Freiburg 2024 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 44: Quantum Information II

Q 44.2: Vortrag

Donnerstag, 14. März 2024, 11:15–11:30, HS 1199

Optimization of Optical Spin Gates for negatively charged Group-IV Colour Centers in Diamond — •Yannick Strocka, Gregor Pieplow, and Tim Schröder — Humboldt-Universität zu Berlin, Department of Physics, Berlin, Germany

The control of the spin of negatively charged Group-IV colour cen- ters in diamond plays an important role in various applications such as quantum computers and quantum repeaters. These applications re- quire high fidelity control of the spin qubit, which is formed by the two lowest lying energy eigenstates of the system. Typically a microwave control is used to manipulate the qubit. In this work, however, we theoretically study the control using optical means. The optical con- trol is composed of two laser pulses, whose frequencies are detuned from the transition between the lowest lying ground and excited state. This way a, so called, Raman spin gate is created. Optical pulses have the advantage that they allow the control over a much larger range of splittings. Under idealized assumptions perfect gates are in theory possible. The details of the color centers, however, are such that fast phononic decay greatly impacts the gate fidelity: Spurious population in the highest lying states, reduce the fidelity of the Raman spin gates due to spontaneous phononic relaxation. In order to counteract that decoherence effect any population in the levels affected must be mini- mized. In this work we combine gradient-free optimization such as the Nelder-Mead algorithm and gradient-based methods like Grape and Krotov to achieve this goal

Keywords: Raman Control; Optimization; Group-IV Colour Centers