On December 10, 2022, the 2022 Nobel Prize in Physics was awarded to three American and European researchers for their contributions to the development of quantum mechanics. As quantum computers and other technologies expected to be the next generation of high-speed computing begin to flourish, we would like to build on the momentum of last year's Nobel Prize in Physics to offer a glimpse into the world of quantum technology. What is it that makes quantum computers so amazing? And what type of social value is NEC capable of creating? We spoke with Masayuki Shirane, Director of NEC's Secure System Platform Laboratories to learn the answers to these and other questions.

What exactly is quantum?
Possibilities made possible by unconventional "ambiguity"

── The 2022 Nobel Prize in Physics was awarded in recognition of experiments on quantum entanglement. As a phenomenon that even Einstein could not be convinced of, quantum entanglement can be a tremendous hurdle for novices.

There do indeed exist things that explain familiar physical phenomena but cannot be explained by classical mechanics, which we regard as common sense. This is precisely what the winners of this year's Nobel Prize in Physics proved through their experiments. For example, let us assume that two quanta in different states, "0" and "1" (e.g., a photon—the smallest unit of light), exist in a quantum entangled state. The view of classical mechanics is that the fact that one state is "0" and the other is "1" is predetermined, regardless of whether or not humans observe it. However, in quantum mechanics, neither quantum is determined to be "0" or "1" until observed by humans, wherein it is determined to be "0" or "1" at the moment of observation.

When two quanta exist in an entangled state, the second quantum changes to a state of "0" at the moment that one quantum is observed and found to be in a state of "1." No matter how far apart the two quanta are, the state of the two quanta is determined instantaneously. In other words, information is transmitted in an instant between two quanta.

── I think I may be starting to understand some of this. How will this quantum research lead to technological innovation?

There are innovations that can be arrived at by quantum systems that are incompatible with common sense. One example is quantum superposition, which is used in quantum computers. The bits of classical mechanics are either "0" or "1," but quantum bits (qubits) can express both "0" and "1" information simultaneously. Since either "0" or "1" is undetermined, "0" and "1" states are described as being superimposed. This is why the amount of information that can be expressed in a single qubit is significantly higher, wherein 100 qubits are equivalent to 1000 trillion by 1000 trillion bits of conventional computers. A quantum computer is a machine with the potential to perform ultra-high-speed processing based on qubits.

There are also applications such as quantum sensing, which reads slight changes in magnetism and frequency by taking advantage of the ease of quantum state changes, and quantum cryptography communication, which detects and prevents information theft by using state changes when quantum states are observed. NEC is engaged in research and development in both of these areas.

Why is this field garnering so much attention? Both the public and private sectors seem intent on commercializing these applications.

── Interest in quantum technology has been increasing in recent years even before the Nobel Prize was awarded.

In 2019, Google's announcement that it had demonstrated quantum supremacy had a tremendous impact. Although there were reservations about practicality, Google's quantum computer could solve in just 200 seconds a problem that would take 10,000 years to calculate on a supercomputer at the time. Governments around the world are actively investing in the technology. The budget allotted for quantum technology-related research and development in FY2022 has reached more than 90 billion yen in the U.S. and 30 billion yen in Japan.

── NEC has been conducting research on quantum technology since the 1990s and is further accelerating its R&D efforts towards commercialization.

NEC is a pioneer in this field. In 1999, it became the first to demonstrate the validity of superconducting solid-state qubit, which is the basic element of a quantum computer. Since then, we have continued our research ahead of the rest of the world, achieving the world's first high-sensitivity readout of qubits using superconducting parametron circuits in 2014. We are currently working on the development of quantum annealing machines using these technologies.

── Speaking of annealing, are there different types of quantum computers?

Quantum computers can be broadly classified into quantum gate systems and quantum annealing systems. In gate systems, the bits of conventional computers are replaced with qubits, and in principle, you can do anything. The ultimate goal is to create a so-called fault-tolerant machine, which is practically error-free, even compared with other gating system machines. The development of a fault-tolerant quantum computer is one of the projects under the Japanese government's Moonshot Research and Development Program. Dr. Tsuyoshi Yamamoto, NEC Research Fellow, is leading the research and development of superconducting technology as project manager. That said, we are likely a long way off from our goal. The Google machine mentioned above is a gated machine, but not a fault-tolerant machine.

Quantum annealing machines are specialized in handling combinatorial optimization problems, and their capabilities are limited compared to general-purpose gate systems. With annealing systems, the goal is to solve problems at high speed by converting mathematical models (equations) usually used for solving problems into specialized equations called Ising models that express quantum states as the north (N) and south (S) poles of a magnet. We believe it is possible to simplify the mechanism compared with the gate system and accelerate the implementation of hardware.

What will happen to society in the future? Soon we will be seeing changes in manufacturing, work, and even everyday life.

── What are the benefits of being able to solve combinatorial optimization problems at high speed?

Famous examples of its application include the solution of the traveling salesman problem to determine how salesmen can travel to many locations efficiently in terms of time and cost, and the work shift problem to design shifting schedules that satisfy all necessary conditions, such as work conditions, the number of people required, job preferences, and compatibility. Combinatorial optimization derives the most efficient solution from a huge number of combinations of options.

The NEC Group has already implemented a system that utilizes quantum-inspired simulated annealing technology using vector supercomputers, reducing the time required to plan the delivery of maintenance parts for the next day from two hours to 12 minutes. In addition, issues involving combinatorial optimization, such as urban development and manufacturing, are found in various aspects of daily life. Quantum computing technology in a broad sense has now reached the stage of social implementation.

── What are the advantages of NEC's quantum technology?

In simulated annealing, high-speed processing of large-scale combinatorial problems is made possible by operating software incorporating proprietary algorithms on SX-Aurora TSUBASA, a vector supercomputer that performs matrix calculations with high memory bandwidth. In terms of quantum annealing, which is expected to solve more complex problems at a higher speed, we announced in March 2022 that NEC had become the first in the world to successfully solve a small-scale combinatorial optimization problem using the LHZ method (ParityQC architecture*). While NEC's ultimate goal is to develop a fault-tolerant quantum computers, we are currently focusing on the annealing method, which is expected to be put into practical use in the near future. In fact, we are setting our sights on the realization of a quantum annealing machine in 2023.

Quantum technology alone will not guarantee a rosy future. However, we believe that beyond the convenience and comfort that will be brought to people's lives, there will be, in fact, the power of our quantum technology. That is the future I hope to create.

Recommended Articles

NEC Stories Top