1,111 research outputs found
Non-perturbative Dynamical Decoupling Control: A Spin Chain Model
This paper considers a spin chain model by numerically solving the exact
model to explore the non-perturbative dynamical decoupling regime, where an
important issue arises recently (J. Jing, L.-A. Wu, J. Q. You and T. Yu,
arXiv:1202.5056.). Our study has revealed a few universal features of
non-perturbative dynamical control irrespective of the types of environments
and system-environment couplings. We have shown that, for the spin chain model,
there is a threshold and a large pulse parameter region where the effective
dynamical control can be implemented, in contrast to the perturbative
decoupling schemes where the permissible parameters are represented by a point
or converge to a very small subset in the large parameter region admitted by
our non-perturbative approach. An important implication of the non-perturbative
approach is its flexibility in implementing the dynamical control scheme in a
experimental setup. Our findings have exhibited several interesting features of
the non-perturbative regimes such as the chain-size independence, pulse
strength upper-bound, noncontinuous valid parameter regions, etc. Furthermore,
we find that our non-perturbative scheme is robust against randomness in model
fabrication and time-dependent random noise
Optimally controlled non-adiabatic quantum state transmission in the presence of quantum noise
Pulse controlled non-adiabatic quantum state transmission (QST) was proposed
many years ago. However, in practice environmental noise inevitably damages
communication quality in the proposal. In this paper, we study the optimally
controlled non-adiabatic QST in the presence of quantum noise. By using the
Adam algorithm, we find that the optimal pulse sequence can dramatically
enhance the transmission fidelity of such an open system. In comparison with
the idealized pulse sequence in a closed system, it is interesting to note that
the improvement of the fidelity obtained by the Adam algorithm can even be
better for a bath strongly coupled to the system. Furthermore, we find that the
Adam algorithm remains powerful for different number of sites and different
types of Lindblad operators, showing its universality in performing optimal
control of quantum information processing tasks
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