Parsing a sequence of qubits

We develop a theoretical framework for frame synchronization, also known as block synchronization, in the quantum domain which makes it possible to attach classical and quantum metadata to quantum information over a noisy channel even when the information source and sink are frame-wise asynchronous. This eliminates the need of frame synchronization at the hardware level and allows for parsing qubit sequences during quantum information processing. Our framework exploits binary constant-weight codes that are self-synchronizing. Possible applications may include asynchronous quantum communication such as a self-synchronizing quantum network where one can hop into the channel at any time, catch the next coming quantum information with a label indicating the sender, and reply by routing her quantum information with control qubits for quantum switches all without assuming prior frame synchronization between users.Comment: 11 pages, 2 figures, 1 table. Final accepted version for publication in the IEEE Transactions on Information Theor

Codebook and marker sequence design for synchronization-correcting codes

We propose a construction based on synchronization and error-correcting block codes and a matched marker sequence. The block codes can correct insertion, deletion and substitution errors within each codeword. The marker sequence allows the decoder to maintain synchronization at codeword boundaries even at high error rates. An upper bound is given for the performance of these codes over a channel with random substitutions and synchronization errors. It is shown that the performance is largely dependent on the code's minimum Levenshtein distance. The performance of these codes is verified by simulation and compared to published results. In concatenation with a non-binary outer code we obtain a significant improvement in frame error rate at similar overall code rates