May, 2014

Date of Issue: May 16, 2014

Superconductivity Web21
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Contents:

Topics:- What’s New in the World of Superconductivity
Feature Article: Superconducting Microwave/Terahertz Wave Device Technology- Recent Trends in Superconducting Microwave/Terahertz Wave Device Technology- Recent Trends in MKIDs Imaging- Recent Trends in High-power Superconducting Filters- Recent Status of Superconducting Detectors and IEC Standardization Activities –Superconducting Sensor and Detector Standardization Proposals (Generic Specification)and International Vote Kick-off!
- Recent Trends of Dual-band Superconducting Bandpass Filter

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Top of Superconductivity Web21: http://www.istec.or.jp/web21/web21-E.html
This work was subsidized by JKA using promotion funds fromKEIRIN RACE
http://ringring-keirin.jp

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What’s New in the World of Superconductivity초전도 뉴스 –세계의 동향超导新闻-世界的动向-chāo dǎo xīnwén

- shìjiè de dòngxiàng-

Yutaka Yamada, Principal Research Fellow
Superconductivity Research Laboratory, ISTEC★News sources and related areas in this issue►Electronics

엘렉트로닉스

电子应用 [diànzǐyè yìngyòng]D-Wave Systems Selected as 2014’s 50 Smartest Companies
D-Wave Systems Inc. (February 18, 2014)
D-Wave Systems, the world’s first commercial quantum computing company, has been named as one of“2014’s 50 Smartest Companies” by the MIT Technology Review in their annual list of the world’s mostinnovative technology companies, an honor that has been previously shared by companies such as
Amazon, Google, IBM, and Microsoft. The companies that are included in this list have all demonstrated
original and valuable technology within the last year and are bringing that technology to market whilestrongly influencing their competitors; these companies are considered to represent the disruptive

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innovations that are most likely to change our lives. D-Wave Systems’ quantum computers are based on
the laws of quantum mechanics, and the resulting product is expected to help solve complex computing
problems in many different domains including machine learning, complex optimization problems in mission
planning, cancer research, and financial modeling.
Source: “D-Wave Systems Named to MIT Technology Review’s 2014 List of the 50 Smartest Companies”
D-Wave Systems Inc. press release (February 18, 2014)
URL:http://www.dwavesys.com/press-releases/d-wave-systems-named-mit-technology-reviews-2014-list-50-smartest-companies
http://time.com/4802/quantum-leap/
Contact: Beth Sanzone, dwave@launchsquad.com

Collaboration Research with NSF’s CHMPR for Quantum Computing
D-Wave Systems Inc. (February 24, 2014)
D-Wave Systems and the National Science Foundation Center for Multicore Productivity Research(CHMPR) at the University of Maryland, Baltimore County, have announced that D-Wave is joining CHMPR
to advance work in combined quantum and classical computing. CHMPR is a research consortium that isaddressing the productivity, performance, and scalability challenges that accompany the need forincreasing computational standards. DWAVE will contribute to this consortium by providing essential
insights into their breakthrough research in the field of quantum computing.
D-Wave Systems was founded in 1999 with the goal of integrating new discoveries in physics andcomputer science into breakthrough approaches to computation. Their flagship product, the 512-qubit
D-Wave Two™ computer, utilizes a novel type of superconducting processor that uses quantum mechanics
to massively accelerate computation. Last year, in 2013, a D-Wave Two system was installed at the new
Quantum Artificial Intelligence Lab, created jointly by NASA, Google, and the USRA. Lockheed Martin has
also purchased an upgrade of their previous 128-qubit D-Wave One™ system to a 512-qubit D-Wave Twocomputer.
Source: “D-Wave Systems Joins the NSF Center for Multicore Productivity Research (CHMPR)”
D-Wave Systems Inc. press release (February 24, 2014)
URL:http://www.dwavesys.com/press-releases/d-wave-systems-joins-nsf-center-multicore-productivity-research-chmpr
Contact: Beth Sanzone, dwave@launchsquad.com►Basics기초 基础[jīchǔ]Superconducting Graphene
University of Vienna (February 11, 2014)
Using a powerful photoemission method known as angle-resolved photoemission spectroscopy (ARPES),
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an international team based at the University of Vienna has reported the superconducting pairing
mechanism that underlies calcium-doped graphene. The material graphene, which is composed of asingle-atom thick layer of carbon atoms, was first discovered in 2004 and is regarded as one of the mostamazing and versatile substances known to exist. The impact of this first, real, two-dimensional material
has been so great that its discoverers received a Nobel Prize. Until recently, no experimental reports ofsuperconductivity in graphene had been made, even though graphene’s close relatives (such as graphite
and fullerenes) can be made superconducting through the intentional introduction of electrons (doping). The
researchers found that calcium was the most promising doping candidate for inducing superconductivity ingraphene, with superconductivity appearing at a critical temperature of about 1.5 K. While this criticaltemperature is rather low (fullerenes become superconducting at around 33 K), graphene offers several
huge advantages over many other materials because it only consists of carbon atoms arranged in single
layers, making chemical functionalization relatively easy. In addition, it can be grown in multiple numbers of
atom layers in various stacking orders, and it can be doped in several different ways. This versatility enables
a multitude of experimental options, potentially enhancing our understanding of superconductivity in generaland carbon materials in particular. The group’s work has been published in Nature Communications.
Source: “How to make the wonder material graphene superconducting”
University of Vienna (February 11, 2014)
URL:
http://medienportal.univie.ac.at/presse/aktuelle-pressemeldungen/detailansicht/artikel/how-to-make-the-wonder-material-graphene-superconducting/Contact: Alexander Grüneis alexander.grueneis@univie.ac.at►Management and Finance 경영정보经营信息[jīngyíng xìnxī]China’s Supreme People’s Court Decides in Favor of AMSCAMSC (February 19, 2014)
AMSC has announced that China’s Supreme People’s Court has decided in favor of AMSC with regard to
the jurisdiction of AMSC’s two software copyright infringement cases against Sinovel Wind Group, Ltd.
(Sinovel), and Guotong Electric. The Supreme People’s Court has ruled that both cases will be heard as
copyright infringement cases separate from the commercial arbitration claims independently in theirrespective court systems. The cases in questions represent two of the four legal cases that AMSC brought
against Sinovel in late 2011 after contractual breaches on Sinovel’s part and the discovery of intellectual
property theft by Sinovel. In addition, AMSC is also engaged in a commercial arbitration case and a trade
secrets case against Sinovel.
Source: “China’s Supreme People’s Court Decides in Favor of AMSC on Jurisdictional Matters”
AMSC press release (February 19, 2014)
URL: http://ir.amsc.com/releasedetail.cfm?ReleaseID=826639
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Contact: Kerry Farrell, kerry.farrell@amsc.com

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Feature Article: Superconducting Microwave/Terahertz Wave Device
Technology- Recent Trends in Superconducting Microwave/Terahertz Wave Device
Technology
Shigetoshi Ohshima, Professor
Graduate School of Science and Engineering, Yamagata University
During February every year, Superconductivity Web21 publishes feature articles relating to the “Recent
trends in superconducting microwave/terahertz wave device technology”. This year, the feature articles arearranged with contributions by Dr. Okubo, AIST, on the “Recent status of superconducting detectors andIEC standardization activities”; Dr. Saito, Yamagata University, on the “Recent trends of high-powersuperconducting filters”; Dr. Ariyoshi, Nagoya Institute of Technology, on the “Recent trends of MKIDs
imaging”; and Dr. Sekiya, Yamanashi University, on the “Recent trends of dual-band superconducting
bandpass filters”. In this issue, the author was invited to provide summary highlights of the current status of
microwave/terahertz wave/X-ray superconducting devices and the development of superconducting probes
designed for NMR, currently undertaken by the author and his group.
Superconducting high-frequency devices are typically divided into the following three categories:
1) Devices having low surface resistance2) Devices exploiting the formation of superconducting quasi-particles
3) Devices exploiting resistance changes due to superconducting transition
A mainstream device exploiting phenomenon 1) is the superconducting filter. It is well known that STI basedin USA 1), has already introduced onto the market superconducting filter systems designed for mobile
telecommunication base stations, under the trade name of “SuperLink”. They clearly publicize that theirsystems enables the operation of Long Term Evolution (LTE) high-speed mobile phone networks (3.9 G).
Also in China, the practical realization of superconducting filter systems is underway. Professor Cao, based
at Tsinghua University, stated at EASSE2013 that more than 300 systems were currently in operation 2). A
question was posed by the author via an email sent to Professor Cao regarding the recent trends, whostated, “ With the receipt of government approval for R&D funding applicable to 4G-networks
superconducting filter systems, R&D activity will soon commence”. The development of high-power filters 3),4)
and dual-band bandpass filters 5), 6) have recently been undertaken extensively by both Japan and China,
in addition to the superconducting receiving filters. However, the area where these filters would beapplicable is yet to be determined. Despite this, since developmental progress of filters exhibiting superior
characteristics is gradually improving, further developments are anticipated in the future. Device
development exploiting phenomenon 2) have been actively performed by research focused on MKIDs 7),8),
which offer promising prospects of terahertz wave sensing devices, and undertaken by an array of research
institutions based around the world. The possibility of fabricating an imaging system operating with a 4.2K
refrigerator increases the likelihood of a system entering the consumer realm. A TES typically exploits

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phenomenon 3) and is already practically realized as a detector in SEM imaging 9), 10). For the three
above-mentioned categories please refer to each of the article as follows:
The following two approaches offer the potential to increase NMR sensitivity;a) Increase the magnetic field strength (increase the measuring frequency)b) Enhance probe detection sensitivity (increase the detection coil Q-value)
An NMR system exceeding 900 MHz has been already developed and now, the development of an NMR
system operating at 1.03 GHz is currently ongoing. However, since approach a) requires the need tosteadily strengthen the magnetostatic field, a high magnetic field of 24.2 T is required to realize 1.03 GHz.
This approach may already be reaching its limitation any time now. An alternative approach is to enhance
the probe detection sensitivity; approach b). The S/N ratio in an NMR employing an ordinary LCR resonatorsystem is given by the equation below 11). Here,
.

⁄ =

.

K, M 0,0 , f 0 ,Vs ,k B , f ,,QL ,Teff ,Tr are coefficients defined by the degree of B1 magnetic field
homogeneity, spin density, vacuum permeability, resonance frequency, sample volume, Boltzmann’sconstant, full width half maximum of the NMR signal, detection coil filling factors, detection coil load,equivalent noise temperature determined from the detection coil and the sample, and the receiver thermal
noise temperature. Of these coefficients the detection coil QL significantly influences the sensitivity. Figure 1
shows the relationship between QL of the coil and S/N ratio of the NMR. Here, the resonance frequency is
set to 700 MHz and a sufficiently small loss in the sample is measured.

Fig. 1

The relationship between QL and the S/N of the NMR detection probe

Figure 1 shows that utilization of a superconducting probe remarkably improves the S/N in NMR. A
research group based at the University of Florida has already developed a 1.5-mm 600MHz NMR HTS

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probe 12), 13). The author and his group are currently developing a 5-mm 700 MHz NMR HTS probe and areaiming for greater NMR sensitivity, under the JST’s S-Innovation program.
References:
1. STI Homepage http://www.suptech.com
2. 7th East Asia Symposium on Superconductive Electronics; Taipei Taiwan (2013).
3. Improving Power-Handling Capability of 4-Pole HTS Filters by Expanding Line Width of Resonator 2 with
Narrow Slits. Y. Tanaka et al. IEEE TRANS. APPLIED SUPERCON. 23 (2013)
4. Power handling capability of transmit filters using stripline structure. N. Sekiya, et al.
PHYSICA C. 471 (2011) 1217-1220
5. A Narrow Band Dual Mode HTS Patch Filter With High Power Capability. Wang, Yuehui et al.; IEEE
MICROWAVE AND WIRELESS COMPONENTS LETTERS 19 (2009) 449-451
6. Dual-Band Superconducting Bandpass Filter Using Stub-Loaded Resonators With Controllable Coupling
and Feeding Structures Heng, Yong et al. IEEE MICROWAVE AND WIRELESS COMPONENTSLETTERS 23 (2013) 400-402.
7. Fabrication of MKIDs for the MicroSpec Spectrometer. A. Patel. et. al.IEEE. TRANS. APPLIED
SUPERCON 23 (2013)
8. NbN-Based Microwave Kinetic Inductance Detector with a Rewound Spiral Resonator for Broadband
Terahertz Detection S. et al. APPLIED PHYSICS EXPRESS 6 (2013) 064103
9. Development of Hard X-ray and Gamma-Ray Spectrometer Using Superconducting Transition Edge
Sensor. S. Hatakeyama, et al. IEEE TRANS.APPLIED SUPERCON. 23 (2013) 2100804
10. Eight-Channel TES Microcalorimeter System for Detector and Source Development
M. Croce, et al. IEEE TRANS. APPLIED SUPERCON. 23 (2013) 1602605
11. Research on superconducting NMR probe coil utilizing MgB2 and Bi2Sr2CaCu2Ox
Hiroyuki Yamamoto, PhD Dissertation (2009 Gunma University)
12. Development of a C-13-optimized 1.5-mm high temperature superconducting NMR probe.
V. Ramaswamy, et al. J. MAGNETIC RESONANCE 235 (2013) 58-65.
13. Design, construction, and validation of a 1-mm triple-resonance high-temperature-superconducting
probe for NMR. W. Brey et al. J. Magnetic Resonance. 179 (2006) 290-293.

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Feature Article: Superconducting Microwave/Terahertz Wave Device
Technology- Recent Trends in MKIDs Imaging
Seiichiro Ariyoshi
Nagoya Institute of Technology
Kensuke Nakajima, Atsushi Saito
Yamagata University
Tohru Taino
Saitama University
Chiko Otani
RIKEN Advanced Science Institute
The Microwave Kinetic Inductance Detector (hitherto MKID) is a relatively new type of superconducting
photon detector with a short history, first developed at California Institute of Technology around ten years
ago 1). The MKID operates based on the phenomenon of incident photons with energies greater than the
superconducting gap energy breaking Cooper pairs (Figure 1). Specifically, a change in quasi-particle
densities caused by Cooper pair-breaking results in changes in the resonance frequency of a microwave
circuit (i.e. superconductor-characteristic kinetic inductance component), located downstream of thereceiver (Figure 1 shows an example of terahertz antenna). Thus, the MKID measures changes inamplitude and phase that permeate microwave signal lines 2).

Fig. 1 Detection principle of an MKID

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Recent years have seen worldwide progress in the development of MKIDs operating at 0.1 K 3). Currently,
millimeter-wave astronomical experimental observations have already begun employing 100-pixel class 2Darrays 4). Also in Japan, a research group based at the High Energy Accelerator Research Organization
and National Astronomical Observatory of Japan has advanced the development of MKID arrays applicableto observational studies of Cosmic Microwave Background 5). However, the mainstream R&D of MKIDs
reported until now have been particularly dedicated to “astronomical observation applications”, whereultimate sensitivity is a key requirement. These developments have been performed under the assumptionthat MKIDs are mainly fabricated by aluminum, which exhibits extremely low superconducting transition
temperatures (1.2 K), and therefore should be cooled and operated utilizing a 0.1K-class cryocooler suchas dilution refrigerator or an adiabatic demagnetization refrigerator. Additionally, for ground-based
astronomical observations a narrow-band detector is essential in order to suppress the ambient
background noise. Such issues lead to MKID performance characteristics that cannot be easily adopted or
widely applicable for broadband measurement instruments.
To address these concerns, the author and his research group has advanced a series of R&D involving
design, fabrication and performance evaluation of MKID arrays operating with a 4He refrigerator (minimum
reaching temperature ~3 K), along with broadband characteristics targeting future commercialization 6-8).
The developmental aim has been to realize terahertz spectroscopy imaging, supported by the Japan
Science and Technology Agency. Figure 2 shows a niobium nitride 2D-MKID array fabricated onto a
10mm-square R-plane sapphire substrate. The agreed targets for the detector performance per pixel for thetime being are to achieve more than 1~5 THz frequency band, a response time of less than 100 μsec andaround 10-14 W/√Hz noise equivalent power. Considering the applicability to 2D-mapping measurements,
the detector pixels are arranged greater than a 5x5 pixel array, which includes the center of measurement
and the periphery. Moreover, the author and his group aim for the stable operation of the MKID array,
constructed with a self-automated 4He refrigerator instead of using conventional complicated coolingsystem employing coolants (liquid helium), making it user-friendly and negating future cryocooling concerns.
The author anticipates that these advances will be applicable to a variety of measurement samples andpurposes, which are required by specific industrial needs such as drastic shortening of measurement times,
thick sample measurements, enabling the integration of spectral and imaging information.

Fig. 2 NbN film MKID-array fabricated on a sapphire substrate (left) and an enlarged photoof one pixel (right)
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References:
1. P. K. Day et al., "A broadband superconducting detector suitable for use in large arrays", Nature, 425
817-821 (2003).
2. J. Baselmans et al., "Noise and Sensitivity of Aluminum Kinetic Inductance Detectors for Sub-mm
Astronomy", J. Low Temp. Phys. 151 524-529 (2008).
3. A. Baryshev et al., "Progress in Antenna Coupled Kinetic Inductance Detectors", IEEE Trans. Terahertz
Sci. Technol., 1 112-123 (2011).
4. A. Monfardini et al., "A Dual-band Millimeter-wave Kinetic Inductance Camera for the IRAM 30 m
Telecsope", Astrophys. J. Suppl. Series194:24 (2011).
5. K. Hattori et al., “Novel frequency-domain multiplexing MKID readout for the LiteBIRD satellite", J. Low
Temp. Phys. 167, 671-677 (2012).
6. S. Ariyoshi et al, “The development of MKID for an Fourier Transform Imaging Terahertz Spectrometer”,
3-4(2013), February Issue of Superconductivity Web21
7. K. Hayashi et al., “Microwave characteristics of microwave kinetic inductance detectors using rewoundspiral resonators array”, Physics Procedia, 45, 213-216 (2013).
8. S. Ariyoshi et al., “NbN-based Microwave Kinetic Inductance Detector with a Rewind Spiral Resonator for
Broadband Terahertz Detection”, Appl. Phys. Express, 6, 064103_1-3 (2013).

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Feature Article: Superconducting Microwave/Terahertz Wave Device
Technology- Recent Trends in High-power Superconducting Filters
Atsushi Saito, Associate Professor
Graduate School of Science and Engineering, Yamagata University
A superconducting filter exhibits low-loss properties over the passband region and steep filter skirt
characteristics at its cutoff. These characteristics arise because the loss in a superconductor over the
microwave region is several orders of magnitude lower than that of ordinary metals 1), 2). Researchers have
exploited these advantageous characteristics and undertaken research into an array of superconducting
filters, already leading to the commercialization of superconducting receiver filters designed for mobile
telecommunication base stations based in USA and China 3), 4). Additionally, a superconducting hybrid filter
designed for weather radar has also been realized for practical use 5). The effectiveness afforded by asuperconducting transmit bandpass filter aimed at mobile telecommunication base stations is far more
anticipated than a receiver system. However, only several such examples have achieved the average 10W
power handling capabilities necessary for practical use - these are based at SII in the USA6), Toshiba7),
Yamagata University8), University of Yamanashi 9) etc. There are no reports achieving 100W capability,
which is momentarily required. Here, the author introduces research on a microstrip line resonatorcomprising a thin film and a high-power filter utilizing a single crystal bulk superconductor, which is seen asa recent trend in high-power superconducting filter development.
① 3D-matrix superconducting resonator filter
A resonator employing ordinary thin film microstrip lines
concentrates high frequency currents on the surface(terminals along its width direction as well as vertical sides),resulting in its destruction and a strain in superconducting
characteristics. Thus, research conducted has involved
introducing slits to slice the resonator pattern along its width10)
and the development of a multilayered thin film resonatorsliced along the film-thickness direction11). These methods
Fig. 1. 3D-matrix schematic diagram
have already been reported to exhibit enhancedof the resonator
power-handling capabilities. Research underway isprogressing towards a 3D-matrix superconducting resonator, sliced along its width and film-thickness
directions at the same time. Figure 1 shows a schematic of the 3D-matrix resonator reducing the current
concentration in both film thickness and width directions. The experimental results of a 3-pole multilayered
filter fabricated comprising of NbN/AlN/NbN, has been confirmed as offering an enhanced 3.1 dB
power-handling capability compared to an ordinary resonator (non-sliced) filter.
② Bulk single crystal superconducting resonator filter
The research employs a single resonator structure (Figure 2), comprised a disc-shaped GdBa2Cu3Oy single
crystal bulk superconductor fabricated onto a ceramic substrate. The design, prototype fabrication andMay, 2014© ISTEC 2014 All rights reserved.

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evaluation of a 3-pole filter that is configured to improve frequency characteristics by tuning/trimming thedielectric rod has been undertaken. The target frequency design characteristics are set as having a center
frequency of 5±0.1 GHz, a 100±5 MHz bandwidth, and an insertion loss of less than 0.2 dB. The frequency
responses of the filter were simulated using a 3D-electromagnetic simulator, MW-Studio. Figure 3 showsan outline picture of the filter package fabricated. Figure 4 shows the typical frequency characteristics of a3-pole bulk filter. The fabricated filter has favourable characteristics without unnecessary resonance in thevicinity of its operating band. Figure 5 shows the power-handling capability of the filter. The maximum
capability is determined to be around 41.7W. This realization of power-handling capability is considered
because of a reduction in maximum current density due to the resonator mechanism, attributed to not only
materials characteristics but also to superconductor thickness. By further designing and fabricating a
multi-pole filter, including analyzing the current density, the author and his group aim for the realization ofsuperconducting filter exceeding 100 W in the future.

Substrat

Fig. 2. 3-pole disc-shaped bulk resonator filter prototype

Fig. 3 Outline picture of filter package

500Output Power [dBm]

Magnitude [dB]-10

T = 20 K

S11

-20
-30

S21

-40
-50
-60
4.6 4.7 4.8 4.9 5 5.1 5.2 5.3 5.4
Frequency [GHz]Fig. 4 Frequency characteristics of 3-pole bulk
resonator filter

4030
41.7 W20
20

30
40
Effective Input Power [dBm]

Fig. 5 Power-handling characteristics of
3-pole bulk resonator filter

References:1) M. J. Lancaster, Passive Microwave Device Applications of High-Temperature Superconductors,
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Cambridge University Press, Chapter 1.
2) A. Saito, et al., Physica C, 426-431, 2, 1606 (2005).
3) http://www.suptech.com/superlink_850.php
4) Z. S. YIN et al, Int. J. Mod. Phys. B 19, 419 (2005).
5) http://www.toshiba.co.jp/rdc/rd/award/1304_01.htm
6) S. K. Remillard, et al., IEEE Microwave and Wireless Components Letters, 14, 5, 234 (2004).
7) Hiroyuki Kayano et al, The Journal of the Institute of Electronics, Information and Communication
Engineers, Electronics J90-C3, 188(2007)
8) A. Saito, et al., IEEE Trans. Appl. Supercond., 19, 1, 889 (2009).
9) N. Sekiya, et al., Physics Procedia, 27, 328 (2012).
10) S. Takeuchi, et al., Physica C468, 1954 (2008).
11) Y. Endo, et al., IEEE Trans. Appl. Supercond., 21, 3,559 (2011).

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Feature Article: Superconducting Microwave/Terahertz Wave Device
Technology- Recent Status of Superconducting Detectors and IEC Standardization
Activities – Superconducting Sensor and Detector Standardization
Proposals (Generic Specification) and International Vote Kick-off!
Masataka Ohkubo, Chief Innovation Coordinator
National Institute of Advanced Industrial Science and Technology
Superconducting detectors or sensors have enabled measurements that proved impossible using othertechnologies (although “detector” and “sensor” are synonymous, IEC standardization now considers theuse of these two terminologies because the way they are used differs). It has been a while now since
SQUIDs realized micro magnetic field detection sensitivities unrivaled by any other technologies, leading totheir practical deployment in magneto-cardiograph, magneto-encephalograph, contamination test, mineral
exploration etc. Now, their application to earthquake prediction is gathering attention. Recently, thedevelopment of an optically pumped atomic magnetometer exceeding SQUID sensitivities and progress ofa non-superconducting sensor utilizing spintronics has advanced. Despite this, the SQUID still maintains its
advantages as a measurement system for practical use. It has been a while now since a
Superconductor-Insulator-Superconductor (SIS) mixer was employed as a heterodyne detector in radio
astronomy applications. Amongst the opinions from individuals at the IEC propose that the term ‘SIS mixer’
should be more appropriate to a Superconducting Tunnel Junction (STJ) mixer. The above-mentioned
superconducting detectors are all that can be categorized under the term coherent detection 1).
Additionally, superconducting detectors operated in direct detection mode emerged around thirty years ago,
initially for the science to detect solar neutrinos and dark matter 2). The development of these types ofdetectors coincided with a now historical international workshop called, International Workshop on Low
Temp Detectors (LTD). The type and performance characteristics of a direct detector are summarized inrefs.1 and 2. Direct detection involves measuring cooper pair breakage caused by single-photon absorption
leading to an energy dispersive spectroscopy of photon energy. This type includes STJ and Microwave
Kinetic Inductance Detector (MKID). In addition to the detection principle, where the destruction ofsuperconductivity is initiated by quantum energy, there are other types of superconducting sensors able tomeasure temperature increases as well as changes in magnetic susceptibility due to single photon
absorption. These types can also be categorized as direct detection and include a Transition Edge Sensor(TES) and Metallic Magnetic Calorimeter (MMC). These detectors are now progressing for practicalrealization in the analysis equipment field to be utilized for R&D, including elemental analysis such assynchrotron radiation material analysis, mass analysis, SEM and TEM, in addition to astronomical studies
such as radio telescope astronomy and cosmic microwave background (CMB) detection. The development
of direct detection has progressed with the use of multi-element arrays that have enlarged the detection
area as well as provided imaging capabilities. The development of an STJ has involved a parallel read-out
with one read-out circuit per element, taking the advantage of high-count rates. A 100-pixel STJ can serve ahigh photon count-rate of 500k cps and suitable for synchrotron radiation applications 3). The developmentof a TES has seen the completion of a 10,000-pixel scale THz imager, by using a time division multiplexer
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KSP, Kawasaki, Kanagawa 213-0012 Japan Tel:+81-44-850-1612, Fax:+81-44-850-1613(frequency-division and code division multiplexing also includes) 4). With regards to MKIDs, a 2024-pixel
has been currently reported. The necessary wires for this read-out are only four in total – two systems, themicrowave input/output pairs. Larger-scale arrays are anticipated in the future 5).
In recent years, a simple-structured Superconducting Strip Detector (SSD) has been developed. The SSD
has been fabricated by forming strips less than 1 μm wide in a superconducting thin film with a thickness
ranging from several-nm to several 10’s nm. This type of detector was initially utilized for single photon
detection at telecommunication wavelengths. Currently, high quantum efficiencies and high-count rates are
anticipated for quantum information communications. With regards to the term Superconducting Single
Photon Detector (SSPD), which has been utilized by adding ‘superconducting’ to Single Photon Detector,
was already used and applicable to semiconductor detectors. However, since any type of superconducting
detectors enable single photon detection, opinions from individuals at the IEC and related communities
state that the term “SSPD” is not appropriate for certain types of superconducting detectors. Currently, theproposal is for SSD. In case of photon detection, the recommended terminology is a Superconducting Strip
Photon Detector (SSPD) and its abbreviation is the same, SSPD, as per its original acronym. SSDs havebeen realized for the detection of electrons, ions and molecules in addition to single photons at
communication wavelengths, and its applicability to analysis equipment is also anticipated 6). There aremany types of superconducting detector already in existence, and the emergence of further new types ofdetectors is expected in the future. The draft idea is to integrate the terminology according to its
classification of structure (or functionality) + what to detect + detector (or sensor, mixer).
The proposal to establish an ad hoc group 4 to explore the standardization of superconducting sensors anddetectors has been raised by Japan and approved at the IEC General Meeting held in 2010, Seattle. With
participants comprising of 11 experts from around the world, standardization activities have been
undertaken over the past three years. The outcomes from these meetings have seen the completion of a
New Working Item Proposal (NWIP) with regards to Generic Specification (categorization of detectors, term,
circuit symbol etc.) at end of 2013. The NWIP, which includes both coherent and direct detections, hasentered international voting with effect from 10th January 2014. The voting period lasts for three months,
closing on 11th April, with the anticipation of the approval from P member countries of IEC TC90. With thesuccessful international approval for this NWIP, the establishment of a new WG is planned together withcollaborations from IEEE. The standardization of terminology and electric circuit symbols 7) that have been
written in draft generic specifications will be progressed in collaborations with other WGs. Detailed
specifications regarding the standardization and performance testing methods of each type of detector will
follow suit in the future.

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References:1) M. Ohkubo, “Introduction to IEC standardization for superconducting sensors and detectors,” Prog.
Supercond. 14, 106 (2012);
http://ocean.kisti.re.kr/is/mv/showPDF_ocean.jsp?method=download&pYear=2012&koi=KISTI1.1003%2
FJNL.JAKO201209857785508&sp=106&CN1=JAKO201209857785508&poid=kss1&kojic=CJDHBL&s
Vnc=v14n2&sFree2) B. Sadoulet, “Recent progress with low temperature particle detectors,” AIP Conf. Proc. 1185, 785(2009); http://dx.doi.org/10.1063/1.3292455
3) Shigetomo Shiki, Masahiro Ukibe, Nobuyuki Matsubayashi, Masaki Koike, Yoshinori Kitajima, Masataka
Ohkubo, “X-ray Absorption Spectroscopy using Superconducting Tunnel Junction Detector for Trace
Light Elements”
http://pfwww.kek.jp/publications/pfnews/31_3/saikin2.pdf
4) W. Holland, et al., “SCUBA-2: a 10,000-pixel submillimeter camera for the James Clerk Maxwell
Telescope,” Proc. SPIE 6275, 62751E (2006); http://dx.doi.org/10.1117/12.671186
5) B. Mazin, et al., “ARCONS: A 2024 Pixel Optical through Near-IR Cryogenic Imaging
Spectrophotometer,” Publications of the Astronomical Society of the Pacific, 2013;
http://www.sciencedaily.com/releases/2013/11/131104162710.htm
6) N. Zen, et al., “Ion-induced dynamical change of supercurrent flow in superconducting strip ion detectors
with parallel configuration,” Appl. Phys. Lett. 104, 012601 (2014), and references therein;
http://dx.doi.org/10.1063/1.4861225
7) “Increasing clarity for Japanese users, IEC databases for graphical symbols now available also inJapanese,” IEC 60617; http://www.iec.ch/etech/2013/etech_0113/store-2.htm?mlref=etech

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Feature Article: Superconducting Microwave/Terahertz Wave Device
Technology- Recent Trends of Dual-band Superconducting Bandpass Filter
Naoto Sekiya
Interdisciplinary Graduate School of Medicine and Engineering
Faculty of Engineering, University of Yamanashi
Recent years has seen an explosive increase in image data communications attributed to the rapid
development of smart phones and tablets. The realization of the next generation mobile communications
equipped with high-speed/high-capacity communication capabilities equivalent to optical fiber
communications is therefore anticipated. Simultaneously, the efficient use of frequency resources isurgently required.
Carrier Aggregation technology as a method to realize high-speed/high-capacity communication has
therefore been proposed. An elemental component for the method is the dual-band bandpass filter (DBPF),
which is attracting attention as it allows the dual bandpass of two frequency bandwidths. In particular, a
DBPF utilizing a high temperature superconductor (HTS) has steep cutoff characteristics at low loss,
offering promising technological prospects for future mobile communications. Furthermore, this is the only
technology anticipated for the realization of high-speed/high-capacity communications and the effective useof frequency resources simultaneously.
DBPF configurations differ according to, 1) communication by contiguous multiple carriers having the same
frequency band and, 2) communication by multiple carriers having different frequency bands1). For type 1),
a proposed design method involves a built-in notch within the bandpass filter (BPF) having a wide
frequency band in order to realize this type of DBPF configuration 2). For type 2), a dual-band resonator has
been proposed in order to accomplish this type of DBPF configuration. Proposals to achieve dual-band
resonator configurations include a methodology utilizing fundamental and higher resonances as well as amethod utilizing even/odd-modes 3), 4).
DBPF development in Japan has been
undertaken by a group based at NTT
Docomo, who are currently leading
pioneering research into HTS-DBPF
since 2008 4). Type 2) DBPFs can realize
two frequency bands (band A, band B)
each employing a single dual-band
resonator, as shown in Figure 1.
Applying similar methodology toconventional single-band bandpass
filters becomes problematic when trying
to individually tune design parameterssuch as the resonance frequency of theFig. 1 Coupling configuration of DBPF utilizing dual-band
two bands and coupling coefficients
resonator
between the resonators. Therefore,

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multi-band filters designs necessary for the HTS-DBPF to realize steep cutoff characteristics, but are
extremely challenging due to increases in the number of design parameters required to be tuned, which
increases in proportion to the number of stages.
To address these challenges, University of Yamanashi has developed their own unique resonator
configurations and coupling coefficient-tuning methodologies 5) that has led to the development of 3.5/5.0
GHz band 5-pole HTS-DBPF 6). Figure 2 shows the schematic of the 5-pole HTS-DBPF fabricated. The
measurement results shown in Figure 3 demonstrate the realization of dual BPF having favorable
frequency characteristics in the 3.5 GHz and 5.0 GHz bands.
Future ongoing research is focused on the unprecedented development of a multi-stage design and a
tri-band bandpass filter with more than 8-poles, operating at three frequency bands.
0-20

S21 [dB]

-40
-60
-80
Simulated_S21-100

Measured_S21-120
3Fig. 2 The DBPF fabricated

3.5

4
4.5
Frequency [GHz]5

Fig. 3 Simulated and measured frequency
characteristics of a 5-pole DBPF

References:
1) Narahashi “Carrier Aggregation and Multi-band Bandpass Filters” February 2012 issue,
Superconductivity Web21,2) A. M. Abu hudrouss et al.,“Triple-band HTS filter using dual spiral resonators with capacitive-loading,”
IEEE Transaction on Applied Superconductivity, vol. 18, No. 3, pp. 1728-1732, 2008.
3) Li-Min Wang et al., “Quarter-Wavelength Stepped-Impedance YBCO Resonators for Miniaturized
Dual-Band High-Tc Superconducting Filters,” IEEE Transaction on Applied Superconductivity, vol. 19, No.
3, pp. 895-898, 2009.
4) Sato et al “4-pole CPW Dual-band Filter”, IEICE Technical Report MW08-36, June
5) Sekiya et al “Superconducting Dual-band Bandpass Filter Using Stub-loaded Hair-pin Resonators”,
IEICE General Conference, C-2-98, 2013.
6) T. Sugiyama et al., “Five-pole HTS dual-band bandpass filters using stub-loaded hair-pin resonators,”
26th International Symposium on Superconductivity (ISS 2013), FDP-29, 2013.
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