Dr. Im Hyang-taek's KIST Research Team
[Asia Economy Reporter Kim Bong-su] Domestic researchers have developed a quantum sensor capable of measuring various physical quantities such as the position, temperature, and time of objects changing in real time with high precision. Through high-sensitivity data precision measurement and acquisition of images and videos, this is expected to serve as a foundation for establishing Korea's unique stronghold in the technological hegemony competition leading the 4th Industrial Revolution, including autonomous vehicles.
The Korea Institute of Science and Technology (KIST) announced on the 16th that Dr. Lim Hyang-taek's quantum information research team implemented a quantum sensor capable of measuring multiple physical quantities changing in real time with precision beyond classical limits.
The research team implemented a quantum state called the ‘multi-mode N00N state,’ which can measure multiple physical quantities changing in real time with high precision. Although the ‘multi-mode N00N state’ is theoretically known to provide the highest precision, it had been difficult to realize experimentally.
The researchers experimentally generated a multi-mode N00N state, an entangled state where two photons simultaneously travel through four paths, and applied it to an interferometer. This enabled the simultaneous measurement of multiple phase changes in the interferometer with precision surpassing classical limits.
Dr. Lim stated, “The core technology of this achievement, the ‘multi-mode N00N state,’ can be utilized as foundational technology for quantum imaging and quantum sensor networks, contributing to the advancement of the quantum sensing field.” He added, “Specifically, it is expected to be applied to high-performance quantum microscopes and bio-imaging sensors.”
The research results were published in the latest issue of the international academic journal Nature Communications.
◇ Terminology Explanation
▲ N00N state = An entangled state where, for two optical paths a and b, when N photons travel, the state simultaneously exists where all N photons travel through path a (with no photons in path b) and where all N photons travel through path b (with no photons in path a).
▲ Multi-mode N00N state = An extended state of the N00N state where, instead of two optical paths, multiple optical paths exist, and the entangled state exists where all N photons travel through only one optical path (with no photons in the other paths) for every optical path. For example, when N photons and four paths a, b, c, d exist, the state where all N photons exist only in path a and none in the others, the state where all N photons exist only in path b and none in the others, and similarly for paths c and d, are superposed. This is an entangled state of the number of photons and optical paths.
▲ Interferometer & Phase = An interferometer is an optical system that measures displacement using the interference phenomenon of light. A single light beam is split into a probe beam and a reference beam using a beam splitter, which then travel through different paths. Two optical detectors receive the signals from these beams. When the path of the probe beam changes due to the measurement target, interference occurs due to the path difference between the probe and reference beams. By analyzing this interference, the value to be measured can be determined. In other words, phase refers to the path difference of light responding to changes in the physical quantity (such as position or temperature) being measured. The simplest interferometer has one reference beam and one probe beam, but generally, in a multi-mode interferometer, multiple probe beams can exist for a single reference beam.
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