Three-Dimensional Wiring for Extensible Quantum Computing: The Quantum Socket
J. H. Béjanin, T. G. McConkey, J. R. Rinehart, C. T. Earnest, C. R. H. McRae, D. Shiri, J. D. Bateman, Y. Rohanizadegan, B. Penava, P. Breul, S. Royak, M. Zapatka, Austin G. Fowler, M. Mariantoni
Reimagining and miniaturizing the huge machines of the World War II era was a great step in the history of computing. Now quantum computers face a similar developmental step, on the way to tomorrow's compact, scalable systems. In analogy with sockets in traditional electronics, the authors present a link for classical control hardware and solid-state qubits, with exceptional properties at microwave frequencies and cryogenic temperatures. This technology should bring us within a few years to a key milestone in quantum computing: quantum error-correction implemented for hundreds of physical qubits.
Reimagining and miniaturizing the huge machines of the World War II era was a great step in the history of computing. Now quantum computers face a similar developmental step, on the way to tomorrow's compact, scalable systems. In analogy with sockets in traditional electronics, the authors present a link for classical control hardware and solid-state qubits, with exceptional properties at microwave frequencies and cryogenic temperatures. This technology should bring us within a few years to a key milestone in quantum computing: quantum error-correction implemented for hundreds of physical qubits.
Quantum computing architectures with ten or more quantum bits (qubits) have been implemented using trapped ions and superconducting devices. The next milestone in the quest for a quantum computer is the realization of quantum error correction codes. Such codes will require a large number of qubits that must be controlled and measured by means of classical electronics. This scaling up leads to a number of problems and sources of error that must be accounted for in order to have an operational system. \n \nOne architectural aspect requiring immediate attention is the realization of a suitable interconnect between the quantum and classical hardware. Our proposed solution to this wiring problem is the quantum socket, a three-dimensional wiring method for qubits with superior performance as compared to two-dimensional methods based on wire bonding. The quantum socket also provides a means to counteract another scaling problem, the coupling of qubits to unwanted cavity modes resulting in coherent leakage error. By following our proposed wiring methodologies, half-wave fencing or antinode pinning, we show how the error due to leakage can be mitigated to orders of magnitude below current state-of-the-art error probabilities.
Quantum computers have gained widespread interest as they can potentially solve problems that are intractable even for today’s supercomputers, such as the simulation of quantum systems as initially proposed by Feynman. To achieve such tremendous progress, a quantum computer relies on processing the information stored in quantum bits (qubits), the fundamental units of quantum computation, similar to the bits in a classical (i.e., non-quantum) processor. In general, a quantum processor comprising several qubits is connected through a quantum-to-classical interface consisting of classical electrical circuits for manipulating and reading out their quantum state. The accuracy of an operation on a qubit is characterized using the fidelity, which is 100 % in case of a perfect operation. In practice, a fidelity between 99 % and 99.9 % is typically achieved in today’s experiments with less than 100 qubits, limited by non-idealities in the control signals and by the implementation of the physical qubit itself. Since such qubit fidelities are too low to execute relevant quantum algorithms, quantum error correction schemes have been developed which rely on a much larger number of qubits to correct for possible errors, resulting in the need for quantum processors with thousands or millions of qubits. Solid-state qubits promise the largescale integration required to scale to millions of qubits, as they exploit the lithographic fabrication techniques borrowed from the semiconductor industry. However, state-of-theart solid-state qubits, such as transmons and single-electron spin qubits, must be typically cooled to cryogenic temperatures in a dilution refrigerator to exhibit quantum behavior. Because of the limited number of qubits (< 100) in state-of-theart solid-state quantum processors, the classical controller is currently implemented by general-purpose instruments or by tailor-made controllers operating at room temperature connected via several wires to the qubits in the cryogenic chamber. However, these systems must scale to support millions of qubits. While scaling up the underlying quantum processor is already exceptionally challenging, building the electronics required to interface such a large-scale processor is just as relevant and arduous.
This paper presents an extensive exploration of quantum computing as an emerging paradigm that operates on the principles of quantum mechanics to process information in ways unattainable by classical systems. It traces the evolution of quantum theory from its early conceptual foundations to its present-day technological applications, highlighting key milestones such as the development of qubits, quantum gates, and essential algorithms including Shor’s and Grover’s. The study examines the fundamental mechanisms of quantum superposition and entanglement, alongside the hardware and software innovations driving scalability and performance. By analysing experimental progress, programming models, and comparative advantages over classical and cloud computing, this paper underscores how quantum computing can transform industries such as data security, medicine, and artificial intelligence. Furthermore, it outlines future prospects involving error correction, neuromorphic integration, and commercialization trends that are shaping the next generation of computational technology.
Abstract Spanning a range of hardware platforms, the building-blocks of quantum processors are today sufficiently advanced to begin work on scaling-up these systems into complex quantum machines. A key subsystem of all quantum machinery is the interface between the isolated qubits that encode quantum information and the classical control and readout technology needed to operate them. As few-qubit devices are combined to construct larger, fault-tolerant quantum systems in the near future, the quantum-classical interface will pose new challenges that increasingly require approaches from the engineering disciplines in combination with continued fundamental advances in physics, materials and mathematics. This review describes the subsystems comprising the quantum-classical interface from the viewpoint of an engineer, experimental physicist or student wanting to enter the field of solid-state quantum information technology. The fundamental signalling operations of readout and control are reviewed for a variety of qubit platforms, including spin systems, superconducting implementations and future devices based on topological degrees-of-freedom. New engineering opportunities for technology development at the boundary between qubits and their control hardware are identified, transversing electronics to cryogenics.
Quantum computing represents a paradigm shift in computation, leveraging the principles of quantum mechanics to solve problems deemed intractable for classical computers. This paper traces the evolution of quantum computing from theoretical foundations to recent technological milestones. It highlights key developments such as quantum algorithms, error correction, and qubit technologies. The paper also examines quantum supremacy, current quantum hardware implementations, and the potential disruption in cryptography, materials science, and artificial intelligence. Despite significant challenges in stability, scalability, and noise, quantum computing is on a trajectory to redefine computational boundaries. Future research directions and policy implications are also discussed.
Quantum computers offer the promise of accelerated solutions for types of problems that are computationally unaffordable or intractable for classical computers, such as the simulation of quantum mechanics itself, quantum chemistry, and mathematical challenges like factoring large numbers. However, the relatively high error rate per quantum computing operation in the systems of today and of those expected to be developed in the future remains a key obstacle. To address this challenge, quantum error correction (QEC), which enables the creation of error-corrected (logical) qubits from a collection of physical qubits, is required. Depending on the choice of QEC code, hundreds of physical qubits may be required to implement a single logical qubit. As a result, the race to the creation of quantum computing systems capable of outperforming classical computing systems is largely a race to create quantum computers at the scale needed to support QEC. The criticality of scaling is evident in the quantum computing roadmaps produced by major research labs in this field, such as the one from IBM shown in Fig. 1. Starting from systems with only a few physical qubits a few years ago, the roadmap projects quantum computers with around 100,000 physical qubits and thousands of logical qubits by 2033 or so.