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 framewise 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.