Simplify proposal for realizing multiqubit tunable phase gate in circuit QED

Universal time-dependent control scheme for realizing arbitrary linear bosonic transformations

We study the implementation of arbitrary excitation-conserving linear transformations between two sets of $N$ stationary bosonic modes, which are connected through a photonic quantum channel. By controlling the individual couplings between the modes and the channel, an initial $N$-partite quantum state in register $A$ can be released as a multiphoton wave packet and, successively, be reabsorbed in register $B$. Here we prove that there exists a set of control pulses that implement this transfer with arbitrarily high fidelity and, simultaneously, realize a prespecified $N\times N$ unitary trans…

Resilient quantum gates on periodically driven Rydberg atoms

Fault-tolerant implementation of quantum gates is one of preconditions for realizing quantum computation. The platform of Rydberg atoms is one of the most promising candidates for achieving quantum computation. We propose to implement a controlled-$Z$ gate on Rydberg atoms where an amplitude-modulated field is employed to induce Rydberg antiblockade. Gate robustness against the fluctuations in the Rydberg-Rydberg interaction can be largely enhanced by adjusting amplitude-modulated field. Furthermore, we introduce a Landau-Zener-Stückelberg transition on the target atom so as to improve the gat…

Realizing an $n$-target-qubit controlled phase gate in cavity QED: An approach without classical pulses

We propose a way to realize a multiqubit controlled phase gate with one qubit simultaneously controlling $n$ target qubits using atoms in cavity QED. In this proposal, there is no need of using classical pulses during the entire gate operation. The gate operation time scales as $\sqrt{n}$ only and thus the gate can be performed faster when compared with sending atoms through the cavity one at a time. In addition, only three steps of operations are required for realizing this $n$-target-qubit controlled phase gate. This proposal is quite general, which can be applied to other physical systems s…

Photonic two-qubit parity gate with tiny cross-Kerr nonlinearity

The cross-Kerr nonlinearity (XKNL) effect can induce efficient photon interactions in principle with which photonic multiqubit gates can be performed using far fewer physical resources than linear optical schemes. Unfortunately, it is extremely challenging to generate giant cross-Kerr nonlinearities. In recent years, much effort has been made to perform multiqubit gates via weak XKNLs. However, the required nonlinearity strengths are still difficult to achieve in the experiment. We here propose an XKNL-based scheme for realizing a two-photon polarization-parity gate, a universal two-qubit gate…

Efficient scheme for realizing a multiplex-controlled phase gate with photonic qubits in circuit quantum electrodynamics

We propose an efficient scheme to implement a multiplex-controlled phase gate with multiple photonic qubits simultaneously controlling one target photonic qubit based on circuit quantum electrodynamics (QED). For convenience, we denote this multiqubit gate as MCP gate. The gate is realized by using a two-level coupler to couple multiple cavities. The coupler here is a superconducting qubit. This scheme is simple because the gate implementation requires only \textit{one step} of operation. In addition, this scheme is quite general because the two logic states of each photonic qubit can be encod…

Single-step implementation of a multiple-target-qubit controlled phase gate without need of classical pulses

We propose a simple method for realizing a multiqubit phase gate of one qubit simultaneously controlling $n$ target qubits, by using three-level quantum systems (i.e., qutrits) coupled to a cavity or resonator. The gate can be implemented using one operational step and without need of classical pulses, and no photon is populated during the operation. Thus, the gate operation is greatly simplified and decoherence from the cavity decay is much reduced, when compared with the previous proposals. In addition, the operation time is independent of the number of qubits and no adjustment of the qutrit…

采用双Transmon耦合器的高性能多量子比特系统：迈向可扩展的超导量子计算机

High-performance multiqubit system with double-transmon couplers: Toward scalable superconducting quantum computers

本文数值分析了由双Transmon耦合器（DTC）耦合的三固定频率量子比特系统，发现DTC在多比特系统中能有效抑制残余耦合，并以超99.99%保真度实现30 ns CZ门和10 ns π/2脉冲，性能优于单Transmon耦合器，有望助力可扩展超导量子计算。

基于极性分子的量子计算可扩展平台

Scalable platform for qudit-based quantum computing using polar molecules

本文提出利用极性分子的旋转态构建可扩展的量子处理器，通过光学镊子阵列实现指数级态空间扩展，无需增加量子比特维度，实现通用量子门集。

Phase gate of one qubit simultaneously controlling $n$ qubits in a cavity

We propose how to realize a three-step controlled-phase gate of one qubit simultaneously controlling $n$ qubits in a cavity or coupled to a resonator. The $n$ two-qubit controlled-phase gates, forming this multiqubit phase gate, can be performed simultaneously. The operation time of this phase gate is independent of the number $n$ of qubits. This phase gate controlling at once $n$ qubits is insensitive to the initial state of the cavity mode and can be used to produce an analogous CNOT gate simultaneously acting on $n$ qubits. We present two alternative approaches to implement this gate. One a…

利用相干冷原子系综实现手性相位调制和可调谐宽带完美吸收体

Chiral phase modulation and tunable broadband perfect absorber using the coherent cold atomic ensemble

本文研究线性空间Kramers-Kronig调制下相干冷原子系综的双通道非互易散射，实现手性相位调制和宽带可调谐相干完美吸收，为低功耗全光器件提供新方案。

用单个电路QED器件对自旋链进行顺序量子模拟

Sequential quantum simulation of spin chains with a single circuit QED device

本文提出用单个transmon-腔cQED器件顺序构建MPS来模拟自旋链基态，利用腔的大状态空间存储纠缠，并通过模拟脉冲控制显著缩短制备时间、降低退相干影响，为简化量子处理器设计提供新途径。