Emergent classicality in general multipartite states and channels
In a quantum measurement process, classical information about the measured system spreads throughout the environment. Meanwhile, quantum information about the system becomes inaccessible to local observers. Here we prove a result about quantum channels indicating that an aspect of this phenomenon is...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften
2021-09-01
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| Series: | Quantum |
| Online Access: | https://quantum-journal.org/papers/q-2021-09-28-555/pdf/ |
| _version_ | 1819131271026049024 |
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| author | Xiao-Liang Qi Daniel Ranard |
| author_facet | Xiao-Liang Qi Daniel Ranard |
| author_sort | Xiao-Liang Qi |
| collection | DOAJ |
| description | In a quantum measurement process, classical information about the measured system spreads throughout the environment. Meanwhile, quantum information about the system becomes inaccessible to local observers. Here we prove a result about quantum channels indicating that an aspect of this phenomenon is completely general. We show that for any evolution of the system and environment, for everywhere in the environment excluding an $O(1)$-sized region we call the "quantum Markov blanket," any locally accessible information about the system must be approximately classical, i.e. obtainable from some fixed measurement. The result strengthens the earlier result of Brandão et al. ($\textit{Nat. comm. 6:7908}$) in which the excluded region was allowed to grow with total environment size. It may also be seen as a new consequence of the principles of no-cloning or monogamy of entanglement. Our proof offers a constructive optimization procedure for determining the "quantum Markov blanket" region, as well as the effective measurement induced by the evolution. Alternatively, under channel-state duality, our result characterizes the marginals of multipartite states. |
| first_indexed | 2024-12-22T09:12:51Z |
| format | Article |
| id | doaj.art-449004441f5640faaa8fd9760c2eb412 |
| institution | Directory Open Access Journal |
| issn | 2521-327X |
| language | English |
| last_indexed | 2024-12-22T09:12:51Z |
| publishDate | 2021-09-01 |
| publisher | Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften |
| record_format | Article |
| series | Quantum |
| spelling | doaj.art-449004441f5640faaa8fd9760c2eb4122022-12-21T18:31:22ZengVerein zur Förderung des Open Access Publizierens in den QuantenwissenschaftenQuantum2521-327X2021-09-01555510.22331/q-2021-09-28-55510.22331/q-2021-09-28-555Emergent classicality in general multipartite states and channelsXiao-Liang QiDaniel RanardIn a quantum measurement process, classical information about the measured system spreads throughout the environment. Meanwhile, quantum information about the system becomes inaccessible to local observers. Here we prove a result about quantum channels indicating that an aspect of this phenomenon is completely general. We show that for any evolution of the system and environment, for everywhere in the environment excluding an $O(1)$-sized region we call the "quantum Markov blanket," any locally accessible information about the system must be approximately classical, i.e. obtainable from some fixed measurement. The result strengthens the earlier result of Brandão et al. ($\textit{Nat. comm. 6:7908}$) in which the excluded region was allowed to grow with total environment size. It may also be seen as a new consequence of the principles of no-cloning or monogamy of entanglement. Our proof offers a constructive optimization procedure for determining the "quantum Markov blanket" region, as well as the effective measurement induced by the evolution. Alternatively, under channel-state duality, our result characterizes the marginals of multipartite states.https://quantum-journal.org/papers/q-2021-09-28-555/pdf/ |
| spellingShingle | Xiao-Liang Qi Daniel Ranard Emergent classicality in general multipartite states and channels Quantum |
| title | Emergent classicality in general multipartite states and channels |
| title_full | Emergent classicality in general multipartite states and channels |
| title_fullStr | Emergent classicality in general multipartite states and channels |
| title_full_unstemmed | Emergent classicality in general multipartite states and channels |
| title_short | Emergent classicality in general multipartite states and channels |
| title_sort | emergent classicality in general multipartite states and channels |
| url | https://quantum-journal.org/papers/q-2021-09-28-555/pdf/ |
| work_keys_str_mv | AT xiaoliangqi emergentclassicalityingeneralmultipartitestatesandchannels AT danielranard emergentclassicalityingeneralmultipartitestatesandchannels |