Quantum search via superconducting quantum interference devices in a cavity

We propose a scheme for implementing the Grover search algorithm with two superconducting quantum interference devices (SQUIDs) in a cavity. Our scheme only requires single resonant interaction of the SQUID-cavity system and the required interaction time is very short. The simplicity of the process and the reduction of the interaction time are important for restraining decoherence.     

Quantum controlled phase gate and cluster states generation via two superconducting quantum interference devices in a cavity

A scheme for implementing 2-qubit quantum controlled phase gate (QCPG) is proposed with two superconducting quantum interference devices (SQUIDs) in a cavity. The gate operations are realized within the two lower flux states of the SQUIDs by using a quantized cavity field and classical microwave pulses. Our scheme is achieved without any type of measurement, does not use the cavity mode as the data bus and only requires a very short resonant interaction of the SQUID-cavity system. As an application of the QCPG operation, we also propose a scheme for generating the cluster states of many SQUIDs.     

Persistent currents in superconducting quantum interference devices

Starting from the reduced dynamical model of a two-junction quantum interference device, it shown that a quantum analog of the system can be exhibited. This quantum model extends the well-known properties of the device when its characteristic dimensions are of the order of mesoscopic length scales. By finding eigenvalues of the corresponding Hamiltonian operator, the persistent currents flowing in the ring have been obtained. The resulting quantum analog of the overdamped two-junction quantum interference device can be seen as a supercurrent qubit operating in the limit of negligible capacitance and finite inductance.     

高温超导量子干涉器中的约瑟夫森结

超导量子干涉器（SQUID）是以约瑟夫森结为核心元件的极其灵敏的磁通-电压转换器.在最近20年间,超导电子学界利用多种铜氧化物高温超导材料,制造出了高温超导约瑟夫森结乃至高温超导量子干涉器（高Tc SQUID）;特别是,利用YBa2Cu3O7-δ（YBCO）制出了多种高温超导约瑟夫森结,并进而制成了具有一定实用性的高Tc SQUID.文章主要是对高Tc SQUID中所使用的高温超导约瑟夫森结进行评述.     

Implementation of quantum partial search with superconducting quantum interference device qudits in cavity QED

We present a method to implement the quantum partial search of the database separated into any number of blocks with qudits,D-level quantum systems.Compared with the partial search using qubits,our method needs fewer iteration steps and uses the carriers of the information more economically.To illustrate how to realize the idea with concrete physical systems,we propose a scheme to carry out a twelve-dimensional partial search of the database partitioned into three blocks with superconducting quantum interference devices(SQUIDs)in cavity QED.Through the appropriate modulation of the amplitudes of the microwave pulses,the scheme can overcome the non-identity of the cavity–SQUID coupling strengths due to the parameter variations resulting from the fabrication processes.Numerical simulation under the influence of the cavity and SQUID decays shows that the scheme could be achieved efficiently within current state-of-the-art technology.     

Low-field magnetic response of multi-junction superconducting quantum interference devices

The magnetic states of multi-junction superconducting quantum interference device containing 2N identical conventional Josephson junctions are studied by means of a perturbation analysis of the non-linear first-order ordinary differential equations governing the dynamics of the Josephson junctions in these devices. In the zero-voltage state, persistent currents are calculated in terms of the externally applied magnetic flux Φ_ex . The resulting d.c. susceptibility curves show that paramagnetic and diamagnetic states are present, depending on the value of Φ_ex . The stability of these states is qualitatively studied by means of the effective potential notion for the system.     

基于SQUIDs和腔场相互作用传送量子信息的方案

本文提出了一个基于SQUIDs和腔场的大失谐相互作用传送量子信息的方案,此方案可以直接地、百分之百地实现量子信息的传送.该方案中腔场和SQUIDs系统之间没有量子信息的传递,腔场只是虚激发,这样对腔的品质因子的要求大大的降低了.同时也可以在SQUIDs之间建立传送量子信息的量子网络.     

基于SQUIDs和腔场相互作用传送量子信息的方案

本文提出了一个基于SQUIDs和腔场的大失谐相互作用传送量子信息的方案,此方案可以直接地、百分之百地实现量子信息的传送。该方案中腔场和SQUIDs系统之间没有量子信息的传递,腔场只是虚激发, 这样对腔的品质因子的要求大大的降低了。同时也可以在SQUIDs之间建立传送量子信息的量子网络。     

利用超导量子相干装置制备纠缠态的方案(英文)

本文提出用两个超导量子相干装置在一个单模大失谐腔中制备一个最大纠缠态的新方案,在这个方案里,腔场态处于虚激发,在超导量子相干装置和腔场之间没有信息传递,因此对腔的品质要求大大减低.     

Holonomic quantum computation with superconducting charge-phase qubits in a cavity

We theoretically propose a feasible scheme to realize holonomic quantum computation with charge-phase qubits placed in a microwave cavity. By appropriately adjusting the controllable parameters, each charge-phase qubit is set as an effective four-level subsystem, based on which a universal set of holonomic quantum gates can be realized. Further analysis shows that our system is robust to the first-order fluctuation of the gate charges, and the intrinsic leakages between energy levels can be ignored.     

用于高温射频超导量子干涉器的介质谐振器的性质研究

介质谐振器是目前高温射频超导量子干涉器较常采用的一种高品质因数微波谐振器.它是由10 mm×10 mm×1 mm的SrTiO₃(STO)标准衬底及覆盖在其上的YBa₂Cu₃O_7-δ(YBCO)薄膜磁通聚焦器共同构成的.为探明磁通聚焦器构形对介质谐振器谐振频率的影响,本文采用Ansoft公司出品的HFSS高频结构仿真软件对磁通聚焦器构形不同的若干介质谐振器的谐振特性进行了仿真.结果表明:增大磁通聚焦器开     

Optimal symmetric economical phase-covariant quantum cloning

We derive the explicit transformation of the optimal symmetric economical 1→M$1\to M$ phase-covariant quantum cloning machine (EPCCM), which works without ancilla, as well as the corresponding fidelities in 2-dimension. The fidelity (1→M=2k+1 EPCCM$1\to M=2k+1\text{EPCCM}$) is covered with previous contributions [G.M. D'Ariano, et al., Phys. Rev. A 71 (2005) 042327]. Meanwhile, the explicit transformation of the optimal symmetric 1→M$1\to M$ phase-covariant quantum cloning machine (PCCM) (working with ancilla) as well as the corresponding fidelities in 2-dimension is also derived. The results of the PCCM agree with previous contributions [H. Fan, et al., Phys. Rev. A 65 (2001) 012304].     

A new type of HTc superconducting film comb-shape resonator for radio frequency superconducting quantum interference devices

A new type of HTc superconducting film combshape resonator for radio frequency superconducting quantum interference devices (RF SQUID) has been designed. This new type of superconducting film comb-shape resonator is formed by a foursquare microstrip line without a flux concentrator. The range of the center frequency of this type of resonator varies from 800 MHz to 1 300 MHz by changing the length of the teeth. In this paper, we report on simulating the relationship of the value of the center frequency and the length of the teeth, and testing the noise of HTc RF SQUID coupling this comb-shape resonator. __________ Translated from Chinese Journal of Low Temperature Physics, 2005, 27(3) (in Chinese)     

Scheme for implementing an economical phase-covariant quantum cloning machine of distant atomic qubits with single-photon interference

By means of cavity-assisted photon interference, a simple scheme is proposed to implement a symmetric economical phase-covariant quantum cloning machine of two remote qubits, with each in a separate cavity. With our present scheme, a high-fidelity cloning machine is realized. Our scheme may be quite useful in terms of distributed quantum information processing.     

腔QED技术实现最优非对称经济型1到3的相位协变克隆方案

本文提出一个在腔QED中实现最优非对称经济型1到3相位协变克隆的可行性方案,这种克隆不需要辅助粒子.在这个方案中,三个原子中的两个同时与腔场发生作用,并且受经典场的作用.此方案不受腔场的态和腔衰变的影响,因此,在实验上是可能实现的.     

利用腔QED技术实现最优非对称经济型1到3的相位协变克隆

本文提出一个在腔QED中实验上可行的方案来实现最优非对称经济型1到3相位协变克隆,这种克隆是不需要辅助粒子的。在这个的方案中,三个原子中的两个同时与腔场发生作用,并且它们受经典场的作用。并且此方案不受腔场的态和腔衰变的影响,因此,在实验上是可能实现的。     

在腔QED中实现最优非对称经济型1到3的相位协变克隆方案

本文提出一个在腔QED中实验上可行的方案来实现最优非对称经济型1到3相位协变克隆,这种克隆是不需要辅助粒子的。在这个的方案中,三个原子中的两个同时与腔场发生作用,并且它们受经典场的作用。并且此方案不受腔场的态和腔衰变的影响,因此,在实验上是可能实现的。     

在腔耦合的超导量子比特中实现几何量子信息处理

用量子空腔耦合的超导电荷比特器件被认为是实现量子信息处理的相当有希望的体系之一.如何在这种可集成的量子体系中实现高保真度的操作是量子信息处理领域的重要课题.文章介绍作者最近提出的在量子腔耦合的超导量子比特中用具有内禀容错功能的几何操作来实现普适量子逻辑门,产生多比特量子纠缠及实现量子纠错编码的一个可行方案.     

超导量子干涉器件

超导现象是一种宏观量子现象.磁通量子化和约瑟夫森效应是两个最能体现这种宏观量子特性的物理现象.超导量子干涉器件(superconducting quantum interference device,SQUID)是利用这两个特性而形成的超导器件.SQUID器件在磁信号灵敏探测方面具有广泛的应用.本文简要介绍低温超导和高温超导SQUID器件的相关背景和发展现状以及应用领域.     

Nanowire acting as a superconducting quantum interference device

We present the results from an experimental study of the magnetotransport of superconducting wires of amorphous indium-oxide having widths in the range 40-120 nm. We find that, below the superconducting transition temperature, the wires exhibit clear, reproducible, oscillations in their resistance as a function of magnetic field. The oscillations are reminiscent of those that underlie the operation of a superconducting quantum interference device.