Realization of adiabatic and diabatic CZ gates in superconducting qubits coupled with a tunable coupler*

Xu, Huikai; Liu, Weiyang; Li, Zhiyuan; Han, Jie; Zhang, Jingning; Linghu, Kehuan; Li, Yongchao; Chen, Mo; Yang, Zhen; Wang, Junhua; Ma, Teng; Xue, Guangming; Jin, Yirong; Yu, Haifeng

doi:10.1088/1674-1056/abf03a

Cited by 21 publications

(16 citation statements)

References 43 publications

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“…For our implementation, the possible range of ZZ shifts should be comparable to the charateristic width of the adiabatic curve, that is in turn limited by the ability to follow the eigenstates adiabatically given by the speed of the gate. Therefore, to reduce the perceptron gate time one could envisage either non-adiabatic versions of the perceptron [39], or an extended range of achievable ZZ coupling by AC [40,41] or DC [42] pulses on the tunable coupler.…”

Section: Discussion and Outlookmentioning

confidence: 99%

Direct implementation of a perceptron in superconducting circuit quantum hardware

Pechal,

Roy,

Wilkinson

et al. 2021

Preprint

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The utility of classical neural networks as universal approximators suggests that their quantum analogues could play an important role in quantum generalizations of machine-learning methods. Inspired by the proposal in [1], we demonstrate a superconducting qubit implementation of an adiabatic controlled gate, which generalizes the action of a classical perceptron as the basic building block of a quantum neural network. We show full control over the steepness of the perceptron activation function, the input weight and the bias by tuning the adiabatic gate length, the coupling between the qubits and the frequency of the applied drive, respectively. In its general form, the gate realizes a multi-qubit entangling operation in a single step, whose decomposition into singleand two-qubit gates would require a number of gates that is exponential in the number of qubits. Its demonstrated direct implementation as perceptron in quantum hardware may therefore lead to more powerful quantum neural networks when combined with suitable additional standard gates.

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Section: Discussion and Outlookmentioning

confidence: 99%

Direct implementation of a perceptron in superconducting circuit quantum hardware

Pechal,

Roy,

Wilkinson

et al. 2021

Preprint

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“…To identify the optimal pulses for implementing singleand two-qubit gates, we parametrize the control pulses in terms of a finite set of variables and identify an appropriate cost function C, which we want to minimize. For such generic optimization problems there are several standard numerical methods available and different versions of such algorithms have already been implemented in the past for optimizing quantum gates [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. However, to obtain a sufficiently fast convergence, smooth pulse shapes, etc., usually a problem-specific tuning of…”

Section: Appendix A: Pulse Optimizationmentioning

confidence: 99%

“…In the development of superconducting quantum computers [2], many important breakthroughs were facilitated by the development of the transmon [3] and related qubit designs, where quantum information is en-coded in the two lowest levels of a weakly anharmonic oscillator. Typical operation timescales for such transmon qubits are in the order of a few tens of nanoseconds, but with the help of optimized control pulses [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] the implementation of single-(two-) qubit gates in about 4 ns [22,23] (12 ns [24,25]) has been demonstrated. To realize much faster operations it is necessary to use qubits with higher nonlinearities, such as flux qubits [26].…”

Section: Introductionmentioning

confidence: 99%

Quantum computing with superconducting circuits in the picosecond regime

Zhu,

Jaako,

et al. 2021

Preprint

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We discuss the realization of a universal set of ultrafast single-and two-qubit operations with superconducting quantum circuits and investigate the most relevant physical and technical limitations that arise when pushing for faster and faster gates. With the help of numerical optimization techniques, we establish a fundamental bound on the minimal gate time, which is determined independently of the qubit design solely by its nonlinearity. In addition, important practical restrictions arise from the finite qubit transition frequency and the limited bandwidth of the control pulses. We show that for highly anharmonic flux qubits and commercially available control electronics, elementary single-and two-qubit operations can be implemented in about 100 picoseconds with residual gate errors below 10 −4 . Under the same conditions, we simulate the complete execution of a compressed version of Shor's algorithm for factoring the number 15 in about one nanosecond. These results demonstrate that compared to state-of-the-art implementations with transmon qubits, a hundredfold increase in the speed of gate operations with superconducting circuits is still feasible.

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“…It overcomes the challenge of incorporating tunable coupling with high coherence devices [24]. Very recently, one simple and generic architecture with an additional qubit (named as "coupler") attract wide attention and become the research forefront of superconducting circuits [25][26][27][28][29][30][31][32][33][34][35][36][37][38]. The impressive achievement is that such architecture made great success in Google's quantum supremacy experiment [4].…”

mentioning

confidence: 99%

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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Realization of adiabatic and diabatic CZ gates in superconducting qubits coupled with a tunable coupler*

Cited by 21 publications

References 43 publications

Direct implementation of a perceptron in superconducting circuit quantum hardware

Direct implementation of a perceptron in superconducting circuit quantum hardware

Quantum computing with superconducting circuits in the picosecond regime

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

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