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quantum search via superconducting quantum interference devices in a cavity

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Chinese Physics B 2007年第12期16卷 3601-3604页

作者：卢艳董萍薛正远曹卓良 Key Laboratory of Opto-electronic Information Acquisition and Manipulation Ministry of Education School of Physics and Material Science Anhui University Hefei 230039 China

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.

关键词： Grover search algorithm superconducting quantum interference devices

Multiplexing technology based on SQUID for readout of superconducting transition-edge sensor arrays

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Chinese Physics B 2022年第10期31卷 220-230页

作者： Xinyu Wu Qing Yu Yongcheng He Jianshe Liu Wei Chen School of Integrated Circuits Tsinghua UniversityBeijing 100084China

Multiplexing technologies based on superconducting quantum interference devices(SQUIDs) are crucial to cryogenic readout of superconducting transition-edge sensor(TES) arrays. Demands for large-scale TES arrays promote the development of multiplexing technologies towards large multiplexing factors and low readout noise. The development of multiplexing technologies also facilitates new applications of TES arrays in a wide range of frequencies. Here we summarize different types of SQUID-based multiplexing technologies including time-division multiplexing, code-division multiplexing, frequency-division multiplexing and microwave SQUID multiplexing. The advances and parameter constraints of each multiplexing technology are also discussed.

关键词： superconducting transition-edge sensor arrays superconducting quantum interference devices multiplexing technology cryogenic readout

Jnconventional Geometric Phase Gate with superconducting quantum interference Device Qubits in Cavity QED

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Communications in Theoretical Physics 2008年第4期49卷 913-918页

作者： YANG Wen-Xing CHEN Ai-Xi Department of Physics Southeast University Nanjing 210096 China State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Center for Cold Atom Physics Wuhan Institute of Physics and Mathematics the Chinese Academy of Sciences Wuhan 430071 China Department of Physics East China Jiaotong University Nanchang 330013 China

In the system with superconducting quantum interference devices （SQUID） in cavity, a scheme for constructing two-qubit quantum phase gate via a conventional geometric phase-shift is proposed by using a quantized cavity field and classical microwave pulses. In this scheme, the gate operation is realized in the subspace spanned by the two lower flux states of the SQUID system mud the population operator of the excited state has no effect on it. Thus the effect of decoherence caused from the levels of the SQUID system is possible to minimize. Under cavity decay, our strictly numerical simulation shows that it is also possible to realize the unconventional geometric phase gate. The experimental feasibility is discussed in detail.

关键词： superconducting quantum interference devices cavity QED geometric quantum gates

Study on signal intensity of low field nuclear magnetic resonance via an indirect coupling measurement

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Chinese Physics B 2013年第4期22卷 36-39页

作者：蒋凤英王宁金贻荣邓辉田野郎佩琳李洁陈莺飞郑东宁 School of Science Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Institute of Physics Chinese Academy of Sciences

We carry out an ultra-low-field nuclear magnetic resonance （NMR） experiment based on high-T c superconducting quantum interference devices （SQUIDs）. The measurement field is in a micro-tesla range （～10 μT-100 μT） and the experiment is conducted in a home-made magnetically-shielded-room （MSR）. The measurements are performed by the indirect coupling method in which the signal of nuclei precession is indirectly coupled to the SQUID through a tuned copper coil transformer. In such an arrangement, the interferences of applied measurement and polarization field to the SQUID sensor are avoided and the performance of the SQUID is not destroyed. In order to compare the detection sensitivity obtained by using the SQUID with that achieved using a conventional low-noise-amplifier, we perform the measurements using a commercial room temperature amplifier. The results show that in a wide frequency range （～1 kHz-10 kHz） the measurements with the SQUID sensor exhibit a higher signal-to-noise ratio. Further, we discuss the dependence of NMR peak magnitude on measurement frequency. We attribute the reduction of the peak magnitude at high frequency to the increased field inhomogeneity as the measurement field increases. This is verified by compensating the field gradient using three sets of gradient coils.

关键词： indirect coupling measurement superconducting quantum interference devices low field nuclearmagnetic resonance

Low-T_c direct current superconducting quantum interference device magnetometer-based 36-channel magnetocardiography system in a magnetically shielded room

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Chinese Physics B 2015年第7期24卷 590-594页

作者：邱阳李华张树林王永良孔祥燕张朝祥张永升徐小峰杨康谢晓明 State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information TechnologyChinese Academy of Sciences Joint Research Laboratory on Superconductivity and Bioelectronics Collaboration between Chinese Academy of Sciences–Shanghai University of Chinese Academy of Sciences

We constructed a 36-channel magnetocardiography（MCG） system based on low-Tc direct current（DC） superconducting quantum interference device（SQUID） magnetometers operated inside a magnetically shielded room（MSR）. Weakly damped SQUID magnetometers with large Steward–Mc Cumber parameter βc（βc≈ 5）, which could directly connect to the operational amplifier without any additional feedback circuit, were used to simplify the readout electronics. With a flux-to-voltage transfer coefficient V / Φ larger than 420 μV/Φ0, the SQUID magnetometers had a white noise level of about 5.5 f T·Hz-1/2when operated in MSR. 36 sensing magnetometers and 15 reference magnetometers were employed to realize software gradiometer configurations. The coverage area of the 36 sensing magnetometers is 210×210 mm2. MCG measurements with a high signal-to-noise ratio of 40 d B were done successfully using the developed system.

关键词： superconducting quantum interference devices magnetometer magnetocardiography noise can-cellation