Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Technical digest - International Electron Devices Meeting/Technical digest

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

Seigo Tarucha

Published Dec 11, 2021• 1 citation
Publisher

Abstract

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.

DOI
10.1109/iedm19574.2021.9720681

Related papers

Fast and High-Fidelity State Preparation and Measurement in Triple-Quantum-Dot Spin Qubits

Jacob Blumoff, Andrew Pan, Tyler Keating +19 more

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:2112.09801•PRX Quantum•Mar 29, 2022•59 citations

Pursuing high-fidelity control of spin qubits in natural Si/SiGe quantum dot

Ning Wang, Shaomin Wang, Run-Ze Zhang +6 more

Electron spins in silicon quantum dots are a promising platform for fault-tolerant quantum computing. Low-frequency noise, including nuclear spin fluctuations and charge noise, is a primary factor limiting gate fidelities. Suppressing this noise is crucial for high-fidelity qubit operations. Here, we report on a two-qubit quantum device in natural silicon with universal qubit control, designed to investigate the upper limits of gate fidelities in a non-purified Si/SiGe quantum dot device. By employing advanced device structures, qubit manipulation techniques, and optimization methods, we have achieved single-qubit gate fidelities exceeding 99% and a two-qubit controlled-Z (CZ) gate fidelity of 91%. Decoupled CZ gates are used to prepare Bell states with an average fidelity of 91%, typically exceeding previously reported values in natural silicon devices. These results underscore that even natural silicon has the potential to achieve high-fidelity gate operations, particularly with further optimization methods to suppress low-frequency noise.

arXiv:2409.09747•Applied Physics Letters•Nov 11, 2024•4 citations

High-fidelity quantum gates in Si/SiGe double quantum dots

Maximilian Rimbach-Russ, D. M. Zajac, Anthony J. Sigillito +4 more

Motivated by recent experiments of Zajac et al. [Science 359, 439 (2018)], we theoretically describe high-fidelity two-qubit gates using the exchange interaction between the spins in neighboring quantum dots subject to a magnetic field gradient. We use a combination of analytical calculations and numerical simulations to provide the optimal pulse sequences and parameter settings for the gate operation. We present a synchronization method which avoids detrimental spin flips during the gate operation and provide details about phase mismatches accumulated during the two-qubit gates which occur due to residual exchange interaction, nonadiabatic pulses, and off-resonant driving. By adjusting the gate times, synchronizing the resonant and off-resonant transitions, and compensating these phase mismatches by phase control, the overall gate fidelity can be increased significantly.

arXiv:1711.00754•Physical review. B./Physical review. B•Feb 15, 2018•115 citations

High-fidelity entangling gate for double-quantum-dot spin qubits

John M. Nichol, Lucas Orona, Shannon P. Harvey +4 more

Abstract Electron spins in semiconductors are promising qubits because their long coherence times enable nearly 10 9 coherent quantum gate operations. However, developing a scalable high-fidelity two-qubit gate remains challenging. Here, we demonstrate an entangling gate between two double-quantum-dot spin qubits in GaAs by using a magnetic field gradient between the two dots in each qubit to suppress decoherence due to charge noise. When the magnetic gradient dominates the voltage-controlled exchange interaction between electrons, qubit coherence times increase by an order of magnitude. Using randomized benchmarking, we measure single-qubit gate fidelities of ~ 99%, and through self-consistent quantum measurement, state, and process tomography, we measure an entangling gate fidelity of 90%. In the future, operating double quantum dot spin qubits with large gradients in nuclear-spin-free materials, such as Si, should enable a two-qubit gate fidelity surpassing the threshold for fault-tolerant quantum information processing.

arXiv:1608.04258•npj Quantum Information•Jan 19, 2017•220 citations

Fast high-fidelity entangling gates for spin qubits in Si double quantum dots

F. A. Calderon-Vargas, George S. Barron, Xiu–Hao Deng +3 more

Implementing high-fidelity two-qubit gates in single-electron spin qubits in silicon double quantum dots is still a major challenge. In this work we employ analytical methods to design control pulses that generate high-fidelity entangling gates for quantum computers based on this platform. Using realistic parameters and initially assuming a noise-free environment, we present simple control pulses that generate cnot, cphase, and cz gates with average fidelities greater than 99.99% and gate times as short as 45 ns. Moreover, using the local invariants of the system's evolution operator, we show that a simple square pulse generates a cnot gate in less than 27 ns and with a fidelity greater than 99.99%. Last, we use the same analytical methods to generate two-qubit gates locally equivalent to $\sqrt{\mathrm{CNOT}}$ and $\sqrt{\mathrm{CZ}}$ that are used to implement simple two-piece pulse sequences that produce high-fidelity cnot and cz gates in the presence of low-frequency noise.

arXiv:1902.02350•Physical review. B./Physical review. B•Jul 9, 2019•32 citations

High-fidelity gate set for exchange-coupled singlet-triplet qubits

Pascal Cerfontaine, René Otten, M. A. Wolfe +2 more

In order to enable semiconductor-based quantum computing with many qubits, issues like residual interqubit coupling and constraints from scalable control hardware need to be tackled to retain the high gate fidelities demonstrated in current single-qubit devices. Here we focus on two exchange-coupled singlet-triplet spin qubits, considering realistic control hardware as well as Coulomb and exchange coupling that cannot be fully turned off. Using measured noise spectra, we optimize realistic control pulses and show that two-qubit (single-qubit) gate fidelities of 99.90% ($\ensuremath{\ge}99.69%$) can be reached in GaAs, while 99.99% ($\ensuremath{\ge}99.95%$) can be achieved in Si.

arXiv:1901.00851•Physical review. B./Physical review. B•Apr 28, 2020•27 citations
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> 99>99%. For the three qubits we control two exchange couplings to generate a three-spin entangled state.
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.
Electron spins in silicon quantum dots are a promising platform for fault-tolerant quantum computing. Low-frequency noise, including nuclear spin fluctuations and charge noise, is a primary factor limiting gate fidelities. Suppressing this noise is crucial for high-fidelity qubit operations. Here, we report on a two-qubit quantum device in natural silicon with universal qubit control, designed to investigate the upper limits of gate fidelities in a non-purified Si/SiGe quantum dot device. By employing advanced device structures, qubit manipulation techniques, and optimization methods, we have achieved single-qubit gate fidelities exceeding 99% and a two-qubit controlled-Z (CZ) gate fidelity of 91%. Decoupled CZ gates are used to prepare Bell states with an average fidelity of 91%, typically exceeding previously reported values in natural silicon devices. These results underscore that even natural silicon has the potential to achieve high-fidelity gate operations, particularly with further optimization methods to suppress low-frequency noise.
Motivated by recent experiments of Zajac et al. [Science 359, 439 (2018)], we theoretically describe high-fidelity two-qubit gates using the exchange interaction between the spins in neighboring quantum dots subject to a magnetic field gradient. We use a combination of analytical calculations and numerical simulations to provide the optimal pulse sequences and parameter settings for the gate operation. We present a synchronization method which avoids detrimental spin flips during the gate operation and provide details about phase mismatches accumulated during the two-qubit gates which occur due to residual exchange interaction, nonadiabatic pulses, and off-resonant driving. By adjusting the gate times, synchronizing the resonant and off-resonant transitions, and compensating these phase mismatches by phase control, the overall gate fidelity can be increased significantly.
Abstract Electron spins in semiconductors are promising qubits because their long coherence times enable nearly 10 9 coherent quantum gate operations. However, developing a scalable high-fidelity two-qubit gate remains challenging. Here, we demonstrate an entangling gate between two double-quantum-dot spin qubits in GaAs by using a magnetic field gradient between the two dots in each qubit to suppress decoherence due to charge noise. When the magnetic gradient dominates the voltage-controlled exchange interaction between electrons, qubit coherence times increase by an order of magnitude. Using randomized benchmarking, we measure single-qubit gate fidelities of ~ 99%, and through self-consistent quantum measurement, state, and process tomography, we measure an entangling gate fidelity of 90%. In the future, operating double quantum dot spin qubits with large gradients in nuclear-spin-free materials, such as Si, should enable a two-qubit gate fidelity surpassing the threshold for fault-tolerant quantum information processing.
Implementing high-fidelity two-qubit gates in single-electron spin qubits in silicon double quantum dots is still a major challenge. In this work we employ analytical methods to design control pulses that generate high-fidelity entangling gates for quantum computers based on this platform. Using realistic parameters and initially assuming a noise-free environment, we present simple control pulses that generate cnot, cphase, and cz gates with average fidelities greater than 99.99% and gate times as short as 45 ns. Moreover, using the local invariants of the system's evolution operator, we show that a simple square pulse generates a cnot gate in less than 27 ns and with a fidelity greater than 99.99%. Last, we use the same analytical methods to generate two-qubit gates locally equivalent to CNOT\sqrt{\mathrm{CNOT}}CNOT​ and CZ\sqrt{\mathrm{CZ}}CZ​ that are used to implement simple two-piece pulse sequences that produce high-fidelity cnot and cz gates in the presence of low-frequency noise.
In order to enable semiconductor-based quantum computing with many qubits, issues like residual interqubit coupling and constraints from scalable control hardware need to be tackled to retain the high gate fidelities demonstrated in current single-qubit devices. Here we focus on two exchange-coupled singlet-triplet spin qubits, considering realistic control hardware as well as Coulomb and exchange coupling that cannot be fully turned off. Using measured noise spectra, we optimize realistic control pulses and show that two-qubit (single-qubit) gate fidelities of 99.90% ($\ensuremath{\ge}99.69%$) can be reached in GaAs, while 99.99% ($\ensuremath{\ge}99.95%$) can be achieved in Si.