Quantum information with optical frequency combs
All optical implementation of scalable quantum information processing: the quantum optical frequency combs.
The last 20 years have seen a rapid development of ideas and proof-of-principle experiments regarding the so-called quantum technologies involving the fields of quantum communication, quantum computation, quantum metrology and quantum simulation. If it is already clear that in principle the quantum world can provide useful advantages in terms of security, efficiency, speed, and sensitivity, we still need to solve the scalability problem. Indeed, generating simple systems for coding and manipulating quantum information is relatively easy. However, it is still not evident how to handle large quantum systems involving many degrees of freedom, in order, for instance, to implement a complete architecture where the quantum approach provides a real advantage compared to conventional systems.
The Quantum Optics group at Laboratoire Kastler Brossel developed in the last years experimental quantum resources based on an Optical Parametric Oscillator Synchronously Pumped by a mode-locked femtosecond laser (SPOPO). The spectrum of this lasers is constituted of hundreds thousands of frequency component. The parametric process couples all these optical frequencies in a non-linear crystal, and generates highly multimode quantum states [1,2]. This resource can be described as quantum networks, where the nodes are different spectral/temporal modes of the e.m. field and the links are given by entanglement properties. The use of ultrafast pulse shaping combined with multi-homodyne-based projective measurements allows the on-demand construction of various quantum networks useful for the implementation of measurement based quantum computing  or to simulate complex quantum network .
The intrinsic number of modes that are involved in the generated network could be of the order of 50, but up to now the projective measurements are able to address a maximum of 16 modes. The multimode homodyne detection technique is in fact based on the interferometric measurement of the signal with a strong local oscillator. The used local oscillator is a portion of the original laser source; whose spectral extension is unfortunately not large enough to efficiently interact with all the generated quantum modes.
The internship project proposed by the group consists in the experimental study of the coherent expansion of the bandwidth of our local oscillator. The process that will be investigated is the self-phase modulation in a short photonic crystal (PC) fiber , with the aim of expanding the spectrum of the original laser by a factor of two.
The internship could be followed by a PhD project based on the developed technique, which combined with controlled pulse shaping of the pump in the parametric process, will give direct access to a large class of Gaussian quantum networks.
The realization of a mode-selective single-photon subtraction, which is currently under implementation in the experimental setup , will also pave the way for non-Gaussian resources that are necessary for the implementation of universal quantum information protocols. The characterization of this new multimode non-Gaussian states will be part of the project, finally followed by the implementation of specific protocols where we will exploit a genuine quantum advantage.
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-  S. Gerke, J. Sperling, W. Vogel, Y. Cai, J. Roslund, N. Treps, and C. Fabre Phys. Rev. Lett. 114, 050501 (2015).
- Y. Cai, J. Roslund, G. Ferrini, F. Arzani, X. Xu, C. Fabreand N. Treps arXiv 1605.02303v1
-  J. Nokkala, F. Galve , R. Zambrini, S. Maniscalco and J. Piilo, Scientific Reports 6, 26861 (2016).
-  Xin Jiang, Nicolas Y Joly, Martin A Finger, Fehim Babic, Meng Pang, Rafal Sopalla, Michael H Frosz, Samuel Poulain, Marcel Poulain, Vincent Cardin, John C Travers, Philip St J Russell, Optics Letters 41, 4245-4248 (2016).
- V. A. Averchenko, V. Thiel, N. Treps, Phys. Rev. A 89, 063808 (2014). V. A. Averchenko, C. Jacquard,V. Thiel, C. Fabre, and N. Treps arXiv :1510.04217
Interested candidates should contact Nicolas Treps (firstname.lastname@example.org), Claude Fabre (email@example.com) or Valentina Parigi (firstname.lastname@example.org)
For more details, please check our website: www.quantumoptics.fr.
Duration: 3 to 6 months. Possible PhD.