A.A. di erogazione 2020/2021

Laurea Magistrale in FISICA
 (A.A. 2020/2021)


Anno di corso: 
Tipologia di insegnamento: 
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Primo Semestre
Ore di attivita' frontale: 
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Lezione (66 ore)

The main objective of the course is to provide the basis to understand the mechanisms of operation of light detectors and the interpretation of the measurement outcomes in order to obtain information on the relevant properties of optical states in the classical and quantum regimes. In particular, emphasis will be put on the measurement procedures of statistical properties and correlation of light. To this aim, the most important achievements of experimental quantum optics will be discussed.
To reach the objective of the course, theoretical lectures will be supported by experimental activities in the research Optics Laboratories of the Department, in which the students will practice making measurements of continuous-wave and pulsed optical states using different kinds of detectors.

At the end of the course, the students will be able to:
- describe classical and quantum optical states
- describe different kinds of detectors
- discuss the differences between classical and quantum states in terms of nonclassicality criteria
- illustrate the operating principles of the different detectors
- analyze the different detection schemes and their applicability to the different optical states
- evaluate the performance and the limits of the different detection schemes related to the kind of light to be detected
- assemble an experimental setup for measuring a light state choosing the optimal detector and detection strategy.

Knowledge of electromagnetism and quantum mechanics.
Having attended the quantum optics course is useful but not mandatory.

Elements of quantum optics
- Classical and quantum description of radiation.
- Quantization of the electromagnetic field.
- Fock states
- Quadrature of the electromagnetic field.
- Coherent states, displacement operator.
- Pure states and mixed states.
- Representation of states.
- Characteristic function and Wigner function.
- Thermal states

Theory of light detection
- Semiclassical theory.
- Quantum theory: POVM.
- Examples of POVM for various class of detectors: ON/OFF and Bernoulli detectors.
- Beam splitter to model a non-ideal detector.
- Statistics of detected light.
- Correlation measurements for detected photons.
- Optical detection schemes: direct and indirect detection.

Light detectors
- General features of real detectors.
- Origin of noise in detectors.
- Acquisition and processing systems for detector signals.
- Different classes of detectors:
-- Photomultipliers.
-- HPD.
-- Photodiodes.
-- APD and SPAD.
-- SiPM.
-- Cryogenic detectors.
-- Superconductor detectors.
-- Cameras (CCD, EMCCD, ICCD, CMOS).
- Characterization of a detector with internal gain and amplification. Self-consistent procedure.
- Characterization of a detectors including dark counts, cross talk and afterpulses.

Application to measurements of optical states
- Review of the state-of-art of light detection
- Experimental measurement of photon statistics and correlation via direct detection.
- Experimental measurement of field quadratures via homodyne detection and tomographic reconstruction of optical states.

The course objectives will be achieved through frontal lectures for a total of 40 hours. The teacher will use presentations and graphic tablet.
The remaining 26 hours will be devoted to laboratory sessions where the students will perform measurements on different states of light using different classes of detectors. The experimental activities will take place in the Laboratories of “Quantum Optics” and “Photophysics and Biomolecules”.
Guided data analysis procedures will be also presented and discussed.

Given the vastness of the subject and the lack of an exhaustive reference textbook, attending the course regularly is strongly recommended.

The exam is in English and oral.
In preparation of the exam, the students are asked to choose one among the experimental measurements performed in the laboratory, analyze the data and examining both the optical state and the detection scheme in depth.

The first part of the exam is devoted to discuss the experimental results with the aim of verifying:
- the knowledge of a specific detector and detection scheme and of the light state to be measured
- the understanding of detector’s features in relation to the specific chosen application
- the capability of deeply analyzing advantages and limitations of the chosen detection strategy.

In the second part of the exam, some questions about the remaining topics are asked, through which the teacher will check if the students
- have acquired a sufficient knowledge of the quantum properties of light and the different ways to measure them
- have acquired the ability of distinguishing among the various detection possibilities and to devise the suitable one for a given physical situation
- are able to properly use the mathematical and technical language to explain the processes involved in light detection.

To pass the exam, a satisfactory presentation of the first part is required.
To successfully pass the exam students should be familiar with all the topics presented in the course. The deeper the knowledge the better the evaluation.
The laude is assigned to students that, in addition to the previous points, are able to critically discuss the different topics establishing connections and comparisons.

Lecture notes and slides will be available at the end of each developed topic.
Some possible reference texts are:
- Morgan W. Mitchell, "Quantum Optics for the Impatient"
- M. Fox "Quantum Optics, An Introduction", Oxford, 2006.
- HAS. Bachor and T.C. Ralph "A Guide to Experiments in Quantum Optics" Wiley 2004
- "Single-Photon Generation and Detection Physics and Applications", in Experimental Methods in Physical Sciences, Vol. 45, Pages 1-562 (2013), Edited by Alan Migdall, Sergey V. Polyakov, Jingyun Fan and Joshua C. Bienfang

Supplemental material will be made available by the lecturer.

For questions/comments students can contact the teacher by e-mail at the address:

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A.A. 2020/2021

Anno di corso: 2