Communicating Quantum Processes
Communicating Quantum Processes
Gay and Nagarajan introduce CQP, combining pi-calculus communication, quantum operations, typing, and unique ownership.
Paper information (2005, POPL, pp. 145–157) — Simon J. Gay and Rajagopal Nagarajan. DOI; arXiv:quant-ph/0409052; author version
Work
The paper introduces CQP (Communicating Quantum Processes) for systems that combine quantum communication, classical communication, and computation. CQP combines pi-calculus communication primitives with measurement and quantum-state transformation, allowing qubits to move between processes along channels. It defines syntax, operational semantics, and a static type system, then uses type preservation and unique ownership to constrain quantum resources in concurrent systems.
Contributions
- An extension of process-calculus communication to qubits and quantum operations.
- Channel types that distinguish classical from quantum data and control quantum-state use.
- Results that the operational semantics preserves typing and that each qubit has a unique owning process in a system.
- Examples of quantum communication systems showing how CQP can support formal analysis and verification.
Limits
Ownership safety is a static resource property; it does not establish protocol confidentiality, functional correctness, or fault tolerance. CQP's operational semantics is an idealized model and does not directly describe hardware noise, network latency, compilation cost, or device connectivity. Complete verification of concurrent systems still needs additional logics, equivalences, and proof tools.
Connections
CQP extends the language and type questions of QPL and A Lambda Calculus for Quantum Computation with Classical Control into concurrent communication. Like A Categorical Semantics of Quantum Protocols, it studies compositional protocols, but CQP centers processes, channels, and operational semantics. Compared with later quantum process algebras and protocol-verification work, it emphasizes unique ownership as a static invariant.
Original paper
Simon J. Gay and Rajagopal Nagarajan, Communicating Quantum Processes, in POPL 2005, pp. 145–157, DOI: 10.1145/1040305.1040318. Author version