Energy spectrum, exchange interaction and gate crosstalk in a pair of double-quantum-dot system: a molecular orbital calculation

Abstract

We present a theoretical study of a four-electron four-quantum-dot system based on molecular orbital methods, which hosts a pair of singlet-triplet spin qubits. We explicitly take into account of the admixture of electron wave functions in all dots, and have found that this mixing of wave functions has consequences on the energy spectrum, exchange interaction and the gate crosstalk of the system. Specifically, we have found that when the two singlet-triplet qubits are close enough, some of the states are no longer dominated by the computational basis states and the exchange interaction can not simply be understood as the energy difference between the singlet and triplet states. Using the Hund-Mulliken calculation of the Hubbard parameters, we characterize the effective exchange interaction of the system and have found good agreement with results calculated by taking energy differences where applicable. We have studied the two commonly conceived schemes coupling two qubits, the exchange and capacitive coupling, and have found that when the inter-qubit distance is at certain intermediate values, the two kinds of coupling are comparable in strength, complicating analyses of the evolution of the two qubits. We also investigate the gate crosstalk in the system due to the quantum mechanical mixing of electron states and have found that while this effect is typically very weak, it should not be ignored if the spacing between the qubits are similar to or less than the distance between the double dots that constitute the qubit.

11 pages, 6 figures

References in corpus (15)

• Demonstration of Entanglement of Electrostatically Coupled Singlet-Triplet Qubits
• Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization
• Scalable gate architecture for densely packed semiconductor spin qubits
• Enhancing the Coherence of a Spin Qubit by Operating it as a Feedback Loop That Controls its Nuclear Spin Bath
• Coherent spin manipulation in an exchange-only qubit
• Gate fidelity and coherence of an electron spin in a Si/SiGe quantum dot with micromagnet
• Universal set of quantum gates for double-dot spin qubits with fixed interdot coupling
• Conditional operation of a spin qubit
• Quantum gates between capacitively coupled double quantum dot two-spin qubits
• Exchange-based two-qubit gate for singlet-triplet qubits
• Directly accessible entangling gates for capacitively coupled singlet-triplet qubits
• Improving the gate fidelity of capacitively coupled spin qubits
• Validity of the single-particle description and charge noise resilience for multielectron quantum dots
• Reliability of the Heitler-London approach for the exchange coupling between electrons in semiconductor nanostructures
• Inverted Singlet-Triplet Qubit Coded on a Two-Electron Double Quantum Dot

Cited by in corpus (5)

• An automated approach for consecutive tuning of quantum dot arrays
• Leakage and sweet spots in triple-quantum-dot spin qubits: A molecular-orbital study
• Suppression of charge noise using barrier control of a singlet-triplet qubit
• Tunable charge qubit based on barrier-controlled triple quantum dots
• Magic angle for barrier-controlled double quantum dots