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Composite Pulses for Quantum Engineering

Periodic Reporting for period 1 - COPQE (Composite Pulses for Quantum Engineering)

Berichtszeitraum: 2016-10-07 bis 2018-10-06

The development of integrated circuit technologies at scales approaching the quantum regime sparked immense interest in the field of quantum information processing (QIP). Simultaneously, quantum algorithms to solve practical problems intractable on classical computers were proposed such as the development of new drugs, modeling of complex chemical processes, secure communication and search, etc. These advances changed our understanding of the relation between information and quantum physics and triggered a vast research effort into quantum engineering, which seeks to meet the practical challenges of controlling quantum systems with extremely high fidelities by encompassing both fundamental physics and engineering.

The main objective of this action was to enable the systematic incorporation of composite pulses into practical quantum engineering. We addressed the outstanding challenges of realizing quantum operations in the presence of fabrication inaccuracies and unwanted interactions with the environment. These lead to a considerable reduction in the fidelities of quantum operations and thus, limit the scope of QIP. During the duration of the action, the researcher Dr Elica Kyoseva carried out cutting-edge research in the field of composite pulses and their wide application to quantum engineering with various physical systems. The results obtained during the duration of the action provide a general roadmap to realize high-fidelity operations in the presence of various experimental errors including errors in the coupling strength and duration, frequency offset, Stark shift, phase jitter, and others.

In conclusion, the work performed during the duration of the action was truly interdisciplinary in nature and contributes substantially to expanding the field of composite pulses for quantum engineering to several other physical systems including photonic, electronic, and nonlinear optics. The derived results were utilized for high-fidelity light transfer in broadband achromatic waveguide couplers; for surface plasmon polariton transfer between graphene waveguides; for robust electron transfer between electron waveguides; and for generation of higher harmonics in non-linear optics. Thus, we believe that our general solutions will be the cornerstone for any quantum information protocols and in particular well-suited for practical realization of high-fidelity quantum computing in integrated photonic circuits.
-- We utilized coupled mode theory (CMT) to model the coupling between surface plasmon-polaritons (SPPs) between multiple graphene sheets. By using the Stimulated Raman Adiabatic Passage (STIRAP) Quantum Control Technique, we proposed a novel directional coupler based on SPPs evolution in three layers of graphene sheets in some curved configuration. Our calculated results show that the SPPs can be transferred efficiently from the input graphene sheet to the output graphene sheet, and the coupling is also robust that it is not sensitive to the length of the device configuration's parameters and excited SPPs wavelength. Published in Carbon 127, 187-192 (2017). Freely available at https://arxiv.org/abs/1708.00147

-- We proposed a novel ultrafast electronic switching device based on dual-graphene electron waveguides, in analogy to the optical dual-channel waveguide device. The design utilizes the principle of coherent quantum mechanical tunneling of Rabi oscillations between the two graphene electron waveguides. Based on a modified coupled mode theory, we construct a theoretical model to analyze the device characteristics and predict that the switching speed is faster than 1 ps and the on-off ratio exceeds 106. Due to the long mean free path of electrons in graphene at room temperature, the proposed design avoids the limitation of low-temperature operation required in the normal semiconductor quantum-well structure. The layout of our design is similar to that of a standard CMOS transistor that should be readily fabricated with current state-of-art nanotechnology. (published in Semiconductor Science and Technology 33, 035014 (2018). Freely available at https://arxiv.org/abs/1702.03748

-- We demonstrated a novel device for complete achromatic optical switching between evanescently coupled waveguides. Utilizing shortcut to adiabaticity design of the coupling and the phase mismatch, we show that the proposed device can operate robustly on a shorter length scale as compared to previous design. We noted that the shortcut to adiabaticity waveguide coupling with phase mismatch model does require a higher coupling strength at the maximum coupling, compared to STA coupling of others models. We showed that the waveguide device can be used effectively for optical switching between two waveguides and for realizing a beam splitter in a system of three waveguides. (under review in Optics Express, Nov 2018) preprint available at https://arxiv.org/abs/1711.05507
During the duration of the action, the researcher Dr Elica Kyoseva carried out cutting-edge research in the field of composite pulses and their wide application to quantum engineering with various physical systems. These include development of novel composite pulses (CPs) perfectly suited for implementation in photonic systems; controlled transfer of surface plasmon polaritons in graphene; novel method for electron switching between electron waveguides; designs of waveguide couplers for robust light transfer in coupled waveguides; and an experimental demonstration of efficient and robust second harmonic generation using adiabatic temperature gradient method. Finally, Dr Kyoseva designed a composite pulse setting capable of controlling the multiple phonon states in optomechanical cavities, and a coupled cavity system for thermal switching. The work carried out during the duration of the action is truly interdisciplinary in nature and contributes substantially to expanding the field of composite pulses for quantum engineering to several other physical systems including photonic, electronic, and nonlinear optics.

The project COPQE enabled the funded researcher, Dr Elica Kyoseva, to apply and be chosen to participate in the MEP-Scientist Pairing Scheme, which aims at enhancing mutual understanding and establishing long-term, intensive cooperation between Members of the European Parliament and researchers.
Elica Kyoseva was chosen among other 104 Marie Curie fellows to be nominated as one of only 15 fellows, whose CVs and application materials were sent to the Members of the Parliament. Elica was chosen by MEP DELVAUX Mady (Luxembourg) and participated in the Brussels week, which took place on 28-30 Nov 2017 in Brussels, Belgium.
More details can be found on http://www.stoa.europarl.europa.eu/stoa/cms/home/panel_meetings/mepscientist
visit to the European Parliament, Dec 2017