
University of Toronto
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Publication
Featured researches published by Nicolás Quesada.
Journal of Modern Optics | 2012
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
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
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
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
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
Paulo Cárdenas; Nicolás Quesada; Herbert Vinck-Posada; Boris A. Rodriguez
n\text{th}
conference on lasers and electro optics | 2015
Nicolás Quesada; Jaspreet Sahota
-order Rabi splitting is observed.
Physical Review A | 2015
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
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
Nicolás Quesada; Juan Miguel Arrazola; Nathan Killoran