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Panel Discussions
A series of panel discussions focused on different aspects of the quantum technology ecosystem. Each panelist offered a brief presentation to set the stage, then engaged in a lively moderated discussion with other workshop participants.
QUBIT-ENABLING TECHNOLOGIES AND MANUFACTURING ISSUES
Stephen Rossnagel, University of Virginia, and Rudy Wojtecki, IBM, introduced three panelists invited to address qubit-enabling technologies and manufacturing issues: William Oliver, Massachusetts Institute of Technology (MIT); Joseph Broz, SRI International; and Jerry Chow, IBM Research. Wojtecki framed the discussion as an exploration of the degree to which the United States is equipped to meet and manufacture the current and future demands for quantum technology. He also asked panelists to address whether there is a pipeline for quantum technologies to supplant existing ones.
William Oliver, Massachusetts Institute of Technology
Oliver began by noting how his own joint appointment at MIT’s physics department and the Lincoln Laboratory, a U.S. Department of Defense (DoD)funded research and development (R&D) center, demonstrates how different fields and facilities are participating in developing quantum technology. The Lincoln
Laboratory combines the flexibility of academic inquiry with processes to develop the types of reproducible systems that industry needs for manufacturing. Its research foundry is able to take ideas generated at the academic level and bring them to a level of technology maturity suitable for adoption by industry.
The Lincoln Laboratory has a quantum information group with more than 100 employees, Oliver said. The group focuses on superconducting qubits, trapped ion qubits, and nitrogen-vacancy (NV) centers for quantum sensing. The laboratory also studies high-performance classical cryogenic computing technologies, including cryogenic complementary metal-oxide semiconductor (CMOS) and single-flux quantum superconducting logic, and integrated photonics. All of these subfields are united in the quantum information group, Oliver noted, because they are all relevant to a technology’s manufacturability, which will be critical to the scaling up of quantum technology.
Joseph Broz, SRI International
In addition to his role at SRI International, Broz serves as executive director of the Quantum Economic Development Consortium (QED-C), an industry group focused on identifying and addressing gaps in enabling quantum technology, creating a robust supply chain and infrastructure, and developing commercially viable and scalable quantum-enabling technologies. The consortium does not support or perform basic research (e.g., study qubits specifically), but rather focuses on everything “around” qubits, essentially the “quantum ecosystem” that supports their existence and the ability to make them stable and useful.
Broz noted several large materials and manufacturing challenges in quantum information systems and the emerging quantum industrial sector, including sensing, computation, communications, and metrology. Materials are especially critical to quantum information system performance, he said, suggesting large gains can be made from researching, developing, and engineering the right materials to create quantum-enabling technologies.
QED-C is working on gaps in device components and instrumentation, and is also looking at the larger picture, working to create manufacturing standards and address quantum workforce and education issues. The consortium also provides U.S. government agencies with a collective voice to help steer investment and research priorities. Consortium members, which include companies both large and small and in the middle range of the technology readiness levels (TRLs), can facilitate industry coordination and collaboration with both academia and government agencies, Broz concluded.
Jerry Chow, IBM Research
IBM is committed to an eventual full-system integration of a quantum computer, and has been working toward this for many years. There is a strong need for the continued development of core software, hardware, and technology infrastructure. To facilitate that process, IBM created the “Quantum Experience,” placing its quantum computing module on the cloud to gauge interest and discover applications. There was a tremendous response, with more than 120,000 users and 150 academic research papers written since the module was made publicly available in 2016, Chow said.
Different parts of IBM’s quantum computing stack cater to different scientific communities. There are applications aimed at chemists or mathematicians who do not need to know how quantum computing works but could still make use of it, as well as applications aimed at experts who want to know exactly what the components are so that they can improve them and advance quantum computing as a whole. Quantum computing fuels and appeals to a broad ecosystem of interests, ranging from academics in many different disciplines to corporations curious about how they can harness and apply quantum technologies. To foster that corporate curiosity, IBM created the “Q Network,” which allows member companies to learn about quantum computing and prepare themselves for its arrival.
In response to a workshop participant’s question, Chow noted that the many business opportunities in meeting the supply needs for quantum computers span elements from circulators to isolators, although the exact needs are still being determined. However, he cautioned that until standardization occurs, it is difficult to create a product to fill a universal need.
Chow also noted that putting its quantum computer on the cloud has helped IBM improve the technology—for example, by helping IBM track down and explain the sources of signal noise or error rates. In addition, some users have been able to contribute to improvements, leading to better pulse shapes and dynamic coupling schemes. There are no current government restrictions on what IBM is allowed to make publicly available, although Chow’s team is still determining how much of the technology should be fully uncovered.
Following Chow’s talk, participants were invited to ask questions of the full panel. Themes included resource allocation, avenues for quantum computing advancement, potential applications, workforce challenges, and the importance of maintaining the United States’ quantum advantage.
Resource Allocation
Haydn Wadley, University of Virginia and workshop chair, asked how each speaker would like to see resources allocated. Oliver responded first, noting that
the answer depends on the goal. If the goal is to develop the leading domestic quantum information ecosystem, it is important to invest resources broadly, especially as quantum technology is still in its early stages. Immediate needs that could be realized in the next 5 years, such as noisy intermediate-scale quantum (NISQ) algorithms, can be prioritized, but refined scalability (perhaps 10 years away) and blue-sky research (15+ years) also remain important, he said. There are many milestones between initial technologies and the eventual applications, and the precise timeline for progress is difficult to predict.
Broz commented that significant strides and commercial successes have already been achieved in quantum sensing, timing, and quantum random number generation, and speculated that large-scale communications networks are probably next on the horizon. China’s demonstrations of both land and satellite quantum-key distribution (QKD) systems, albeit with limitations, represent an important step in that direction. Broadly speaking, success breeds success, he said, and each new successful application is helping to build an infrastructure of enabling technologies that will eventually help realize the full vision for quantum computing. The NISQ era has been impressive, he said, and urged continued investment in areas where applications and advantages are most likely.
Chow replied that resource allocation will depend on who is allocating the resources. Companies and governments will prioritize things differently. The U.S. government, which looks 2-3 decades ahead, may, for example, invest in a broad swath of technologies that can build an infrastructure to support quantum development while also looking at high-risk, high-reward areas, such as qubit materials. Industry, by contrast, would focus on developing better NISQ processors to gain near-term value and to build a thriving ecosystem of quantum users.
Materials for Quantum Computing
Oliver listed some key priorities toward advancing quantum computing: improving coherence, reducing defects in surfaces of materials and substrates, creating tools for identifying and analyzing these defects, and establishing specialized, clean manufacturing and fabrication processes. Materials, he stressed, are important to all of those processes, which is why MIT’s recently established Center for Quantum Engineering includes materials scientists and research. In particular, he pointed to a need to study how defects arise in materials and materials interfaces.
Chow agreed that core materials challenges are limiting progress, and suggested that experimentation with multiple materials would open new opportunities for innovation. Broz suggested that materials scientists could try reducing the number of variables by creating a basic, simpler model that optimizes fidelity and coherence time, analogous to the genetics community’s decision to use the fruit fly as a key model organism. A brief pause in the race to improve qubits, he suggested, could
allow the community to establish a model and develop a thorough understanding of it.
Oliver expressed support for this proposal, and added that such studies require time and stable funding. The National Quantum Initiative (NQI) can help by continuing to create collaborations among government, industry, and academia to answer key questions. Chow added that materials improvements will require a focused, well-defined set of metrics and parameters.
Fabrication Issues
Wojtecki asked the panelists what progress has been made in fabricating quantum materials for customers. Chow replied that IBM currently does not fabricate such materials for customers because the components are fine-tuned to IBM’s particular process. New designs cannot be easily transferred, so he suggested prototyping smaller fabrications to support other designs. However, IBM would consider altering its production process if a new design offered a substantial improvement.
Oliver added that quantum is a competitive landscape with substantial intellectual property remaining to be developed and instantiated, making companies hesitant to fabricate components for others without explicit partnership agreements. Yet in the research sphere, having access to high-yield, high-quality fabrication can take years off the research process. Universities and government laboratories should continue to generate new ideas and tools, he said, but it is not realistic to expect every university to have sophisticated fabrication capabilities. It makes more budgetary sense to have a few shared and centralized advanced fabrication facilities to support research activities across multiple laboratories that specialize in higher-complexity devices, and to complement the exploratory, fundamental research being performed at many facilities.
Broz agreed, noting that such a system would work not only for producing qubits but also for many of the potential enabling technologies. Typical quantum experiments need 2-3 years just to ensure that the equipment is usable. A better model, he suggested, would be to encourage the development of cheap, readily available fit-for-use components that have technical and economic scalability.
The Value of Collaboration
Noting that there are no rigid boundaries between what academia, industry, and government laboratories can offer, Oliver suggested the different sectors should work together to facilitate the handoff from basic research to product development. The government’s role is to create the environment to make this happen, he said. Broz added that government leadership is needed to direct assets to where they can have the most impact, which can subsequently lead to rapid gains.
Chow agreed, adding that this process must be optimized holistically across the different capabilities and deficiencies of all the stakeholders. Appropriate and shared resource allocation will optimize the entire domestic quantum landscape.
Potential Applications
Applications, whether in the realm of defense, biology, machine learning, or a variety of other areas, will come at different times. Broz highlighted the efforts of the QED-C’s Technical Advisory Council to create opportunities to “de-risk” the advancement of quantum-enabling technologies such as cryostats, stable lasers, and microwave pulse generators. Oliver added that it is also essential to identify dual-use or off-ramp technologies, in order to encourage industry to develop these pieces without a fully mature market. Private–public partnerships can help advance such efforts, he noted.
Chow said that NISQ techniques offer approximations for chemical simulations but that it will take longer for quantum technologies to support more complex chemistry and biology applications such as determining the complex structure of macromolecules. Eventually, however, fault-tolerant quantum computing will enable more complex structural determinations than high-performance computing, he said. Broz noted that tasks such as pattern recognition could be achieved before the more complex chemical simulations, and IBM’s cloud-based quantum computing is helping researchers make progress in this area. Oliver reiterated that quantum computing is in its early stages. While it is expected that a universal fault-tolerant computer can solve these problems, it has not yet been built. Thus, it is important to cultivate near-term, revenue-generating algorithms that are possible with NISQ computers in order to help encourage continued investment in quantum technologies.
Workforce Needs
Panelists also addressed quantum computing workforce needs. Broz stated that QED-C is currently assessing the workforce needs of its members, asking newer employees to identify training gaps, and creating quantum curricula for universities. In addition to creating a workforce pipeline, he noted that QED-C seeks to improve the quantum literacy of the existing engineering and applied sciences workforce.
Oliver described MIT’s Center for Quantum Engineering, which aims to serve existing quantum information systems workers in addition to graduate students and postdocs. With IBM’s support, MIT has established four professional development courses in this area. Quantum engineering is emerging as a new discipline, bridging quantum science and traditional engineering, and although its curriculum still needs to be defined, it is an important part of creating a quantum-literate
workforce, he stressed. Successful infrastructure includes more than just capital equipment and facilities—it also depends on human capital, he added.
Maintaining a U.S. Advantage
Wojtecki asked each speaker to identify the most important consideration toward maintaining the United States’ advantage when it comes to quantum technology. Broz expressed his belief that a strong domestic quantum industry is extremely important to maintaining overall economic and national security. The United States inadvertently exported portions of aerospace, semiconducting, and automotive engineering when manufacturing moved offshore, he said. To prevent this from happening with quantum, it is essential to foster a strong domestic workforce, infrastructure, and supply chain.
Building on this, Chow said that the key is a fully domestic quantum ecosystem. While quantum software developers are making progress, in his view, the hardware and supply chain infrastructure are not. That is worrisome, he said, because those elements are critical to the domestic development of quantum hardware.
Oliver stated that national security and economic security are synonymous. While many earlier technologies did move offshore, often a natural evolution of the business cycle as those technologies age, being the first to develop them was key to deriving economic benefits here in the United States and being able to chart subsequent business development. For quantum, he said, it is essential for the United States to be first and fast, while adding protections to keep quantum expertise from leaking overseas. While international interaction and collaboration can certainly be useful, and some leakage is unavoidable, he said the U.S. quantum community should careful and thoughtful to build and control the infrastructure domestically to the extent that is possible.
TECHNOLOGY GAPS
Alan Willner, University of Southern California, introduced four panelists invited to address technology gaps: Pat Gumann, IBM Research; Stuart Gray, Corning; Paul Kwiat, University of Illinois, Urbana-Champaign; and Alexander Sergienko, Boston University. The panelists offered brief opening thoughts before Elias Towe, Carnegie Mellon University, moderated a wide-ranging discussion.
Pat Gumann, IBM Research
Gumann said that other nations are pursuing research and development in quantum communications and quantum networking more aggressively than the United States and that in his view U.S. funders need to increase investment in these
areas. He also urged domestic industry, currently focused on quantum computing, to broaden its focus to advance these applications of quantum technology, as well.
Stuart Gray, Corning
Corning is an advanced materials company covering a wide range of industries, including telecommunications, precision and fiber optics, and laser processing. Corning’s ultra-low-loss optical fiber products have been used in several quantum key distribution (QKD) experiments. In 2009, QKD was achieved at 15 bps over 250 km, and 12,000 bps with a maximum transmission of 421 km was achieved in 2018.1,2
To continue quantum communication technology advancements, optical fibers will need to possess many qualities, such as low loss, low dispersion, polarization control, and dispersion compensation. Additionally, materials need to be developed to create quantum memories. Corning is actively pursuing rare-earth-doped solids to create a quantum memory, with special attention to loss mechanisms. Erbium-doped transparent ceramics such as yttrium oxide are especially promising, Gray said, yielding very narrow homogeneous line width transitions that are compatible with low-loss telecom wavelengths. They have good coherence properties, and their cubic crystal structure has a polycrystalline phase that minimizes scattering.3,4 Laser written Type I and Type II waveguides have also been demonstrated in this material.
Paul Kwiat, University of Illinois, Urbana-Champaign
While Kwiat recognized the importance of developing a fiber-based quantum network, he noted that there are also advantages to free-space quantum communications and suggested the United States could be doing more in this area. China, Japan, Canada, and multiple European countries have already established or are planning to establish QKD-focused airborne or space missions.
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1 D. Stucki, N. Walenta, F. Vannel, R.T. Thew, N. Gisin, H. Zbinden, S. Gray, C.R. Towery, and S. Ten, 2009, High rate, long-distance quantum key distribution over 250 km of ultra low loss fibres, New Journal of Physics 11:075003, https://doi.org/10.1088/1367-2630/11/7/075003.
2 A. Boaron, G. Boso, D. Rusca, C. Vulliez, C. Autebert, M. Caloz, M. Perrenoud, et al., 2018, Secure quantum key distribution over 421 km of optical fiber, Physical Review Letters 121:190502, https://doi.org/10.1103/PhysRevLett.121.190502.
3 H. Zhang, J. Yang, S. Gray, J.A. Brown, T.D. Ketcham, D.E. Baker, A. Carapella, R.W. Davis, J.G. Arroyo, and D.A. Nolan, 2017, Transparent Er3+-doped Y2O3 ceramics with long optical coherence lifetime, ACS Omega 2(7):3739-3744, https://pubs.acs.org/doi/10.1021/acsomega.7b00541.
4 J. Yang, H. Zhang, S. Gray, T.D. Ketcham, and D.A. Nolan, 2018, Er3+-doped Y2O3 transparent ceramic for quantum memory applications, Proceedings Volume 10771, Quantum Communications and Quantum Imaging XVI, 1077109, https://doi.org/10.1117/12.2320693.
Free-space quantum communications are interesting from a fundamental physics standpoint, but more importantly, they are interesting as a step toward quantum networking, which has long-term applications such as quantum distributed computing, super-resolution telescopic imaging, and truly secure communication, Kwiat said.5 Another step toward quantum networking is “blind” quantum computing, a secure method of programming a remote quantum computer. Like other aspects of quantum technology, this approach relies on the development of quantum repeaters.
Another valuable application for quantum networking is ship-to-ship cryptography for the U.S. Navy, a situation where a fiber-based network is unfeasible. To create this system, Kwiat’s team is designing drones, which have much greater reconfigurability than fiber-based systems, that can exchange quantum information. The goal is to create an interconnected array of aerial and fiber-based systems that could operate on a ship deck’s highly variable environment.
Kwiat pointed to a number of technology gaps including the lack of quantum repeaters, low-loss switches, integrated photonics, compact sources of pure and entangled photons, and photon detection methods without absorption (“quantum nondemolition” measurements). He said that his team is particularly focused on creating efficient and reliable sources for single photons. Quantum memory synchronization has been successful in enhancing single-photon sources and may also be scalable, he noted.
Alexander Sergienko, Boston University
Sergienko began his remarks by reflecting on the evolution of quantum technologies and engineering over the past several decades, then highlighted current and future opportunities. The generation of entangled photon states set the stage for quantum communication and networking many years ago, he said, leading to quantum imaging, a multitude of applications such as quantum metrology, and the overall rise of quantum research. Quantum cryptography also has a long history, he said, pointing to a Defense Advanced Research Projects Agency (DARPA) quantum cryptography network that communicated via commercial fiber in the mid-2000s.
Once entanglement was understood, it became possible to engineer it. Today, engineers are able to manipulate polarization, frequency, or direction, each of which presents opportunities for applications. For example, quantum-inspired imaging, tomography, and microscopy are all related to the spatial distribution of
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5 D.P. Rideout, T. Jennewein, G. Amelino-Camelia, T.F. Demarie, B.L. Higgins, A. Kempf, A. Kent, et al., 2012, Fundamental quantum optics experiments conceivable with satellites—reaching relativistic distances and velocities, Classical and Quantum Gravity 29:224011, https://doi.org/10.1088/0264-9381/29/22/224011.
the electromagnetic field and photons. These applications are not pure quantum, but they enable the transfer of ideas from the quantum domain to a semiclassical one.
Sergienko’s team is experimenting with multi-ports, which allow for bigger metrics than beam-splitters, are reversible, conserve resources, and enable more applications. For example, they can be used in quantum simulations of solid-state electrons, the design of new materials with desired properties and topological features, and quantum walks using Grover’s coin for faster search and information processing. Quantum neural networks represents another intriguing area of research, he noted.
After the introductory remarks, participants were invited to ask questions. Themes included the complexities of achieving quantum communication, security concerns, market forces, and other considerations.
Achieving Quantum Communications
Wadley asked panelists to comment on how close the field is to cross-country, quantum-encrypted conversations with more than two people sharing the same entangled photons. Kwiat said that cross-country point-to-point quantum-encrypted communication is still not possible: the longest current distance is a few hundred kilometers on the ground and 1,200 kilometers via trusted satellite (and that is not a pure quantum system, he added). Multiple-person communication, meanwhile, will require entangled, key-correlated pairs generated and shared through a central storing house; quantum memories; and a quantum repeater network, satellite connection, or a combination of the two.
Gumann added that current quantum communication systems have physical constraints, and overcoming them will require individual quantum computers connected via a quantum network, something still a long way away. Establishing blind quantum computing could help, but that requires transduction devices, which are also a long way away. Prem Kumar, Northwestern University, added that transduction devices, when they are created, will allow quantum networks, and repeaters will extend the reach of quantum communication links, but those are also not yet created. Developing quantum repeaters will still require significant work, including well-designed memory and architecture, and while intermediate technologies are creating advancements, a two-node system of quantum communication with a repeater is also still far away.
A participant asked if China was improving the quality of communications by using entangled photons distributed by satellites. Kwiat pointed out that those result in rates that are too low to achieve secure quantum communication, and a large amount of improvement is still needed. Gray stated that quantum communication rates depend on whether the goal is distance, speed, n-bit keys, or other objectives.
Kwiat added that scientists are starting to experiment with various types of multiplexing to address rate limitations. Quantum dots have some potential in terms of photon sources, although performance is still inadequate for applications. Quantum memory is also needed, which in turn needs its own wide bandwidth. Although rare-earth-ion-doped materials have potential in this area, no experiment has successfully demonstrated a memory with simultaneously high fidelity, storage time, efficiency, and bandwidth. Researchers are also exploring optical switches, waveguides, integrated photonic sources, and other ideas to address rate limitations.
In response to a question, Sergienko noted that entangled electron spins could be used at nodes of a quantum communication network, but they still depend on photons to connect them. Photons could carry information over large distances, but are uncontrollable, and they do not produce reliable control-not gates. Small-scale quantum computers linked together over long distances need shared entanglement to communicate securely, but there is a trade-off between security and coherent quantum entanglement.
A participant asked if cross-country quantum communications would require its own dedicated network. Gray answered that sending quantum and classical data on the same fiber creates noise and cross talk on the quantum channel that degrades performance, and successful long-distance QKD experiments used a single quantum channel on fiber because the cross talk limits the distances that are possible. To achieve the highest performance in quantum communication, quantum channels will require dedicated fibers. Despite this, researchers are exploring creating QKD systems in fibers also carrying classical data channels because of the cost efficiencies.
Security Issues
A participant asked if it would be cheaper to use existing technology and cryptography algorithms instead of creating a new quantum infrastructure for secure communications. Gray answered that existing cryptography will be vulnerable to quantum-enabled attacks, and fully secured quantum encryption will require investments to achieve the technologies that are needed.
Quantum computing attacks are a long way off, one participant pointed out, but distributed quantum computing could affect the entire ecosystem of information exchange. Are companies worried? Gray replied that, in his view, quantum is the key to security for the future. Quantum computers are not here yet, but smart planning will include them, and quantifying a company’s security needs is the best way to determine a plan. Kumar agreed, noting that security needs vary but will be a large part of distributed quantum computing.
A participant asked if connecting processes was as important as secure communications. Gumann affirmed that connecting computers is an important overall problem, whereas security is just one part of quantum communication. There remain many gaps, however, such as a timeline for when new technologies will emerge, where the performance enhancements will be, and what distributed quantum computing will enable, he said.
In response to a question, Kwiat confirmed that many quantum applications are susceptible to side channel attacks or leakages, but the difference is that they are detectable. The detectors themselves are not perfect, however, so other hardware solutions are needed. Kumar added that, as in classical cryptography, one can never be sure of all the side channels, and potential vulnerabilities must be designed for. Gray agreed, noting that several teams are designing to protect against side channel attacks.
Market Forces
A participant pointed out that many research innovations are labor-intensive and domain-specific. How can the United States encourage cross-discipline, industry-wide access to needed technology or components? For example, trapped ions are created with deep UV lasers, which are not broadly useful enough to be commercially viable but are still a critical resource for quantum technology. Niche technologies, he continued, are enabling this multidisciplinary, nascent domain, but they need to be economically viable to exist.
Gray agreed, noting that this is a hard question to answer. Another participant added that national laboratories may be better suited to housing such niche technologies than industry. A third participant agreed, noting the struggle between accelerating innovation for the United States’ global economic standing and industry’s real need to make money.6 Is it possible for industry to facilitate technology sharing?
Several participants discussed how companies and other organizations approach the provision of such technologies. Companies like IBM do sponsor basic research and engage with the academic community, and the American Institute for Manufacturing (AIM) sometimes makes specialized equipment for research, but companies operate differently from research laboratories. Without sufficient demand, manufacturing small quantities of highly specialized components is not cost-effective. A participant suggested that a repository of needed equipment could be very effective with the right funding model.
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6 Small companies making components for quantum computing can be successful. See for instance http://Qdevil.com.
Gray highlighted the difficulty of obtaining QKD and other photonics components domestically. In the 2000s, technology components manufacturing migrated overseas, and he expressed his belief that it is important not to let that happen with quantum technology manufacturing. A participant asked: Is an entirely new manufacturing infrastructure needed to meet this demand? Gray replied that this will depend on the components that are required, but will probably grow from a mix of established companies and start-ups. Kumar agreed, noting that many QED-C members are small start-ups, and as the demand rises, companies will find a way to meet it. The good news is that with the exception of special cables made only in Japan, the United Kingdom, and China, most components can currently be made in the United States, including cryogenic devices.
Other Considerations
In response to a question, Sergienko clarified that photonic quantum metrology involves entangled photons that must be generated and manipulated. This has many advantages, such as increased sensitivity and faster interferometers. In metrology, accuracy depends on interface visibility and the gradient. Reducing the period increases the gradient and thus the resolution interface, making it possible to calibrate transmission, efficiency, loss, and other factors more accurately than with conventional methods.
Kumar stated that it remains unclear whether it is better to scale up individual computers or connect multiple small ones because of gaps in understanding of computation depth, latency, delays, and other factors. At today’s quantum computing level, distributed computers will not provide an advantage, but progress is being made, such as increased coherence times. Gumann reiterated that distributed quantum computing requires transduction devices that are not yet available, suggesting that it is better to scale up individual computers than to pursue distribution, but research in the coming years could change that.
In terms of quantum sensors and coherent systems, Kwiat noted, researchers are closer to communication between sensors in different modalities. Communication, sensing, and imaging are likely to be nearer-term applications than computation, and they can be used to secure nodes on the electrical grid or can use optical clocks for navigation. However, the United States is apparently not as interested in pursuing those communication security goals, he added.
SCIENCE AND TECHNOLOGY GAPS, IMPLEMENTATION, CHALLENGES, AND SCALABLE MANUFACTURING ISSUES
Robert Hull, Rensselaer Polytechnic Institute, introduced the panelists for the workshop’s final panel discussion: Greg Boebinger, National High Magnetic Field
Laboratory; Juliet Gopinath, University of Colorado, Boulder; and Michael Liehr, AIM Photonics. Susan Sinnott, Pennsylvania State University, moderated a Q&A period following the panelists’ introductory remarks.
Greg Boebinger, National High Magnetic Field Laboratory
Quantum matter follows its own rules, and research is uncovering new electron behaviors with implications for both fundamental science and technological applications. Boebinger spoke of the wide range of opportunities that quantum materials offer and detailed two in particular: novel solar cells and quantum spin states.
Using high magnetic fields can reveal the complexities within quantum materials and unlock new applications, especially in defense. When using them to probe novel solar cells, standard electronic spin resonance can pinpoint where the electron is sitting in a solar cell at very high resolution, Boebinger said.
Quantum spin systems can greatly impact quantum computing, and frustrated electrons in particular present a new frontier in thermoelectric materials and applications of quantum entanglement. Frustrated electrons are electrons arranged in a lattice such that their magnetic fields cannot arrange into a pattern to make the lowest-energy alignment, a situation called “magnetic frustration.” For example, electrons on a triangular lattice can form a liquid of spins, in which the excitations carry spin but no charge, meaning that they transport entropy without creating an electrical current. This can avoid overheating other components and potentially provide unprecedented performance as ferroelectrics or other applications requiring massive entanglement.7
Organic chemistry offers a variety of ways to build systems of localized electron spins, including building a quantum computer out of materials that have arrays of multidimensional spin spaces. One chemistry framework in particular, metallo-organic complexes, is useful for controlling and positioning qubits, because nuclear spins in metallo-organic materials can be engineered to have a wider array of local symmetry groups than are available in simpler crystals. The spins can be manipulated using magnetic and/or electric fields and they can read off the nuclear spin states in microseconds. Boebinger speculated that a scalable quantum computer could be built from these complexes in which each qubit is at the single-molecule size.8
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7 L. Balents, 2010, Spin liquids in frustrated magnets, Nature 464:199-208, https://doi.org/10.1038/ nature 08917.
8 A. Gaita-Ariño, F. Luis, S. Hill, and E. Coronado, 2019, Molecular spins for quantum computation, Nature Chemistry 11:301-309, https://doi.org/10.1038/s41557-019-0232-y.
Juliet Gopinath, University of Colorado, Boulder
Gopinath discussed the importance of, and the challenges to, integrating multicomponent, highly complex quantum systems onto single, scalable platforms. Such platforms would leverage existing technology into a compact form, where conventional semiconducting materials hold a natural edge at room temperature. Once these platforms are scalable, it will be possible to increase data rates and bandwidth speed. While loss can be problematic, ultra-low-loss silicon waveguides recently demonstrated that it is possible to solve this problem.9
Integration presents many challenges. First, many materials do not have second-order nonlinearity, making spontaneous parametric down-conversion difficult. In addition, current switching technology does not enable integration. Pump filtering and achieving best performance for a particular device are also important missing pieces that will require multiple materials (heterogeneous integration). And, while advances are being made with detectors, the cryogenic requirements of current superconducting nanowire detectors are a limiting factor.
In Gopinath’s laboratory, research on Ge-Se-Sb/S devices are addressing some of the problems in generating entangled photons, and optical orbital angular momentum is also promising for quantum systems.10,11 In addition, potentially game-changing research from the Bank and Campbell groups is demonstrating the possibility of room-temperature detection and low-noise III-V avalanche photo-diodes (APD) alloys, she noted.12
Michael Liehr, AIM Photonics
AIM Photonics is a nonprofit industrial-scale microelectronics and integrated photonics development facility, full-service integrative photonics provider, and specialty, low-volume foundry. It is also the largest of the Manufacturing USA Institutes, a consortium whose partner organizations provide licensing, services, and customers for AIM Photonics’ work. AIM Photonics builds products and
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9 M.A. Tran, D. Huang, T. Komljenovic, J. Peters, A. Malik, and J.E. Bowers, 2018, Ultra-low-loss silicon waveguides for heterogeneously integrated silicon/III-V photonics, Applied Sciences 8(7):1139, https://siliconphotonics.ece.ucsb.edu/sites/default/files/2018-07/tran18ap.pdf.
10 G. Kang, M.R. Krogstad, M. Grayson, D.-G. Kim, H. Lee, J.T. Gopinath, and W. Park, 2017, High quality chalcogenide-silica hybrid wedge resonator, Optics Express 25(13):15581-15589, https://doi.org/10.1364/OE.25.015581.
11 R.D. Niederriter, M.E. Siemens, and J.T. Gopinath, 2016, Simultaneous control of orbital angular momentum and beam profile in two-mode polarization-maintaining fiber, Optics Letters 41(24):5736-5739, https://doi.org/10.1364/OL.41.005736.
12 J.C. Campbell and S.R. Bank, 2018, “Low-Noise Digital Alloy Avalanche Photodiodes,” Paper IW1B.5, Advanced Photonics, Integrated Photonics Research, Silicon, and Nanophotonics, Zurich, Switzerland, https://doi.org/10.1364/IPRSN.2018.IW1B.5.
research samples and tests new technologies for universities and small and midsize companies, enabling advancements outside the larger commercial sector. It is supported by more than $10 billion in capital investment and co-hosts large and small companies for proprietary development, which is typical for a semiconducting manufacturing line but unusual in that its investment is primarily for R&D.
AIM Photonics’ large 135,000-square-foot fabrication facility is a class-one compatible cleanroom and well beyond the capabilities of university laboratories, with a state-of-the-art 300 mm platform that enables state-of-the-art semiconductor and photonics processes, product design, and packaging. Processing capability spans from 65 nm all the way to the cutting-edge 5 nm CMOS.
Although the majority of AIM Photonics’ work is with silicon-based technologies, the organization is interested in broadening its reach by working with new materials, designing new tools, and creating new parts, all of which is beyond the typical industry focus, Liehr noted. He said the organization has translated lessons from the semiconducting industry to photonics, with the goal of reducing fabrication costs to make components widely available and enable advancements.
AIM Photonics’ quantum group can build and is developing superconducting qubits, single-photon detectors, and workable materials useful for quantum qubits, detectors, and signal transduction, such as niobium nitride and aluminum nitride, Liehr said. They have also had success with magnetic and superconducting materials, and plan to fabricate quantum dot lasers, low-loss waveguides, and other design elements.
Liehr also noted that AIM Photonics’ wafer bonding expertise could inform the heterogeneous integration of new materials that other speakers mentioned. However, new materials must be introduced very carefully to avoid cross-contamination to not impact other users of the cleanroom. AIM development focuses on laser and fiber edge coupling and lower-loss waveguides.
AIM Photonics has also successfully grown quantum lasers directly in silicon at the laboratory scale, and is working on scaling up on the 300 mm platform. While this laser work is using telecom and datacom wavelengths (1310/1550 nm) and moving to 350 mm would require new materials and recharacterization of existing devices, Liehr said the work is quite promising and illustrative of the type of years-long research that AIM Photonics and universities undertake together.
Last, Liehr noted that AIM Photonics has built an open, shared library of component elements for researchers, including enough pieces to design and submit transceiver plans for AIM Photonics to build.
Following the panelists’ remarks, participants discussed quantum sensing applications and challenges, the need for collaboration, workforce needs, single-molecule magnets, and ship-drone communications.
Applications for Quantum Sensing
Sinnott asked the panelists to speak about near-term and long-term applications for quantum sensing. Gopinath answered that precision navigation and timing were near-term applications, one intermediate application is to deploy sensors on useful platforms, and a very important long-term application is the ability to study fundamental new properties of materials. Liehr agreed, but speculated that navigation and timing were likely closer to 5-10 years away, although he said AIM Photonics could probably accelerate that timeline.
Boebinger reflected that advances happen at surprising paces and in unpredictable directions, making near-term predictions difficult, especially as researchers still do not know what materials will enable the overcoming of current limitations. Liehr added that quantum technology is in a very exciting phase right now, and while researchers may be able to predict some near-term applications, it is the ones that are not seen that could be the true game-changers.
Mohammad Soltani, Raytheon BBN Technologies, suggested that the lack of clarity for quantum sensors was a barrier for identifying specific applications, because except in a few cases, like atomic clocks, it is unclear what they will replace or improve. However, he noted that, when measurement gets to a regime that the quantum state needs to be measured or monitored, there are good opportunities for quantum sensors and probes. One example is that the device dimensions in the nanoelectronics industry are becoming so small that the traditional measurement probes and sensors may not provide an accurate quantification of what happens in the device, potentially necessitating a new generation of quantum probes.
Challenges to Quantum Sensing
Sinnott asked the panelists to identify the greatest challenge to quantum sensing. Liehr replied that while ideas are important, implementing them requires stable funding sources. Fully funded facilities are needed to overcome challenges, he stressed, but the Manufacturing USA Institutes are facing funding uncertainties, and industry is reluctant to take over when the time to product is long, as is the case in quantum. Policy pushes funding, and the government must believe that this research is critical enough to properly fund, favoring both long-term projects and “low-hanging fruit” that can advance capabilities and progress in the near term.
Boebinger sees materials as the greatest challenge. He cautioned that materials experts can find it hard to fit into the narrow slots (i.e., “chemist” or “physicist”) required for research and career advancement in academia. While national laboratories are making spaces to support such work, these structural factors currently limit progress toward needed materials.
Gopinath reiterated the importance of policy, suggesting that a concerted national focus on funding and shared goals, similar to the space race of the 1960s, and incorporating lessons from the BRAIN Initiative, could push the United States ahead of China, whose Micius launch reignited the urgency of quantum research. There have been many significant short-term achievements, but to achieve something of the magnitude of the moon landing, a more concerted, policy-backed focus is needed, she said.
Asked how such a focus could be sparked, Boebinger noted that the space race started with a gauntlet thrown by the President himself, laying out the priorities and organizing principles. Liehr added that bipartisan support is crucial, and the moon landing had strong support and funding across the board, while collaboration is a struggle in today’s climate. Gopinath agreed, noting that researchers respond well to a well-defined problem, but without focus, collaboration, and a noncompetitive environment, it is hard to move forward.
Boebinger added that in this polarized time, presidential support for a scientific initiative might not mean as much as it once did. However, national security is a unifying bipartisan issue, and a convincing national security argument can be made for quantum technology. Another participant noted that the space race was spurred by public fear inspired by Sputnik, suggesting that a similar threshold, such as China establishing secure quantum communications, could inspire a similar fear.
A participant countered that DoD, for its part, is already feeling that fear. Its new national defense strategy addresses a variety of fronts, including quantum. He stressed that all disciplines and departments should unite to ensure funding for quantum goals as a security issue. Liehr noted that AIM Photonics is DoD-funded, and while it makes things specifically for DoD, it also aligns with industry needs. For example, it has created photonic high-frequency radio-frequency cables for DoD and a digital version for industry. Similar alignments, such as using quantum sensing in oil exploration, a near-term application generating industry interest, will be necessary to advance sensing, he suggested.
Creating Collaboration
A participant noted that there are many experts using relevant materials in other realms, and asked if they could be invited to collaborate on these quantum challenges. Liehr agreed that close collaboration, especially among those with different areas of expertise, could bring many new opportunities. Boebinger added that his work on high magnetic fields materials and instrumentation, although not quantum-specific, nevertheless attracted enough interest to pull him into the quantum community. With the disappearance of large corporate laboratories, he suggested, industry and academic experts could build a clearinghouse of ideas to answer these questions, much like SEMATECH did for the semiconductor industry decades ago.
Liehr pointed out that SEMATECH was formed because component offshoring was seen as an emergency. It included separate membership tiers, and core members were able to agree on noncompetitive areas, but the partnership fell apart when interests and competencies diverged. Sinnott asked if a new SEMATECH-like organization is needed, and whether other countries were pursuing similar collaborations. Liehr replied that there are big programs in China and Europe, and added that it may be possible for the National Academies of Sciences, Engineering, and Medicine to initiate knowledge exchanges with China, especially in the basic science arena, where sharing privileged information is less of a concern.
Broz noted that QED-C, with government support, intends to engage the academic community, standards developers, foreign and domestic supply chain manufacturers, and professional societies on the problems this burgeoning field faces, and expand QED-C’s scope to potentially resemble a SEMATECH-like entity, with an emphasis on domestic manufacturing of quantum-enabling technologies. Another participant suggested a DARPA-like Grand Challenge could be used to define quantum, identify DoD applications, and determine which roadblocks to tackle.
Building on this suggestion, another participant suggested that the time is ripe for two such efforts in this area. First, DoD should focus on integrative photonics and sensing for quantum communications. Second, to build a real quantum computer, researchers need an open source effort similar to IBM’s, to push algorithm development and other activities beyond what is useful to DoD. These initiatives would also invite deeper multidisciplinary collaboration, he concluded.
Workforce Issues
In response to a question, Liehr stated that there is definitely a quantum workforce problem. Quantum expertise is rare, and the path to an advanced degree is too long to rely exclusively on Ph.D.’s. It may be possible to design tools that a non-Ph.D. could use, an approach that helped speed advancement in the semiconductor industry. It will be important to provide mechanisms for proper training and broad access to educational materials, he said, adding that this is an area in which AIM Photonics has an active program for photonics and hence can also contribute to for quantum.
Single-Molecule Magnets
In response to a question about single-molecule magnets, Boebinger replied that he was struck by their flexibility, because they are approaching 1-second coherence times at relatively elevated temperatures, have a nearly infinite phase space with regard to creating organic crystalline structures, and give near-perfect
quantum states with appropriate mixing. He said that he is not aware of any fundamental limits, although there surely are defect states in the framework. Furthermore, if single molecules work as magnets, they may be infinitely reproducible, perhaps with tunnel junctions, as long as the width is set not by fluctuations but by chemistry, which can regulate the tunnel barrier precisely.
Ship-Drone Communication
Bunning asked how DoD could enable the impressive vision Kwiat laid out for ship-drone quantum communication. Liehr replied that for an atomic system based on ions, all the components must be integrated on a wafer and miniaturized, a process that requires a fundamental change in the current telecom materials system and characterization. The structures required are close to becoming a reality, but there is still work needed on the materials and processing end, especially if aluminum nitride, which has better waveguide ultraviolet transparency is chosen.
Gopinath added that it also depends on DoD’s comfort with risk and its preferred timeline. A model with today’s materials could be created quickly, but it is unlikely to achieve the desired performance. Liehr pointed out that new materials systems will require time, hard work, and close collaboration to understand the problems, solve them, and optimize the current system’s boundaries. For example, ions for clocks require frequencies not yet available, and may even be radioactive, although that is a solvable problem.
WRAP-UP DISCUSSION
Workshop chair Haydn Wadley moderated the final portion of the workshop, a wrap-up discussion reflecting on the entire 2-day meeting. Participants explored several themes: getting to quantum communications, the need for collaboration, critical weaknesses, qubit device ideas, scalability, and supply chain needs.
Getting to Quantum Communications
Wadley kicked off the discussion by noting that details can make it difficult to understand how each component and technology fits together, yet getting to quantum communications is the ultimate goal. With that in mind, he asked the audience how to overcome the challenges, find the missing pieces, and make that goal a reality.
One participant replied that without classical Global Positioning System (GPS), quantum communication requires alternative sensing and timing modalities to create situational awareness. Mohammad Soltani added that DARPA has struggled to define a program for classical free-space communication, mainly because an agile enough
aperture has not been found. It may be overly optimistic to think that researchers can solve this same problem for free-space quantum communications, he said.
Robert Hull asked if DoD also sought the capability to communicate through water, and Soltani answered that internal research is attempting to counter water absorption with optical communication, but not at the quantum level. A participant added that the Office of Naval Research and DARPA have been working on underwater communications for a long time, but have yet to succeed over long distances. Another participant noted that nuclear submarines make water communication just as important as air communication.
The Need for Collaboration
Participants discussed opportunities for experts to collaborate to solve these problems. Agencies like the Office of Science and Technology Policy and the National Science Foundation can, for example, help influence government policy and research directions, and also work with industry giants to develop a platform and push the technology in the right direction. Gopinath added that it is important to expand funding to include not just single or paired investigators, but teams of researchers with varied expertise.
Michael Liehr agreed that teams were necessary, especially to understand the materials and algorithmic components. There is also a need for facilities to build and test prototypes openly, with multiple participants and clear IP protocols, he said. Another participant noted that IBM’s open access to a quantum system is having a trickle-down effect and improving collaboration, learning, and progress.
Critical Weaknesses
Asked to identify critical weaknesses, one participant stressed that quantum is a broad-based problem that will not benefit from preselecting one route, issuing patents, or creating high-cost structures. Instead, he emphasized the need to allow for breadth.
The participant also added that widely available enabling technologies are crucial for empowering government laboratories and companies of all sizes to explore the many different trajectories within the quantum ecosystem. For example, if the goal is atomic systems for quantum networking, computing, and gravitational sensing, those depend on very narrow line width atomic transitions that are manipulable using radiant coherent sources. However, there is a severe shortage of suitable lasers available, with most sourced from overseas. Given that these lasers are a key enabling technology, research into laser platforms that are compact, stable, and address a range of colors is essential. Unfortunately, fiber-based lasers are unsuitable for this work.
The participant identified improved atomic clocks as another necessary ingredient for quantum networking and computing. Clocks with longer holdover that can run autonomously without synchronization or GPS can serve as a baseline for communication protocols, he said. He also noted that despite many advances, there is still insufficient understanding of how entanglement affects quantum measurement, making entanglement a key area of focus for future work.
Qubit Device Concepts
Noting that the vision for quantum computing is still a long way away, a participant asked which qubit device concepts are most promising for moving toward the fault-tolerant range. Responding, a participant said coherence is important, but so is gate fidelity. Adding more gates, even at a low level of qubits, will introduce errors, and understanding and reducing the error rates of different technologies is crucial.
Another participant added that within the quantum community, there are benchmarks to compare the gate fidelity of different platforms. Multiple teams are working on solving these problems using different processors and algorithms. It would be beneficial if, as these different approaches develop, there were a way to compare them, he suggested. While this is not an approach toward developing qubits, it is a reminder of the value of comparing technologies that take different approaches to qubit development.
Ravi Pillarisetty noted that proof-of-concept for silicon-based qubits has been demonstrated, which has high fidelity and fits with transistor manufacturing. What is needed now, he suggested, is a high volume of experiments to understand the parameters and how they affect fidelity. Joseph Broz said that, in his view, the best route to near-term quantum device operationalization could be photonic integrated circuits in small packages with silicon nitride systems.
Scalability
A participant noted that work with silicon suggests that it is a very promising material for single-electron-based quantum devices, and Intel may have a scalable platform for these devices soon. It is important to identify these types of scalable elements, the participant suggested, although that can make it difficult for university researchers to participate in key work. Rudy Wojtecki pointed out that when scaling up to more qubits, the fidelity problem becomes more complicated.
Supply Chain Needs
Wadley noted the issue of supply chain gaps and invited Broz to share industry’s view of supply chain needs, using the superconducting qubit as an example.
Broz stated that for stability, these qubits need enhanced thermal isolation, and vibration isolation, radio-frequency shielding, scalable input and output, and very clean microwave engineering. As Liehr mentioned, low-cost, scalable fabrication techniques, with low error margins, are very important to device and component manufacturing. There is also a need for characteristics like low-loss packaging for highly mobile sensing, Broz noted.
Standards and performance metrics are also very important, and QED-C is working with the Institute of Electrical and Electronics Engineers and other standards development organizations to develop common terminology, benchmarks, and supplier metrics. For example, there should be a formula to determine when a quantum technology deserves more attention and investment than a classical system, taking into consideration size, weight, and power restrictions, Broz said.
In addition, industry is concerned about component interoperability and availability and several key enabling technology gaps. According to the QED-C’s Technical Advisory Council, some of these gaps are superconducting cabling (which is expensive and not readily available in large quantities domestically), high-density interconnects, ion traps, magnetic shielding, improved dilution refrigerators, miniaturized cryo-microwave components, cryostat control electronics (with the included materials challenges), custom microwave components, inexpensive room-temperature qubit control and readout electronics, qubit foundry services, and low-cost electronics compatible with cryostats. Compact, reliable, tunable, and stable laser and modulation sources are also critical, as other workshop participants had noted.
While this list is different from what an academic might need—largely because these components have to be manufacturable—it is still beneficial to understand how industry views the enabling technology, fabrication, and materials challenges, Broz noted. On the positive side, he noted his view that AIM Photonics is servicing this new industry very well, the advances with photonics are very promising, and the emerging 5G industry could provide dual-use opportunities for pulse generators for superconducting qubit technologies. Nonetheless, materials and manufacturing issues remain critical, he concluded.
Pillarisetty agreed with Broz’s assessment, adding that another important need is high-velocity, high-throughput characterization, without which it is impossible to move beyond the proof-of-concept stage. Broz noted that these gaps will not be filled unless companies develop products that respond to these needs.
In closing, Wadley observed that a systems roadmap was emerging and suggested that the important step now is to put resources behind it and see what the next few years bring. Another participant stressed the importance of maintaining the United States’ competitive edge by investing in pursuits that can maximally impact a range of quantum technologies. To that end, Wojtecki underscored the importance of consistent, long-term funding.
