2020/11/23 by Somshubhro Bandyopadhyay
Computer Science · Mathematics · Physics and Astronomy · #Algorithm #Impossibility #Law #Mathematics #Physics #Political science #Protocol (science) #Quantum #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum algorithm #Quantum cloning #Quantum error correction #Quantum mechanics #Quantum state #Quantum superposition #State (computer science) #Superposition principle #Theoretical physics #quant-ph
paper · pdf · doi:10.1103/physreva.102.050202
published as Phys. Rev. A 102, 050202(R) (2020) · 4 pages; v2: title change and other minor edits, published version
openalex publication_date 2020/11/23 · arxiv created 2020/11/24 · arxiv updated 2020/11/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The superposition principle is fundamental to quantum theory. Yet a recent no-go theorem has proved that quantum theory forbids superposition of unknown quantum states, even with nonzero probability. The implications of this result, however, remain poorly understood so far. In this Rapid Communication we show that the existence of a protocol that superposes two unknown pure states with nonzero probability (allowed to vary over input states) leads to the violation of other no-go theorems. In particular, such a protocol can be used to perform certain state discrimination and cloning tasks that are forbidden not only in quantum theory but in no-signaling theories as well.