Quantum communication through devices with indefinite input-output direction

Journal article

Abstract Certain quantum devices, such as half-wave plates and quarter-wave plates in quantum optics, are bidirectional, meaning that the roles of their input and output ports can be exchanged. Bidirectional devices can be used in a forward mode and a backward mode, corresponding to two opposite choices of the input-output direction. They can also be used in a coherent superposition of the forward and backward modes, giving rise to new operations with indefinite input-output direction. In this work we explore the potential of input-output indefiniteness for the transfer of classical and quantum information through noisy channels. We first formulate a model of communication from a sender to a receiver via a noisy channel used in indefinite input-output direction. Then, we show that indefiniteness of the input-output direction yields advantages over standard communication protocols in which the given noisy channel is used in a fixed input-output direction. These advantages range from a general reduction of noise in bidirectional processes, to heralded noiseless transmission of quantum states, and, in some special cases, to a complete noise removal. The noise reduction due to input-output indefiniteness can be experimentally demonstrated with current photonic technologies, providing a way to investigate the operational consequences of exotic scenarios characterised by coherent quantum superpositions of forward-time and backward-time processes.

Authors: Liu, Z; Yang, M; Chiribella, G

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: IOP Publishing
• Journal: New Journal of Physics
• Volume: 25
• Issue: 4
• Pages: 043017-043017
• Publication date: 2023-03-30
• DOI: 10.1088/1367-2630/acc8f2
• EISSN: 1367-2630
• ISSN: 1367-2630
• Language: English
• Keywords: Telecommunications; Quantum information science; Topology (electrical circuits); Channel (broadcasting); Quantum channel; Reduction (mathematics); Physics; Quantum; Electrical engineering; Quantum entanglement; Mathematics; Communication source; Noise (video); Computer science; Quantum information; Quantum mechanics; Superposition principle; Transmission (telecommunications)