No abstract

Measurement-device-independent quantum key distribution (MDIQKD) with the decoy-state method negates security threats of both the imperfect single-photon source and detection losses. Lengthening the distance and improving the key rate of quantum key distribution (QKD) are vital issues in practical applications of QKD. Herein, we report the results of MDIQKD over 404 km of ultralow-loss optical fiber and 311 km of a standard optical fiber while employing an optimized four-intensity decoy-state method. This record-breaking implementation of the MDIQKD method not only provides a new distance record for both MDIQKD and all types of QKD systems but also, more significantly, achieves a distance that the traditional Bennett-Brassard 1984 QKD would not be able to achieve with the same detection devices even with ideal single-photon sources. This work represents a significant step toward proving and developing feasible long-distance QKD.

We report the development of an all-fiber-optic scanning endomicroscope capable of high-resolution second harmonic generation (SHG) imaging of biological tissues and demonstrate its utility for monitoring the remodeling of cervical collagen during gestation in mice. The endomicroscope has an overall 2.0 mm diameter and consists of a single customized double-clad fiber, a compact rapid two-dimensional beam scanner, and a miniature compound objective lens for excitation beam delivery, scanning, focusing, and efficient SHG signal collection. Endomicroscopic SHG images of murine cervical tissue sections at different stages of normal pregnancy reveal progressive, quantifiable changes in cervical collagen morphology with resolution similar to that of bench-top SHG microscopy. SHG endomicroscopic imaging of ex vivo murine and human cervical tissues through intact epithelium has also been performed. Our findings demonstrate the feasibility of SHG endomicroscopy technology for staging normal pregnancy, and suggest its potential application as a minimally invasive tool for clinical assessment of abnormal cervical remodeling associated with preterm birth.nonlinear endomicroscopy | fiber-optic scanning probe | cervical collagen remodeling | parturition T he cervix is a connective tissue-rich structure just caudal to the uterus in female mammals. Appropriate remodeling of the cervix during gestation is an essential component of the birth process (1, 2). The cervix must remain closed during pregnancy to maintain the fetus in the womb, and then open sufficiently to allow passage of the fetus at term. This shift in responsibility requires a massive rearrangement of the cervical connective tissue, in particular fibrillar collagen. Collagen is the main structural protein in the cervix. Animal studies reveal rearrangement of collagen structure is achieved in part by a decline in collagen crosslink formation, a reduction in matricellular proteins that regulate collagen fibrillogenesis, and increased synthesis of the matrix disorganizing molecule, hyaluronan (3, 4). Evidence to support a conservation of these processes in cervical remodeling in women is mounting (5). Abnormal or inappropriately timed cervical remodeling can lead to premature birth.Preterm birth (PTB), which accounts for 12.7% of all births in the United States, is the second leading cause of infant mortality and often leads to serious morbidity in surviving infants (6). Despite considerable research, the cause of PTB in 50% of cases remains elusive, and diagnostic methods to detect women at risk of PTB are limited (7). Because clinical and animal studies suggest that cervical changes precede the onset of uterine contractility in both term and PTB, premature cervical changes could be indicative of impending PTB (4, 8-10). The progressive structural changes in fibrillar collagens are directly related to cervical rigidity and thus potentially can serve as a diagnostic indicator for women at risk for PTB.Second harmonic generation (SHG) microscopy is the most effective ...

This manuscript reports on the first two-photon, label-free, metabolic imaging of biological tissues in vivo at histological resolution on an extremely compact, fiber-optic endomicroscopy platform. This system provides new opportunities for performing non-invasive and functional histological imaging of internal organs in vivo, in situ and in real time. As a routine clinical procedure, traditional histology has made significant impacts on medicine. However, the procedure is invasive and time consuming, suffers random sampling errors, and cannot provide in vivo functional information. The technology reported here features an extremely compact and flexible fiber-optic probe ~2 mm in diameter, enabling direct access to internal organs. Unprecedented two-photon imaging quality comparable to a large bench-top laser scanning microscope was achieved through technological innovations in double-clad fiber optics and miniature objective lenses (among many others). In addition to real-time label-free visualization of biological tissues in situ with subcellular histological detail, we demonstrated for the first time in vivo two-photon endomicroscopic metabolic imaging on a functioning mouse kidney model. Such breakthroughs in nonlinear endoscopic imaging capability present numerous promising opportunities for paradigm-shifting applications in both clinical diagnosis and basic research.

No abstract