近日，法国斯特拉斯堡大学的Guido Pupillo及其研究团队取得一项新进展。他们通过驱动腔实现了非局部多量子比特量子门。相关研究成果已于2024年12月16日在国际知名学术期刊《物理评论A》上发表。

该研究团队提出两种协议，用于在耦合到公共腔模的量子比特上，实现确定性的非局域多量子比特量子门。这两种协议仅依赖于对腔模的经典驱动，而无需对量子比特进行外部驱动。当应用于仅两个量子比特时，这两种协议与单量子比特门一起，提供了量子计算的通用门集。

在第一种协议中，腔的状态在相空间中遵循一条闭合轨迹，并根据量子比特的状态积累一个几何相位。这个几何相位门可以与全局单量子比特门结合使用，以生成高保真度的格林伯格-霍恩-蔡林格（GHZ）态。第二种协议利用量子比特-腔组合系统的绝热演化，来积累一个动态相位。通过重复应用此协议，可以实现具有任意相位的相位门族，例如相位旋转门和多控Z门。

对于这两种协议，研究人员提供了误差率的分析解，在存在相关损耗的情况下，误差率与N/√C成比例，其中C是协同性，N是量子比特数。这一协议适用于各种系统，并且可以通过将腔替换为不同的玻色子模式（如声子模式）来进行推广。研究人员提供了原子和分子量子比特，以及耦合到光学或微波腔的超导fluxonium量子比特的门保真度，和持续时间的估计，并概述了对量子纠错的影响。

附：英文原文

Title: Nonlocal multiqubit quantum gates via a driven cavity

Author: Sven Jandura, Vineesha Srivastava, Laura Pecorari, Gavin K. Brennen, Guido Pupillo

Issue&Volume: 2024/12/16

Abstract: We present two protocols for realizing deterministic nonlocal multiqubit quantum gates on qubits coupled to a common cavity mode. The protocols rely only on a classical drive of the cavity mode, while no external drive of the qubits is required. Applied to just two qubits, both protocols provide a universal gate set for quantum computing, together with single-qubit gates. In the first protocol, the state of the cavity follows a closed trajectory in phase space and accumulates a geometric phase depending on the state of the qubits. This geometric phase gate can be used together with global single-qubit gates to generate high-fidelity Greenberger–Horne–Zeilinger (GHZ) states. The second protocol uses an adiabatic evolution of the combined qubit-cavity system to accumulate a dynamical phase. Repeated applications of this protocol allow for the realization of a family of phase gates with arbitrary phases, e.g., phase-rotation gates and multi-controlled-Z gates. For both protocols, we provide analytic solutions for the error rates, which scale as ～N/√C in the presence of relevant losses, with C the cooperativity and N the qubit number. Our protocols are applicable to a variety of systems and can be generalized by replacing the cavity by a different bosonic mode, such as a phononic mode. We provide estimates of gate fidelities and durations for atomic and molecular qubits as well as superconducting fluxonium qubits coupled to optical or microwave cavities, and we outline implications for quantum error correction.

DOI: 10.1103/PhysRevA.110.062610

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.062610