On the Oblivious Transfer Capacity of the Degraded Wiretapped Binary Erasure Channel

We study oblivious transfer (OT) between Alice and Bob in the presence of an eavesdropper Eve over a degraded wiretapped binary erasure channel from Alice to Bob and Eve. In addition to the privacy goals of oblivious transfer between Alice and Bob, we require privacy of Alice and Bob's private data from Eve. In previous work we derived the OT capacity (in the honest-but-curious model) of the wiretapped binary independent erasure channel where the erasure processes of Bob and Eve are independent. Here we derive a lower bound on the OT capacity in the same secrecy model when the wiretapped binary erasure channel is degraded in favour of Bob.Comment: To be presented at the IEEE International Symposium on Information Theory (ISIT 2015), Hong Kon

Secure Source Coding with a Helper

We consider a secure source coding problem with a rate-limited helper. In particular, Alice observes an independent and identically distributed (i.i.d.) source X and wishes to transmit this source losslessly to Bob over a rate-limited link. A helper (Helen), observes an i.i.d. correlated source Y and can transmit information to Bob over a separate rate-limited link. A passive eavesdropper (Eve) can observe the coded output of Alice, i.e., the link from Alice to Bob is public. The uncertainty about the source X at Eve, is measured by the conditional entropy of the source given the coded output of Alice. We completely characterize the rate-equivocation region for this secure source coding model, where we show that Slepian-Wolf binning of X with respect to the coded side information received at Bob is optimal. We next consider a modification of this model in which Alice also has access to the coded output of Helen. For the two-sided helper model, we characterize the rate-equivocation region. While the availability of side information at Alice does not reduce the rate of transmission from Alice, it significantly enhances the resulting equivocation at Eve. In particular, the resulting equivocation for the two-sided helper case is shown to be min(H(X),R_y), i.e., one bit from the two-sided helper provides one bit of uncertainty at Eve. From this result, we infer that Slepian-Wolf binning of X is suboptimal and one can further decrease the information leakage to the eavesdropper by utilizing the side information at Alice. We finally generalize these results to the case in which there is additional un-coded side information W available at Bob and characterize the rate-equivocation regions under the assumption that Y-X-W forms a Markov chain.Comment: IEEE Transactions on Information Theory, to appea

Countering Quantum Noise with Supplementary Classical Information

We consider situations in which i) Alice wishes to send quantum information to Bob via a noisy quantum channel, ii) Alice has a classical description of the states she wishes to send and iii) Alice can make use of a finite amount of noiseless classical information. After setting up the problem in general, we focus attention on one specific scenario in which Alice sends a known qubit down a depolarizing channel along with a noiseless cbit. We describe a protocol which we conjecture is optimal and calculate the average fidelity obtained. A surprising amount of structure is revealed even for this simple case which suggests that relationships between quantum and classical information could in general be very intricate.Comment: RevTeX, 5 pages, 2 figures Typo in reference 9 correcte

Performance of Calorimetry in ALICE

The ALICE experiment at LHC studies the strong interaction sector of the Standard Model with pp, pA and AA collisions. Within the scope of the physics program, measurements of photons, neutral mesons and jets in ALICE are performed by two electromagnetic calorimeters. Precise and high-granularity photon spectrometer (PHOS) composed of lead-tungstate crystals, along with a wide-aperture lead-scintillator sampling calorimeter (EMCal) provide complementary measurements of photon observables in a wide kinematic range. The calorimeter trigger system allows the experiment to utilize efficiently the full delivered luminosity, recording a data sample enhanced with high-energy photons and jets. Performance of the ALICE calorimeters from proton-proton to heavy-ion collision systems is discussed and illustrated by physics results derived from data collected by ALICE with its electromagnetic calorimeter system.Comment: 7 pages, 5 figures. Sixth Annual Conference on Large Hadron Collider Physics (LHCP2018), 4-9 June 2018, Bologna, Ital