This course gives you access to basic tools and concepts to understand research articles and books on modern quantum optics. You will learn about quantization of light, formalism to describe quantum states of light without any classical analogue, and observables allowing one to demonstrate typical quantum properties of these states. These tools will be applied to the emblematic case of a one-photon wave packet, which behaves both as a particle and a wave. Wave-particle duality is a great quantum mystery in the words of Richard Feynman. You will be able to fully appreciate real experiments demonstrating wave-particle duality for a single photon, and applications to quantum technologies based on single photon sources, which are now commercially available. The tools presented in this course will be widely used in our second quantum optics course, which will present more advanced topics such as entanglement, interaction of quantized light with matter, squeezed light, etc...

## About this Course

## Offered by

### École Polytechnique

École polytechnique combines research, teaching and innovation at the highest scientific and technological level worldwide to meet the challenges of the 21st century. At the forefront of French engineering schools for more than 200 years, its education promotes a culture of multidisciplinary scientific excellence, open in a strong humanist tradition.\n

## Syllabus - What you will learn from this course

**8 hours to complete**

## Quantization of light: one mode

In this first lesson, you will discover what is canonical quantization, apply it to the quantization of a single mode of the electromagnetic field, and find that it behaves as a quantum harmonic oscillator. The notion of photon will then naturally emerge, as well as the weird but fundamental notion of vacuum fluctuations.

**8 hours to complete**

**5 hours to complete**

## One photon state in a single mode: particle-like behaviour

In this lesson, you will discover how the quantum optics formalism leads to the particle-like behaviour of a one photon wave-packet. For this, you will have to learn the quantum optics expressions of the simple and joint photodetection signals. A comparison with the semi-classical expressions will illustrate the necessity of quantum optics.

**5 hours to complete**

**5 hours to complete**

## One photon interference: Wave-Particle duality

In this lesson, you will address the fascinating question of a single photon interfering with itself, by calculating the interference pattern for a single photon launched into a Mach-Zehnder interferometer. In order to do it you will first learn how to treat a beam-splitter in quantum optics, a very important tool that you need to know. You will also learn that when you want to describe an optical instrument in quantum optics, it is very useful to master its classical optics description. This lesson is an opportunity to think about the mysterious concept of wave-particle duality, and about the power of the quantum formalism, which can deal consistently with two behaviours apparently contradictory .

**5 hours to complete**

**4 hours to complete**

## Multimode quantized radiation: quantum optics in a real lab

In the real world there is nothing like purely monochromatic radiation. A correct description of radiation necessarily involves several modes. In this lesson, you will learn how canonical quantization can be easily generalized to the case of several modes, and how various observables or important quantities introduced in the single mode case are expressed in the multimode case. Beyond the formalism that you must learn to be able to read papers and books describing real situtations, you will encounter in this lesson some intriguing features of the quantum formalism: firstly, the unbelievably large size of the space of states, which is the reason for the unlimited potential power of quantum information; secondly, the question of infinities, a problem which was solved by the general procedure of renormalization. Note that optional readings are proposed as resources of some lectures.

**4 hours to complete**

## Reviews

### TOP REVIEWS FROM QUANTUM OPTICS 1 : SINGLE PHOTONS

This was an awesome course. I recommend it to all who are working with Quantum physics, Quantum mechanics, Quantum Optics, Quantum Computing and Information Science, Quantum Communication

Very clear and informative. The courses are short respectively and they are very exciting. The quizzes are a very good review to keep you concentrated.

Fantastic course. I do not have a quantum optics course at my university this course had immediate benefits to my graduate research in quantum optics.

beautiful explanation with in depth coursework in quantum optics. one should must study this course if interested in quantum physics.

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