As a newly developed method for fabricating Josephson junctions,a focused helium ion beam has the advantage of producing reliable and reproducible junctions.We fabricated Josephson junctions with a focused helium ion ...As a newly developed method for fabricating Josephson junctions,a focused helium ion beam has the advantage of producing reliable and reproducible junctions.We fabricated Josephson junctions with a focused helium ion beam on our 50 nm YBa_(2)Cu_(3)O_(7-δ)(YBCO)thin films.We focused on the junction with irradiation doses ranging from 100 to 300 ions/nm and demonstrated that the junction barrier can be modulated by the ion dose and that within this dose range,the junctions behave like superconductor–normal conductor–superconductor junctions.The measurements of the I–V characteristics,Fraunhofer diffraction pattern,and Shapiro steps of the junctions clearly show AC and DC Josephson effects.Our findings demonstrate high reproducibility of junction fabrication using a focused helium ion beam and suggest that commercial devices based on this nanotechnology could operate at liquid nitrogen temperatures.展开更多
Besides serving as promising candidates for realizing quantum computing, superconducting quantum circuits are one of a few macroscopic physical systems in which fundamental quantum phenomena can be directly demonstrat...Besides serving as promising candidates for realizing quantum computing, superconducting quantum circuits are one of a few macroscopic physical systems in which fundamental quantum phenomena can be directly demonstrated and tested, giving rise to a vast field of intensive research work both theoretically and experimentally. In this paper we report our work on the fabrication of superconducting quantum circuits, starting from its building blocks： Al/AlOx/Al Josephson junctions. By using electron beam lithography patterning and shadow evaporation, we have fabricated aluminum Josephson junctions with a controllable critical current density （jc） and wide range of junction sizes from 0.01 μm2 up to 1 μm2. We have carried out systematical studies on the oxidation process in fabricating Al/AlOx/Al Josephson junctions suitable for superconducting flux qubits. Furthermore, we have also fabricated superconducting quantum circuits such as superconducting flux qubits and charge-flux qubits.展开更多
As a platform for holding Majorana zero models(MZMs),the two-dimensional planar topological Josephson junction that can be used as carriers for topological quantum computing faces some challenges.One is a combination ...As a platform for holding Majorana zero models(MZMs),the two-dimensional planar topological Josephson junction that can be used as carriers for topological quantum computing faces some challenges.One is a combination of mirror and time-reversal symmetries may make the system hold multiple pairs of MZMs.The other is that a soft gap dominated by a large momentum occurs in a clean system.To solve these problems,asymmetric junction can be introduced.Breaking this symmetry changes the symmetry class from class BDI to class D,and only a single pair of MZMs can be left at the boundary of the system.We numerically study four cases that create an asymmetric system and find out different superconducting pairing potential,different coupling coefficients between two-dimensional electron gases(2DEGs)and two superconducting bulks,different widths of two superconducting bulks make the gap of the system decrease at the optimal value,but make the gap at the minimum value increases.And the zigzag-shape quasi-one-dimensional junction eliminates the large momentum parallel to the junction and enhances the gap at the large momentum.However,the zigzag-shape junction cannot increase the gap at the region of multiple pairs of MZMs in a symmetric system.We show that by combining zigzag-shape junction with different coupling coefficients,the system can maintain a large gap(≈0.2△)in a wide region of the parameter space.展开更多
The design,fabrication,and the characterization of a 0.5-V Josephson junction array device are presented for the quantum voltage standards in the National Institute of Metrology(NIM)of China.The device consists of fou...The design,fabrication,and the characterization of a 0.5-V Josephson junction array device are presented for the quantum voltage standards in the National Institute of Metrology(NIM)of China.The device consists of four junction arrays,each of which has 12003-stacked Nb/NbxSi1-x/Nb junctions and an on-chip superconducting microwave circuit which is mainly a power divider enabling each Josephson array being loaded with an equal amount of microwave power.A direct current(dc)quantum voltage of about 0.5 V with a~1-mA current margin of the 1 st quantum voltage step is obtained.To further prove the quality of NIM device,a comparison between the NIM device with the National Institute of Standards and Technology(NIST)programmable Josephson voltage standard(PJVS)system device is conducted.The difference of the reproduced 0.5-V quantum voltage between the two devices is about 0.55 nV,which indicates good agreement between the two devices.With the homemade device,we have realized a precise and applicable 0.5-V applicable-level quantum voltage.展开更多
CSIRO has had a long-term research effort in superconductivity, in particular, since the discovery of HTS which promised big prospects. Significant progress has been made in research and development of HTS electronic ...CSIRO has had a long-term research effort in superconductivity, in particular, since the discovery of HTS which promised big prospects. Significant progress has been made in research and development of HTS electronic devices and systems for practical applications such as mineral and exploration as well as some niche applications in emerging science and technology areas. This article presents an overview of the CSIRO research activities in HTS supercon- ducting electronics since 1987, outlining the HTS junction and device technology as well as various application systems developed by the group.展开更多
Superconducting qubits are Josephson junction-based circuits that exhibit macroscopic quantum behavior and can be manipulated as artificial atoms. Benefiting from the well-developed technology of microfabrication and ...Superconducting qubits are Josephson junction-based circuits that exhibit macroscopic quantum behavior and can be manipulated as artificial atoms. Benefiting from the well-developed technology of microfabrication and microwave engineering, superconducting qubits have great advantages in design flexibility, controllability, and scalability. Over the past decade, there has been rapid progress in the field, which greatly improved our understanding of qubit decoherence and circuit optimization. The single-qubit coherence time has been steadily raised to the order of 10 to 100 p.s, allowing for the demonstration of high-fidelity gate operations and measurement-based feedback control. Here we review recent progress in the coherence and readout of superconducting qubits.展开更多
The transport characteristics of high temperature superconductor current and Josephson current is inves-tigated in the framework of the modified time-dependent Ginzburg-Landau model and the Lawrence-Doniach model.We e...The transport characteristics of high temperature superconductor current and Josephson current is inves-tigated in the framework of the modified time-dependent Ginzburg-Landau model and the Lawrence-Doniach model.We evaluated the vortex equation and found that the signs of the high temperature superconductor current and theJosephson current can reverse. Some explicit expressions for different cases are derived, which accord with experimentaldata.展开更多
We report the circuit simulations and experiments of millimeter-wave radiation from a high temperature superconducting(HTS) bicrystal Josephson junction(BJJ) array. To study the effects of junction characteristic para...We report the circuit simulations and experiments of millimeter-wave radiation from a high temperature superconducting(HTS) bicrystal Josephson junction(BJJ) array. To study the effects of junction characteristic parameters on radiation properties, new radiation circuit models are proposed in this paper. The series resistively and capacitively shunted junction(RCSJ) models are packaged into a Josephson junction array(JJA) model in the simulation. The current-voltage characteristics(IVCs) curve and radiation peaks are simulated and analyzed by circuit models, which are also observed from the experiment at liquid nitrogen temperature. The experimental radiation linewidth and power are in good agreement with simulated results. The presented circuit models clearly demonstrate that the inconsistency of the JJA will cause a broad linewidth and a low detected power. The junction radiation properties are also investigated at the optimal situation by circuit simulation. The results further confirm that the consistent JJA characteristic parameters can successfully narrow the radiation linewidth and increase the power of junction radiation.展开更多
The transport characteristics of high temperature superconductor current and Josephson current is inves-tigated in the framework of the modified time-dependent Ginzburg-Landau model and the Lawrence-Doniach model.We e...The transport characteristics of high temperature superconductor current and Josephson current is inves-tigated in the framework of the modified time-dependent Ginzburg-Landau model and the Lawrence-Doniach model.We evaluated the vortex equation and found that the signs of the high temperature superconductor current and theJosephson current can reverse. Some explicit expressions for different cases are derived, which accord with experimentaldata.展开更多
Future wireless communication systemembraces physical-layer signal detection with highsensitivity, especially in the microwave photon level.Currently, the receiver primarily adopts the signal detection based on semi-c...Future wireless communication systemembraces physical-layer signal detection with highsensitivity, especially in the microwave photon level.Currently, the receiver primarily adopts the signal detection based on semi-conductor devices for signal detection, while this paper introduces high-sensitivityphoton-level microwave detection based on superconducting structure. We first overview existing works onthe photon-level communication in the optical spectrum as well as the microwave photon-level sensingbased on superconducting structure in both theoreticaland experimental perspectives, including microwavedetection circuit model based on Josephson junction,microwave photon counter based on Josephson junction, and two reconstruction approaches under background noise. In addition, we characterize channelmodeling based on two different microwave photondetection approaches, including the absorption barrierand the dual-path Handury Brown-Twiss (HBT) experiments, and predict the corresponding achievablerates. According to the performance prediction, it isseen that the microwave photon-level signal detectioncan increase the receiver sensitivity compared withthe state-of-the-art standardized communication system with waveform signal reception, with gain over 10dB.展开更多
YBa 2Cu 3O 7-δ weak link junctions with width from 0.1 mm to 0.3 mm and length from 0.2 mm to 0.5 mm was made by hand with a razor blade. The current voltage characteristics of the microbridges show, under...YBa 2Cu 3O 7-δ weak link junctions with width from 0.1 mm to 0.3 mm and length from 0.2 mm to 0.5 mm was made by hand with a razor blade. The current voltage characteristics of the microbridges show, under microwave irradiation, pronounced Shapiro steps up to transition temperature. A careful measurement of the dependence of the critical supercurrent on the external magnetic field and laser light is presented.展开更多
The superconducting quantum interference device（SQUID） amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with...The superconducting quantum interference device（SQUID） amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with identical junctions and the series SQUIDs with different junctions were successfully fabricated. The Nb/Al-AlOx/Nb trilayer and input Nb coils were prepared by asputtering equipment. The SQUID devices were prepared by a sputtering and the lift-off method.Investigations by AFM, OM and SEM revealed the morphology and roughness of the Nb films and Nb/Al-AlOx/Nb trilayer.In addition, the current–voltage characteristics of the SQUID devices with identical junction and different junction areas were measured at 2.5 K in the He^3 refrigerator. The results show that the SQUID modulation depth is obviously affected by the junction area. The modulation depth obviously increases with the increase of the junction area in a certain range. It is found that the series SQUID with identical junction area has a transimpedance gain of 58 Ω approximately.展开更多
We report our progress in the high-temperature superconductor(HTS)Josephson junction fabrication process founded on utilizing a focused helium ion beam damaging technique and discuss the expected device performance at...We report our progress in the high-temperature superconductor(HTS)Josephson junction fabrication process founded on utilizing a focused helium ion beam damaging technique and discuss the expected device performance attainable with the HTS multi-junction device technology.Both the achievable high value of characteristic voltage V_(C)=I_(C)R_(N)of Josephson junctions and the ability to design a large number of arbitrary located Josephson junctions allow narrowing the existing gap in design abilities for lowtemperature superconductor(LTS)and HTS circuits even with using a single YBa_(2)Cu_(3)O_(7-x) film layer.A one-layer topology of active electrically small antenna is suggested and its voltage response characteristics are considered.展开更多
The superconducting tunneling effect in heterostructures,describing the process where single electrons or Cooper pairs tunnel through the barrier,can always play a significant role in understanding the phase coherence...The superconducting tunneling effect in heterostructures,describing the process where single electrons or Cooper pairs tunnel through the barrier,can always play a significant role in understanding the phase coherence and pairing mechanisms in superconductors.Taking advantage of the easy cleavage to atomically-thin monolayer structure of layered superconductors and resulting quantum confinement of electrons or Cooper pairs at two-dimensional limit,van der Waals superconducting materials hosting superconducting order in monolayers or heterostructures can exhibit extensive emergent phenomena associated with quantum phase transitions of vortex and anti-vortex pairs.Examples of superconducting tunnel junctions(STJs)based on layered superconductors have been demonstrated to achieve novel phenomena,including Andreev bound states,Majorana bound states and 0/π-phase junctions.Since the characteristic parameters of quasiparticle tunneling through the barrier are directly associated with the energy gap values of superconductors,such critical parameter can be obtained within the STJ device geometry,which helps us understand and control the pairing states and emerging phenomena in superconductors.In this review,from the perspective of STJs with single electron tunneling and Cooper pair tunneling,we discuss Andreev reflection,Majorana bound states,photon-induced tunneling effects,non-reciprocal transport and superconducting diode phenomena,as well as prospects for layered-superconductor-based STJs.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2017YFC0601901)the National Natural Science Foundation of China(Grant No.61571019)。
文摘As a newly developed method for fabricating Josephson junctions,a focused helium ion beam has the advantage of producing reliable and reproducible junctions.We fabricated Josephson junctions with a focused helium ion beam on our 50 nm YBa_(2)Cu_(3)O_(7-δ)(YBCO)thin films.We focused on the junction with irradiation doses ranging from 100 to 300 ions/nm and demonstrated that the junction barrier can be modulated by the ion dose and that within this dose range,the junctions behave like superconductor–normal conductor–superconductor junctions.The measurements of the I–V characteristics,Fraunhofer diffraction pattern,and Shapiro steps of the junctions clearly show AC and DC Josephson effects.Our findings demonstrate high reproducibility of junction fabrication using a focused helium ion beam and suggest that commercial devices based on this nanotechnology could operate at liquid nitrogen temperatures.
基金supported by the Science Foundation of the Ministry of Science and Technology of China (Grant Nos. 2011CBA00106 and 2009CB929102)the National Natural Science Foundation of China (Grant Nos. 11104333,10974243,and 11161130519)the Knowledge Innovation Program of the Chinese Academy of Sciences
文摘Besides serving as promising candidates for realizing quantum computing, superconducting quantum circuits are one of a few macroscopic physical systems in which fundamental quantum phenomena can be directly demonstrated and tested, giving rise to a vast field of intensive research work both theoretically and experimentally. In this paper we report our work on the fabrication of superconducting quantum circuits, starting from its building blocks： Al/AlOx/Al Josephson junctions. By using electron beam lithography patterning and shadow evaporation, we have fabricated aluminum Josephson junctions with a controllable critical current density （jc） and wide range of junction sizes from 0.01 μm2 up to 1 μm2. We have carried out systematical studies on the oxidation process in fabricating Al/AlOx/Al Josephson junctions suitable for superconducting flux qubits. Furthermore, we have also fabricated superconducting quantum circuits such as superconducting flux qubits and charge-flux qubits.
基金Project supported by the National Natural Science Foundation of China(Grant No.11974271)。
文摘As a platform for holding Majorana zero models(MZMs),the two-dimensional planar topological Josephson junction that can be used as carriers for topological quantum computing faces some challenges.One is a combination of mirror and time-reversal symmetries may make the system hold multiple pairs of MZMs.The other is that a soft gap dominated by a large momentum occurs in a clean system.To solve these problems,asymmetric junction can be introduced.Breaking this symmetry changes the symmetry class from class BDI to class D,and only a single pair of MZMs can be left at the boundary of the system.We numerically study four cases that create an asymmetric system and find out different superconducting pairing potential,different coupling coefficients between two-dimensional electron gases(2DEGs)and two superconducting bulks,different widths of two superconducting bulks make the gap of the system decrease at the optimal value,but make the gap at the minimum value increases.And the zigzag-shape quasi-one-dimensional junction eliminates the large momentum parallel to the junction and enhances the gap at the large momentum.However,the zigzag-shape junction cannot increase the gap at the region of multiple pairs of MZMs in a symmetric system.We show that by combining zigzag-shape junction with different coupling coefficients,the system can maintain a large gap(≈0.2△)in a wide region of the parameter space.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFF02000402)
文摘The design,fabrication,and the characterization of a 0.5-V Josephson junction array device are presented for the quantum voltage standards in the National Institute of Metrology(NIM)of China.The device consists of four junction arrays,each of which has 12003-stacked Nb/NbxSi1-x/Nb junctions and an on-chip superconducting microwave circuit which is mainly a power divider enabling each Josephson array being loaded with an equal amount of microwave power.A direct current(dc)quantum voltage of about 0.5 V with a~1-mA current margin of the 1 st quantum voltage step is obtained.To further prove the quality of NIM device,a comparison between the NIM device with the National Institute of Standards and Technology(NIST)programmable Josephson voltage standard(PJVS)system device is conducted.The difference of the reproduced 0.5-V quantum voltage between the two devices is about 0.55 nV,which indicates good agreement between the two devices.With the homemade device,we have realized a precise and applicable 0.5-V applicable-level quantum voltage.
文摘CSIRO has had a long-term research effort in superconductivity, in particular, since the discovery of HTS which promised big prospects. Significant progress has been made in research and development of HTS electronic devices and systems for practical applications such as mineral and exploration as well as some niche applications in emerging science and technology areas. This article presents an overview of the CSIRO research activities in HTS supercon- ducting electronics since 1987, outlining the HTS junction and device technology as well as various application systems developed by the group.
基金Project supported by the National Basic Research Program of China(Grant No.2012CB927404)the National Natural Science Foundation of China(Grant Nos.11222437 and 11174248)+2 种基金the Natural Science Foundation of Zhejiang Province,China(Grant No.LR12A04001)the Program for New Century Excellent Talents in University of Ministry of Education of China(Grant No.NCET-11-0456)the Synergetic Innovation Center of Quantum Information and Quantum Physics
文摘Superconducting qubits are Josephson junction-based circuits that exhibit macroscopic quantum behavior and can be manipulated as artificial atoms. Benefiting from the well-developed technology of microfabrication and microwave engineering, superconducting qubits have great advantages in design flexibility, controllability, and scalability. Over the past decade, there has been rapid progress in the field, which greatly improved our understanding of qubit decoherence and circuit optimization. The single-qubit coherence time has been steadily raised to the order of 10 to 100 p.s, allowing for the demonstration of high-fidelity gate operations and measurement-based feedback control. Here we review recent progress in the coherence and readout of superconducting qubits.
文摘The transport characteristics of high temperature superconductor current and Josephson current is inves-tigated in the framework of the modified time-dependent Ginzburg-Landau model and the Lawrence-Doniach model.We evaluated the vortex equation and found that the signs of the high temperature superconductor current and theJosephson current can reverse. Some explicit expressions for different cases are derived, which accord with experimentaldata.
基金Project supported by the National Natural Science Foundation of China(Grant No.51002081)the Fundamental Research Funds for the Central Universities,China+1 种基金the China Manned Space Advance Research Program,China(Grant No.030201)the Research Program of Application Foundation and Advanced Technology of Tianjin,China(Grant No.15JCQNJC01300)
文摘We report the circuit simulations and experiments of millimeter-wave radiation from a high temperature superconducting(HTS) bicrystal Josephson junction(BJJ) array. To study the effects of junction characteristic parameters on radiation properties, new radiation circuit models are proposed in this paper. The series resistively and capacitively shunted junction(RCSJ) models are packaged into a Josephson junction array(JJA) model in the simulation. The current-voltage characteristics(IVCs) curve and radiation peaks are simulated and analyzed by circuit models, which are also observed from the experiment at liquid nitrogen temperature. The experimental radiation linewidth and power are in good agreement with simulated results. The presented circuit models clearly demonstrate that the inconsistency of the JJA will cause a broad linewidth and a low detected power. The junction radiation properties are also investigated at the optimal situation by circuit simulation. The results further confirm that the consistent JJA characteristic parameters can successfully narrow the radiation linewidth and increase the power of junction radiation.
文摘The transport characteristics of high temperature superconductor current and Josephson current is inves-tigated in the framework of the modified time-dependent Ginzburg-Landau model and the Lawrence-Doniach model.We evaluated the vortex equation and found that the signs of the high temperature superconductor current and theJosephson current can reverse. Some explicit expressions for different cases are derived, which accord with experimentaldata.
基金National Key Research and Development Program of China(Grant No.2018YFB1801904)Key Program of National Natural Science Foundation of China(Grant No.61631018)Key Research Program of Frontier Sciences of CAS(Grant No.QYZDY-SSW-JSC003).
文摘Future wireless communication systemembraces physical-layer signal detection with highsensitivity, especially in the microwave photon level.Currently, the receiver primarily adopts the signal detection based on semi-conductor devices for signal detection, while this paper introduces high-sensitivityphoton-level microwave detection based on superconducting structure. We first overview existing works onthe photon-level communication in the optical spectrum as well as the microwave photon-level sensingbased on superconducting structure in both theoreticaland experimental perspectives, including microwavedetection circuit model based on Josephson junction,microwave photon counter based on Josephson junction, and two reconstruction approaches under background noise. In addition, we characterize channelmodeling based on two different microwave photondetection approaches, including the absorption barrierand the dual-path Handury Brown-Twiss (HBT) experiments, and predict the corresponding achievablerates. According to the performance prediction, it isseen that the microwave photon-level signal detectioncan increase the receiver sensitivity compared withthe state-of-the-art standardized communication system with waveform signal reception, with gain over 10dB.
文摘YBa 2Cu 3O 7-δ weak link junctions with width from 0.1 mm to 0.3 mm and length from 0.2 mm to 0.5 mm was made by hand with a razor blade. The current voltage characteristics of the microbridges show, under microwave irradiation, pronounced Shapiro steps up to transition temperature. A careful measurement of the dependence of the critical supercurrent on the external magnetic field and laser light is presented.
基金Project supported by the National Natural Science Foundation of China(Grant No.11653001)the National Basic Research Program of China(Grant No.2011CBA00304)Tsinghua University Initiative Scientific Research Program,China(Grant No.20131089314)
文摘The superconducting quantum interference device（SQUID） amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with identical junctions and the series SQUIDs with different junctions were successfully fabricated. The Nb/Al-AlOx/Nb trilayer and input Nb coils were prepared by asputtering equipment. The SQUID devices were prepared by a sputtering and the lift-off method.Investigations by AFM, OM and SEM revealed the morphology and roughness of the Nb films and Nb/Al-AlOx/Nb trilayer.In addition, the current–voltage characteristics of the SQUID devices with identical junction and different junction areas were measured at 2.5 K in the He^3 refrigerator. The results show that the SQUID modulation depth is obviously affected by the junction area. The modulation depth obviously increases with the increase of the junction area in a certain range. It is found that the series SQUID with identical junction area has a transimpedance gain of 58 Ω approximately.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1603900)in part by the Russian Science Foundation(RSCF)(Grant No.19-72-10016-P).
文摘We report our progress in the high-temperature superconductor(HTS)Josephson junction fabrication process founded on utilizing a focused helium ion beam damaging technique and discuss the expected device performance attainable with the HTS multi-junction device technology.Both the achievable high value of characteristic voltage V_(C)=I_(C)R_(N)of Josephson junctions and the ability to design a large number of arbitrary located Josephson junctions allow narrowing the existing gap in design abilities for lowtemperature superconductor(LTS)and HTS circuits even with using a single YBa_(2)Cu_(3)O_(7-x) film layer.A one-layer topology of active electrically small antenna is suggested and its voltage response characteristics are considered.
基金support of the National Natural Science Foundation of China(Grant Nos.92365203,52072168,51861145201).
文摘The superconducting tunneling effect in heterostructures,describing the process where single electrons or Cooper pairs tunnel through the barrier,can always play a significant role in understanding the phase coherence and pairing mechanisms in superconductors.Taking advantage of the easy cleavage to atomically-thin monolayer structure of layered superconductors and resulting quantum confinement of electrons or Cooper pairs at two-dimensional limit,van der Waals superconducting materials hosting superconducting order in monolayers or heterostructures can exhibit extensive emergent phenomena associated with quantum phase transitions of vortex and anti-vortex pairs.Examples of superconducting tunnel junctions(STJs)based on layered superconductors have been demonstrated to achieve novel phenomena,including Andreev bound states,Majorana bound states and 0/π-phase junctions.Since the characteristic parameters of quasiparticle tunneling through the barrier are directly associated with the energy gap values of superconductors,such critical parameter can be obtained within the STJ device geometry,which helps us understand and control the pairing states and emerging phenomena in superconductors.In this review,from the perspective of STJs with single electron tunneling and Cooper pair tunneling,we discuss Andreev reflection,Majorana bound states,photon-induced tunneling effects,non-reciprocal transport and superconducting diode phenomena,as well as prospects for layered-superconductor-based STJs.
