Ronchi, Bruno M. (2021) Amplificando información de sensores cuánticos con el efecto zenon cuántico / Amplifying information of quantum sensors with quantum zenon effect. Maestría en Ciencias Físicas, Universidad Nacional de Cuyo, Instituto Balseiro.
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Resumen en español
La mecánica cuántica introdujo fenómenos novedosos, cuyo aprovechamiento permite una potencial mejora de las tecnologías respecto de aquellas que no cuentan con ellos. Estas tecnologías son denominadas las \tecnologías cuánticas", que engloban la computación cuántica, criptografía cuántica, comunicación cuántica y a los sensores cuánticos. En el caso de los sensores cuánticos, sus propiedades cuánticas son utilizadas como recurso para el proceso de estimación de magnitudes (parámetros) de interés. La máxima precisión admisible, lo que se llama información, depende fuertemente del esquema de control implementado en el sensor [11]. En particular, dado que en la cuántica, las mediciones afectan al estado del sistema, éstas representan un recurso disponible para definir el esquema de control. El efecto Zenón cuántico congela la evolución del sistema sensor a través de mediciones proyectivas frecuentes, mientras que el efecto anti-Zenón cuántico acelera su evolución temporal. En ambos casos, el control consiste de mediciones estroboscópicas cada algún intervalo de tiempo y ha demostrado ser una herramienta de control de la señal de un espín al que utilizaremos como sensor. En particular, se encontró experimentalmente que esta forma de control reduce la cantidad de parámetros involucrados en la dinámica [17] y, en determinadas circunstancias mejora su precisión [11]. En este trabajo, con el objetivo de desarrollar un marco teórico base, consideramos el control por mediciones proyectivas de sistema de dos niveles regido por un Hamiltoniano independiente del tiempo, para estimar el acople entre los dos niveles. Este modelo posee los elementos escenciales presentes en dinámicas cuánticas más complejas para evaluar la información extraíble utilizando el efecto Zenón cuántico. El acople entre niveles induce una dinámica oscilatoria de intercambio de excitación entre un nivel y otro, mientras que la separación de energía representa un \offset", poniendo al sistema fuera de resonancia. Encontramos que el tiempo óptimo entre mediciones proyectivas para maximizar la información depende de la intensidad del offset. Para valores altos de offset, cuyo valor está denido por el tiempo de evolución del sensor, las mediciones proyectivas son más efcientes para estimar el acople. Denominamos este concepto amplicación de información a través del efecto Zenón cuántico. Ejemplicamos este principio mediante la particularización de este desarrollo a sistemas de interés práctico. También presentamos un mecanismo de medición alternativa, donde el colap so del sistema es causado por la interacción con un ambiente ruidoso. Recuperamos en estas circunstancias los resultados obtenidos bajo la suposición de proyección ideal, y exploramos la posibilidad de utilizar el colapso parcial inducido por este ambiente bajo cortos tiempos de interacción como herramienta para medir parámetros del ambiente eficientemente y de forma no invasiva.
Resumen en inglés
Quantum Mechanics has introduced novel effects, the use of which allows for a potential improvement of the technologies with respect to those that don't count on them. These technologies are called \Quantum Technologies", and encompass Quantum Computation, Quantum Criptography, Quantum Communication and Quantum Sensors. In the case of Quantum Sensors, their quantum properties can be used as resource for the process of estimation of magnitudes (parameters) of interest. The maximum attainable precision, called \information", depends strongly on the control protocol implemented on the sensor [11]. In particular, given that quantum measurements affect the state of the system, they represent a resource when dening the control scheme. The Quantum Zeno Effect freezes the sensor system's evolution through frequent projective measurements, while the Quantum Anti-Zeno Effect speeds up the temporal evolution. In both cases, the control protocol consists of stroboscopic measurements and has proven to be a control tool for the signal of a spin which we'll use as sensor. In particular, it was experimentally shown that this form of control reduces the amount of parameters involved in the dynamics [17] and, in certain circumstances, improve its precision [11]. In this work, with the aim of developing a theoretical basis for this phenomenon, we consider control through projective measurements on a two-level systems governed by a time-independent Hamiltonian, in order to estimate the coupling between the two levels. This model presents the essential elements in more complex quantum dynamics, so as to assess the maximum attainable information by using the Quantum Zeno Eect. The coupling between levels induces an oscillatory exchange of excitation between levels, while the energy splitting represents an \offset", leading the system off-resonance. We nd that the optimal time between measurements for maximizing the information depends on the intensity of the offset. For high values of offset, the value of which is dened by the evolution time of the sensor, projective measurements are more ecients for estimating the coupling. We name this concept information amplication through Quantum Zeno Effect. We exemplify this principle by particularizing this framework to systems of practical interest. We also present an alternative measurement mechanism, where the collapse of the system is caused by the interaction with a noisy environment. We recover in these circumstances the results obtained through the assumption of ideal projective measurements, and explore the possibility of using the partial collapse induced by this environment under short interaction times as a tool for the effective and non-invasive measurement of environment parameters.
| Tipo de objeto: | Tesis (Maestría en Ciencias Físicas) |
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| Palabras Clave: | Quantum information; Información cuántica; [Quantum zeno effect; Efecto zenón cuántico; Quantum metrology; Metrología cuántica] |
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| Materias: | Física |
| Divisiones: | Gcia. de área de Investigación y aplicaciones no nucleares > Gcia. de Física > Física médica |
| Código ID: | 948 |
| Depositado Por: | Marisa G. Velazco Aldao |
| Depositado En: | 23 Jul 2021 12:08 |
| Última Modificación: | 23 Jul 2021 12:08 |
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