Research

Light is an ideal quantum system to encode, transmit, and control quantum information. At its fundamental level, light is a quantum harmonic oscillator, which can be described by continuous-variable observables, \( \hat{x}=\hat{a}+\hat{a}^{\dagger} \) and \( \hat{p}=\left(\hat{a}-\hat{a}^{\dagger}\right)/i. \) Continuous-variable quantum information is a quantum state associated with such continuous-variable observables, and thus, is in an infinite-dimensional Hilbert space. Interestingly, a collection of quantum harmonic oscillators can exhibit quantum correlations (or entanglement) of continuous-variable quantum information, which is necessary for developing quantum technologies. We explore this continuous-variable quantum information both in experiment and theory.

Optical frequency comb has revolutionized optical technologies, finding broad applications in high-precision spectroscopy, optical communication, and frequency stabilization. We develop Quantum Optical Frequency Comb (QOFC), in which quantum features of light prevail in an optical frequency comb. QOFC is generated in a special optical cavity called synchronously pumped optical parametric oscillator (SPOPO), which exhibits quantum correlations and reduced quantum fluctuations. QOFC will find a broad application in quantum metrology, quantum communication, and quantum computing.

Classical light (e.g. laser) is widely used in many research areas, ranging from sensing and communication to computing. Quantum light, when properly engineered, can outperform classical light and realize quantum technologies.

In classical techniques, measurement precision is limited by standard quantum limit (shot noise limit), but a quantum light called squeezed vacuum can surpass the limit, leading to quantum-enhanced sensitivity. A notable example is the use of a squeezed vacuum to enhance the sensitivity of gravitational-wave detection. Another important quantum technology is quantum communication, where the use of quantum superposition or quantum entanglement enables secure communication. Finally, large-scale entangled states called cluster states can be used to implement measurement-based quantum computing.

Continuous-variable quantum information is advantageous in realizing those quantum technologies with scalability because an on-demand generation of large-scale entanglement is available in the experiment. We study how quantum states of light can be exploited to develop quantum technologies.

1. 앙자 계측

• 앙자 광학 계측 (K-Light, 2019년 4월)

2. 양자 얽힘

• 양자측정 과정에서 손상된 양자얽힘을 되돌리는 기술 (KAIST 연구뉴스, 2023년 10월)
• 양자역학의 실험적 검증에 관해 (물리학과 첨단기술, 2022년 12월)

3. 양자 컴퓨팅

• 빛으로 양자컴퓨터 만들기 (APCTP 크로스로드, 2023년 10월)