Theory of barrier vs tilt exchange gate operations in spin-based quantum computing

Abstract

We present a theory for understanding the exchange interaction between electron spins in neighboring quantum dots, either by changing the detuning of the two quantum dots or independently tuning the tunneling barrier between quantum dots. The Hubbard model and a more realistic confining-potential model are used to investigate how the tilting and barrier control affect the effective exchange coupling and thus the gate fidelity in both the detuning and symmetric regimes. We show that the exchange coupling is less sensitive to the charge noise through tunnel barrier control (while allowing for exchange coupling operations on a sweet spot where the exchange interaction has zero derivative with respect to the detuning). Both GaAs and Si quantum dots are considered and we compare our results with experimental data showing qualitative agreements. Our results answer the open question of why barrier gates are preferable to tilt gates for exchange-base gate operations.

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• Induced quantum dot probe for material characterization
• Democratizing Spin Qubits
• Interacting Two-Level Systems as a Source of 1/f Charge Noise in Quantum Dot Qubits
• Charge noise suppression in capacitively coupled singlet-triplet spin qubits under magnetic field
• Tunable charge qubit based on barrier-controlled triple quantum dots
• Microscopic theory on magnetic-field-tuned sweet spot of exchange interactions in multielectron quantum-dot systems
• Sign-switching of superexchange mediated by few electrons under non-uniform magnetic field
• Pauli Spin Blockade in a Resonant Triple Quantum Dot Molecule