Title: Heralded quantum controlled phase gates with dissipative dynamics in macroscopically-distant resonators Show Chinese title

Title: 具有宏观距离共振器中耗散动力学的受 heralded 量子受控相位门

Abstract: Heralded near-deterministic multi-qubit controlled phase gates with integrated error detection have recently been proposed by Borregaard et al. [Phys. Rev. Lett. 114, 110502 (2015)]. This protocol is based on a single four-level atom (a heralding quartit) and $N$ three-level atoms (operational qutrits) coupled to a single-resonator mode acting as a cavity bus. Here we generalize this method for two distant resonators without the cavity bus between the heralding and operational atoms. Specifically, we analyze the two-qubit controlled-Z gate and its multi-qubit-controlled generalization (i.e., a Toffoli-like gate) acting on the two-lowest levels of $N$ qutrits inside one resonator, with their successful actions being heralded by an auxiliary microwave-driven quartit inside the other resonator. Moreover, we propose a circuit-quantum-electrodynamics realization of the protocol with flux and phase qudits in linearly-coupled transmission-line resonators with dissipation. These methods offer a quadratic fidelity improvement compared to cavity-assisted deterministic gates. Show Chinese abstract

Abstract: 通过集成错误检测的有报信近确定性多量子比特受控相位门最近由Borregaard等人提出。[Phys. Rev. Lett. 114, 110502 (2015)]。该协议基于一个四能级原子（报信四量子）和$N$个三能级原子（操作三量子）耦合到一个单共振器模式，该模式作为腔总线。在此，我们对该方法进行了推广，用于两个远距离共振器，而无需在报信原子和操作原子之间使用腔总线。具体而言，我们分析了两量子比特受控-Z门及其多量子比特受控推广（即类似Toffoli的门），作用于一个共振器内$N$个三量子的最低两个能级，其成功操作由另一个共振器内的辅助微波驱动四量子进行报信。此外，我们提出了一种电路量子电动力学实现方案，使用通量和相位四量子，在具有耗散的线性耦合传输线共振器中实现该协议。这些方法相比腔辅助确定性门实现了二次保真度提升。