Non-Markovian relaxation in an open quantum system

Shingo Kukita, Yasushi Kondo, Mikio Nakahara

Abstract Recently remarkable progress in quantum technology has been witnessed. In view of this it is important to investigate an open quantum system as a model of such quantum devices. Quantum devices often require extreme conditions for the devices to operate: dynamics can be non-Markovian here. This observation necessitates us to investigate a non-Markovian open quantum system, both theoretically and experimentally. In this paper, we report two important results: (1) exact solution of a simple but non-trivial theoretical model and (2) demonstration of this model by NMR experiments, where non-Markovianity is continuously controllable. We observe qualitative agreement between theory and experiment.

Horacio M. Cataldo

Carole Addis

Le Bin Ho, Yuichiro Matsuzaki, Masayuki Matsuzaki +1 more

Abstract An open quantum system is now attracting much attention because a quantum device such as quantum computers and quantum sensors is an emerging technology. Here, we present a model of the open system that shows either time-homogeneous Markovian relaxations or non-Markovian relaxations depending on its parameters that we can control. This model is fully described with the master equation that is analytically solvable. More importantly, this model can be easily realized with molecules in isotropic liquids and measured with NMR techniques.

Heinz‐Peter Breuer

Rafael Bruno Barbosa Lima

Open quantum systems have been aim of several theoretical and experimental studies over the last years.In particular, research related to non-Markovianity and how it influences the dynamics of the system has become relatively important, because this way we can have the return the initial quantum characteristics present in the system.In this thesis two related works were developed about the influence of non-Markovianity in open quantum systems.In the first, it was used a one qubit system in contact with a bosonic reservoir and also under the influence of a classic stochastic pumping, thus generating an effective coupling of the system with the stochastic noise and the thermal reservoir.Thus, it was investigated how the dynamics of the qubit is modified through the production of non-Markovianity in the system due to the effective coupling and also how the mean system energy, with and without pumping, behaves in both Markovian and non-Markovian regime.Additionally, an analysis of non-Markovianity production was performed using exponential, Gaussian and power law stochastic noises.Applying the Andersson, Cresser, Hall and Li (ACHL) measure, it was possible to make a comparison of how much non-Markovianity was produced for each stochastic noise.In the second work, a study was performed on how it is possible to generate the transition between Markovian to non-Markovian regimes through the control of the spin-lattice relaxation time of an ancillary qubit, which acts as an environment.The decoherence of the system was simulated through the formulation of quantum channels.In addition, it was discussed how the relaxation mechanism is modified by the action of an external magnetic field.Finally, an experimental demonstration of the model is presented and the experimental data were compared with the theoretically simulated ones.