Mach - Zehnder 간섭계의 광자분포

엄자윤, 김용수

김헌오, 고정훈, 박구동 +1 more

Mach-Zehnder 간섭계에 매개하향변환과정에서 발생한 광자쌍을 입사시켰을 때 두 광자의 상관관계가 간섭계의 분해능에 미치는 영향을 Bayes 정리에 근거한 전산 시늉으로 분석하였다. 발생과정에서 두 광자는 100%의 상관관계를 가지지만 진행중에 반사, 흡수, 산란 등에 의해 소멸되므로 상관관계가 감소하고, 이러한 상관관계의 감소는 간섭계의 위상분해에 있어서 저하를 가져오는 주요 요인이 되며, 또한 간섭계의 분해능은 검출기의 양자효율에 관련됨을 확인하였다. 전산시늉으로 얻은 결과, 간섭계의 위상차가 적을수록 위상정밀도는 좋아지고 위상차가 증가할수록 위상의 불확정도는 점점 증가하는 경향을 나타내었다.

김영철, 노재우, 김기식

Siddharth Singh, Rohan Katti

In this paper, a Mach–Zehnder interferometer is analyzed with a single photon Gaussian wave packet at one of its input ports and vacuum state at the other input port. Various noises arising in the Mach–Zehnder interferometer such as photon flux noise and quadrature noise are mathematically analyzed. The effect of variation in device parameters on the power spectral density at the output ports of the Mach–Zehnder interferometer is studied. It is observed that the power spectral density of photon flux noise autocorrelation at the output ports of a Mach–Zehnder interferometer is a function of phase shift, whereas the power spectral density of quadrature noise autocorrelation at the output ports of a Mach–Zehnder interferometer is a function of frequency of a single photon wave packet and the phase shift. The analysis carried out in this paper will be helpful in understanding the quantum fluctuations in the design of quantum logic devices and circuits where the Mach–Zehnder interferometer is a core building block.

권경복

Quan Liao, Hongmei Ma, L. Q. Chen +2 more

The presence of phase diffusion can lead to the loss of the advantages of quantum measurements. Squeezing is considered to be an effective method to reduce the detrimental effect of phase diffusion on the measurement. The Mach-Zehnder (MZ) interferometer has been exploited as a generic tool for precise phase measurement. Describing the reduction in quantum advantage caused by phase diffusion in an MZ interferometer that can be mitigated by squeezing is not easy to handle analytically, because the input state will change from a pure state to a mixed state after experiencing the diffusion noise in the MZ interferometer. We introduce a truncated MZ interferometer that can achieve the same potential phase sensitivity as the conventional MZ interferometer. This scheme can theoretically explain how phase diffusion reduces phase estimation and why squeezing counteracts in the presence of phase diffusion. Using the Gaussian property of the input state and the characteristic of Gaussian operation in the squeezing, the two orthogonal field quantities of the quantum state are squeezed and anti-squeezed to different degrees, and the analytic results are obtained. The truncated MZ interferometer is simpler to build and operate than the conventional MZ interferometer, and also mitigates the phase diffusion noise by the squeezing operation, thus making it useful for applications in precision metrology.