Travis Humble

Quantum Computing Institute, Oak Ridge National Laboratory

Over a few short decades, the world witnessed a remarkable development in transistor-based information technologies that started with stand-alone, mainframe computer systems and led to the current global network of mobile phones, tablets, and wearable sensors. Fueling this progress was a predictable reliance on greater transistor density supported by better material synthesis and fabrication methods as well as clever designs. But these approaches are constrained by fundamental physical limits, such as the size of the individual atoms and the scale required to solve modern data-centric problems. Overcoming these constraints requires new ideas that not only maintain growth in computing technology but also change the restrictions governing its behavior.

Quantum computing has emerged as a fundamental change in the equations of information. Based on the quantum physics that dictates how individual atoms and electrons behave at the microscopic scale, quantum computing enables a host of new opportunities for storing and processing information. Theorists have long predicted that quantum computers would enable highly efficient methods for solving complex problems, and for more than 25 years there has been a world-wide effort to realize these promises.

Making these systems robust enough for widespread adoption is lacking, however, and only beginning to be recognized as an important part of the broader impact.

Multiple advances have indeed pushed the ideas of quantum computing technology forward. Heroic experiments using individual atoms, molecules, and photons have steadily demonstrated progress in the ability to control quantum physical systems, and recent Nobel prizes for the control of quantum systems underscore the achievements made during this time. These developments continue today with experiments focused on a broad variety of physical system types. Examples include using arrays of individual atoms entangled with one another to highlight the unique interactions possible with quantum physics, or individual particles of light passing through microscopic networks of fibers.

Recent efforts in quantum computing are now delivering working prototype devices that can correctly calculate solutions for small problems.

For example, state-of-the-art devices based on pairs of superconducting devices have demonstrated the ability to solve complex scientific problems in chemistry, nuclear physics, and materials science. While current demonstrations fall short of surpassing transistor-based computers, they underscore the ongoing advancements toward that goal. These early demonstrations also help define the software required for future integration of quantum processing units (QPUs) with conventional high-performance computing systems.

Developments in quantum computers continue to push the limits of materials synthesis, nanoscale fabrication, electrical engineering and computer science, and the technical barriers to consumer applications should not be underestimated. These recent proof-of-principle QPUs are remarkable efforts and progress appears to be picking up. But the impact of quantum computing on our global information technology is far less clear than these trends indicate. Current quantum processors are delicate experimental systems, hosted by leading physics laboratories, with users represented by a highly qualified cadre of computer scientists and engineers. Making these systems robust enough for widespread adoption is lacking, however, and only beginning to be recognized as an important part of the broader impact.