Probing two-qubit capacitive interactions beyond bilinear regime using dual Hamiltonian parameter estimations

Abstract

We report the simultaneous operation and two-qubit coupling measurement of a pair of two-electron spin qubits that are actively decoupled from quasistatic nuclear noise in a GaAs quadruple quantum dot array. Coherent Rabi oscillations of both qubits (decay time $\approx$2 μs; frequency few MHz) are achieved by continuously tuning the drive frequency using rapidly converging real-time Hamiltonian estimators. By state conditional exchange oscillation measurements, we also observe strong two-qubit capacitive interaction (> 190 MHz). We show that the scaling of the capacitive interaction with respect to intra-qubit exchange energies is stronger than the bilinear form, consistent with recent theoretical predictions. We observe a high ratio (>16) between coherence and conditional phase-flip time, which supports the possibility of generating high-fidelity and fast quantum entanglement between encoded spin qubits using a simple capacitive interaction.

30 pages, 7 figures

References in corpus (10)

• Single-shot read-out of an individual electron spin in a quantum dot
• Demonstration of Entanglement of Electrostatically Coupled Singlet-Triplet Qubits
• Universal control of a six-qubit quantum processor in silicon
• Electrometry Using Coherent Exchange Oscillations in a Singlet-Triplet-Qubit
• Two-qubit silicon quantum processor with operation fidelity exceeding 99%
• Suppressing qubit dephasing using real-time Hamiltonian estimation
• Singlet-triplet decoherence due to nuclear spins in a double quantum dot
• Conditional operation of a spin qubit
• Approaching ideal visibility in singlet-triplet qubit operations using energy-selective tunneling-based Hamiltonian estimation
• Capacitative coupling of singlet-triplet qubits in different inter-qubit geometries

Cited by in corpus (5)

• Real-time two-axis control of a spin qubit
• Physics-informed tracking of qubit fluctuations
• Passive and active suppression of transduced noise in silicon spin qubits
• Pursuing high-fidelity control of spin qubits in natural Si/SiGe quantum dot
• Limitations on the maximal level of entanglement of two singlet-triplet qubits in GaAs quantum dots