Superconducting qubits are a promising candidate for building a quantum computer. A continued challenge for fast yet accurate gates to minimize the effects of decoherence. Here we apply numerical methods to design fast entangling gates, specifically the controlled Z, in an architecture where two qubits are coupled via a resonator. We find that the gates can be sped up by a factor of two and reach any target fidelity. We also discuss how systematic errors arising from experimental conditions affect the pulses and how to remedy them, providing a strategy for the experimental implementation of our results. We discuss the shape of the pulses, their spectrum and symmetry.
Recent experiments with silicon qubits demonstrated strong coupling of a microwave resonator to the spin of a single electron in a double quantum dot, opening up the possibility of long-range spin-spin interactions. We present our theoretical calculation of effective interactions between distant quantum dot spins coupled by a resonator, and propose a protocol for fast, high-fidelity two-qubit gates consistent with experimentally demonstrated capabilities. Our simulations show that, in the presence of noise, spin-spin entangling gates significantly outperform cavity-mediated gates on charge qub…
A double-resonator coupler for high-fidelity two-qubit gates between superconducting qubits
NextQuantum Center, Seoul National University（首尔大学 NextQuantum 中心）；Department of Physics and Astronomy, Seoul National University（首尔大学物理与天文学系）；Institute of Applied Physics, Seoul National University（首尔大学应用物理研究所）；Samsung Advanced Institute of Technology, Samsung Electronics（三星电子三星先进技术研究院）
Parallelization of frequency domain quantum gates: manipulation and distribution of frequency-entangled photon pairs generated by a 21 GHz silicon micro-resonator
We propose to simulate quantum gates by \textit{LC} resonators, where the amplitude and the phase of the voltage describe the quantum state. By controlling capacitance or inductance of resonators, it is possible to control the phase of the voltage arbitrarily. A set of resonators acts as the phase-shift, the Hadamard and the CNOT gates. They constitute a set of universal quantum gates. We also discuss an application to an artificial neuron. As an example, we study a pattern recognition of numbers and alphabets by evaluating the similarity between an input and the reference pattern. We also stu…
High-fidelity CZ gate for resonator-based superconducting quantum computers
最近已经证明了可扩展量子计算机的可能构建块[M. Mariantoni等人，Science 334，61（2011）]。这种架构由超导量子位电容耦合到单独的存储器谐振器以及公共总线。在这项工作中，我们研究了一个自然的原始纠缠门这个和相关的谐振器为基础的架构，其中包括一个量子位和总线之间的CZ操作。CZ门是在非计算量子比特的帮助下实现的|2> state [F. W. Strauch等人，物理修订版信函91，167005（2003）]。假设相位或transmon量子比特具有300 MHz的非谐性，我们表明，通过仅使用低频量子比特偏置控制，可以在大约17 ns（23 ns）的时间内实现具有99.9%（99.99%）保真度的量子比特总线CZ门，具有现实的双参数脉冲轮廓，加上两个辅助z旋转。我们在这里所指的保真度测量是状态平均的内在过程保真度，它不包括任何噪声或退相干的影响。这些结果适用于包括强耦合存储器谐振器的多量子位器件。我们研究了量子位总线CZ门的性能作为量子位非谐性的函数，确定占主导地位的固有误差机制并推导出相关的保真度估计器，量化脉冲形状灵敏度和精度要求，模拟由总线谐振器介导的量子位-量子位CZ门，并尝试对系统参数（包括谐振器频率和耦合）进行全局优化。我们的研究结果与广泛的超导硬件设计相关，这些设计包括谐振器，并表明应该可以用现有的transmon量子位演示99.9%CZ门，这将…
A key challenge for semiconductor quantum-dot charge qubits is the realization of long-range qubit coupling and performing high-fidelity gates based on it. Here, we describe a new type of charge qubit formed by an electron confined in a triple-quantum-dot system, enabling single and two-qubit gates working in the dipolar and quadrupolar detuning sweet spots. We further present the form for the long-range dipolar coupling between the charge qubit and the superconducting resonator. Based on the hybrid system composed of the qubits and the resonator, we present two types of entangling gates: the …
发展快速、准确和可扩展的量子态读出技术是基于光子晶体的量子计算的一个活跃领域。在这里，我们提出的硅角态量子点耦合到集总元件电谐振器通过栅极的色散传感的结果。量子器件的栅极电容被配置为与超导螺旋电感器并联，从而产生具有400-800范围内的加载Q因子的谐振器。对于工作在330 MHz的谐振器，我们实现了7.7 $μ$ e $/\sqrt{\text{Hz}}$的电荷灵敏度，并且当工作在616 MHz时，我们得到1.3 $μ$ e $/\sqrt{\text{Hz}}$。我们进行的谐振器的参数研究，以揭示其最佳的工作点，并进行电路分析，以确定最佳的谐振器设计。结果将基于栅极的感测与最佳报道的射频单电子晶体管灵敏度相提并论，同时为量子态读出提供了快速且紧凑的方法。
The resonator-induced phase gate is a two-qubit operation in which driving a bus resonator induces a state-dependent phase shift on the qubits equivalent to an effective $ZZ$ interaction. In principle, the dispersive nature of the gate offers flexibility for qubit parameters. However, the drive can cause resonator and qubit leakage, the physics of which cannot be fully captured using either the existing Jaynes-Cummings or Kerr models. In this paper, we adopt an ab-initio model based on Josephson nonlinearity for transmon qubits. The ab-initio analysis agrees well with the Kerr model in terms o…
In the quantum-computation scenario, geometric phase-gates are becoming increasingly attractive for their intrinsic fault tolerance to disturbance. With an adiabatic cyclic evolution, Berry phase appears to realize a geometric transformation. Performing the quantum gates as many as possible within the timescale of coherence, however, remains an inconvenient bottleneck due to the systematic errors. Here we propose an accelerated adiabatic quantum gate based on the Berry phase, the transitionless driving, and the dynamical decoupling. It reconciles a high fidelity with a high speed in the presen…
We propose a quantum non-demolition Majorana qubit readout protocol based on parametricmodulation of a longitudinal interaction between a pair of Majorana bound states and a resonator. The interaction can be modulated through microwave frequency gate-voltage or flux control of a tunable tunnel barrier. The qubit-resonator coupling is quantum non-demolition to exponential accuracy, a property inherited from the topological nature of the Majorana zero modes. The same mechanism as used for single-qubit readout can also be extended to perform multi-qubit measurements and be used to enact long rang…
A semiconductor-based charge qubit, confined in double quantum dots, can be a platform to implement quantum computing. However, it suffers severely from charge noises. Here, we provide a theoretical framework to implement universal geometric quantum gates in this system. We find that, while the detuning noise can be suppressed by operating near its corresponding sweet spot, the tunneling noise, on the other hand, is amplified and becomes the dominant source of error for single-qubit gates, a fact previously insufficiently appreciated. We demonstrate, through numerical simulation, that the geom…
Optimized ancillary drive for fast Rydberg entangling gates
East China Normal University（华东师范大学）；Shanghai Jiao Tong University（上海交通大学）；Chongqing Institute of East China Normal University（华东师范大学重庆研究院）；Shanxi University（山西大学）
Voltage-tunable superconductor-semiconductor devices offer a unique platform to realize dynamic tunability in superconducting quantum circuits. By galvanically connecting a gated InAs-Al Josephson junction to a coplanar waveguide resonator, we demonstrate the use of a wide-range gate-tunable superconducting element. We show that the resonant frequency is controlled via a gate-tunable Josephson inductance and that the non-linearity of the voltage-controlled InAs-Al junction is non-dissipative as is the case with conventional Al-AlO$_{x}$ junctions. As the gate voltage is decreased, the inductiv…
Holonomies, arising from non-Abelian geometric transformations of quantum states in Hilbert space, offer a promising way for quantum computation. These holonomies are not commutable and thus can be used for the realization of a universal set of quantum logic gates, where the global geometric feature may result in some noise-resilient advantages. Here we report the first on-chip realization of a non-Abelian geometric controlled-Not gate in a superconducting circuit, which is a building block for constructing a holonomic quantum computer. The conditional dynamics is achieved in an all-to-all con…
High-Fidelity Universal Quantum Gate Compilation for Non-semisimple Ising Anyons via Genetic Algorithm-Optimized Solovay-Kitaev Decomposition
School of Physics and Optoelectronics, Xiangtan University（湘潭大学物理与光电工程学院）；School of Physics and Electronic Science, Hunan Institute of Science and Technology（湖南理工学院物理与电子科学学院）；Center for Quantum Science and Technology, Department of Physics, Shanghai University（上海大学物理学部量子科学与技术中心）
