FEATURE QUANTUM PHOTONICS
and counting and quantum random number generation – a lot of other technologies such as computing, internet and network communication and gravimetry “are still at low maturity levels and at a proof- of-concept stage with some industrial applications being investigated”. “A lot of these technologies
require a lot of research and development efforts and skills and talent that are still under development,” she says. “Some of the barriers to speeding up quantum adoption include the reliability and preservation of quantum properties at certain environmental conditions, as well as end-user awareness to develop compelling use cases that can demonstrate a quantum advantage and interoperability and ease of integration into existing systems like factories, telecoms and healthcare. “For a range of areas of application, such as healthcare, finance and telecommunications, the use of regulations can also be very important for setting a framework for emerging technologies to accelerate adoption by end users,” she told Electro Optics.
What is the ‘rainbow problem’ in quantum technology? Sidqi says there is already a lot of collaboration “between photonics and quantum” in the UK through the auspices of several training and R&D schemes to develop custom products and solutions for quantum technologies. “There is also an increase in PICS to allow scalable and compact quantum technologies that can be easily adopted and integrated into existing systems,” she says. A recent QED-C workshop- based report on PICs for quantum applications also made a number of findings and recommendations. The report focuses on advances viewed as crucial for scaling up and commercialising PICs. Some of the gaps highlighted in it include the need for better packaging, control, integration, and ‘ruggedisation.’
24 Electro Optics March 2024
“Any quantum system that utilises an optical approach, either by using entangled photons or interacting with atoms or ions, can benefit from the use of PICs”
As Merzbacher explains, one of the key findings is that quantum systems use light at a variety of wavelengths “depending on the application and fundamental physics” – with each wavelength requiring specific materials, waveguides and optical components, “all of which must be miniaturised and made reliable and robust”. “This so-called ‘rainbow
problem’ could prove to be the industry’s greatest challenge. In addition, quantum systems often require higher powers and narrower linewidths,” she says. According to Merzbacher,
interconnect fabrication is also a challenge, including fibre-to-chip, chip-to-chip and chip-to-free space connections. Modular PIC architectures can contain several interconnects, and may require skilled workers to perform complex alignment procedures, which “can be prohibitively expensive on a large scale”.
“In addition, new functionalities needed for quantum applications may require new or multiple material systems, and the technology to efficiently combine and integrate these multi-material platforms and components is still a work in progress,” says Merzbacher.
Leveraging PIC investments The QED-C workshop report also points out that the reliability and ruggedisation of PICs for quantum applications ‘will need to be assessed and verified for the technology to scale and to move from the lab to fielded products’. It’s an important point. While some products, including cloud- based quantum computers,
PICs enable drastic size, weight, power, and cost reduction. The example above provides integrated laser, amplifier, tuner, and photodetector functionality with advanced passive components in a single chip of a few millimetres in size
may operate in controlled environments, Merzbacher emphasises that others “will be subject to temperature, space radiation, and other extremes” where PICs “will need to perform for extended periods of time without maintenance or technical service”. “Commercial PICs for quantum applications also require innovative packaging solutions that enable efficient and cost-effective integration of PICs into larger systems. Packaging requirements include efficient coupling between the on-chip photonic components and the external optical fibres, other PICs, or free-space optics,” she says. “PIC packaging also involves
direct current/radio frequency (DC/RF) electrical connectivity through wire bonds or solder bumps, as well as thermal management,” she adds. Other key recommendations highlighted in the report that stand out include the need to ‘create or enhance low- volume foundry capabilities, leveraging existing nascent commercial capabilities and US Government-supported resources such as the Microelectronics Commons hubs’. Funded by the CHIPS and Science Act, these hubs are tasked with expanding America’s leadership in microelectronics, including ‘accelerating domestic
prototyping and growing a pipeline of US-based semiconductor talent’. Other fruitful long-term
strategies highlighted include leveraging PIC investments made for other applications, such as the telecoms market, boosting the skills and talent ‘pipeline’ and ensuring long- term investment, especially by the government, for the ‘development and transition to manufacturing of PICs for quantum in order to capture both technological advantages and economic benefits’.
Developing modular PIC components Merzbacher also calls for the stimulation of low-volume, high-cost markets for PICs and growth of the foundational ecosystem – for example, by identifying dual-use applications and developing modular PIC components. “Government should
accelerate development of such markets by being an early adopter of quantum technologies based on PICs for government missions. “[We need to] encourage
long-term partnerships between universities, national laboratories, and industry, each of which addresses parts of the innovation process from research to development to commercial deployment,” she adds. EO
www.electrooptics.com
Nexus Photonics
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