HTS Quasi-Particle Injection Devices for Interfaces between SFQ and CMOS Circuits(<特集>Special Issue on Superconductive Electronics)

We have fabricated a prototype of interface devices between SFQ and CMOS circuits using HTS quasi-particle injection devices. By the injection of quasi-particles, the bridge area becomes resistive and high voltage appears at the drain electrode. As a test of device operation, we applied the signal of a function generator to the gate electrode and observed that the device successfully repeated on/off operation. We also succeeded in explaining the device characteristics by considering the thermal effects

Illumination Normalization of Face Images with Cast Shadows

Abstract We propose a method for extractin

発振系の安定性と雑音

本論文では発振器の自由発振、注入同期発振、相互同期発振について、その安定性や系内の雑音を中心にして延べる。つまり、発振器をある動作点でできるだけ安定に自由発振させるには発振器を含む系をどのように設計したらよいか、またそのとき発振器から発生する雑音はどのような形になるのか、あるいは他発振器から同期信号が系に注入されたら以上のことがどう変るかなどについて議論する。さらに多数の発振器を相互に同期させて用いる相互同期系についても同様の議論を行う。University of Tokyo (東京大学

Photometric stereo with auto-radiometric calibration

We propose a novel method for estimating surface nor-mals and a radiometric response function of a camera at the same time. Photometric stereo assumes that a camera is radiometrically calibrated in advance, so that image ir-radiance values can be determined from observed pixel val-ues. Our proposed method avoids such often cumbersome radiometric calibration of a camera by the simultaneous estimation of surface normals and a radiometric response function. The key idea of our method is to make use of the consistency; the irradiance values converted from pixel values by using the radiometric response function should be equal to the corresponding irradiance values calculated from the surface normals. We show that the simultaneous estimation results in a linear least-square problem with lin-ear constraints. The experimental results demonstrate that our method can estimate surface normals accurately even when images are captured by using cameras with nonlinear radiometric response functions. 1

Quasi-particle injection devices for interfaces between superconductors and semiconductors

We have fabricated an injection type 3-terminal device for interface between superconductor and semiconductor circuits using a high temperature superconductor. When quasi-particles are injected from the Au electrode to a YBa2Cu3O7-x (YBCO) bridge, superconductivity of the bridge area is weakened and Ic of the bridge decreases. Therefore, we can easily make the bridge in resistive state by injecting sufficient amount of current Iinj . The length, width, and thickness of the bridge are 20 μm, 10 μm, and 100 nm, respectively. The Au-YBCO contact area is 200 μm 2. When the bridge became resistive, the resistance was about 100 Ω. The current gain |ΔIc/ΔIinj| was as high as 9. However, the contact resistance was about 17 Ω, which is 200 times as large as the required value for the operation as an interface device. This shortcoming might be overcome by appropriate annealin

SUPERCONDUCTION AND NORMAL CONDUCTING CHARACTERISTICS OF (YXPR1-X)BA2CU3O7-DELTA THIN-FILMS

The ratio of Yttrium (Y) to Praseodymium (Pr) is varied in (YxPr1-x)Ba2Cu3O7-delta (YPBCO) thin films to consider the relation between superconducting YBa2Cu3O7-delta (YBCO) and insulating PrBa2Cu3O7-delta (PBCO) thin films. The critical temperature (T-c) of the superconducting YPBCO thin film is decreased by substituting more Pr in place of Y, because Pr reduces the carrier density on the CuO2 plane in YPBCO. The electrical characteristic of the YBCO film can be explained by the weakly coupled chain model. The addition of Pr reinforces the superconducting links among the grains in the YPBCO thin film. The normal state YPBCO film shows two types of transport systems. Behavior similar to impurity semiconductors appears at high temperatures and the variable range hopping mechanism governs their conductance at low temperatures

New BSFQ circuit designs with wide margins

Recently we have proposed novel Boolean Single-Flux-quantum (BSFQ) circuits, which Just like CMOS circuits support Boolean primitives directly, and do not require local synchronization for each operation cell. However, previous BSFQ AND, OR, and XOR cells suffered from problems with narrow margin, where their critical margins hardly exceeded +/- 10% due to low flux gain. Furthermore, while being suitable for combinational circuits, previous BSFQ NOT cells had initialization problems in sequential circuits. In this paper, new versions of these circuits with simulated margins beyond +/- 30% are proposed. Moreover, a Muller C-element, an error canceller, a destructive read-out (DRO), and a demultiplexer are also newly created. The operation time, parameter margins, and circuit size of these BSFQ cells are comparable to those of the conventional RSFQ cells

Interface-Modified Ramp-Type Josephson Junctions in Trilayer Structures

We have fabricated ramp-type Josephson junctions in trilayer structures. A bilayer of YBa_2Cu_3O_ (YBCO)/CeO_2 was deposited on a SrTiO_3 (100) substrate. Then, circle patterns with a diameter of 2 μm were etched on the bilayer surface using standard photolithography process. During the Ar ion milling with an incident angle of 45 degrees to the bilayer surface, the sample was rotated. This process led to upside-down conical formations. After the ramp-edge surface was modified, another YBCO film was deposited for the top electrode. The junctions showed the I-V characteristics between resistively shunted junction and flux-flow types