Private Data Transfer over a Broadcast Channel

We study the following private data transfer problem: Alice has a database of files. Bob and Cathy want to access a file each from this database (which may or may not be the same file), but each of them wants to ensure that their choices of file do not get revealed even if Alice colludes with the other user. Alice, on the other hand, wants to make sure that each of Bob and Cathy does not learn any more information from the database than the files they demand (the identities of which will be unknown to her). Moreover, they should not learn any information about the other files even if they collude. It turns out that it is impossible to accomplish this if Alice, Bob, and Cathy have access only to private randomness and noiseless communication links. We consider this problem when a binary erasure broadcast channel with independent erasures is available from Alice to Bob and Cathy in addition to a noiseless public discussion channel. We study the file-length-per-broadcast-channel-use rate in the honest-but-curious model. We focus on the case when the database consists of two files, and obtain the optimal rate. We then extend to the case of larger databases, and give upper and lower bounds on the optimal rate.Comment: To be presented at IEEE International Symposium on Information Theory (ISIT 2015), Hong Kon

Super-resolution and super-sensitivity of quantum LiDAR with multi-photonic state and binary outcome photon counting measurement

Here we are investigating the enhancement in phase sensitivity and resolution in Mach-Zehnder interferometer (MZI) based quantum LiDAR. We are using multi-photonic state (MPS), superposition of four coherent states [1], as the input state and binary outcome parity photon counting measurement and binary outcome zero-nonzero photon counting measurement as the measurement schemes. We thoroughly investigate the results in lossless as well as in lossy cases. We found enhancement in resolution and phase sensitivity in comparison to the coherent state and even coherent superposition state (ECSS) based quantum LiDAR. Our analysis shows that MPS may be an alternative nonclassical resource in the field of quantum imaging and quantum sensing technologies, like in quantum LiDAR.Comment: We welcome comment

Stroke mortality: predictive value of simple laboratory tests and acute physiology, age, chronic health evaluation III scoring system: a hospital based study

Background: Acute stroke is a heterogeneous condition with respect to prognosis. This study was undertaken with the aim to evaluate the significance of routine simple blood parameters and APACHE (acute physiology, age, chronic health evaluation) III scoring system as methods of prediction of 1-month mortality in stroke patients and to assess the sensitivity and specificity of APACHE III scoring system in predicting short term outcome in critically ill patients having stroke.Methods: Patients of stroke presenting within 48 hours of onset were included in the study irrespective of age, sex or type of stroke. The clinical evaluation, neuroimaging and blood investigations were performed. APACHE III scoring system was applied for each patient to calculate the score for each one. The outcome of the patients at the end of one month was determined as survivors and expired.Results: Among the total 120 cases in the study, 54.16% (n=65) patients survived at the end of one month. The mean APAPCHE III Score among the survivors was 45.3 and in expired patients it was 88.6. Taking a cut-off value of 50, APACHE III Score was significantly associated in predicting the mortality in stroke patients (P-value<0.0001).Conclusions: The study concluded that a low GCS at the time of admission and increased serum creatinine were independent predictors of mortality among patients presenting to the hospital within 48 hours with first time acute stroke.  APACHE III scoring system was found to be sensitive and reasonably specific in predicting short term outcome in patients having cerebral stroke.