Source-linked AI summary
Memory effects in quantum channel discrimination
Giulio Chiribella, Giacomo M. D'Ariano, Paolo Perinotti
TL;DR
The paper asks whether memory-assisted protocols are necessary for discriminating quantum channels with memory and for multiple-use unitary channels. It uses testers to represent general parallel, sequential, and combined schemes, showing that causal protocols can be essential for memory channels but are unnecessary for unitary-channel discrimination and estimation.
Problem
The paper examines optimal discrimination of memory channels, where later actions can depend on earlier uses, and compares this with discrimination and estimation for multiple-use unitary channels.
Method
The paper uses testers to describe general channel-use schemes, including parallel, sequential, and combined setups, and analyzes their discrimination and estimation criteria.
Results
Memory-assisted causal schemes are required for optimal discrimination of some memory channels, whereas memory-assisted protocols are not required for unitary-channel discrimination and multiple-use estimation.
Takeaways & Limitations
Memory effects induce a distinct notion of distance for channels with memory, while unitary-channel discrimination and estimation can be optimized without memory effects.
Abstract
from arXiv · showhide
We consider quantum-memory assisted protocols for discriminating quantum channels. We show that for optimal discrimination of memory channels, memory assisted protocols are needed. This leads to a new notion of distance for channels with memory. For optimal discrimination and estimation of sets of unitary channels memory-assisted protocols are not required.