# Reconstructing non-Markovian quantum dynamics with limited control

@article{Milz2016ReconstructingNQ, title={Reconstructing non-Markovian quantum dynamics with limited control}, author={Simon Milz and Felix A. Pollock and Kavan Modi}, journal={Physical Review A}, year={2016} }

The dynamics of an open quantum system can be fully described and tomographically reconstructed if the experimenter has complete control over the system of interest. Most real-world experiments do not fulfill this assumption, and the amount of control is restricted by the experimental set-up. That is, the set of performable manipulations of the system is limited. For instance, imagine a set-up where unitary operations are easy to make, but only one measurement at the end of the experiment is…

## 23 Citations

### Dynamics of initially correlated open quantum systems: Theory and applications

- MathematicsPhysical Review A
- 2019

We show that the dynamics of any open quantum system that is initially correlated with its environment can be described by a set of $d^2$ (or less) completely positive maps, where $d$ is the…

### When Is a Non-Markovian Quantum Process Classical?

- PhysicsPhysical Review X
- 2020

More than a century after the inception of quantum theory, the question of which traits and phenomena are fundamentally quantum remains under debate. Here we give an answer to this question for…

### Experimental non-Markovian process characterisation and control on a quantum processor

- Computer Science
- 2020

This work develops and experimentally test a framework for characterising non-Markovian dynamics in quantum systems, based on the recently proposed process tensor, and demonstrates that the dynamical characterisation remains high in fidelity where conventional Markovian characterisation models suffer from an appreciable reduction in quality.

### Demonstration of non-Markovian process characterisation and control on a quantum processor

- PhysicsNature communications
- 2020

This work develops a framework for characterising non-Markovian dynamics in quantum systems and experimentally test it on multi-qubit superconducting quantum devices, showing it leads to superior quantum control and extension of coherence time by effective decoupling from the non- Markovian environment.

### Non-Markovian Quantum Process Tomography

- Computer SciencePRX Quantum
- 2022

This work formally introduces a generalisation of quantum process tomography, which it is suggested could form the core for carefully developed software that may help hardware consistently pass the fault-tolerant noise threshold.

### Operational approach to quantum stochastic thermodynamics.

- PhysicsPhysical review. E
- 2019

The theory is used to compute the thermodynamic efficiency of recent experiments reporting on the stabilization of photon number states using real-time quantum feedback control and points out various interesting problems, which the theory is able to address rigorously, including the detection of quantum effects in thermodynamics.

### Memory effects in quantum processes

- Computer ScienceInternational Journal of Quantum Information
- 2020

This paper solves the long standing question of unambiguously describing the memory length of a quantum processes and introduces an instrument-specific notion of memory strength that allows for a meaningful quantification of the temporal correlations between the history and the future of a process for a given choice of experimental intervention.

### Machine Learning Non-Markovian Quantum Dynamics.

- MathematicsPhysical review letters
- 2020

A method to extract the information about the unknown environment from a series of projective single-shot measurements on the system (without resorting to the process tomography) and the developed algorithm to learn unknown quantum environments enables one to efficiently control and manipulate quantum systems.

### Preparations and weak-field phase control can witness initial correlations

- Physics
- 2019

The dynamics of a system that is initially correlated with an environment is almost always non-Markovian. Hence it is important to characterise such initial correlations experimentally and witness…

### Resource theories of multi-time processes: A window into quantum non-Markovianity

- Computer ScienceQuantum
- 2021

This work investigates the conditions under which an uncontrollable background processes may be harnessed by an agent to perform a task that would otherwise be impossible within their operational framework, and proposes a resource theory of quantum processes across multiple points in time.

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