3.10 Tesis doctorado

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Browsing 3.10 Tesis doctorado by Author "Orszag Posa, Miguel"

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    Control of wave-particle duality via atom-field interaction in double-slit schemes
    (2022) Miranda Rojas, Mario Ernesto Brayan; Orszag Posa, Miguel; Pontificia Universidad Católica de Chile. Instituto de Física
    The dual nature of light and matter represents an important challenge for science. Since the origins of quantum mechanics, several theoretical and experimental works have studied the wave and corpuscular properties of photons, atoms, electrons, etc. The main model that has been considered in the development of them has been the Young's double-slit scheme, by means of which the wave nature of light was demonstrated. However, it also can be used to obtain the particle-like properties of the systems. In case of considering identical slits, this model allows to obtain total fringe visibility on a screen located at a certain distance from the double-slit, and thus, null knowledge about the path followed by the object that crosses the scheme. Therefore, the system shows a wave behavior. In order to obtain information about the path taken by the objects (photons, atoms, electrons, etc), several authors have studied the coupling of external systems to double-slit schemes, which allows to know the path followed by the particle. As a consequence, the implementation of any type of path-detector results in the loss of fringe visibility, according to the principle of complementarity postulated by Bohr. In this research, we have considered the use of double-slit schemes and atom-field interactions to control the balance between fringe visibility and which-path information. We consider field cavities which act as path-detectors and they are represented by different quantum states. Instead of photons, our schemes are crossed by atoms, whose internal levels are correlated to the paths of the schemes. Therefore, based on the peparation of both, field and atom, we can study the balance between distinguishability, visibility and the concurrence present in the system. Our results show that the wave-particle duality can be controlled by atomic and field parameters, depending on the behavior that the experimenter wishes to observe, wave-like or particle-like. Additionally, we present a model in which a classical field can control the quantum atom-field interaction. Therefore, the amplitude of the classical field can also be considered as a controlling parameter of the wave-particle duality. Finally, based on our results, we propose a theoretical model to be implemented in quantum eraser and delayed choice experiments, which nowadays arouses great interest among researchers. Our results suggest that the wave-particle duality can be controlled even at times after the atom is registered on a screen, which allows us to choose the behavior of the system, wave-like or particle-like, at any moment.
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    Quantum measurement transition and entanglement of trapped ions and optomechanical systems
    (2024) Araya Sossa, Kevin Jordan; Orszag Posa, Miguel; Pontificia Universidad Católica de Chile. Instituto de Física
    Although quantum mechanics has been able to explain a wide range of physical, chemical, and even biological events with unprecedented accuracy, fundamental problems remain. For instance, the problem of quantum measurement and quantum entanglement, which are the most perplexing problems that have persisted since the foundation of quantum mechanics. Both are crucial quantum resources with broad applications in quantum information science, quantum computing and quantum optics. For this reason, this thesis is devoted to research the quantum measurement from the weakest regime to the strongest one as well as the dynamics of entanglement of different quantum systems. In this work, we study the measurement transition for a coherent-squeezed pointer state through a transition factor Γ that involves a system-pointer coupling by using an arbitrary measured observable A. In addition, we show that the shift in the pointer’s position and momentum establishes a relationship with a new value defined as the transition value, which generalizes the weak value as well as the conditional expectation value. Furthermore, a new strategy is introduced to achieve different measurement regimes by just adjusting the r and ϕξ parameters of the coherent-squeezed pointer state, opening an interesting way to test quantum mechanics foundations. Our scheme has been theoretically applied in a trapped ion illuminated by a bichromatic laser beam, with a high potential to be implemented in future experimental setups. Besides, we propose a method to regulate the quantum entanglement in the system mentioned before as well as a dispersive-hybrid system where a qubit is directly coupled to a cavity and a mechanical resonator. Entanglement can be controlled by only tuning the squeezing parameters associated with the vibrational mode. As the squeezing amplitude becomes larger, the maximal entanglement abruptly falls to zero at specific squeezing phases. For the hybrid system, it is also possible to generate entanglement for bipartitions from the qubit-cavity-resonator system after applying this strategy. Entangled qubit-cavity states are created through squeezing, even though there is no direct interaction between them. We also analyze the effect of atomic, optical, and vibrational losses on the quantum entanglement. We finally discuss our schemes to be implemented in future experimental setups and promote further studies to generalize the concept of “monogamy of entanglement” in tripartite systems outside qubit-composite states, in particular, (2 ⊗ 2 ⊗ n)-dimensional systems.
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    Weak value amplification in an optomechanical system with mach-zehnder interferometer
    (2021) Carrasco Novoa, Sergio; Orszag Posa, Miguel; Pontificia Universidad Católica de Chile. Instituto de Física
    In this work an optomechanical system inside a Mach-Zehnder interferometer is studied from the perspective of the weak value amplification effect. The optomechanical system consists of a Fabry-Perot cavity with a moving mirror in the middle. Single photons are post-selected in the detector in one of the output ports of the interferometer (dark port), which allows to enlarge the displacement caused by a single photon over the moving mirror of the cavity. Since the interaction between a single photon and the mirror is weak, the amplification factor of the displacement corresponds to a weak value. By making the initial and final states of the photon quasi-orthogonal, the weak value becomes large and the radiation pressure force exerted by the photon is increased, making a single photon behave as ``many photons'' will do. The amplification effect comes, however, at the cost of the lost of data. The usefulness of weak values for parameter estimation in our setup is analysed from the perspective of the Fisher information. Although the precision of the estimation does not change either by using weak values or by implementing measurements that do not rely on post-selection, in the first scenario all the information can be put in a small amount of post-selected events, which is a verification of a well known general result in the existing literature on the subject.