We demonstrate rapid high-fidelity state preparation and measurement in exchange-only Si/SiGe triplequantum-dot qubits.Fast measurement integration (980-ns) and initialization (approximately 300-ns) operations are performed with all-electrical baseband control.We emphasize a leakage-sensitive joint initialization and measurement metric, developed in the context of exchange-only qubits but applicable more broadly, and report an infidelity of 2.5 ± 0.5×10 -3 .This result is enabled by a high-valley-splitting heterostructure, initialization at the two-to three-electron charge boundary, and careful assessment and mitigation of T 1 during spin-to-charge conversion.The ultimate fidelity is limited by a number of comparably important factors and we identify clear paths toward further improved fidelity and speed.Along with an observed single-qubit randomized benchmarking error rate of 1.7 × 10 -3 , this work demonstrates initialization, control, and measurement of Si/SiGe triple-dot qubits at fidelities and durations that are promising for scalable quantum information processing.We demonstrate rapid high-fidelity state preparation and measurement in exchange-only Si/SiGe triplequantum-dot qubits.Fast measurement integration (980-ns) and initialization (approximately 300-ns) operations are performed with all-electrical baseband control.We emphasize a leakage-sensitive joint initialization and measurement metric, developed in the context of exchange-only qubits but applicable more broadly, and report an infidelity of 2.5 ± 0.5×10 -3 .This result is enabled by a high-valley-splitting heterostructure, initialization at the two-to three-electron charge boundary, and careful assessment and mitigation of T 1 during spin-to-charge conversion.The ultimate fidelity is limited by a number of comparably important factors and we identify clear paths toward further improved fidelity and speed.Along with an observed single-qubit randomized benchmarking error rate of 1.7 × 10 -3 , this work demonstrates initialization, control, and measurement of Si/SiGe triple-dot qubits at fidelities and durations that are promising for scalable quantum information processing.

arXiv:2112.09801PRX QuantumMar 29, 202259 citations

Direct transfer of two-electron quantum states in ac-driven triple quantum dots

Jordi Picó-Cortés, Fernando Gallego-Marcos, Gloria Platero

We propose a protocol to prepare a state in the left and center quantum dots of a triple dot array and transfer it directly to the center and right dots. Initially the state is prepared combining the exchange interaction and magnetic field gradients. Once in the desired state, ac gate voltages in the outer dots are switched on, allowing to select a given photoassisted long-range path and to transfer the prepared state directly from one edge to the other with high fidelity. We investigate the effect of charge noise on the protocol and propose a configuration in which the transfer can be performed with high fidelity. Our proposal can be experimentally implemented and is a promising avenue for transferring quantum states between two spatially separated two-level systems.We propose a protocol to prepare a state in the left and center quantum dots of a triple dot array and transfer it directly to the center and right dots. Initially the state is prepared combining the exchange interaction and magnetic field gradients. Once in the desired state, ac gate voltages in the outer dots are switched on, allowing to select a given photoassisted long-range path and to transfer the prepared state directly from one edge to the other with high fidelity. We investigate the effect of charge noise on the protocol and propose a configuration in which the transfer can be performed with high fidelity. Our proposal can be experimentally implemented and is a promising avenue for transferring quantum states between two spatially separated two-level systems.

arXiv:1810.06517Physical review. B./Physical review. BApr 24, 201913 citations

High-fidelity Two and Three Spin Operations in Si with Triple Quantum Dots

Seigo Tarucha

We use Si/SiGe triple quantum dots to operate two and three spin qubits with high fidelities. For the two qubit we speed up the single qubit and exchange control to achieve the fault tolerance threshold fidelity of $> 99$ %. For the three qubits we control two exchange couplings to generate a three-spin entangled state.We use Si/SiGe triple quantum dots to operate two and three spin qubits with high fidelities. For the two qubit we speed up the single qubit and exchange control to achieve the fault tolerance threshold fidelity of$> 99$%. For the three qubits we control two exchange couplings to generate a three-spin entangled state.

Technical digest - International Electron Devices Meeting/Technical digestDec 11, 20211 citation

> 99

%. For the three qubits we control two exchange couplings to generate a three-spin entangled state.