State preparation and detector effects in quantum measurements of rotation with circular polarization-entangled photons and photon counting
Longzhu Cen, Zijing Zhang, Jiandong Zhang, Shuo Li, Yifei Sun, Linyu Yan, Yuan Zhe Zhao, Feng Wang · Physical Review A · 2017
Circular polarization-entangled photons can be used to obtain an enhancement of the precision in a rotation measurement. In this paper, the method of entanglement transformation is used to produce NOON states in circular polarization from a readily generated linear polarization-entangled photon source. Detection of $N$-fold coincidences serves as the postselection and $N$-fold superoscillating fringes are obtained simultaneously. A parity strategy and conditional probabilistic statistics contribute to a better fringe, saturating the angle sensitivity to the Heisenberg limit. The impact of imperfect state preparation and detection is discussed both separately and jointly. For the separated case, the influence of each system imperfection is pronounced. For the joint case, the feasibility region for surpassing the standard quantum limit is given. Our work pushes the state preparation of circular polarization-entangled photons to the same level as that in the case of linear polarization. It is also confirmed that entanglement can be transformed into different frames for specific applications, serving as a useful scheme for using entangled sources.