单结unimon电路上的原生多量子比特门
Native multi-qubit gates on a single-junction unimon circuit
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中文总结 AI 辅助
本文提出multiunimon超导多模电路，基于单约瑟夫森结实现原生多量子比特门，模拟12种受控-受控-NOT门平均保真度达99.5%，有望用于构建大型超导量子处理器。
中文摘要 AI 辅助
带有原生多量子比特门的量子处理器可在含噪声硬件上高效实现近期量子算法。本文提出multiunimon，一种超导多模电路，可编码多个量子比特并实现原生多量子比特门，该器件包含嵌入共面波导结构的单个约瑟夫森结。它与unimon量子比特密切相关，继承了高非谐性、完全抵御低频电荷噪声、部分抵御磁通噪声等特性。通过设计约瑟夫森-电感能量比大于1的三量子比特器件，并采用针对计算态的感知泄漏编码方案，我们用与单量子比特门长度相当的简单正弦平方脉冲模拟了全部12种不同的受控-受控-NOT门，平均保真度达99.5%。性能受限于以介电损耗为主的非相干误差。模拟结果表明，通过改进噪声防护、设计和脉冲整形，保真度接近99.99%是可实现的。我们的结果证明了multiunimon作为大型超导量子处理器中高连通性多量子比特单元的潜力。
英文摘要
Quantum processors with native multi-qubit gates may offer very efficient implementations of near-term quantum algorithms on noisy hardware. Here, we introduce the multiunimon, a superconducting multimode circuit that encodes multiple qubits and enables native multi-qubit gates in a device consisting of a single Josephson junction embedded in a coplanar waveguide structure. Closely related to the unimon qubit, it inherits properties such as high anharmonicity, full protection against low-frequency charge noise, and partial protection against flux noise. By designing such a three-qubit device with Josephson-to-inductive energy ratio above unity and using a leakage-aware encoding scheme for the computational states, we simulate all twelve different controlled-controlled-NOT gates with a mean fidelity of 99.5% with simple sine-squared pulses of comparable length to single-qubit gates. The performance is limited by incoherent errors dominated by dielectric loss. With improvements in noise protection, design, and pulse shaping, the simulations suggest that fidelities approaching 99.99% are within reach. Our results demonstrate the potential of the multiunimon as a highly connected multi-qubit unit for larger superconducting quantum processors.
