As the fields of quantum computing, quantum sensing, and quantum communication mature into engineering disciplines, a robust measurement infrastructure is needed that is available to all developers of quantum technology. This requirement for measurement capabilities is immediate, and will grow more urgent as planned use cases, such as quantum networks, are developed and brought online. Thus, it is essential to address this need now. An accurate, easily accessible, fast-turnaround measurement capability is key to accelerating the development process of quantum components. This need is particularly acute for single-photon sources and detectors, which are critical components of many quantum systems for sensing, communications, and computing. At present, characterizing the performance of these components is not straightforward, and new measurement methods and tools need to be developed and/or existing methods must be more widely shared. It is within this context that an invitation-only QED-C workshop was held (September 2021) with the goals of (1) understanding the quantum industry’s measurement needs for single-photon sources and detectors, (2) assessing the state of the art in single-photon source and detector characterization, and (3) clarifying the gaps in measurement capabilities.

Quantum industry stakeholders are faced with the dual challenges of not only commercializing emerging quantum technologies, but also implementing or developing their own internal metrology tools¹ for validating device and component performance. The underlying metrology services pertinent to single-photon sources and detectors are currently being formulated by national metrology institutions such as the National Institute of Standards and Technology (NIST), which have unique capabilities and a mission to support industry needs. By bringing together quantum technology developers and metrology experts from industry, government, and academia, the workshop collected the information needed to help prioritize single-photon sources and detector measurement service needs. This report describes the highest-priority measurement needs of quantum device and system researchers and developers, as well as recommendations for addressing the needs identified in the workshop.

To develop the necessary metrology and metrology services required to promote advances in single-photon source and detector technology, a committee of experts was formed to summarize the issues and needs brought forth from the workshop, categorize them to identify specific research tasks, and highlight activity and funding priorities. With input from the workshop attendees, the committee identified four focus areas that would significantly advance the development and adoption of single-photon technologies and developed priority recommendations (see Section 4) for each of these areas:

1. Information: The commercial development of single-photon technologies is being hindered by a lack of clearly defined single-photon metrics and measurement methods. A common language of terms and a compendium of best metrological practices is needed, as well as a means to disseminate that information and related expertise.
2. People: Although quantum information development is driven by pockets of deep expertise, there is an overall expertise deficit across large parts of the community. Addressing this deficit requires a concerted and coordinated effort to broaden participation of all communities involved in these quantum efforts. Thus, there is a need for an accessible training network to provide appropriate best practices to the wider single-photon technology community, for active outreach to underrepresented communities, and for introductory training in appropriate fundamentals. A specific goal should be to broaden participation of all communities involved in these quantum efforts.
3. Components: As single-photon technologies scale up and “proof of principle” demonstrations progress into common adoption, there will be an increasing need for significantly improved performance from classical system components so that they meet quantum system requirements. There is a need for standardized, reliable, repeatable, and widely available off-the-shelf components relevant to single-photon technologies such as laser sources, fiber connectors, attenuators, and detectors. These building blocks will enable consistent performance across laboratories and applications as systems scale up, which in turn will facilitate pathways to mass-market manufacturability.
4. Services: Better access to calibration capabilities/services is needed, whether it is through national measurement labs, third-party labs, in-house equipment that maintains high accuracy (perhaps through some QED-C portal) or some other mechanism to access the expertise to ensure that high accuracy calibration can be made with confidence. In addition, rugged devices that do not need regular calibration, or that can be self-calibrated would facilitate pathways to market adoption and technology proliferation.

¹ Metrology is the science of measurement