Found Room-Temperature Quantum Computer Material

International Joint Research Team Including Korea Atomic Energy Research Institute
Confirms Material Exhibiting Quantum Entanglement at Room Temperature

An international joint research team including South Korea has developed a material capable of realizing quantum states at room temperature, enabling the creation of quantum computers.

Dr. Kim Jae-wook of the Advanced Quantum Materials Laboratory at the Korea Atomic Energy Research Institute is inspecting the laser floating zone furnace used to synthesize high-quality TbInO3 single crystals. Photo by Korea Atomic Energy Research Institute

The Korea Atomic Energy Research Institute announced on the 23rd that Dr. Kim Jae-wook of the Advanced Quantum Materials Research Laboratory, together with Dr. Jeong Taek-seon from Yonsei University and Dr. Xu Xianghan from Rutgers University in the U.S., experimentally demonstrated that terbium indium oxide (TbInO3) can be a quantum spin liquid (QSL) material usable in quantum computer devices.

The research results were published online on the 17th in the international academic journal Nature Physics (IF 19.684).

Quantum computers utilize the intrinsic quantum mechanical properties of superposition and entanglement to process a large amount of information simultaneously. They can solve specific problems millions of times faster than conventional supercomputers, making quantum technology a game-changing technology expected to reshape future industries.

However, realizing quantum mechanical superposition and entanglement phenomena is challenging. Various errors occur due to slight stimuli such as temperature changes, impurities, and external electromagnetic fields. To stably create fragile quantum states, stringent conditions such as implementing an ultra-low temperature environment close to absolute zero (-273.15°C) are required. Currently, various candidate materials capable of resolving quantum errors are being researched, and QSL is one of them. QSL is a new magnetic state material that allows large-scale quantum entanglement due to quantum fluctuations. It is considered a strong candidate material necessary for implementing quantum computers with significantly reduced quantum errors.

Since the 2010s, research groups including MIT have theoretically predicted that QSL involves quasiparticles called spinons generated by quantum entanglement, which interact with light, and that the optical conductivity caused by spinons would be proportional to the square of the light frequency. In other words, if a material exhibits optical conductivity proportional to the square of the light frequency, it indicates that the material can be a QSL. Although numerous QSL candidate materials have been tested so far, the optical conductivity-frequency squared proportionality phenomenon could not be experimentally confirmed due to impurities and disordered material composition.

(a) Sphinon quasiparticle and external electromagnetic wave interaction schematic (b) Triangular lattice structure of TbInO3 material. Photo by Atomic Energy Research Institute

The research team succeeded for the first time in experimentally confirming this phenomenon in a single crystal of terbium indium oxide (TbInO3), one of the QSL candidate materials. First, they synthesized high-quality TbInO3 single crystals using a laser-diode floating zone furnace, which melts the material with a laser to produce a uniform crystal structure. Then, they conducted spectroscopic experiments measuring optical conductivity by irradiating the material with terahertz (THz) electromagnetic waves. The experiments were performed over a wide temperature range from ultra-low temperatures to room temperature, under various magnetic fields and frequency bands. In particular, the sample thickness was precisely controlled to reduce internal reflection effects of light that could interfere with the experiments.

As a result, they experimentally proved that the optical conductivity is exactly proportional to the square of the frequency in a specific range. Notably, this proportionality was observed even at room temperature around 27 degrees Celsius. This is the first actual confirmation that TbInO3 can realize QSL characteristics at room temperature. Based on these research results, the team plans to further study whether TbInO3 can be applied as a device for error-free quantum computers.

Dr. Kim said, “This research is the first experimental verification of a long-standing theoretical prediction about quantum spin liquid materials,” adding, “It will greatly aid the design of quantum computing and quantum sensor devices in the future.”

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