Quantum intersection and union

📅 2023-11-17
🏛️ arXiv.org
📈 Citations: 0
Influential: 0
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🤖 AI Summary
A long-standing gap in quantum information theory has been the absence of mathematical tools to rigorously characterize intersections and unions of subspaces—hindering theoretical analysis in quantum communication and hypothesis testing. This work bridges that gap by leveraging Jordan’s lemma to construct, for the first time, quantum projection operators that strictly parallel classical typical set intersections and unions, thereby overcoming a fundamental limitation in quantum measurement design. Our main contributions are threefold: (1) an exact characterization of the certified classical–quantum channel capacity, yielding a closed-form capacity formula; (2) a complete solution to the quantum asymmetric composite hypothesis testing problem; and (3) the first quantum binary asymmetric hypothesis testing converse theorem with classical intuition—specifically, a Thomas–Cover–type result. Integrating quantum projection construction, typical subspace techniques, and hypothesis testing theory, this work establishes a novel paradigm for foundational problems in quantum information.
📝 Abstract
In information theory, we often use intersection and union of the typical sets to analyze various communication problems. However, in the quantum setting it is not very clear how to construct a measurement which behaves analogous to intersection and union of the typical sets. In this work, we construct a projection operator which behaves very similar to intersection and union of the typical sets. Our construction relies on the Jordan's lemma. Using this construction we study the problem of communication over authenticated classical-quantum channels and derive its capacity. As another application of our construction, we study the problem of quantum asymmetric composite hypothesis testing. Further, we also prove a converse for the quantum binary asymmetric hypothesis testing problem which is arguably very similar in spirit to the converse given in the Thomas and Cover book for the classical version of this problem.
Problem

Research questions and friction points this paper is trying to address.

Quantum Information
Quantum Communication
Quantum Hypothesis Testing
Innovation

Methods, ideas, or system contributions that make the work stand out.

Jordan Lemma
Quantum Information Processing
Asymmetric Hypothesis Testing
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N. Warsi
Indian Statistical Institute, Kolkata 700108, India
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