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QI: Fachverband Quanteninformation

QI 11: Semiconductor Spin Qubits II: Si, Ge, and Color Centers

QI 11.2: Vortrag

Dienstag, 11. März 2025, 11:30–11:45, HS II

Singlet-triplet and exchange-only flopping-mode spin qubits — •Simon Stastny and Guido Burkard — University Konstanz, Konstanz, Germany

Electron or hole spins in quantum dots coupled to a microwave cavity are an established platform to realize qubits. In the first part of this work we combine the ST₀ qubit with the versatile flopping-mode method to achieve tunable cavity coupling. We therefore introduce a spin qubit consisting of two electrons in three quantum dots in a magnetic field gradient. Tunnel couplings between the dots allow for an orbital degree of freedom. The system operates in the ST₀ regime near the |1,0,1⟩ ↔ |0,1,1⟩ charge transition. We calculate the effective transversal and longitudinal spin-photon couplings in this regime and investigate them by observing the cavity transmission near the dressed ST₀ resonance. In the second part of this work these calculations are extended to the exchange-only qubit, a setup which comprises four dots and three electrons is introduced. This system can be controlled only by the electrically tunable exchange parameters. In addition a analysis of the three charge states of this system and possible coupling protocols are discussed.

Keywords: Spin photon coupling; Exchange-only; Singlet-triplet Qubit; Input-output theory; microave cavity