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arXiv:1906.08303 · Physical Review A

High-fidelity single-qubit gates in a strongly driven quantum-dot hybrid qubit with 1/f charge noise

Yuan‐Chi Yang, S. N. Coppersmith, Mark G. Friesen

Published Aug 28, 2019• 22 citations
arXivHTMLPDF

Abstract

Semiconductor double quantum-dot hybrid qubits are promising candidates for high-fidelity quantum computing. However, their performance is limited by charge noise, which is ubiquitous in solid-state devices, and phonon-induced dephasing. Here we explore methods for improving the quantum operations of a hybrid qubit, using strong microwave driving to enable gate operations that are much faster than decoherence processes. Using numerical simulations and a theoretical method based on a cumulant expansion, we analyze qubit dynamics in the presence of $1/f$ charge noise, which forms the dominant decoherence mechanism in many solid-state devices. We show that, while strong-driving effects and charge noise both reduce the quantum gate fidelity, simple pulse-shaping techniques effectively suppress the strong-driving effects. Moreover, a broad AC sweet spot emerges when the detuning parameter and the tunneling coupling are driven simultaneously. Taking into account phonon-mediated noise, we find that it should be possible to achieve ${X}_{\ensuremath{\pi}}$ gates with fidelities higher than $99.9%$.

DOI
10.1103/physreva.100.022337

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Semiconductor double quantum-dot hybrid qubits are promising candidates for high-fidelity quantum computing. However, their performance is limited by charge noise, which is ubiquitous in solid-state devices, and phonon-induced dephasing. Here we explore methods for improving the quantum operations of a hybrid qubit, using strong microwave driving to enable gate operations that are much faster than decoherence processes. Using numerical simulations and a theoretical method based on a cumulant expansion, we analyze qubit dynamics in the presence of 1/f1/f1/f charge noise, which forms the dominant decoherence mechanism in many solid-state devices. We show that, while strong-driving effects and charge noise both reduce the quantum gate fidelity, simple pulse-shaping techniques effectively suppress the strong-driving effects. Moreover, a broad AC sweet spot emerges when the detuning parameter and the tunneling coupling are driven simultaneously. Taking into account phonon-mediated noise, we find that it should be possible to achieve X\ensuremathπ{X}_{\ensuremath{\pi}}X\ensuremathπ​ gates with fidelities higher than 99.999.9%99.9.
High-Fidelity Single-Qubit Gates Via Strongly Driving of a Double Quantum Dot Hybrid Qubit with 1/f1/f1/f Charge Noise
Semiconductor double quantum dot hybrid qubits are promising candidates for high-fidelity quantum computing. However, their performance is limited by charge noise, which is ubiquitous in solid-state devices, and phonon-induced dephasing. Here we explore methods for improving the quantum operations of a hybrid qubit, using strong microwave driving to enable gate operations that are much faster than decoherence processes. Using numerical simulations and a theoretical method based on a cumulant expansion, we analyze qubit dynamics in the presence of 1/f1/f1/f charge noise, which forms the dominant decoherence mechanism in many solid-state devices. We show that, while strong-driving effects and charge noise both reduce the quantum gate fidelity, simple pulse-shaping techniques effectively suppress the strong-driving effects. Moreover, a broad AC sweet spot emerges when the detuning parameter and the tunneling coupling are driven simultaneously. Taking into account phonon-mediated noise, we find that it should be possible to achieve XπX_{\pi}Xπ​ gates with fidelities higher than 99.9%99.9\%99.9%.
Abstract Charge qubits formed in double quantum dots represent quintessential two-level systems that enjoy both ease of control and efficient readout. Unfortunately, charge noise can cause rapid decoherence, with typical single-qubit gate fidelities falling below 90%. Here we develop analytical methods to study the evolution of strongly driven charge qubits, for general and 1/ f charge-noise spectra. We show that special pulsing techniques can simultaneously suppress errors due to strong driving and charge noise, yielding single-qubit gates with fidelities above 99.9%. These results demonstrate that quantum dot charge qubits provide a potential route to high-fidelity quantum computation.
Semiconductor quantum dots in silicon are promising qubits because of long spin coherence times and their potential for scalability. However, such qubits with complete electrical control and fidelities above the threshold for quantum error correction have not yet been achieved. We show theoretically that the threshold fidelity can be achieved with ac gate operation of the quantum dot hybrid qubit. Formed by three electrons in a double dot, this qubit is electrically controlled, does not require magnetic fields, and runs at gigahertz (GHz) gate speeds. We analyze the decoherence caused by 1/f1/f1/f charge noise in this qubit, find parameters that minimize the charge noise dependence in the qubit frequency, and determine the optimal working points for ac gate operations that drive the detuning and tunnel coupling.
Quantum-dot hybrid qubits exploit an extended charge-noise sweet spot that suppresses dephasing and has enabled the experimental achievement of high-fidelity single-qubit gates. However, current proposals for two-qubit gates require tuning the qubits away from their sweet spots. Here, we propose a two-hybrid-qubit coupling scheme, based on exchange interactions, that allows the qubits to remain at their sweet spots at all times. The interaction is controlled via the interqubit tunnel coupling. By simulating such gates in the presence of realistic quasistatic and 1/f1/f1/f charge noise, we show that our scheme should enable controlled-ZZZ gates of length $\ensuremath{\sim}5\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$, and zero-controlled-not gates of length $\ensuremath{\sim}7\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$, both with fidelities >99.9>99.9%>99.9.
The charge qubit based on semiconductor double quantum dots is promising to realize fast and scalable quantum information processing. However, due to its strong coupling to charge noise, experimental realization of two-qubit gates has fidelities below 90%. Here, we provide a theoretical framework to achieve precise gate operations on a charge qubit using geometric quantum phase, namely geometric quantum gates. Single-qubit operations are implemented using the microwave-driven X-Y interacting Hamiltonian near certain sweet spots, where the charge noise is effectively suppressed. Meanwhile, we find that the performance of the geometric gates can be further improved up to 99.86% using composite pulses. In addition, to obtain a nontrivial two-qubit gate, we introduce a hybrid system which consists of charge qubits interacting with a high-impedance superconducting resonator. We find that when the individual charge qubit is in resonance with the resonator, it is possible to construct a SWAP-like gate with fidelity over 97%. Therefore, our results suggest that the geometric quantum gates in combination with the microwave-driven fields are powerful tools to achieve high-fidelity manipulation for the charge qubit.
Implementing two-qubit gates via strong coupling between quantum-dot qubits and a superconducting microwave cavity requires achieving coupling rates that are much faster than decoherence rates. Typically, this involves tuning the qubit either to a sweet spot, where it is relatively insensitive to charge noise, or to a point where it is resonant with the microwave cavity. Unfortunately, such operating points seldom coincide. Here we theoretically investigate protocols, based on transverse or longitudinal sideband driving, for implementing two-qubit gates between quantum-dot hybrid qubits, mediated by a microwave cavity. The rich physics in these qubits gives rise to two types of sweet spots, which can occur at operating points with strong charge dipole moments. Such strong interactions provide new opportunities for off-resonant gating, thereby removing one of the main obstacles for long-distance two-qubit gates. We find that the transverse driving scheme yields faster gates, while longitudinal driving yields gates that are more resilient to photon decay. Our results suggest that the numerous tuning knobs of quantum-dot hybrid qubits make them good candidates for strong coupling. In particular, we show that off-resonant red-sideband-mediated two-qubit gates can exhibit fidelities greater than 9595%95 for realistic operating parameters, and we describe improvements that could potentially yield gate fidelities greater than 9999%99.