18,493 research outputs found
All-optical logic circuits based on polarization properties of nondegenerate four-wave mixing
All-optical logic circuits based on the polarization properties of nondegenerate four-wave mixing are proposed. Schemes to perform multiple triple-product logic functions are discussed, and it is shown that higher-level Boolean operations that involve several bits can be implemented without resorting to the standard two-input gates. As a simple illustration of the idea, a circuit that performs error correction on a (3, 1) Hamming code is demonstrated. Error-free performance (bit error rate of <10^(−9)) at 2.5 Gbit/s is achieved after single-error correction on the Hamming word with 50% errors
The Optical Frequency Comb as a One-Way Quantum Computer
In the one-way model of quantum computing, quantum algorithms are implemented
using only measurements on an entangled initial state. Much of the hard work is
done up-front when creating this universal resource, known as a cluster state,
on which the measurements are made. Here we detail a new proposal for a
scalable method of creating cluster states using only a single multimode
optical parametric oscillator (OPO). The method generates a continuous-variable
cluster state that is universal for quantum computation and encoded in the
quadratures of the optical frequency comb of the OPO. This work expands on the
presentation in Phys. Rev. Lett. 101, 130501 (2008).Comment: 20 pages, 8 figures. v2 corrects minor error in published versio
Electronic marking and identification techniques to discourage document copying
Modern computer networks make it possible to distribute documents quickly and economically by electronic means rather than by conventional paper means. However, the widespread adoption of electronic distribution of copyrighted material is currently impeded by the ease of illicit copying and dissemination. In this paper we propose techniques that discourage illicit distribution by embedding each document with a unique codeword. Our encoding techniques are indiscernible by readers, yet enable us to identify the sanctioned recipient of a document by examination of a recovered document. We propose three coding methods, describe one in detail, and present experimental results showing that our identification techniques are highly reliable, even after documents have been photocopied
An Adaptive Entanglement Distillation Scheme Using Quantum Low Density Parity Check Codes
Quantum low density parity check (QLDPC) codes are useful primitives for
quantum information processing because they can be encoded and decoded
efficiently. Besides, the error correcting capability of a few QLDPC codes
exceeds the quantum Gilbert-Varshamov bound. Here, we report a numerical
performance analysis of an adaptive entanglement distillation scheme using
QLDPC codes. In particular, we find that the expected yield of our adaptive
distillation scheme to combat depolarization errors exceed that of Leung and
Shor whenever the error probability is less than about 0.07 or greater than
about 0.28. This finding illustrates the effectiveness of using QLDPC codes in
entanglement distillation.Comment: 12 pages, 6 figure
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