Guest lecture: On-chip generation of complex optical quantum states and their coherent control

Dr. Michael Kues, National Scientific Research Institute, Montreal, Canada.

04.10.2017 | Anja Torup Hansen

Dato man 09 okt
Tid 13:00 14:00
Sted Room 408, building 5125, Finlandsgade 22, 8200 Aarhus N

Abstract
Entangled optical quantum states are essential towards solving questions in fundamental physics, and are at the heart of applications in quantum information science [1]. For advancing the research and development of quantum technologies (such as quantum-secured communications and quantum-enhanced computing), practical access to the generation and manipulation of complex photon states characterized by large information contents is required. Recently, integrated photonics has become a leading platform for the compact and cost-efficient generation and processing of optical quantum states [2]. However, on-chip sources are limited to basic two-photon systems formed by two-dimensional states (i.e. qubits), and the currently exploited concepts show limited scalability (both in terms of dimensionality and number of photons), leading to a drastic restriction on information processing ability. Within this presentation, we will show that exploiting a frequency-domain approach using integrated frequency combs (light sources with a broad spectrum of evenly-spaced frequency modes) based on on-chip nonlinear microring resonators can provide solutions for scalable complex quantum state generation and enable practical state control. In particular, by using spontaneous four-wave mixing within the microring resonators, we demonstrate the generation of bi- and multi-photon entangled qubit states over a broad frequency comb spanning the telecommunications band, and control these states coherently to perform quantum interference measurements and a tomographic reconstruction of the state density matrix [3-6]. Moreover, we report the on-chip generation of high-dimensional entangled states (quDits), wherein the photons are created in a coherent superposition of multiple pure frequency modes [7,8]. We experimentally verify the realization of a quantum system with at least one hundred dimensions on a compact photonic chip. Furthermore, using off-the-shelf telecommunications components, we introduce a platform for the coherent manipulation and control of time- and frequency-entangled states. The results suggest that microcavity-based entangled photon states and their coherent control using accessible telecommunications infrastructure can open up new venues for reaching the processing capabilities required for meaningful quantum information science. Finally, inspired by these results and in the broader framework of transforming quantum information science towards practical applications, I will discuss the future prospects of using multi-mode and high-dimensional representations for advancing quantum machine learning.

Michael Kues, Ph.D., is an early-career researcher. He received his Diploma and Ph.D. in Physics (full honors) in 2009 and 2013, respectively, from the University of Münster, Germany. Supported by a scholarship from the government of Quebec (Canada), he began his integrated quantum optics work in 2014 at the National Scientific Research Institute – Energy, Materials, and Telecommunications (INRS-EMT) in Montreal, Canada, where he currently holds a Marie Skłodowska–Curie Individual Fellowship (in collaboration with the University of Glasgow) and is leading the nonlinear integrated quantum optics sub-group of Prof. Morandotti’s research lab. Dr. Kues is interested in a broad and interdisciplinary range of topics at the intersection of photonics, quantum science, and information processing, with his past research exploring nonlinear dynamics in optical passive systems, light transport in randomized optical structures, and the physics of nonlinear optical processes in integrated optical systems. In his current research, he focuses on the development and realization of compact on-chip optical quantum systems, and studies new and scalable optical approaches for present and future practical quantum information processing.

References

[1] J. L. O’Brien, “Optical quantum computing,” Science 318, 1567 (2007).

[2] S. Tanzilli, A. Martin, et al. “On the genesis and evolution of integrated quantum optics,” Laser Photonics Review 6, 115 (2012).

[3] C. Reimer, M. Kues, et al., “Integrated frequency comb source of heralded single photons,” Optics Express 22, 1023 (2014).

[4] C. Reimer, M. Kues, et al., “Cross-polarized photon-pair generation and bi-chromatically pumped optical parametric oscillation on a chip,” Nature Communications 6, 8236 (2015).

[5] C. Reimer, M. Kues, et al., “Generation of multiphoton entangled quantum states by means of integrated frequency combs,” Science 351, 1176 (2016).

[6] L. Caspani, M. Kues, et al., “Multifrequency sources of quantum correlated photon pairs on-chip: a path toward integrated Quantum Frequency Combs,” Nanophotonics doi:10.1515/nanoph-2016-0029 (2016 - Published online).

[7] M. Kues, C. Reimer, et al., “On-chip generation of high-dimensional entangled quantum states and their coherent control,” Nature 546, 622 (2017).

[8] P. Roztocki, M. Kues, et al., “Practical system for the generation of pulsed quantum frequency combs,” Optics Express 25, 18940 (2017).

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