Floating tunable coupler for scalable quantum computing architectures

Sete, Eyob A.; Chen, Angela Q.; Manenti, Riccardo; Kulshreshtha, Shobhan; Poletto, Stefano

doi:10.48550/arxiv.2103.07030

Cited by 5 publications

(5 citation statements)

References 15 publications

(22 reference statements)

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“…Beyond the architecture and dispersive regime discussed in this paper, new coupler architecture connecting fixed-frequency floating qubits and new regime were also studied and high-fidelity gates were realized very recently [31,64,65]. Therefore, it would be also interesting to study the interesting physical mechanism behind and explore more possibility.…”

Section: Summary and Perspectivesmentioning

confidence: 91%

Implementing High-fidelity Two-Qubit Gates in Superconducting Coupler Architecture with Novel Parameter Regions

Jin¹

2021

Preprint

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Superconducting circuits with coupler architecture receive considerable attention due to their advantages in tunability and scalability. Although single-qubit gates with low error have been achieved, high-fidelity two-qubit gates in coupler architecture are still challenging. This paper pays special attention to examining the gate error sources and primarily concentrates on the related physical mechanism of ZZ parasitic couplings using a systematic effective Hamiltonian approach. Benefiting from the effective Hamiltonian, we provide simple and straightforward insight into the ZZ parasitic couplings that were investigated previously from numerical and experimental perspectives. The analytical results obtained provide exact quantitative conditions for eliminating ZZ parasitic couplings, and trigger four novel realizable parameter regions in which higher fidelity two-qubit gates are expected. Beyond the numerical simulation, we also successfully drive a simple analytical result of the two-qubit gate error from which the trade-off effect between qubit energy relaxation effects and ZZ parasitic couplings is understood, and the resulting two-qubit gate error can be estimated straightforwardly. Our study opens up new opportunities to implement high-fidelity two-qubit gates in superconducting coupler architecture. I. BACKGROUND AND MOTIVATION

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Section: Summary and Perspectivesmentioning

confidence: 91%

Implementing High-fidelity Two-Qubit Gates in Superconducting Coupler Architecture with Novel Parameter Regions

Jin¹

2021

Preprint

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“…Cross-Kerr interactions are a source of infidelity for a iSWAP-type gate, as well as in other gate implementations [10][11][12][13][14]47]. In the firstorder RWA Hamiltonian, to cancel the cross-Kerr interaction between the two transmons, we use a coupler with a positive anharmonicity [41] α c > 0, together with α a , α b < 0, which is distinct from using qubits of opposite anharmonicities [10,40], or couplers with negative anharmonicity [14,48]. Equation (20) forms the basis for the optimization of the gate parameters.…”

Section: B Black-box Quantization Approach To the Toy Modelmentioning

confidence: 99%

Accurate methods for the analysis of strong-drive effects in parametric gates

Petrescu,

Calonnec,

Leroux

et al. 2021

Preprint

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The ability to perform fast, high-fidelity entangling gates is an important requirement for a viable quantum processor. In practice, achieving fast gates often comes with the penalty of strong-drive effects that are not captured by the rotating-wave approximation. These effects can be analyzed in simulations of the gate protocol, but those are computationally costly and often hide the physics at play. Here, we show how to efficiently extract gate parameters by directly solving a Floquet eigenproblem using exact numerics and a perturbative analytical approach. As an example application of this toolkit, we study the space of parametric gates generated between two fixed-frequency transmon qubits connected by a parametrically driven coupler. Our analytical treatment, based on time-dependent Schrieffer-Wolff perturbation theory, yields closed-form expressions for gate frequencies and spurious interactions, and is valid for strong drives. From these calculations, we identify optimal regimes of operation for different types of gates including iSWAP, controlled-Z, and CNOT. These analytical results are supplemented by numerical Floquet computations from which we directly extract drive-dependent gate parameters. This approach has a considerable computational advantage over full simulations of time evolutions. More generally, our combined analytical and numerical strategy allows us to characterize two-qubit gates involving parametrically driven interactions, and can be applied to gate optimization and cross-talk mitigation such as the cancellation of unwanted ZZ interactions in multi-qubit architectures.

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“…( 2)). However, they may be engineered to have opposite signs as demonstrated in [36,65]. Hence, one can idle the coupler below the qubit frequencies to implement this adiabatic CZ gate scheme by pulsing the coupler uptowards in an almost reversed process.…”

Section: Generalized Control Schemesmentioning

confidence: 99%

Coupler-Assisted Controlled-Phase Gate with Enhanced Adiabaticity

Chu,

Yan

2021

Preprint

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High-fidelity two-qubit entangling gates are essential building blocks for fault-tolerant quantum computers. Over the past decade, tremendous efforts have been made to develop scalable high-fidelity two-qubit gates with superconducting quantum circuits. Recently, an easy-to-scale controlled-phase gate scheme that utilizes the tunable-coupling architecture with fixed-frequency qubits [Phys. Rev. Lett. 125, 240502; Phys. Rev. Lett. 125, 240503] has been demonstrated with high fidelity and attracted broad interest. However, in-depth understanding of the underlying mechanism is still missing, preventing us from fully exploiting its potential. Here we present a comprehensive theoretical study, explaining the origin of the high-contrast ZZ interaction. Based on improved understanding, we develop a general yet convenient method for shaping an adiabatic pulse in a multilevel system, and identify how to optimize the gate performance from design. Given state-of-the-art coherence properties, we expect the scheme to potentially achieve a two-qubit gate error rate near 10 −5 , which would drastically speed up the progress towards fault-tolerant quantum computation.

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Floating tunable coupler for scalable quantum computing architectures

Cited by 5 publications

References 15 publications

Implementing High-fidelity Two-Qubit Gates in Superconducting Coupler Architecture with Novel Parameter Regions

Implementing High-fidelity Two-Qubit Gates in Superconducting Coupler Architecture with Novel Parameter Regions

Accurate methods for the analysis of strong-drive effects in parametric gates

Coupler-Assisted Controlled-Phase Gate with Enhanced Adiabaticity

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