排序方式: 共有144条查询结果,搜索用时 71 毫秒
41.
LI Chong GAO Yi-Bo 《理论物理通讯》2007,48(5):935-942
We revisit the protocols to create maximally entangled states between two Josephson junction (33) charge phase qubits coupled to a microwave field in a cavity as a quantum data bus. We analyze a novel mechanism of quantum decoherence due to the adiabatic entanglement between qubits and the data bus, the off-resonance microwave field. We show that even if the variable of the data bus can be adiabatically eliminated, the entanglement between the qubits and data bus remains and can decohere the superposition of two-particle state. Fortunately we can construct a decoherencefree subspace of two-dimension to against this adiabatic decoherence. To carry out the analytic study for this decoherence problem, we develop Frohlich transformation to re-derive the effective Hamiltonian of these systems, which is equivalent to that obtained from the adiabatic elimination approach. 相似文献
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Shiv P. Patel J.C. PivinA.K. Chawla Ramesh ChandraD. Kanjilal Lokendra Kumar 《Journal of magnetism and magnetic materials》2011,323(22):2734-2740
The magnetic properties of Zn1−xCoxS (x=0.025 and 0.05) thin films grown on α-quartz substrates at different temperatures (TS) of 200, 400 and 600 °C by means of pulsed laser deposition are presented. The films are crystallized with wurtzite structure. Optical absorption and transmission electron microscopy measurements indicate that Co ions are substituted to Zn on tetrahedral sites. Their magnetic response is composed of ferromagnetic and paramagnetic components of which respective strengths depend on TS and Co concentration. This behavior is interpreted as due to fluctuations in the magnetic ordering, depending on grain size and site location in grain boundaries or in crystal cores. 相似文献
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A K Gupta Neeraj Khare D K Walia V S Tomar V N Ojha H C Pandey S K Bhatnagar Y K Jain 《Pramana》1990,35(2):L193-L198
DC SQUID structure consisting of two microbridges and a circular hole was patterned on BSCCO thick film using laser ablation
technique. Quantum interference effects on these patterned films were studied at fixed biasing current by applying changing
magnetic field. The SQUID with 100 μm × 70 μm microbridges showed noisy and irregular V-B behaviour whereas the SQUID containing
smaller microbridges showed better V-B characteristic. Temperature dependence of the I-V and V-B characteristics of the SQUID
is also reported. 相似文献
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从量子力学诞生以来,关于宏观物体的运动是否遵循量子力学的辩论就一直没有停止过。上世纪八十年代初期以来,一系列在约瑟夫森结和超导量子干涉器件(SQUID)中观测到的实验结果,包括相位和磁通的宏观量子隧穿,能级量子化,宏观共振隧穿,和在微波驱动下的相干动力学过程对认为宏观物体的运动在满足一定条件下同样遵循量子力学规律的观点提供了强有力的实验证据。在众多已观察到的宏观量子现象中,宏观共振隧穿结合了能级分立和隧穿这两个最具特征的量子现象。由于宏观共振隧穿的观测无需使用高频电磁波激发,这就避免了实验结果也可以用经典物理解释的可能,所以在一个系统中观测到宏观共振隧穿可以说是展示该系统的量子属性的最有力证据。本文讨论近年来从理论和实验两方面理解耗散和磁通噪声对类似SQUID的双势阱系统宏观共振隧穿率和谱线形状的影响。评述宏观共振隧穿谱的测量在探寻、理解、克服超导磁通量子比特中的退相干机制并最终实现规模化量子计算方面的应用。 相似文献
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S. Arumugam S. Natarajan V. S. Sastry T. Geethakumary T. S. Radhakrishnan V. Sankaranarayanan 《Phase Transitions》2013,86(3-4):251-258
A new compound, NdBa2Ca3Sr4Cu5Ox, has been synthesised using the conventional solid state reaction technique. The material was characterised by powder XRD, electrical resistivity, ac susceptibility and dc magnetisation studies. The results of powder X-ray diffraction show that the structure is pseudo orthorhombic, having unit cell dimensions a = 5.47 Å, b = 5.46 Å and c = 14.58 Å. Magnetisation studies on a SQUID magnetometer showed a superconducting transition at 52 K. This was confirmed by the measurements of electrical resistance and ac susceptibility of this sample, which also showed superconductivity at 52 K. Details of preparation and characterisation are discussed. 相似文献
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文提出了一种新型磁通聚焦器和谐振器. 磁通聚焦器引入了单互补开环谐振器结构 (单CSRR); 谐振器则采用环绕着绕磁通聚焦器的发夹型3阶阶梯阻抗谐振器 (SIR). 采用ANSYS HFSSv.11高频结构仿真软件对提出的磁通聚焦器和谐振器进行了仿真, 并对单CSRR进行了理论分析. 仿真和理论分析表明: 单CSRR的引入, 提高了磁通聚焦器的聚磁效果, 改善了磁通聚焦器与RF SQUID垫圈的耦合(耦合系数ksc为引入单CSRR前的2倍), 并且有效面积增大到1.227 mm2. 相似文献
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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。 相似文献