Integrated superconducting nanobridge fast readout electronics for single photon detector arrays

Lead Research Organisation: University of Glasgow
Department Name: School of Engineering


Our objective is to develop nanobridge Josephson junction superconducting circuits (based on single flux quantum (SFQ)
design) for high bandwidth, low noise digital signal processing (DSP) of signals from single photon detector arrays (in
particular SSPD (superconducting single photon detector) arrays) and assess their suitability for commercialisation.
SSPD arrays have many applications; as a fast, high efficiency, low noise detector for quantum key distribution, as a
component in quantum computing and for enhanced quantum imaging. The major hurdle to commercialisation of SSPD
array systems is the lack of suitable readout electronics able to process a large number of signals without significant heat
loading of the detector cold stage. SFQ readout offers a low power solution, enabling multiple pixels in a marketable,
mechanically cooled system. Nanobridge SFQ circuits for SSPD array readout are a new, undemonstrated alternative to
conventional tunnel junction SFQ circuits, with the advantage of predominantly single layer fabrication, smaller device size
and potential for integration on the same chip as the SSPD array

Planned Impact

Nanobridge SFQ consists of a single layer pattern "written" via e-beam lithography (and some additional components
fabricated via a simple lithographic technique) which is scalable to large number of pixels and offers the potential for future
integration on a single chip with the SSPD.
* Expected route to market: The feasibility project will provide proof of concept for nanobridge readout electronics. The next
stage would be to develop full readout electronics based on this concept. This would then be suitable for commercial
development. In addition there would be further development of integrated SSPD and readout electronics on a single chip.
A direct route to commercialisation is via the GU James Watt Nanofabrication Centre spin-out company Kelvin
Nanotechnology. The team will engage with academic end users through the National Network of Quantum Technologies
* Size of market: The emerging quantum communications and infrared detection market has been closely monitored [1-4].
The value of the global quantum communications market is estimated to reach $1billion by 2018. In[3], DSTL report that
the quantum communications area is set to grow over the next 3 -10 years and quantum simulation and computing is set to
grow in the longer term with large scale systems estimated to be built around 2025 - 30. Quantum imaging, applied to
biomedical and military and security application is also expect to grow substantially in the 10 year time frame [4].
The successful output of this project will be suitable for development to serve all the above mentioned areas. The ability to
process large amounts of data at high speed will be key as quantum based systems increase in complexity over the next
15 years. Therefore this work has the potential to realise significant impact and growth.
* How to explore market potential: In this feasibility project, the final part of the project will involve an assessment of the
success of this work and the application of it to various quantum technology areas. A report detailing the findings of the
project will be produced. In particular, describing suitability of nanobridge SFQ for producing a commercial, bench-top,
multi-pixel single photon detector array system. There is no competitor in Nanobridge SFQ electronics for SSPD array
readout, so the UK would gain an advantage in exploiting future market potential.
The output of the project will be a fully characterised key component of the nanobridge SFQ readout electronics (dc to SFQ
converter). This will be exploited in the following ways:
* Report detailing findings of feasibility study and a proposal of the next stages of development of system for commercialisation. It is expected that these would include fabrication of other components of the circuity (transmission
lines, buffers etc.), scaling of design for multiple pixels, and integration on single chip with SSPD array. The report will be
circulated to key stakeholders.
* Publication of results in leading international journal and international conference within a year of the project end.
* Further development, building on successful proof of concept, potentially co-funded by NPL via the NMS (National
Measurement System) programme.
* Potential commercial exploitation via the spin-off fabrication company Kelvin Nanotechnology at Glasgow University.
[1] SECOQC White Paper on Quantum Key Distribution and Cryptography 2007, [2] ETSI White Paper of Quantum Safe
Cryptography and Security 2014, [3] Pritchard, Till UK Quantum Technology Landscape DSTL 2014, [4] IR Detectors
Surveying the Market Ahead Laser Focus World 7/2011, [5] Global Industry Analysts Quantum Cryptography Global Market
Report 2014


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Description This project demonstrated the feasibilty of superconducting nanobridge electronics as a readout scheme for superconducting single photon detectors. This scheme as the advantage of single layer fabrication (as opposed to complex multilayer fabrication used by foundries in Germany, the US and Japan). The project enabled us to establish a strong UK consortium (Glasgow, UCL, NPL) with core expertise in this field and establish the backbone of a UK supply chain for the technology (via the JWNC cleanroom in Glasgow). We reached out to end-users and stakeholders through exhibiting at the UK Quantum Technology showcase in Nov 2016 and hosting a Superconducting Electronics Industry Day in Glasgow in June 2017.
Exploitation Route This scheme for superconducting electronics has potential applications in readout of infrared photon counting superconducting detector arrays, rapid on-chip processing for quantum photonic circuits. These technologies have a role in emerging sensing, communication and computing applications.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Electronics

Description This quantum technology feasbility study was highly rated by the Innovate programme assessor. Due to the change in status of NPL from private to public, we were not permitted to follow up this work through an Innovate Collaborative R&D project. NPL have sponsored a PhD student Jon Collins through the QuantIC hub at U Glasgow (supervisor Dr Alessandro Casaburi). We have reshaped this work into an EPSRC standard mode submission (submitted Nov 2017).
First Year Of Impact 2017
Sector Digital/Communication/Information Technologies (including Software),Electronics
Impact Types Economic

Description European Research Council Consolidator Grant
Amount £1,330,336 (GBP)
Funding ID 648604 IRIS 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 05/2015 
End 10/2019
Description Innovate UK Quantum Technology Feasibility Study
Amount £250,000 (GBP)
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 08/2016 
End 07/2017
Description QUANTIC - the UK quantum technology hub in quantum enhanced imaging
Amount £23,056,154 (GBP)
Funding ID EP/M01326X/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 10/2014 
End 09/2019
Description Royal Society of London
Amount £378,481 (GBP)
Funding ID University Research Fellowship (renewal) 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2011 
End 09/2014
Description NPL 2015-2017 
Organisation NPL Ltd
Country United Kingdom 
Sector Private 
PI Contribution NPL led the Innovate UK quantum technology feasibility study on superconducting nanobridge readout electronics
Collaborator Contribution NPL coordinated the project and provided access to measurement facilities
Impact To date joint conference presentations and exhibit at National QT showcase in Nov 2016. No peer-reviewed publications yet.
Start Year 2015
Description QuantIC innovation space opening University of Glasgow November 2016 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact Participation in the opening of the QuantIC quantum technology hub innovation space at the University of Glasgow
Keith Brown MSP, the Scottish Government's Cabinet Secretary for Economy, Jobs and Fair Work
Live demonstration of miniaturized cooling platform for superconducting detectors
Year(s) Of Engagement Activity 2016
Description Superconducting Electronics Industry Day June 2017 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact At the conclusion of the Innovate UK feasibility study we hosted a one-day workshop with support from the QuantIC quantum technology hub. We invited a cross section of academic researchers and industry end users. We succeeded in creating new linkages across the community and laying the foundation for future joint projects and commercialization activity.
Year(s) Of Engagement Activity 2017
Description UK National Quantum Technology Showcase 2016 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Live demonstration of miniaturized cooling platform for superconducting single photon detectors
QE2 conference centre, Westminster, London 3/11/2016
Work completed for the QuantIC quantum technology hub in partnership with STFC/RAL
Year(s) Of Engagement Activity 2016