Quantum Markov chain

In mathematics, the quantum Markov chain is a reformulation of the ideas of a classical Markov chain, replacing the classical definitions of probability with quantum probability.

Introduction

Very roughly, the theory of a quantum Markov chain resembles that of a measure-many automaton, with some important substitutions: the initial state is to be replaced by a density matrix, and the projection operators are to be replaced by positive operator valued measures.

Formal statement

More precisely, a quantum Markov chain is a pair $(E,\rho )$ with $\rho$ a density matrix and $E$ a quantum channel such that

E:{\mathcal {B}}\otimes {\mathcal {B}}\to {\mathcal {B}}

is a completely positive trace-preserving map, and ${\mathcal {B}}$ a C^*-algebra of bounded operators. The pair must obey the quantum Markov condition, that

\operatorname {Tr}\rho (b_{1}\otimes b_{2})=\operatorname {Tr}\rho E(b_{1},b_{2})

for all $b_{1},b_{2}\in {\mathcal {B}}$ .

References

Gudder, Stanley. "Quantum Markov chains." Journal of Mathematical Physics 49.7 (2008): 072105.

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Quantum Markov chain

Introduction

Formal statement

See also

References