Last year, the Netflix original 'The Three-Body Problem' features a scene where alien life four light-years away from Earth communicates with humans in real-time. Four light-years is a vast distance that even light takes four years to travel. Even in science fiction, was it truly possible to converse with beings from deep space without any signal delay, as if talking on a mobile phone from Earth? The secret lies in 'quantum communication.'
Quantum communication refers to advanced technology that uses the unique physical properties of quanta to exchange information. Specifically, it includes 'quantum cryptography communication,' which enhances information security using quantum encryption; 'quantum transmission,' which exchanges quantum information between two points; and 'quantum networks,' which connect multiple points to exchange information like a web.
It is easier to understand by analogy with delivery. Quantum communication is the overall technology for delivering objects (quantum information), while quantum cryptography communication is the method of protecting the safe delivery of those objects. Quantum transmission and networks involve creating new pathways for exchanging items.
Once considered the realm of science fiction, quantum communication is now approaching reality. In particular, quantum cryptography communication is on the verge of commercialization, with demonstrations of quantum transmission and network technologies occurring outside laboratories. It is no longer technology from distant aliens depicted in novels and dramas.
◇China leads quantum cryptography communication... South Korea also keeps pace
Quantum cryptography communication is the fastest area of commercialization within quantum communication technology. The core of this technology lies in quantum key distribution (QKD), which securely shares secret keys for encrypting and decrypting data. Because any attempt at eavesdropping changes the quantum state, it can be immediately detected, making it highly secure.
China is the leading country in this field. In 2021, researchers at the University of Science and Technology of China built a 2,000-kilometer wired network connecting Beijing and Shanghai to implement wired quantum cryptography communication. They also succeeded in wireless quantum cryptography communication over a distance of 2,600 kilometers using the world's first quantum communication satellite, 'Micius,' launched in 2016. This means they have established a total communication network of 4,600 kilometers that includes both wired and wireless systems.
The United States and Europe have also been developing quantum cryptography communication technology using wired optical networks since the early 2000s. In 2018, U.S. corporation Quantum Xchange began offering quantum cryptography communication services over an 800-kilometer segment connecting Washington, New Jersey, New York, and Boston. The European Union (EU) has been investing 1 billion euros (approximately 1.5 trillion won) over ten years since 2018 through its quantum flagship program to establish a quantum cryptography communication network in key regions of Europe.
South Korea is also embarking on technology development. The Electronics and Telecommunications Research Institute (ETRI) is currently developing long-distance wired quantum cryptography communication with a goal of demonstrating a 100-kilometer range by the beginning of this year. Telecommunications companies like SK Telecom and KT, along with government-funded research institutes, are also dedicating efforts to research.
◇Quantum transmission and networks are still in their infancy
Quantum transmission and networks utilize quantum entanglement phenomena. Quantum entanglement refers to the synchronization phenomenon where determining the state of one of two particles, even if they are far apart, also determines the state of the other particle. The entangled quantum pairs can experience quantum entanglement at speeds faster than light, allowing for rapid information exchange. In 'The Three-Body Problem,' the 'Gija' that facilitates communication between Earth and the three-body civilization is also based on this quantum entanglement.
In this field, the United States has succeeded in seizing the 'first' opportunity. A collaborative research team from Harvard University and Amazon Web Services (AWS) successfully transmitted quantum information over an optical fiber spanning about 35 kilometers between Boston and Cambridge. This achievement is notable as it marks the first demonstration of information transmission using quantum entanglement in an urban area, and it is regarded as establishing key technology for building a large-scale quantum network.
Professor Song Young-ik from KAIST noted, "(The U.S. research achievement) confirmed that it is possible to exchange information between two points in Seoul and Daejeon," adding, "Quantum networks involve consolidating several points like Seoul, Daejeon, Daegu, Busan, and Incheon in a spiderweb-like manner, which requires improvements in technologies including quantum relay systems that amplify or connect quantum signals."
◇The goal of quantum communication is 'quantum internet'... What South Korea must lead
Ultimately, the goal of quantum communication is the 'quantum internet.' This represents a super-fast and ultra-secure communication network that combines quantum cryptography communication, quantum networks, and quantum computer technologies, garnering attention as a technology that surpasses the limitations of the existing internet.
However, quantum communication still has limitations, as it is sensitive to external environments and prone to signal loss over long distances. Therefore, developing stable quantum relay systems and quantum memory is essential, and challenges remain regarding minimizing initial expenses and ensuring compatibility with existing networks.
Experts believe that if investments accelerate at this point, South Korea could join the forefront of the quantum internet. Professor Song Young-ik stated, "In terms of quantum cryptography communication, South Korea can be considered a leader, but there is a gap of over ten years in quantum relay technology for quantum networks compared to the world's top groups," adding, "Continuous government support for foundational technologies like quantum relays is necessary."
Professor Heo Jun from Korea University emphasized, "Alongside government-led investments, there should also be an increase in specialized personnel capable of researching quantum communication," adding, "Just as companies like Google, IBM, and IonQ lead the quantum field in the U.S., South Korea should actively utilize the capabilities of private corporations."