Sudden deafness with or without vertigo presents a difficult diagnostic problem. This article describes 12 patients with enhancement of the cochlea and/or vestibule on gadolinium-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (MRI), correlating the enhancement with the auditory and vestibular function. All patients were studied with T2-weighted axial images taken through the whole brain, enhanced 3-mm axial T1-weighted images taken through the temporal bone, and enhanced T1-weighted sagittal images taken through the whole brain. Cochlear enhancement on the side of hearing loss was found in all the patients. The vestibular enhancement correlated with both subjective vestibular symptoms and objective measures of vestibular function on electronystagmography. In 2 patients, the resolution of symptoms 4 to 6 months later correlated with resolution of the enhancement on MRI. No labyrinthine enhancement was seen in a series of 30 control patients studied with the same MRI protocol. Labyrinthine enhancement in patients with auditory and vestibular symptoms is a new finding and is indicative of labyrinthine disease. While abnormalities on electronystagmograms and audiograms are nonspecific and only indicate a sensorineural problem, enhanced MRI may separate patients with retrocochlear lesions, such as acoustic neuromas, from those in whom the abnormal process is in the labyrinth or the brain.

In the last two decades, many quantum optics experiments have demonstrated small-scale quantum information processing applications with several photons [1][2][3]. Beyond such proof-of-principle demonstrations, efficient preparation of large, but definite, numbers of photons is of great importance for further scaling up and speeding up photonic quantum information processing [4][5][6].Typical single-photon generation techniques based on nonlinear parametric processes face challenges of probabilistic generation. Here we demonstrate efficient synchronization of photons from multiple nonlinear parametric heralded single-photon sources (HSPSs), using quantum memories (QMs). Our low-loss optical memories greatly enhance (∼ 30×) the generation rate of coincidence photons from two independent HSPSs, while maintaining high indistinguishability (95.7 ± 1.4%) of the synchronized photons. As an application, we perform the first demonstration of HSPSbased measurement-device-independent quantum key distribution (MDI-QKD). The synchronized HSPSs demonstrated here will pave the way toward efficient quantum communication and larger scale optical quantum computing.

Fiber-based quantum key distribution (QKD) networks are limited without quantum repeaters. Satellite-based QKD links have been proposed to extend the network domain. We developed a quantum communication system, suitable for a realistic space-to-ground link, and executed an entanglement-based QKD protocol, achieving quantum bit error rates (QBER) below 2%. More importantly, we demonstrate low QBER execution of a higher dimensional QKD protocol. Using a finite-key security analysis and Doppler-shift compensation, we show it is better suited for a space-to-ground link. MOTIVATION AND BACKGROUNDImplementing quantum key distribution (QKD) or other quantum communication protocols over long distances is a major goal and challenge for establishing a global quantum network. To lay dedicated dark fiber over long distances is expensive and non-reconfigurable, and, without quantum repeaters, such links have very low transmission. The low transmission is due the exponential scaling of absorption in fiber with distance. It has been proposed to instead use space-based links where there are quantum channels between a ground station and an orbiting platform [1,2]. Such a channel has much lower loss than fiber over the same distance, allowing much more efficient protocol execution over comparable distances; for example, the recent achievement of entanglement distribution from a satellite to two ground stations realized a loss reduction of some 12 orders of magnitude [3], though the detection

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