Search

We have investigated the microwave response of a transmon qubit coupled directly to a transmission line. In a transmon qubit, owing to its weak anharmonicity, a single driving field may generate dressed states involving more than two bare states. We confirmed the formation of three-state dressed states by observing all of the six associated Rabi sidebands, which appear as either amplification or attenuation of the probe field. The experimental results are reproduced with good precision by a theoretical model incorporating the radiative coupling between the qubit and the microwave. [ABSTRACT FROM AUTHOR]

We have developed high-quality epitaxial NbN/AlN/NbN Josephson tunnel junctions with a wide range of current density Jc. The junctions show excellent tunneling properties with a large gap voltage of 5.6 mV and a large IcRN product of 3.5 mV. The quality factor Rsg/RN is about 60 for the junctions with a Jc of 2.2 A/cm2, and above 10 for the junctions with a Jc of 25 kA/cm2. The crystal structures across the junction barrier are investigated using x-ray diffraction and cross-sectional scanning transmission electron microscopy, and demonstrate epitaxial growth of the NbN/AlN/NbN trilayers for the wide range of Jc. [ABSTRACT FROM AUTHOR]

We developed an optical input module consisting of built-in metal-semiconductor-metal photodiodes (MSM-PDs) and co-planar waveguide transmission lines fabricated on an InP substrate, which is flip-chip bonded with a single-flux-quantum (SFQ) circuit fabricated on a Si substrate. To improve photosensitivity of the MSM-PD for a wavelength above 1530 nm at 4 K, we tested the MSM-PDs made of lattice mismatched In1-xGa_xAs films on InP substrates. By employing In1-xGa_xAs with x=0.44, an apparent reduction of photosensitivity for a wavelength above 1530 nm was suppressed. We also tested newly designed DC/SFQ converters with higher input current sensitivities. The observed current sensitivity was improved to 41 \muA, while that in the conventional DC/SFQ converter was 140 \muA. [ABSTRACT FROM AUTHOR]

Superconducting qubit circuits require high quality low critical current density Josephson tunnel junctions. We have developed high quality epitaxial NbN/AlN/NbN tunnel junctions with critical current density, Jc, ranging from as low as a few A/cm^2 to a few tens of kA/cm^2. In this work, we measured current–voltage characteristics for junctions with a Jc\sim 32\ \rm A/cm^2 in the temperature range from 17 mK to above 6.7 K. All the junctions are in good quality and have a high gap voltage (>5.5 mV). We found that the junctions' sub-gap resistances were temperature dependent above 2.5 K and saturated at temperatures below 2.5 K. A junction sub-gap leakage current Ir of about 23 pA was measured. The voltage noise power spectral density for 3 junctions with different sizes has been measured at the base temperature of 17 mK with the junctions biased above the gap voltage. The spectral densities clearly show 1/f behavior at low frequency and are proportional to the junction's linear dimension. [ABSTRACT FROM AUTHOR]

A group of 23 patients with partial atrophic change of the tongue was examined for candidiasis. All of them reported pain in the tongue on eating hot or spicy food. The intensity of the tongue pain was evaluated before and after treatment using a visual analogue scale. Of the 23 patients, 10 (43.5%) had predisposing factors for candidiasis such as diabetes mellitus and anaemia. In the culture examination, candidal species were isolated in 65.2%, all Candida albicans. Direct cytological examination performed in 10 of the 23 patients revealed fungal pseudohyphae in 8 patients. After antifungal treatment, tongue pain had disappeared or improved markedly in 82.6%. Simultaneously, the filiform papilla of the atrophic site was observed to have begun to regenerate in these patients. Candida infection should be suspected in patients with partial atrophic tongue associated with pain on eating. [ABSTRACT FROM AUTHOR]

Objective: Occasionally, the clinical diagnosis of Candida-associated lesion is difficult because of a variety of its clinical manifestations. There have been a few reports on Candida-associated lip lesion except angular cheilitis. In this paper, we investigate the relation of Candida in persistent lesions of the lip. Subjects and methods: The present study includes consecutive nine patients with persistent erosive lip lesion. For each patient the age at presentation, gender, duration of the disease, other symptoms or signs, complete medical history and prior treatment or medications for the symptom were obtained. Then, mycological examination and the direct cytologic examination were performed. Results: The reported average duration of the disease was 7 months. Six of nine patients had received prior treatments with topical steroids at the other clinic, which failed to resolve their symptoms. Six of nine patients had a predisposing factor for candidiasis. In the culture examination, Candida albicans were isolated in seven patients (77.8%). Five of nine patients received the direct cytologic examination, and four of them revealed pseudohyphae of fungi. The anti-fungal treatment was miconazol gel 25 mg four times per day, and average duration of the treatment was 2 weeks. The outcome was as follows: complete remission in five, remarkable response in two and no response in two. Conclusion: Our results suggested that one form of the varieties of Candida-associated lesions might be considered in the case of lip lesion with unknown origin that was persistent and ineffective to the topical steroids treatment. [ABSTRACT FROM AUTHOR]

BACKGROUND: Traditionally, total atrophic tongue has been due to nutritional deficiencies, such as vitamin B12, folic acid, or iron deficiencies, and partial atrophic tongue has been well known as median rhomboid glossitis or geographic tongue. The other cause of atrophic tongue is oral candidiasis. METHODS: Forty patients with atrophic change of the tongue were examined on a relation to candidiasis. All of them complained of tongue pain on spicy or hot diet. Laboratory examinations included blood examination for diabetes and anemia, culture test and direct cytologic examination. The intensity of tongue pain was evaluated pre- and post-treatment using visual analogue scale (VAS). RESULTS: Twenty-four of 40 (60%) had pre-disposing factors of candidiasis including diabetes mellitus, malignancy, systemic steroid therapy, long-term antibiotic therapy and others in their medical history. Blood examinations revealed mild anemia and/or Fe deficiency in 5 (12.5%), mild diabetes in 4 (10.0%), both in two, while residual 29 patients (72.5%) were within reference levels. In the culture examination, candidal species were isolated in 72.5%, and almost all of them were candida albicans. The direct cytologic examination performed in 17 of 40 patients, witch revealed pseudohyphae of fungi in 14 patients (82.4%). After the antifungal treatment, the tongue pain disappeared or improved markedly in 80%. Simultaneously, the regenerative tendency of filifolm papilla of the tongue dorsum was observed in these patients. CONCLUSION: Atrophic tongue associated with pain at eating, even though it is mild atrophic change, has a high probability of being a candida-induced lesion. Long disease duration and no benefit by topical steroids are suggestive and diagnostic factors of this disease. [ABSTRACT FROM AUTHOR]

We demonstrate superconducting qubits using epitaxially grown Josephson junctions. A fully epitaxial NbN/AlN/NbN trilayer on MgO (100) substrate is processed by photolithography and dry-etching into transmon qubits with a large Josephson energy. The tunnel barrier made of cubic-phase AlN, rather than the ordinary hexagonal phase, is the key to avoid piezoelectric coupling to the phonon bath. The energy-relaxation time and the spin-echo decay time of ∼500 ns are observed in the qubits that are coupled to a monolithically made coplanar waveguide resonator. [ABSTRACT FROM AUTHOR]

Objective: We investigated patients with tongue pain to examine whether the differential diagnosis of burning mouth syndrome and Candida-associated lesion was possible. Patients and methods: Sixty patients with tongue pain were divided into three groups according to the intensity of pain at rest and that when eating using the visual analogue scale: Group A: Functional pain group. Group B: Non-functional pain group. Group C: Mixed pain group. Antifungal treatment was scheduled for patients suspected clinically, mycologically or cytologically as having candidal infection. Results: The results of the culture test and direct examination indicated that group A was different from others by its high positivity for Candida, a good response to the antifungal treatment was obtained. On the other hand, antifungal treatment was not useful in group B, and the low possibility of Candida infection in the direct examination supported the result in this group. In group C, the positivity of Candida and the effect of the antifungal treatment were between groups A and B. Conclusion: These results may suggest that tongue pain in group A is Candida-associated, that in group B is burning mouth syndrome-induced and that of group C is mixed conditions. [ABSTRACT FROM AUTHOR]

Proposes and demonstrates a high-temperature superconductor multilayer structure. Details on the isolation resistance between the ground plane and other layers of the YBCO; Effects of the high temperature process during ground plane formation; Information on the measured voltage modulations of the super-conducting quantum interference device.

We demonstrate the operation of a coincidence photon detector with a short timing jitter consisting of two superconducting nanowire single photon detectors (SSPDs) and a single flux quantum (SFQ) circuit. By utilizing the timing discrimination capability of the SFQ coincidence circuit, the full width at half maximum timing jitter of the entire coincidence photon detector was evaluated as 32.3 ps, which is 36 ps less than that of the standard commercial time correlated single photon counting module, and the timing jitter of the SSPD was estimated as ∼15 ps. Owing to the short timing jitter characteristics, our coincidence photon detector could correctly capture the effect of pulse-width broadening by insertion of an optical bandpass filter. We have also demonstrated that our coincidence photon detection clearly shows Hong-Ou-Mandel interference with a weak coherent pulse. These results are a crucial step to realizing high timing resolution coincidence measurements, ushering in a technology for timing measurement based multi-photon quantum interference. [ABSTRACT FROM AUTHOR]

We report two patients with chronic tongue ulceration who were successfully treated using sulpiride. The clinical diagnosis was oral candidiasis related to long-term steroid treatment. The results of the culture test and cytological examination supported this diagnosis, but antifungal treatment was ineffective and the tongue pain in these patients became more severe. Furthermore, the pain could not be relieved by nonsteroidal anti-inflammatory drugs (NSAIDs). We therefore prescribed sulpiride in addition to NSAIDs to reduce the tongue pain. A consequent improvement in both pain severity and ulceration was observed 2–3 weeks after sulpiride administration. [ABSTRACT FROM AUTHOR]

Study Design: Prospective multicenter study. Objective: To identify radiographic or magnetic resonance (MR) images of fresh vertebral fractures that can predict a high risk for delayed union or nonunion of osteoporotic vertebral fractures (OVFs). Summary Of Background Data: Vertebral body fractures are the most common fractures in osteoporosis patients. Conservative treatments are typically chosen for OVFs, and associated back pain generally subsides within several weeks with residual persistent deformity of the vertebral body. In some patients, OVF healing is impaired and correlated with prolonged back pain. However, assessments such as plain radiograph or MR images taken during the early phase to predict high risks for nonunions of OVFs and/or poor prognoses have not been identified. Methods: A total of 350 OVF patients from 25 institutes were enrolled in this clinical study. Plain radiograph and MR images of the OVFs were routinely taken at enrollment at the respective institutes. The findings on the plain radiograph and MR images were classified after enrollment in the study. All the patients were treated conservatively without any surgical intervention. After a 6-month follow-up, the patients were classified into two groups, a union group and a nonunion group, depending on the presence of an intravertebral cleft on plain radiograph or MR images. The associations of the images from the first visit with those of the corresponding nonunions at the 6-month follow-up were analyzed by multivariate logistic regression to elucidate specific image characteristics that may predict a high risk for nonunion of OVFs. Results: Forty-eight patients (49 vertebrae) among the 350 patients (363 vertebrae) were classified as nonunions, indicating a nonunion incidence of 13.5% for conventional conservative treatments for OVFs. The statistical analyses revealed that a vertebral fracture in the thoracolumbar spine, presence of a middle-column injury, and a confined high intensity or a diffuse low intensity area in the fractured vertebrae on T2-weighted MR images were significant risk factors for nonunion of OVFs. Conclusion: The results of this study revealed significant relationships between plain radiograph and MR images of acute phase OVFs and the incidence of nonunion. As these risk factors are defined more clearly and further validated, they may become essential assessment tools for determining subsequent OVF treatments. Patients with one or more of the earlier-described risk factors for nonunion should be observed carefully and provided with more intensive treatments. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine factors affecting the severity of neurological deficits and intractable back pain in patients with insufficient bone union following osteoporotic vertebral fracture (OVF). Reports of insufficient union following OVF have recently increased. Patients with this lesion have various degrees of neurological deficits and back pain. However, the factors contributing to the severity of these are still unknown. A total of 45 patients with insufficient union following OVF were included in this study. Insufficient union was diagnosed based on the findings of vertebral cleft on plain radiography or CT, as well as fluid collection indicating high-intensity change on T2-weighted MRI. Multivariate logistic regression analysis was performed to determine the factors contributing to the severity of neurological deficits and back pain in the patients. Age, sex, level of fracture, duration after onset of symptoms, degree of local kyphosis, degree of angular instability, ratio of occupation by bony fragments, presence or absence of protrusion of flavum, and presence or absence of ossification of the anterior longitudinal ligament (OALL) in the adjacent level were used as explanatory variables, while severity of neurological deficits and back pain were response variables. On multivariate analysis, factors significantly affecting the severity of neurological deficits were angular instability of more than 15 degrees [adjusted odds ratio (OR), 9.24 (95% confidence interval, CI 1.49-57.2); P < 0.05] and ratio of occupation by bony fragments in the spinal canal of more than 42% [adjusted OR 9.23 (95%CI 1.15-74.1); P < 0.05]. The factor significantly affecting the severity of back pain was angular instability of more than 15 degrees [adjusted OR 14.9 (95%CI 2.11-105); P < 0.01]. On the other hand, presence of OALL in the adjacent level reduced degree of back pain [adjusted OR 0.14 (95%CI 0.03-0.76); P < 0.05]. In this study, pronounced angular instability and marked posterior protrusion of bony fragments in the canal were factors affecting neurological deficits. In addition, marked angular instability was a factor affecting back pain. These findings are useful in determining treatment options for patients with insufficient union following OVF. [ABSTRACT FROM AUTHOR]

We experimentally evaluated the effect of crosstalk between crossing microstrip lines (MSLs) on our MSL receiver. The measurement circuit consisted of two crossing MSLs, referred to as the upper MSL and lower MSL. At the crossing area, the upper MSL and lower MSL were separated by a 400-nm thickness of SiO2 thin film. The parasitic capacitance between them was estimated to be about 0.1 pF. We measured bias margin of the receiver connected to the lower MSL under two conditions: with a pulse train running through the upper MSL, i.e., with crosstalk noise, and without a pulse train in the upper MSL, i.e., without crosstalk noise. Our measurements showed that (i) crosstalk mainly reduced the lower limit of the receiver’s bias margin, and (ii) this reduction of bias margin was enhanced by resonance when the repetition frequency of pulses in the upper ring satisfied resonance condition. [Copyright &y& Elsevier]

Microporous, non-woven poly(&epsiv;-caprolactone) (PCL) scaffolds were made by electrostatic fiber spinning. In this process, polymer fibers with diameters down to the nanometer range, or nanofibers, are formed by subjecting a fluid jet to a high electric field. Mesenchymal stem cells (MSCs) derived from the bone marrow of neonatal rats were cultured, expanded and seeded on electrospun PCL scaffolds. The cell-polymer constructs were cultured with osteogenic supplements under dynamic culture conditions for up to 4 weeks. The cell-polymer constructs maintained the size and shape of the original scaffolds. Scanning electron microscopy (SEM), histological and immunohistochemical examinations were performed. Penetration of cells and abundant extracellular matrix were observed in the cell-polymer constructs after 1 week. SEM showed that the surfaces of the cell-polymer constructs were covered with cell multilayers at 4 weeks. In addition, mineralization and type I collagen were observed at 4 weeks. This suggests that electrospun PCL is a potential candidate scaffold for bone tissue engineering. [Copyright &y& Elsevier]

To expand designable circuit scale, we have developed a new cell-based circuit design for single flux quantum (SFQ) circuit. We call it CONNECT cell library. The CONNECT cell library has over 100 cells at present. Each CONNECT cell consists of a Verilog digital behavior model, circuit information, and a physical layout. All circuit parameter values have been optimized for obtaining the widest margins and minimizing interactions between cells. At the layout level, we have defined a minimum standard cell size and made cell height and width a multiple of the size. Using this cell library, we can easily expand circuit scale without the time-consuming dynamic simulations of whole circuits. For estimation of the reliability of the library, we designed and fabricated test circuits using CONNECT cells. We demonstrated experimentally correct operations, which means the CONNECT cell library is sufficiently reliable. [Copyright &y& Elsevier]

Abstract: Fabricating high quality Josephson junction is essential in superconducting qubit circuits. In this letter, high quality tunnel junctions with a low critical current density of ∼32A/cm2 were fabricated. The 1/f noise parameter η was obtained from junctions’ low frequency voltage noise power spectral density . Our findings showed that the noise spectrum is junction linear dimension dependent, indicating the junction’s side leakage current induced by defects in the amorphous oxide insulator dominates the origin of the 1/f noise in our epitaxial NbN/AlN/NbN tunnel junctions. [Copyright &y& Elsevier]

We report on the fabrication of Josephson tunnel junctions with as-grown MgB[sub 2] thin films and on the Josephson tunneling properties of the junctions. MgB[sub 2]/AlN/NbN trilayers were continuously deposited on sapphire (0001) substrates in the same vacuum run. The as-grown MgB[sub 2] thin films were fabricated using the conventional sputtering method at the low-substrate temperature of 250°C, and the AlN tunnel barrier and the NbN counter electrode were deposited by reactive sputtering at the ambient substrate temperature. The T[sub c] of the MgB[sub 2] thin films was 28 K. The junctions demonstrated clear Josephson tunneling characteristics with evident supercurrents, gap voltages, and small subgap leakage currents. The normal resistance of these junctions had an ideal dependence on the junction areas and on the AlN-barrier thickness. The temperature dependence of the gap voltages and the external dc magnetic-field dependence of the supercurrents were measured to investigate the Josephson tunneling behaviors in the MgB[sub 2]/AlN/NbN junctions. The junctions showed BCS-like temperature dependence of the gap voltage and ideal Fraunhofer patterns. [ABSTRACT FROM AUTHOR]

We have demonstrated highly pure single-photon emissions from an InAs/InP quantum dot at the wavelength of 1.5 μm. By applying quasi-resonant excitation, one exciton is deterministically generated in an excited state, which then relaxes to the exciton ground state before recombining to emit a single photon. The photon-correlation function of the emission from the exciton ground state exhibits a record g(2)(0) value of (4.4±0.2) ×10-4 measured using high-performance super-conducting single-photon detectors, without any background subtraction. This single-photon source with extremely low multi-photon emission probability paves the way to realize long distance quantum key distribution and low error-rate quantum computation. [ABSTRACT FROM AUTHOR]

STUDY DESIGN.: Prospective cohort study. OBJECTIVE.: To elucidate the prognostic factors indicating reduced activities of daily living (ADL) at the time of the 6-month follow-up after osteoporotic vertebral fracture (OVF). SUMMARY OF BACKGROUND DATA.: OVF has severe effects on ADL and quality of life (QOL) in elderly patients and leads to long-term deteriorations in physical condition. Many patients recover ADL with acceleration of bony union and spinal stability, but some experience impaired ADL even months after fracture. Identifying factors predicting reduced ADL after OVF may prove valuable. METHODS.: Subjects in this prospective study comprised 310 OVF patients from 25 institutes. All patients were treated conservatively without surgery. Pain, ADL, QOL, and other factors were evaluated on enrollment and at 6 months. ADL were evaluated using the criteria of the Japanese long-term care insurance system to evaluate the degree of independence. We defined reduced ADL as a reduction of at least single grade at 6 months after fracture and investigated factors predicting reduced ADL after OVF, using uni- and multivariate regression analysis. RESULTS.: ADL were reduced at 6 months after OVF in 66 of 310 patients (21.3%). In univariate analysis, age more than 75 years (P = 0.044), female sex (P = 0.041), 2 or more previous spine fractures (P = 0.009), presence of middle column injury (P = 0.021), and lack of regular exercise before fracture (P = 0.001) were significantly associated with reduced ADL. In multivariate analysis, presence of middle column injury (odds ratio [OR], 2.26; P = 0.022) and lack of regular exercise before fracture (OR, 2.49; P = 0.030) were significantly associated with reduced ADL. CONCLUSION.: These results identified presence of middle column injury of the vertebral body and lack of regular exercise before fracture as prognostic factors for reduced ADL. With clarification and validation, these risk factors may provide crucial tools for determining subsequent OVF treatments. Patients showing these prognostic factors should be observed carefully and treated with more intensive treatment options. [ABSTRACT FROM AUTHOR]

Abstract: We have observed vortex penetration into Nb thin films with square arrays of square holes with variable sizes and lattice constants. We find that when the lattice spacing is large and the width of superconducting line is narrow, vortices penetrate diagonally rather than parallel to the nearest neighbor direction. This phenomenon is also confirmed in NbTiN samples with the same geometry. We also confirm that the direction of edge relative to that of hole array is not relevant. Possible origin of such a preferential penetration is proposed. [ABSTRACT FROM AUTHOR]

Abstract: We measured the delay times of several components of the rapid single-flux-quantum (RSFQ) circuit using ring oscillators so as to improve the precision in the timing design. The delay time deviates from the designed value because of wafer-to-wafer and on-wafer parameter spreads. In addition, three-dimensional structures of the actual circuits generate unpredictable parasitic inductances, which occasionally lead to the large timing deviation from the design. The 1-σ local spread of the delay time originating from the fabrication was found to be 5.2% for a Josephson transmission line (JTL) composed of two junctions. This result provides a quantitative indication of timing margins required between SFQ pluses. However, the delay times tended to be smaller than those in numerical simulation by approximately 20%. We think that this is because the timing parameters were extracted without any considerations of the parasitic inductance of shunt resistors in the simulation. To examine the influence of the parasitic inductance, we designed four JTLs having additional inductances in series with shunt resistors, and measured each delay time. The decreasing ratio of delay time to the parasitic inductance was found to be 0.32ps per 1 pH. We estimated that the parasitic inductance connected in series with a shunt resistor was 1.6 pH for the JTL. This timing consideration is applicable to all the cells because the junctions used in the actual circuits have roughly the same geometry as that of the JTL. [Copyright &y& Elsevier]

Abstract: We have designed, fabricated and tested a time-to-digital converter (TDC) using SFQ logic circuits. The proposed TDC consists of two sets of ring oscillators and binary counters, and a coincidence detector (CD), which detects the coincidence of the arrival of two SFQ pulses from two ring oscillators. The advantage of the proposed TDC is its simple circuit structure with wide measurement range in addition to the high resolution and the high sensitivity of the SFQ TDC compared to semiconductor TDCs. The time resolution of the proposed TDC is limited by the resolution of the CD. In order to improve the resolution, we have developed a dynamic AND (DAND) gate, which can detect two simultaneous SFQ signal inputs with high accuracy. It was demonstrated that the time resolution of the TDC using the DAND gate is improved to be ±4ps. [Copyright &y& Elsevier]

A pipelined 8-bit-serial single-flux-quantum (SFQ) microprocessor, called CORE1β, was designed and tested. The CORE1β has two cascaded arithmetic logic units (ALUs) based on forwarding architecture, which can perform two register operations from one instruction. Pipelining is also extensively adopted to enhance the performance. A new design method, known as one-hot encoding, has been introduced into the design of the control circuit. The 4-stage-pipelined SFQ microprocessors, CORE1β8, have been implemented using the CONNECT cell library and the SRL 2.5 kA/cm2 Nb process. The frequency for the instruction fetch is 25 GHz, and 20 GHz for the bit-serial data operation. The peak performance and the power consumption of the CORE1β8 are estimated to be 1400 MOPS (million instructions per second) and 3.4 mW, respectively. We have experimentally demonstrated 4-stage pipelining and all functionalities of the CORE1β8 microprocessors by on-chip high-speed tests. [ABSTRACT FROM AUTHOR]

Abstract: We propose an integer multiplier with systolic array structure for single-flux-quantum (SFQ) technology. Since SFQ logic circuits work by pulse logic, suitable circuit structure for SFQ logic circuits is different from one for semiconductor logic circuits. The systolic array is a circuit structure for VLSIs and consists of regularly arranged simple processing elements. All signals of the proposed systolic multiplier flow from input to output unidirectionally. This feature matches concurrent-flow clocking well. For evaluating the proposed systolic multiplier, we have designed a 4-bit systolic multiplier, as well as a 4-bit array multiplier which is one of the most typical parallel multipliers, and have compared them with each other. From the results of the design and the digital simulation, the number of Josephson junctions (JJs) of the 4-bit systolic multiplier is almost the half of that of the 4-bit array multiplier, and the latency of the former is about 1.5 times longer than that of the latter. Our estimation of the performance of larger-scale multipliers shows that the proposed systolic multiplier achieves comparable latency to the array multiplier, using extremely smaller number of JJs when the bit-width of input becomes large. We have fabricated a 1-bit cell of the systolic multiplier using NEC standard Nb process and have successfully tested it at low speed. The proposed systolic integer multiplier is attractive for SFQ technology. [Copyright &y& Elsevier]

Abstract: We designed a single-flux-quantum (SFQ) scheduler for a 4×4 network switch. It receives requests serially and arbitrates them. Fair scheduling is achieved by using a round-robin priority pointer at each output port. The pointer is updated so that the input port that was granted permission has the lowest priority in the next scheduling cycle. We divided the scheduler into sub-blocks, which were separately designed. The sub-blocks, which have asynchronous interfaces, were then connected with passive transmission lines. Ladder-type on-chip clock generators were included in the circuit for high-speed operation. Using logic simulation, we verified the scheduler test circuit. The scheduler test circuit was composed of about 3000 Josephson junctions. We tested the scheduler circuit at high speed and confirmed correct operations at over 40GHz. [Copyright &y& Elsevier]

Abstract: We have demonstrated the components of datapath toward single-flux-quantum microprocessors based on our new architecture called the forwarding architecture. In the forwarding architecture, we improve the performance by utilizing multiple ALUs to conceal the inefficiency of bit-serial processing. The key components of the datapath are a register file and cascaded ALUs. We have designed the register file to hold four bit-serial data with two read ports and one write port. In each ALU, we have implemented six functionalities: addition, subtraction, logical AND, OR and Exclusive OR operations, and comparison with zero. We have tested the register file and the ALU using high-speed on-chip testing, and confirmed the correct operations up to 18GHz and 23GHz, respectively. [Copyright &y& Elsevier]

Abstract: We have designed, fabricated and tested a time-to-digital converter (TDC) using SFQ logic circuits. The proposed TDC consists of two sets of ring oscillators and binary counters, and a coincidence detector (CD), which detects the coincidence of the arrival of two SFQ pulses from two ring oscillators. The advantage of the proposed TDC is its simple circuit structure with wide measurement range. The time resolution of the proposed TDC is limited by the resolution of the CD, which is about 10ps because it is made by an NDRO cell in this study. The circuits are implemented using NEC 2.5kA/cm2 Nb standard process and the CONNECT cell library. We have demonstrated the measurement of the propagation delay of a Josephson transmission line by the TDC with the time resolution of about 10ps. [Copyright &y& Elsevier]

Abstract: We have calculated a bit-error-rate (BER) of Josephson latching drivers using the Monte-Carlo simulations taking into account the thermal noise at the Josephson junctions. The latching driver under investigation is composed of parallel 8-junction stacks and a SQUID input gate. We have optimized the structure of the SQUID input gate based on the BER simulation to get larger bias margins with acceptable BER. We have shown that the bias margins of the latching driver with a 3-junction SQUID input gate are better than that using a 2-junction SQUID input gate. The high-speed measurement of the Josephson latching driver confirms the validity of the BER based optimization. We have obtained the BER lower than 10−12 at 5GHz and 10−5 at 10GHz in the Josephson latching driver with the 3-junction SQUID input gate by the high-speed test. [Copyright &y& Elsevier]

Abstract: In this paper we have considered how to perform logic synthesis of the single-flux-quantum (SFQ) logic circuits by using logic synthesis tools for semiconductor logic circuits. Fundamental difference of the SFQ logic gates from the semiconductor logic gates in terms of logic synthesis is that typical SFQ gates are clocked gate, where gates have to be clocked by SFQ pulses. In our approach, we divided the procedure into two steps; logic synthesis and clock distribution. In the logic synthesis step, the logic function is optimized using a logic synthesis tool without considering the clock network. The Design Analyzer provided from Synopsys is used in this study. We have developed an SFQ cell library for the logic synthesis. In the clock distribution step, clock networks for every clocked SFQ gates are designed taking account of timing. We used a clock-followed-data clocking scheme in this study. We have classified every clocked gate into stages, where the clocked gates in the same stage are clocked simultaneously. To demonstrate the validity of our approach, we have designed a controller of an 8-bit SFQ microprocessor. [Copyright &y& Elsevier]

Abstract: Background: PRKAR1A gene encodes the type 1A regulatory subunit of protein kinase A. The mutation of this gene causes Carney complex which is an autosomal dominant multiple neoplasia syndrome characterized by spotty pigmentations, endocrine overactivity and cardiac myxoma. We hypothesized that cardiac myxoma may be associated with PRKAR1A gene mutation and determined whether mutation in the PRKAR1A gene is the cause of familial and sporadic cardiac myxoma. Methods: We studied seven patients (three males and four females) with cardiac myxoma. Two of them had familial cardiac myxoma complicated with Carney complex. The other five patients were characterized as sporadic cardiac myxomas. We analyzed the PRKAR1A gene of all patients by the polymerase chain reaction (PCR)–single-strand conformation method, followed with direct sequence analysis. Results: We identified a novel mutation (494delTG) in exon 4A of the PRKAR1A gene in the patients with Carney complex. A 16-year-old proband had a left atrial myxoma, pituitary adenoma and skin pigmentation. His father also had left atrial myxoma and skin pigmentation. In contrast, no mutations in the PRKAR1A gene were identified in the other five patients with sporadic cardiac myxomas. Conclusions: These results suggest that mutation of the PRKAR1A gene may be associated with familial cardiac myxoma in Carney complex but may not be associated with sporadic cardiac myxoma. [Copyright &y& Elsevier]

With regard to sustaining future capacity of network traffic, the current hardware technology has a big bottleneck in terms of power consumption and insufficient operation speed. To overcome this bottleneck, we have developed a single flux quantum (SFQ) packet-switching circuit. We report recent progress in developing the SFQ packet-switching application. First, we demonstrate a 40 GHz, 160 Gb/s, 4 × 4 packet switching circuit, which is currently the fastest clock frequency reported packet switch. Then, we describe a currently possible switching module using SFQ technology. Finally, we consider how SFQ technology can be used to scale the packet-switching capacity up to 100 Tbps. [ABSTRACT FROM AUTHOR]

We have successfully demonstrated an 8-bit microprocessor using passive transmission lines based on single-flux-quantum LSI technology, in the microprocessor designed here, called CORE1α6, a simple bit-serial architecture with seven instructions was employed. In the CORE1α6, the floor plan was designed with consideration toward integration of a memory, and superconductive passive transmission lines (PTLs) were used to connect circuit blocks. Utilization of PTLs helped us reduce the propagation delay in long interconnections The design flexibility of the floor plan was enhanced and the performance of the microprocessor was improved by 20% compared with our previous design. The CORE1α6 was composed of 6319 Josephson junctions and 15 PTLs with power consumption of 2.1 mW. We have confirmed the complete operations of the CORE1Ξ6 by on-chip high-speed tests. The maximum clock frequencies for bit operation and instruction execution have been found to be 18 GHz and 1.2 GHz, respectively, where the performance corresponds to 240 million instructions per second (MIPS). [ABSTRACT FROM AUTHOR]

We have been investigating a design methodology of SFQ logic circuits based on the binary decision diagram (BDD). In the previously proposed BDD SFQ logic circuits, we have used one-to-two binary switches as a node cell in a BDD tree. In this study we will propose a new implementation method of SFQ BDD circuits, in which two nodes are implemented by using a 2-input 2-output switch gate. By employing the new approach, we have designed and implemented a one-bit full adder using the NEC 2.5 kA/cm² Nb standard process and the CONNECT cell library. The maximum operating frequency of the full adder was found to be 40 GHz by circuit simulations and 32.8 GHz by on-chip high- speed tests. [ABSTRACT FROM AUTHOR]

We demonstrated the 4 × 4-cross/bar-40 Gbps/ch switch which is functionally compatible with a commercial semiconductor one in order to evaluate the current SFQ circuit technology quantitatively in both a operating speed and power consumption. According to our numerical simulations, the SFQ switch has one or two orders of magnitude higher throughput per a single channel than that of the semiconductor, and has much smaller exchanging times between routing paths. In an actual test based on the NEC Nb-2.5 kA/cm² junction technology, correct operation using an on-chip test system made up of 4700 Josephson junctions was confirmed up to 37 Gbps/ch which is about 14 times faster than the semiconductor of 2.7 Gbps/ch speed. We also confirmed that SFQ circuits consumed 1/800 power compared with those of semiconductor. The reason why data rates obtained experimentally did not reach the designed speed of 40 Gbps/ch is due to both the liming error and the influence of magnetic fields caused by large bias currents exceeding 500 mA. These results of quantitative evaluation show that the SFQ technology has much greater potentials than the semiconductor one in both the operating speed and the power consumption, which means it is very effective to apply the SFQ technology to digital applications. [ABSTRACT FROM AUTHOR]

We have been developing an SFQ shift register memory, which is one candidate to realize high-throughput and high-density superconductive memories. We have modified our memory architecture in order to adapt it to our SFQ microprocessor, CORE1. The new version of the shift register memory is composed of shift registers with non-destructive readout operation, which have an internal feedback. We have also studied the availability of passive transmission line (PTL) wiring in the memory system at high speed. The tested circuit is a 4-byte shift register file, where four kinds of wiring circuits are used between a decoder and shift registers. We have measured the dependences of the DC bias margin on the operating frequency for all wiring methods, and obtained almost the same dependences, which shows the availability of the PTL wiring in the memory system. We have used the NEC 2.5 kA/cm2 Nb standard process and the CONNECT cell library. [Copyright &y& Elsevier]

We have designed and implemented an SFQ programmable clock generator (PCG), which can generate the variable number of SFQ pulses according to its internal state. The PCG is composed of an SFQ ring oscillator, a control circuit which counts up the number of SFQ pulses and stops the operation of the ring oscillator, and a decoder which defines the initial state of the control circuit. The PCG can generate the variable number of SFQ pulses ranging from 2 to 2N, where N is the number of T flip-flops in the control circuit. The oscillation frequency of the PCG is designed to be ranging from 6.2 to 18.8 GHz. In this study, we have implemented a PCG generating SFQ pulses ranging from 2 to 24 using a cell-based design methodology and confirmed its correct functionality. [Copyright &y& Elsevier]

Internet traffic is still growing rapidly. Link capacity is easily increased by bundling optical fibers, but the packet switching capacity at a node is limited by the performance of a semiconductor switch facing problems of packaging density, operation speed, and power consumption. Photonic technology is therefore emerging from the link technology into the packet switch technology. A photonic packet switch can analyze the packet label optically and control optical switches, but packet scheduling must be done in the non-optical domain because photonic technology lacks arithmetic characteristics. Increases in the line speed and the number of ports will make this scheduling a bottleneck. Because single flux quantum (SFQ) circuits can operate at several tens of gigahertz, a speed comparable to optical link speed, they will be able to eliminate this bottleneck. To improve the performance of the nodes in the photonic network, we propose an SFQ-circuit-controlled optical packet switch core. Here we describe and discuss two photonic packet switch architectures using SFQ-circuit-controlled photonic switches. [Copyright &y& Elsevier]

We have developed essential components for most of microarchitectures based on the single-flux-quantum (SFQ) logic. The circuit under test is composed of two registers, an ALU and a control unit, and made up of about 540 cells, 1600 Josephson junctions on 1.5 × 2.4 mm area. We have obtained the correct results by a sequence of several instructions, in which two integers are written into the registers with the LOAD and COPY operations, and then execute the ADD operation. Some of their functions were tested at both low and high frequencies. As a result, we found that the designed components could work at 15 GHz for the designed bias current and up to 18 GHz for higher bias currents. [Copyright &y& Elsevier]

The performance of high-end routers will soon reach the limits of conventional technology. Single flux quantum (SFQ) digital technology is a key technology for achieving a breakthrough. We have already proposed a high-end router using SFQ technology. In this paper, we report on the latest innovation of SFQ router technology. First we describe a design methodology development. We have developed a new SFQ logic cell library for cell-based top-down circuit design. To expand the circuit scale further, a novel pseudo-automatic Josephson transmission line (JTL) routing technique has also been developed. And then, we discuss issues of passive interconnection, and show the operation of a passive transmission line interconnected circuit up to 40-Gbps throughput. Second we describe a packet switch circuit demonstration. We designed a 2 × 2 crossbar packet switch circuit, which is a key element in the packet switch. We successfully tested the circuit up to a clock frequency of 35 GHz. Finally we discuss an SFQ circuit application in the optical router as an alternative application strategy. [Copyright &y& Elsevier]

Objective: To evaluate the relation between QT variables and disproportion of left ventricular wall hypertrophy in patients with hypertrophic cardiomyopathy. Design: Retrospective analysis of the results of echocardiography and electrocardiography. Setting: University hospital (tertiary referral centre). Patients: 70 patients with hypertrophic cardiomyopathy were divided into four groups according to the distribution of left ventricular wall hypertrophy on cross sectional echocardiography: group A-hypertrophy confined to the interventricular septum; group B-hypertrophy confined to the interventricular septum and left ventricular anterior wall; group C-hypertrophy confined to the interventricular septum, left ventricular anterior wall, and lateral free wall; group D-hypertrophy involving all portions of the left ventricle. Main outcome measures: QT intervals and QT dispersion in precordial six lead ECGs. Results: There were no significant differences in the maximum left ventricular wall thickness among the four groups, and maximum and minimum QTc intervals also did not differ. QTc dispersion was increased significantly in groups A and B compared with groups C and D. Dispersions of the interval from the J point to the end of the T wave (JTc dispersions) in groups A and B were also increased significantly compared with groups C and D. By linear regression analysis, QTc and JTc dispersions correlated with the ratio of the interventricular septal thickness to left ventricular posterior wall thickness (p = 0.0152 and p = 0.0075, respectively). Conclusions: QT dispersion may be affected by not only electrical inhomogeneity but also by morphological inhomogeneity of the left ventricle in patients with hypertrophic cardiomyopathy. [ABSTRACT FROM AUTHOR]

We have studied electrical properties of YBCO/Y/sub 0.7/Ca/sub 0.3/Ba/sub 2/Cu/sub 3/O/sub 7-x/ (Ca-YBCO)/YBCO trilayer junctions using c-axis oriented films. The Ca-YBCO films used here are the overdoped version of YBCO and show transition temperatures around 55 K. All of the junctions show RSJ-like current-voltage characteristics in a certain temperature range, though the range decreases with the Ca-YBCO interlayer thickness. For an applied magnetic field, the junctions show Fraunhofer pattern, indicating a Josephson coupling through the interlayers. The normal resistance of the junctions is proportional to the thickness of the interlayer, suggesting little interface resistance. The exponential dependence of the critical current on temperature and that on the interlayer thickness mean that the junctions behave as SNS junctions. These experimental results imply the proximity effect along c-axis in high temperature superconductors. [ABSTRACT FROM PUBLISHER]

The origin of the decoherence in superconducting nanowire single-photon detectors, the so-called dark count, was investigated. We measured the direct-current characteristics and bias-current dependencies of the dark count rate in a wide range of temperatures from 0.5 K to 4.0 K, and analyzed the results by theoretical models of thermal fluctuations of vortices. Our results indicate that the current-assisted unbinding of vortex-antivortex pairs is the dominant origin of the dark count. [ABSTRACT FROM AUTHOR]

Abstract: We have observed vortex motion in superconducting networks with relatively large holes. Vortices penetrate the network along the diagonal direction more easily than the parallel direction. This phenomenon is also confirmed in NbTiN networks as well as Nb networks. The mechanism for the diagonal vortex penetration is discussed on the basis of the enhancement of flux density near the vertices of square holes. [ABSTRACT FROM AUTHOR]