Development of Quantum Interconnects (QuICs) for Next-Generation Information Technologies
David Awschalom, Karl K. Berggren, Hannes Bernien, Sunil Bhave, Lincoln D. Carr, Paul Davids, Sophia E. Economou, Dirk Englund, Andrei Faraon, M. M. Fejer, Saikat Guha, Martin V. Gustafsson, Evelyn Hu, Liang Jiang, Jungsang Kim, Boris Korzh, Prem Kumar, Paul G. Kwiat, Marko Lončar, Mikhail D. Lukin, David A. B. Miller, Christopher Monroe, Sae Woo Nam, Prineha Narang, Jason S. Orcutt, Michael G. Raymer, Amir H. Safavi‐Naeini, Maria Spiropulu, Kartik Srinivasan, Shuo Sun, Jelena Vuckovic A, Edo Waks A, Ronald Walsworth, Andrew M. Weiner, Zheshen Zhang
Just as "classical" information technology rests on a foundation built of interconnected informationprocessing systems, quantum information technology (QIT) must do the same.A critical component of such systems is the "interconnect," a device or process that allows transfer of information between disparate physical media, for example, semiconductor electronics, individual atoms, light pulses in optical fiber, or microwave fields.While interconnects have been well engineered for decades in the realm of classical information technology, quantum interconnects (QuICs) present special challenges, as they must allow the transfer of fragile quantum states between different physical parts or degrees of freedom of the system.The diversity of QIT platforms (superconducting, atomic, solid-state color center, optical, etc.) that will form a "quantum internet" poses additional challenges.As quantum systems scale to larger size, the quantum interconnect bottleneck is imminent, and is emerging as a grand challenge for QIT.For these reasons, it is the position of the community represented by participants of the NSF workshop on "Quantum Interconnects" that accelerating QuIC research is crucial for sustained development of a national quantum science and technology program.Given the diversity of QIT platforms, materials used, applications, and infrastructure required, a convergent research program including partnership between academia, industry, and national laboratories is required.
Just as "classical" information technology rests on a foundation built of interconnected informationprocessing systems, quantum information technology (QIT) must do the same.A critical component of such systems is the "interconnect," a device or process that allows transfer of information between disparate physical media, for example, semiconductor electronics, individual atoms, light pulses in optical fiber, or microwave fields.While interconnects have been well engineered for decades in the realm of classical information technology, quantum interconnects (QuICs) present special challenges, as they must allow the transfer of fragile quantum states between different physical parts or degrees of freedom of the system.The diversity of QIT platforms (superconducting, atomic, solid-state color center, optical, etc.) that will form a "quantum internet" poses additional challenges.As quantum systems scale to larger size, the quantum interconnect bottleneck is imminent, and is emerging as a grand challenge for QIT.For these reasons, it is the position of the community represented by participants of the NSF workshop on "Quantum Interconnects" that accelerating QuIC research is crucial for sustained development of a national quantum science and technology program.Given the diversity of QIT platforms, materials used, applications, and infrastructure required, a convergent research program including partnership between academia, industry, and national laboratories is required.
Just as "classical"information technology rests on a foundation built of interconnected information-processing systems, quantum information technology (QIT) must do the same. A critical component of such systems is the "interconnect,"a device or process that allows transfer of information between disparate physical media, for example, semiconductor electronics, individual atoms, light pulses in optical fiber, or microwave fields. While interconnects have been well engineered for decades in the realm of classical information technology, quantum interconnects (QuICs) present special challenges, as they must allow the transfer of fragile quantum states between different physical parts or degrees of freedom of the system. The diversity of QIT platforms (superconducting, atomic, solid-state color center, optical, etc.) that will form a "quantum internet"poses additional challenges. As quantum systems scale to larger size, the quantum interconnect bottleneck is imminent, and is emerging as a grand challenge for QIT. For these reasons, it is the position of the community represented by participants of the NSF workshop on "Quantum Interconnects"that accelerating QuIC research is crucial for sustained development of a national quantum science and technology program. Given the diversity of QIT platforms, materials used, applications, and infrastructure required, a convergent research program including partnership between academia, industry, and national laboratories is required.
Quantum interconnects (QuICs), which connect multiple quantum devices to build distributed quantum systems, are essential for large-scale quantum information processing. While various software tools have been developed to analyze quantum programs running on QuICs, there are very few frameworks for formal reasoning about them on actual quantum devices. The lack of such tools may make distributed systems unreliable because of the complicated behavior of concurrent quantum processes and the physical constraints of quantum devices. This paper discusses the need for an infrastructure, including a distributed quantum programming language, to realize reliable distributed quantum computing.
Entanglement is a quintessential quantum mechanical phenomenon with no classical equivalent. First discussed by Einstein, Podolsky, and Rosen and formally introduced by Schrödinger in 1935, entanglement has grown from a scientific debate to a radically new resource that sparks a technological revolution. This review focuses on fundamentals and recent advances in entanglement-based quantum information technology (QIT), specifically in photonic systems. Photons are unique quantum information carriers with several advantages, such as their ability to operate at room temperature, their compatibility with existing communication and sensing infrastructures, and the availability of readily accessible optical components. Photons also interface well with other solid-state quantum platforms. We first provide an overview on entanglement, starting with an introduction to its development from a historical perspective followed by the theory for entanglement generation and the associated representative experiments. We then dive into the applications of entanglement-based QIT for sensing, imaging, spectroscopy, data processing, and communication. Before closing, we present an outlook for the architecture of the next-generation entanglement-based QIT and its prospective applications.
Quantum simulators are a promising technology on the spectrum of quantum devices from specialized quantum experiments to universal quantum computers. These quantum devices utilize entanglement and many-particle behaviors to explore and solve hard scientific, engineering, and computational problems. Rapid development over the last two decades has produced more than 300 quantum simulators in operation worldwide using a wide variety of experimental platforms. Recent advances in several physical architectures promise a golden age of quantum simulators ranging from highly optimized special purpose simulators to flexible programmable devices. These developments have enabled a convergence of ideas drawn from fundamental physics, computer science, and device engineering. They have strong potential to address problems of societal importance, ranging from understanding vital chemical processes, to enabling the design of new materials with enhanced performance, to solving complex computational problems. It is the position of the community, as represented by participants of the NSF workshop on "Programmable Quantum Simulators," that investment in a national quantum simulator program is a high priority in order to accelerate the progress in this field and to result in the first practical applications of quantum machines. Such a program should address two areas of emphasis: (1) support for creating quantum simulator prototypes usable by the broader scientific community, complementary to the present universal quantum computer effort in industry; and (2) support for fundamental research carried out by a blend of multi-investigator, multi-disciplinary collaborations with resources for quantum simulator software, hardware, and education.
Classical computers just won't cut it when it comes to tackling the greatest challenges in biology and medicine. Even accurately simulating the relatively simple caffeine molecule, far simpler than DNA or even proteins, would take an impossibly large classical computer. That's why we need a paradigm shift in the field of computing, like a shift from the steam locomotive to a starship's warp drive. That's why we need quantum computers. At IBM Quantum, we've already started building quantum computers based on superconducting transmon qubit technology, and have been making this transformative technology available to the world. Back in 2016, we made history when we put our quantum computers on the Cloud for anyone from enterprise developers to students to program. Last fall, we announced an aggressive roadmap toward building a 1121-qubit device by 2023. However, even that device will not be large enough to solve science's greatest challenges. That will require fault-tolerant quantum processors containing potentially millions or even billions of qubits working together. The technology required to build a processor with a few million superconducting qubits will likely surpass the limits of dilution refrigerator scaling (Figure 1), so we have to come up with alternative ideas for scaling up our devices efficiently. We think that constructing the fault-tolerant quantum computers of the future will require a distributed approach similar to today's supercomputers, where smaller processors each in their own fridge share quantum information coherently and without loss to tackle problems in parallel. This will only be possible if we can develop quantum interconnects to link processors together into a quantum intranet. This requirement for a quantum intranet is distinct from the more commonly discussed context of a quantum Internet. Quantum communications advances typically center around data transfer security such as long-distance entanglement and quantum key distribution. IBM has long been involved in this field; IBM researchers debuted the BB84 QKD protocol in 1984 [1], for example. However, we must not lose sight of the fact that short-distance quantum interconnect technology may play a key role in extending computational systems to a scale sufficient for solving practical problems. A quantum Internet connecting and interfacing such scaled quantum computers would follow as a next step to enable new applications. [2]. Quantum interconnects capable of supporting our vision of a quantum intranet will require fundamental advances in physics. The no-cloning theorem makes it impossible to convert an arbitrary, unknown quantum state into classical bits and then use these bits to recreate that exact state elsewhere, so we must devise schemes that stay coherent as we transfer quantum information from the states of superconducting qubits onto the states of photons, transmit these photons over wires, and recreate the quantum state on the superconducting qubits of another processor. At the same time, the microwave photons we use to manipulate and read out our superconducting qubits require wiring overheads, and a significantly different cryogenic infrastructure to permit coherent transfer of quantum states even over short distances. Hence, converting microwave photons into optical photons allows for low-loss quantum state transfer through fiber optic infrastructure that the telecom industry has spent decades maturing. Academic groups have been working for over a decade to transfer quantum information from microwave to optical photons in a coherent manner with a variety of systems and mechanisms, and while this has not been conclusively demonstrated, progress has been made [3]. At IBM Research's Thomas J. Watson Research Center in Yorktown Heights, NY, we have been developing a silicon-germanium microwave-optical transducer (funded by the Army Research Office and the Laboratory for Physical Sciences) that's integrated with our own transmon qubit platform. Meanwhile, our IBM Research lab in Zurich is exploring a different platform, to develop piezo-optomechanical transducers in gallium phosphide. Implementing and perfecting each of these solutions will be challenges on their own—plus, we must devise distributed error correcting codes to run on these systems. IBM Quantum “super-fridge” photo: https://flic.kr/p/2jHrEGw. IBM is developing a suite of scalable and increasingly larger and better processors, with a 1000-plus qubit device targeted for the end of 2023. In order to house even more advanced processors to the thousands and eventually million-plus qubit systems of the future, the IBM Quantum team is building a dilution refrigerator larger than any currently available commercially. (Credit: Connie Zhou for IBM) Our primary research focus is in scaling up transmon qubit processors, but the issues surrounding scale-up are important to every qubit architecture. We think that quantum interconnect research, and a quantum intranet, will be the likely solution to scale-up across the field. The community has already deemed quantum interconnects as "crucial for sustained development of a national quantum science and technology program" [4]. Other recent work involving connecting spatially separated qubits with microwave includes Zhong, Y. et al.’s “Deterministic multi-qubit entanglement in a quantum network,” [5], and Magnard, P. et al.’s “Microwave Quantum Link between Superconducting Circuits Housed in Spatially Separated Cryogenic Systems.” [6] Given the importance of these devices, and the impact of scale, we cannot tackle these challenges alone. In August of last year, the US Department of Energy announced that it would allocate up to $625 million in funding over five years to support multidisciplinary Quantum Information Science (QIS) Research Centers. We expect that the work carried out at these centers will be essential to realizing the quantum intranet. Specifically, IBM Quantum will work with the Q-NEXT center led by Argonne National Laboratory to co-design technological building blocks and system needs that will allow us to realize these quantum interconnects. The IBM Quantum team is developing quantum computers because we think that these devices have the capability to change the world, but seeing them through to completion will take innovative solutions to physics problems that physicists have never faced before. If we can realize quantum interconnects and a quantum intranet, then we think we have a clear path to making these devices, and their abilities, a reality.
To advance quantum information science and technologies, a wide variety of quantum machines and protocols are being developed based on different physical systems. Interconnecting these systems is a grand challenge to scale up quantum information architectures. This effort requires to develop specialized photonic devices and capabilities, ranging from efficient photon extraction for qubit connectivity to the implementation of advanced optical memories. In this talk, I will provide an overview of the opportunities presented by networking, including long-distance quantum communications and distributed quantum computing. I will also present our recent experimental demonstrations, which enable the realization of a quantum-bit-encoding converter, the implementation and use of highly-efficient quantum memories based on laser-cooled neutral atoms, and the development of nanophotonic devices for qubit coupling.