Towards High Dimensional Hyperentanglement

The goal of the present PSG is to trigger an active scientific and educational collaboration between the Institute of Applied Physics at the University of Bern (UBE) and Department of Quantum Electronics at the Lomonosov Moscow State University (MSU). In order to rapidly start a collaboration, a topic has been selected in which both applicant groups are world experts: Photonic High Dimensional entanglement.

The processing of quantum information requires the coherent control of complex quantum states. Photons are the medium of choice for studying and transmitting entanglement, thanks to their insensitivity to decoherence. The distribution of complex entangled states is relevant both to answer fundamental questions related to non-locality and for practical applications, the most direct being quantum cryptography. However, the generation and manipulation of complex photonic states is hampered by the absence of direct photon-photon interaction. Fortunately, spontaneous parametric downconversion creates photon pairs that are directly entangled in polarization, in transverse momentum or in energy. Most of the experiments involving photonic entanglement for quantum information have been performed with entangled two dimensional systems. However, higher dimensional entangled states are a key resource for advanced device-independent quantum cryptography protocols, but also for a better fundamental understanding of the relation between non-locality and entanglement. Therefore, there is a recent growing interest in studying photonic spatial or energy modes that provide in principle very high entanglement.

The group of Prof. Kulik at MSU has recently develop a range of new methods for the generation  [1] and detection  [2,3] of spatially entangled photon pairs. Those methods rely strongly on the ability to shape the transverse field distribution of the photons with spatial light modulators (SLM). The group of Prof. Stefanov at UBE has introduced the use of so-called “pulse shaping” to manipulate the energy of entangled photons for encoding of quantum information  [4]. This is performed by addressing each energy component of the photons spectra with the combination of a diffractive element and a SLM  [5,6]. In addition the flexibility of the SLM allows to perform adaptive quantum state reconstruction both in the spatial  [7,8] and in the energy  [9] domains.

In order to further increase the complexity and dimensionality of the quantum states, it will be relevant to develop new methods allowing to simultaneously access both spatial and energy degree of freedom of the states. The present project aims at evaluating their feasibility by exchanging the know-how from both applicant groups, with the future goal of achieving the control and detection of the whole spatio-temporal states of entangled photons. This will be the first step towards a more intensive collaboration, supported by common applications of collaborative projects. This topic will also be ideal for future join PhD students.

[1]        E. V. Kovlakov, I. B. Bobrov, S. S. Straupe, and S. P. Kulik, Phys. Rev. Lett. 118, 1 (2017).
[2]        I. B. Bobrov, E. V. Kovlakov, A. A. Markov, S. S. Straupe, and S. P. Kulik, Opt. Express 23, 649 (2015).
[3]        I. B. Bobrov, S. S. Straupe, E. V. Kovlakov, and S. P. Kulik, New J. Phys. 15, (2013).
[4]        S. Schwarz, B. Bessire, A. Stefanov, and Y.-C. Liang, New J. Phys. 18, 035001 (2016).
[5]        B. Bessire, C. Bernhard, T. Feurer, and A. Stefanov, New J. Phys. 16, 033017 (2014).
[6]        C. Bernhard, B. Bessire, T. Feurer, and A. Stefanov, Phys. Rev. A 88, 032322 (2013).
[7]        I. A. Pogorelov, G. I. Struchalin, S. S. Straupe, I. V. Radchenko, K. S. Kravtsov, and S. P. Kulik, Phys. Rev. A 95, 1 (2017).
[8]        G. Struchalin, E. Kovlakov, S. Straupe, and S. Kulik, arXiv:1804.05226 (2018).
[9]        S. Lerch and A. Stefanov, Opt. Lett. 39, 5399 (2014).



Prof. André Stefanov
University of Bern
Institute of Applied Physics

Dr. Bänz Bessire
University of Bern
Institute of Applied Physics

Prof. Sergey Kulik
Lomonosov Moscow State University
Department of Quantum Electronics, Faculty of Physics

Dr. Stanislav Straupe
Lomonosov Moscow State University
Department of Quantum Electronics, Faculty of Physics