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Contents

Idea

Consider a pair of quantum systems, $Q$ and $E$, where $Q$ is some system of interest and $E$ is some system that is external to $Q$ and that is in some fixed pure state $\vert e \rangle$. Now let us suppose that the two systems interact and evolve via some unitary operator on the tensor product Hilbert space of each, $\mathscr{Q} \otimes \mathscr{E}$. If one is interested in the $\mathscr{E}$-trace of density operators on this system, then $Q$ is known as an open system and $E$ is the environment.

Related concepts

• quantum measurement

• quantum decoherence

References

• Stéphane Attal, Alain Joye, Claude-Alain Pillet (eds.), Open Quantum Systems I – The Hamiltonian Approach, Lecture Notes in Mathematics 1880, Springer (2006) [[doi:10.1007/b128449](https://doi.org/10.1007/b128449)]

• Stéphane Attal, Alain Joye, Claude-Alain Pillet (eds.), Open Quantum Systems II – The Markovian approach, Lecture Notes in Mathematics 1881, Springer (2006) [[doi:10.1007/b128451](https://doi.org/10.1007/b128451)]

• Stéphane Attal, Alain Joye, Claude-Alain Pillet (eds.), Open Quantum Systems III – Recent Developments, Lecture Notes in Mathematics 1882, Springer (2006) [[doi:10.1007/b128453](https://doi.org/10.1007/b128453)]

• Heinz-Peter Breuer, Francesco Petruccione, The Theory of Open Quantum Systems, Oxford University Press (2007) [[doi:10.1093/acprof:oso/9780199213900.001.0001](https://doi.org/10.1093/acprof:oso/9780199213900.001.0001)]

• Benjamin Schumacher, Michael Westmoreland, Quantum Processes, Systems, and Information, Cambridge University Press (2010) [[doi:10.1017/CBO9780511814006](https://doi.org/10.1017/CBO9780511814006)]

See also:

• Wikipedia, Open quantum systems