arXiv subjects

Alejandra Valencia

Publications and source records attributed to Alejandra Valencia.

At least 19 recordsLinked to original sources

arXiv2025

Quantum Interference of Distinguishable Photons Based on Spatially-Resolved Measurements

We present experimental results demonstrating the quantum interference of two photons distinguishable in their transverse momenta, each entering the input ports of a balanced beam splitter. This counterintuitive interference effect is made possible through spatially resolved measurements in the near field, i.e., by resolving the conjugate variable in which the photons are distinguishable. Our experimental findings agree with theoretical predictions. We contrast our results with a non-spatially resolved measurement where averaging over the photons' positions washes out the quantum interference observed in spatially resolved measurements.

quant-ph↗

arXiv2024

Decoherence-assisted quantum key distribution

We present a theoretical and experimental study of a controllable decoherence-assisted quantum key distribution scheme. Our method is based on the possibility of introducing controllable decoherence to polarization qubits using the spatial degree of freedom of light. We show that our method reduces the amount of information that an eavesdropper can obtain in the BB84 protocol under the entangling probe attack. We demonstrate experimentally that Alice and Bob can agree on a scheme to that gives low values of the quantum bit error rate, despite the presence of a large amount of decoherence in the transmission channel of the BB84 protocol.

quant-ph↗

arXiv2023

The quantum beam splitter with many partially indistinguishable photons: multiphotonic interference and asymptotic classical correspondence

We present the asymptotic analysis of the quantum two-port interferometer in the $n \rightarrow \infty$ limit of $n$ partially indistinguishable photons. Using the unitary-unitary duality between port and inner-mode degrees of freedom, the probability distribution of output port counts can be decomposed as a sum of contributions from independent channels, each associated to a spin-$j$ representation of $SU(2)$ and, in this context, to $2 j$ effectively indistinguishable photons in the channel. Our main result is that the asymptotic output distribution is dominated by the $O(\sqrt{n})$ channels around a certain $j^*$ that depends on the degree of indistinguishability. The asymptotic form is essentially the doubly-humped semi-classical envelope of the distribution that would arise from $2 j^*$ indistinguishable photons, and which reproduces the corresponding classical intensity distribution.

quant-ph↗

arXiv2023

Measuring Wigner functions of quantum states of light in the undergraduate laboratory

In this work, we present an educational activity aimed at measuring the Wigner distribution functions of quantum states of light in the undergraduate laboratory. This project was conceived by students from various courses within the physics undergraduate curriculum, and its outcomes were used in an introductory Quantum Optics course at the Universidad de los Andes in Bogotá, Colombia. The activity entails a two-hour laboratory practice in which students engage with a pre-aligned experimental setup. They subsequently employ an open-access, custom-made computational graphical user interface to reconstruct the Wigner distribution function for various quantum states of light. Given that the testing phase coincided with the COVID-19 pandemic, we incorporated the capacity to analyze simulated data into the computational user interface. The activity is now part of the course syllabus and its virtual component has proven to be highly valuable for the implementation of distance learning in quantum optics.

physics.ed-ph↗

arXiv2023

On Safety of Passengers Entering a Bus Rapid Transit System from Scheduled Stops

In this paper, we address the vehicle scheduling problem for improving passenger safety in bus rapid transit systems. Our focus is on passengers waiting at street stops to enter terminal stations. To enhance their safety, we minimize deviations from the proposed timetable, thereby minimizing passengers' initial waiting time. We formulate an optimization problem considering the position, speed deviation, and passenger count at each stop, solved using dynamic programming. Numerical simulations validate the effectiveness of our approach in enhancing passenger safety. Our work is the first attempt to minimize waiting time for improved safety and the first to utilize position tracking for departure time matching.

eess.SY↗

arXiv2022

Performance Analysis of Optimally Coordinated Connected and Automated Vehicles in a Mixed Traffic Environment

Trajectory planning of connected and automated vehicles (CAVs) poses significant challenges in a mixed traffic environment due to the presence of human-driven vehicles (HDVs). In this paper, we apply a framework that allows coordination of CAVs and HDVs traveling through a traffic corridor consisting of an on-ramp merging, a speed reduction zone, and a roundabout. We study the impact of different penetration rates of CAVs and traffic volumes on the efficiency of the corridor. We provide extensive simulation results and report on the benefits in terms of total travel time and fuel economy.

eess.SY↗

arXiv2018

Controlling Non-Markovian Dynamics Using a Light-based Structured Environment

We present the experimental control of Non-Markovian dynamics of open quantum systems simulated with photonic entities. The polarization of light is used as the system, whereas the surrounding environment is represented by light's spatial structure. The control of the dynamics is achieved by the engineering of the environment via spatial interference. Using the behavior of the trace distance, we are able to identify each dynamics and characterize the position of maximum revival of information.

quant-ph↗

arXiv2018

Correlation control for pure and efficiently generated heralded single photons

We present a detailed study on the properties of single photons generated by spontaneous parametric down conversion (SPDC) when both the spectral and spatial degrees of freedom are controlled by means of filters. Our results show that it is possible to obtain pure heralded single photons with high heralding efficiency despite the use of filters. Moreover, we report an asymmetry on the single photon properties exhibited in type-II SPDC sources that depends on choosing the signal or the idler photon as the heralding one.

quant-ph↗

arXiv2017

Implementation and characterization of a controllable dephasing channel based on coupling polarization and spatial degrees of freedom of light

We present the experimental implementation and theoretical model of a controllable dephasing quantum channel using photonic systems. The channel is implemented by coupling the polarization and the spatial distribution of light, that play, in the perspective of Open Quantum Systems, the role of quantum system and environment, respectively. The capability of controlling our channel allows us to visualize its effects in a quantum system. Differently from standard dephasing channels, our channel presents an exotic behavior in the sense that the evolution of a state, from a pure to a mixed state, shows an oscillatory behavior if tracked in the Bloch sphere. Additionally, we report the evolution of the purity and perform a quantum process tomography to obtain the χmatrix associated to our channel.

physics.optics↗

arXiv2016

Entangled two photon absorption cross section on the 808 nm region for the common dyes Zinc tetraphenylporphyrin and Rhodamine B

We report the measurement of the entangled two photon absorption cross section, $σ_E$, at 808 nm on organic chromophores in solution in a low photon flux regime. We performed measurements on Zinc tetraphenylporphyrin (ZnTPP) in Toluene and Rhodamine B (RhB) in Methanol. This is, to the best of our knowledge, the first time that $σ_E$ is measured for RhB. Additionally, we report a systematic study of the dependence of $σ_E$ on the molecular concentration for both molecular systems. In contrast to previous experiments, our measurements are based on detecting the pairs of photons that are transmitted by the molecular system. By using a coincidence count circuit it was possible to improve the signal to noise ratio. This type of work is important for the development of spectroscopic and microscopic techniques using entangled photons.

quant-ph↗

arXiv2016

Experimental verification of a quantumness criterion for single systems based on a Bell-like inequality

In this letter, we propose and experimentally test a quantumness criterion for single systems. The criterion is based on the violation of an already reported classical inequality. This inequality is expressed in terms of joint probabilities that we identify as realizations of preparation-and-measurement schemes. Our analysis points out that superposition is the key notion to grasp the quantum nature of physical systems. We verify our criterion in an all-optical experimental setup with heralded single photons generated via spontaneous parametric down conversion and use exclusively projective preparations and projective measurements.

quant-ph↗

arXiv2015

Measuring different types of transverse momentum correlations in the biphoton's Fourier plane

In this work, we present a theoretical and experimental study about the spatial correlations of paired photons generated by type-II spontaneous parametric down-conversion. In particular, we show how these correlations can be positive or negative depending on the direction in which the far field plane is scanned and the polarization post-selected. Our results provide a straightforward way to observe different kind of correlations, that complement other well known methods to tune the spatial correlations of paired photons.

quant-ph↗

arXiv2015

Demonstration of a highly-sensitive tunable beam displacer with no movable elements based on the concept of weak value amplification

We report the implementation of a highly sensitive beam displacer based on the concept of weak value amplification that allows to displace the centroid of a Gaussian beam a distance much smaller than its beam width without the need to use movable optical elements. The beam's centroid position can be displaced by controlling the linear polarization of the output beam, and the dependence between the centroid's position and the angle of polarization is linear.

quant-ph↗

arXiv2015

Tunable beam displacer

We report the implementation of a tunable beam displacer, composed of a polarizing beam splitter (PBS) and two mirrors, that divides an initially polarized beam into two parallel beams whose separation can be continuously tuned. The two output beams are linearly polarized with either vertical or horizontal polarization and no optical path difference is introduced between them. The wavelength dependence of the device as well as the maximum separation between the beams achievable is limited mainly by the PBS characteristics.

physics.optics↗

arXiv2014

Observation of spectral interference for any path difference in an interferometer

We report the experimental observation of spectral interference in a Michelson interferometer, regardless of the relationship between the temporal path difference introduced between the arms of the interferometer and the spectral width of the input pulse. This observation is possible by introducing the polarization degree of freedom into a Michelson interferometer using a typical weak value amplification scenario.

physics.optics↗

arXiv2010

Cancelation of dispersion and temporal modulation with non-entangled frequency-correlated photons

The observation of the so-called dispersion cancelation (Opt. Express 17, 19244, 2009) and temporal phase modulation (Phys. Rev. Lett. 103, 163601, 2009) of paired photons is generally attributed to the presence of frequency entanglement between two frequency anticorrelated photons. In this paper, it is shown that by introducing the appropriate amount of chromatic dispersion or phase modulation between non-entangled photons, it is also possible to observe these effects. Indeed, it is found that the relevant characteristic for the observation of dispersion cancelation or the cancelation of temporal phase modulation is the presence of certain frequency correlations between the photons.

quant-ph↗

arXiv2008

Spatiotemporal correlations in entangled photons generated by spontaneous parametric down conversion

In most configurations aimed at generating entangled photons based on spontaneous parametric down conversion (SPDC), the generated pairs of photons are required to be entangled in only one degree of freedom. Any distinguishing information coming from the other degrees of freedom that characterize the photon should be suppressed to avoid correlations with the degree of freedom of interest. However, this suppression is not always possible. Here, we show how the frequency information available affects the purity of the two-photon state in space, revealing a correlation between the frequency and the space degrees of freedom. This correlation should be taken into account to calculate the total amount of entanglement between the photons.

quant-ph↗

arXiv2008

Space-QUEST: Experiments with quantum entanglement in space

The European Space Agency (ESA) has supported a range of studies in the field of quantum physics and quantum information science in space for several years, and consequently we have submitted the mission proposal Space-QUEST (Quantum Entanglement for Space Experiments) to the European Life and Physical Sciences in Space Program. We propose to perform space-to-ground quantum communication tests from the International Space Station (ISS). We present the proposed experiments in space as well as the design of a space based quantum communication payload.

quant-ph↗