We demonstrate the conditional reversal of a weak (partial-collapse) quantum measurement on a photonic qubit. The weak quantum measurement causes a nonunitary transformation of a qubit which is subsequently reversed to the original state after a successful reversing operation. Both the weak measurement and the reversal operation are implemented linear optically. The state recovery fidelity, determined by quantum process tomography, is shown to be over 94% for partial-collapse strength up to 0.9. We also experimentally study information gain due to the weak measurement and discuss the role of the reversing operation as an information erasure.PACS numbers: 03.65.Wj, 42.50.Dv, The projection postulate states that measurement of a variable of a quantum system irrevocably collapses the initial state to one of the eigenstates (corresponding to the measurement outcome) of the measurement operator and is one of the basic postulates of the standard quantum theory [1,2]. The initial state can never be recovered after a projection measurement on a quantum system.If the measurement is not sharp (i.e., non-projective measurement), however, the situation is different. It is possible to reverse the measurement-induced state collapse and the unsharpness of a measurement has been shown to be related to the probabilistic nature of the reversing operation which can serve as a probabilistic quantum error correction [3]. In particular, practical schemes for reversing the state collapse due to a weak (or partialcollapse) measurement in a solid-state qubit have been proposed in Ref.[4] and one of the schemes has recently been demonstrated using a superconducting phase qubit in Ref. [5].Since single-photon states and linear optics play important roles in quantum communication and quantum computing research [6,7,8,9], it is of interest and importance to investigate how the measurement-induced state collapse due to a weak measurement can be reversed for a photonic qubit. In this letter, we report a linear optical implementation of conditional reversal of weak (or partial-collapse) quantum measurements on a photonic qubit. We demonstrate experimentally that a nonunitary transformation of a photonic qubit, caused by a weak quantum measurement, can be reversed by applying an appropriately designed reversing operation. We also quantify and experimentally study information gain due to the weak measurement and discuss the role of the reversing operation as an information erasure.Consider the initial state of a qubit represented in the computational basis, |ψ o = α|0 + β|1 , where * Electronic address: yskim25@postech.ac.kr † Electronic address: yoonho@postech.ac.kr |α| 2 + |β| 2 = 1. Ordinary projection measurement in the computational basis would collapse the state into |0 (or |1 ) with the probability equal to |α| 2 (or |β| 2 ). The projection measurement cannot be reversed because the projection operators P 0 = |0 0| = ( 1 0 0 0 ) and P 1 = |1 1| = ( 0 0 0 1 ) do not have mathematical inverse. An unsharp measurement on the qubit, however, ...
We demonstrate sub-Rayleigh limit imaging of an object via speckle illumination. Imaging beyond the conventional Rayleigh limit is achieved by illuminating the object with pseudo-thermal light which exhibits a random speckle pattern. An object image is reconstructed from the second-order correlation measurement and the resolution of the image, which exceeds the Rayleigh limit, is shown to be related to the size of the speckle pattern that is tied to the lateral coherence length of the pseudo-thermal light.
We investigate light absorption in metal films, silver and aluminum, with different surface roughness. Measurements using an integrating sphere show that the reflectance in silver decreases significantly with increasing surface roughness whereas the reflectance in aluminum is almost constant. The experimental results agree well with numerical simulations in which the surface roughness of metal is described properly. In particular, the simulations demonstrate that the absorption by surface-plasmon-polaritons excited on a rough silver surface causes the surface-dependent reflectance in silver. This study suggests a convenient and feasible rule to rationally design a backside metal reflector toward high-efficiency light-emitting diodes and photovoltaics.
Background When gastric mesenchymal tumors (GMTs) measuring 2-5 cm in size are found, whether to undergo further treatment or not is controversial. Endoscopic ultrasonography (EUS) is useful for the evaluation of malignant potential of GMTs, but has limitations, such as subjective interpretation of EUS images. Therefore, we aimed to develop a scoring system based on the digital image analysis of EUS images to predict gastrointestinal stromal tumors (GISTs). Methods We included 103 patients with histopathologically proven GIST, leiomyoma or schwannoma on surgically resected specimen who underwent EUS examination between January 2007 and June 2018. After standardization of the EUS images, brightness values, including the mean (T mean ), indicative of echogenicity, and the standard deviation (T SD ), indicative of heterogeneity, in the tumors were analyzed. Results Age, T mean , and T SD were significantly higher in GISTs than in non-GISTs. The sensitivity and specificity were almost optimized for differentiating GISTs from non-GISTs when the critical values of age, T mean , and T SD were 57.5 years, 67.0, and 25.6, respectively. A GIST-predicting scoring system was created by assigning 3 points for T mean ≥ 67, 2 points for age ≥ 58 years, and 1 point for T SD ≥ 26. When GMTs with 3 points or more were diagnosed as GISTs, the sensitivity, specificity, and accuracy of the scoring system were 86.5%, 75.9%, and 83.5%, respectively. Conclusions The scoring system based on the information of digital image analysis is useful in predicting GISTs in case of GMTs that are 2-5 cm in size. Table 5 Sensitivity, specificity, positive and negative predictive values, and accuracy of the gastrointestinal stromal tumor (GIST)-predicting scoring system for differentiating GISTs from non-GISTs GIST gastrointestinal stromal tumor, PPV positive predictive value, NPV negative predictive value, CI confidence interval Predicting GIST Sensitivity, % (95% CI) Specificity, % (95% CI) PPV, % (95% CI) NPV, % (95% CI) Accuracy, % (95% CI) Score ≥ 3 points 86.5 (80.3-91.0) 75.9 (60.0-87.4) 90.1 (83.7-94.8) 68.8 (54.4-79.2) 83.5 (74.6-90.0)Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.