Witnessing quantum memory in non-Markovian processes
- Publisher:
- Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften
- Publication Type:
- Journal Article
- Citation:
- Quantum, 2021, 5, pp. 1-12
- Issue Date:
- 2021-04-26
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We present a method to detect quantum memory in a non-Markovian process. We
call a process Markovian when the environment does not provide a memory that
retains correlations across different system-environment interactions. We
define two types of non-Markovian processes, depending on the required memory
being classical or quantum. We formalise this distinction using the process
matrix formalism, through which a process is represented as a multipartite
state. Within this formalism, a test for entanglement in a state can be mapped
to a test for quantum memory in the corresponding process. This allows us to
apply separability criteria and entanglement witnesses to the detection of
quantum memory. We demonstrate the method in a simple model where both system
and environment are single interacting qubits and map the parameters that lead
to quantum memory. As with entanglement witnesses, our method of witnessing
quantum memory provides a versatile experimental tool for open quantum systems.
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