Editing Quantum entanglement (section)

===Multipartite entanglement===
{{main|Multipartite entanglement}}
Quantum states describing systems made of more than two pieces can also be entangled. An example for a three-qubit system is the [[Greenberger–Horne–Zeilinger state|Greenberger–Horne–Zeilinger (GHZ) state]],
<math display="block">|\mathrm{GHZ}\rangle = \frac{|000\rangle + |111\rangle}{\sqrt{2}}.</math>
Another three-qubit example is the [[W state]]:
<math display="block">|\mathrm{W}\rangle = \frac{|001\rangle + |010\rangle + |100\rangle}{\sqrt{3}}.</math>
Tracing out any one of the three qubits turns the GHZ state into a separable state, whereas the result of tracing over any of the three qubits in the W state is still entangled. This illustrates how multipartite entanglement is a more complicated topic than bipartite entanglement: systems composed of three or more parts can exhibit multiple qualitatively different types of entanglement.<ref name="Bengtsson2017"/>{{rp|493–497}} A single particle cannot be maximally entangled with more than a particle at a time, a property called [[Monogamy of entanglement|monogamy]].<ref>{{Cite book |last1=Bertlmann |first1=Reinhold |url=https://books.google.com/books?id=uzHaEAAAQBAJ&dq=monogamy+of+entanglement&pg=PA511 |title=Modern Quantum Theory: From Quantum Mechanics to Entanglement and Quantum Information |last2=Friis |first2=Nicolai |date=2023-10-05 |publisher=Oxford University Press |isbn=978-0-19-150634-5 |language=en |page=511}}</ref>