quantum coupling
{{Short description|Effect on quantum mechanics in which quantum systems are bound}}
{{More citations needed|date=May 2025}}
{{Coupling in molecules}}
Although the term quantum coupling does not have a universally accepted definition in scientific literature—unlike quantum entanglement or the coupling constant—it is often used by physicists to describe any interaction or linkage between quantum entities that affects their states or evolution, as could be inferred from Osada, Yamazaki, and Noguchi, {{cite book
| last1 = Osada
| first1 = Alto
| last2 = Yamazaki
| first2 = Rekishu
| last3 = Noguchi
| first3 = Atsushi
| title = Introduction to Quantum Technologies
| publisher = Springer
| year = 2022
| series = Lecture Notes in Physics
| volume = 1004
| pages = 185–207
| doi = 10.1007/978-981-19-4641-7_9
| isbn = 978-981-19-4641-7
| url = https://link.springer.com/chapter/10.1007/978-981-19-4641-7_9
}} and Cui et al.{{cite journal
| last1 = Cui
| first1 = Jiabin
| last2 = Panfil
| first2 = Yossef E.
| last3 = Koley
| first3 = Somnath
| last4 = Shamalia
| first4 = Doaa
| last5 = Waiskopf
| first5 = Nir
| last6 = Remennik
| first6 = Sergei
| last7 = Popov
| first7 = Inna
| last8 = Oded
| first8 = Meirav
| last9 = Banin
| first9 = Uri
| title = Colloidal quantum dot molecules manifesting quantum coupling at room temperature
| journal = Nature Communications
| volume = 10
| pages = 5401
| date = December 2019
| doi = 10.1038/s41467-019-13349-1
| pmid = 31848357
| pmc = 6912682
| url = https://www.nature.com/articles/s41467-019-13349-1
}} Therefore, in broad terms quantum coupling is used to describe an effect in quantum mechanics in which two or more quantum systems are bound such that a change in one of the quantum states in one of the systems will cause an instantaneous change in all of the bound systems. It is a state similar to quantum entanglement, but whereas quantum entanglement can take place over long distances, quantum coupling is typically restricted to quantum-scale interactions.
However, due to the lack of a standardized definition, the meaning of the term quantum coupling may vary slightly depending on the field of specialization in which it is used. For instance, in the field of quantum computing, the term assumes a more specific definition, referring to qubit coupling, as illustrated by Milvus.{{cite web
| last = Milvus
| title = How do qubits interact with each other in a quantum computer?
| website = Milvus
| date = December 21, 2017
| url = https://milvus.io/ai-quick-reference/how-do-qubits-interact-with-each-other-in-a-quantum-computer
| access-date = May 25, 2025
}}