Course code  TPT18 
Course title  Quantum entanglement for communications: from theory to experiments 
Institution  TELECOM ParisTech 
Course address  The theoretical part (4 days) will take place at TELECOM ParisTech (Paris 13) and the experimental part (1 full day) at Institut d'Optique Graduate School in Palaiseau (accessible with RER B ; the students will be guided) 
City  Paris and Palaiseau 
Minimum year of study  4th year 
Minimum level of English  Good 
Minimum level of French  None 
Key words  entanglement, spontaneous down conversion, quantum optics, EPR paradox, Bell inequalities, quantum teleportation 
Language  English 
Professor responsible  Isabelle Zaquine 
Telephone  01 45 81 78 39 
Fax  01 45 81 76 46 
isabelle.zaquine@telecomparistech.fr  
Participating professors  Gaëtan Messin, Lionel Jacubowiez, Eleni Diamanti, Damian Markham, Isabelle Zaquine 
Number of places  Minimum: 8, Maximum: 12, Reserved for local students: 2 
Objectives  Quantum entanglement is the basic ressource for the future quantum relays or repeaters. The objective of this course is to acquire a thorough understanding of this concept from the theoretical definition to the practical implementation of entangled photons states, using non linear optics and to see how it can be used in various quantum communications devices. 
Programme to be followed  Basic quantum physics Entanglement, EPR paradox, Field quantization, beamsplitters Introduction to nonlinear optics (second order nonlinear phenomena) Entangled photons: polarization, timeenergy, timebin Physical implementation of entangled photon pairs sources Quantum teleportation, entanglement swapping Quantum cryptography protocols using entangled states Two experiments in IOGS: 1) Quantum coalescence of identical bosons : twophoton interference effect using pairs of identical photons produced by degenerate spontaneous downconversion. Identical photons can exhibit a very strange property: when they enter a different input port of a balanced beam splitter, they leave the beam splitter through the same output port. This effect, can be understood as a twophoton quantum interference between two possible paths taken by the photons. The contrast of the interference signal is a measurement of the degree of indistinguishability of the light particles. Recent proposals for the building of a quantum computer rely on the ability to produce indistinguishable photons and rely on this so called HOM interference. 2) Quantum mechanics non locality test: violation of Bell's inequalities using polarization entangled photons produced by spontaneous downconversion. The famous EPR paradox about completeness of quantum mechanics raised by Einstein, Podolsky and Rosen in 1935 [1], initially seen as a philosophical question, became a physical problem when John Bell published an article in 1964 suggesting that it was possible to actually test the hypothesis of local hidden variables [2]. It took ten more years before an experimental implementation of the test could be conducted by Clauser et al. [3], and a little more before a clear and widely accepted demonstration of the Bell's inequality violation, by A. Aspect et al., at Institut d'Optique [4]. This test is now routinely used in labs to measure the quality of entanglement, a fundamental ressource for quantum information processing and communications. 
Prerequisites  Maxwell equations 
Course exam 
Daily exercises and the laboratory session
