This paper analyzes the decoherence induced on a single qubit by the interaction with a spin chain with nontrivial internal dynamics ( $XY$ -type interactions). The aim of the paper is to study the existence and properties of the so-called universal regime, in which the decoherence time scale becomes independent of the strength of the coupling with the environment. It is shown that, although such a regime does exist, as previously established by Cucchietti et al. [Phys. Rev. A 75, 032337 (2007)], it is not a clear signature of a quantum phase transition in the environment. In fact, this kind of universality also exists in the absence of quantum phase transitions. A universal regime can be related to the existence of an energy scale separation between the Hamiltonian of the environment and the one characterizing the system-environment interaction. The results presented also indicate that in the strong-coupling regime the quantum phase transition does not produce an enhancement of decoherence (as opposed to what happens in the weak-coupling regime).This paper analyzes the decoherence induced on a single qubit by the interaction with a spin chain with nontrivial internal dynamics ($XY$-type interactions). The aim of the paper is to study the existence and properties of the so-called universal regime, in which the decoherence time scale becomes independent of the strength of the coupling with the environment. It is shown that, although such a regime does exist, as previously established by Cucchietti et al. [Phys. Rev. A 75, 032337 (2007)], it is not a clear signature of a quantum phase transition in the environment. In fact, this kind of universality also exists in the absence of quantum phase transitions. A universal regime can be related to the existence of an energy scale separation between the Hamiltonian of the environment and the one characterizing the system-environment interaction. The results presented also indicate that in the strong-coupling regime the quantum phase transition does not produce an enhancement of decoherence (as opposed to what happens in the weak-coupling regime).

arXiv:0709.2622Physical Review AFeb 14, 200842 citations

On the phase transitions in quantum spin systems

R. Micnas, K. A. Chao

Physics Letters AJul 1, 19853 citations

Decoherence as a signature of an excited-state quantum phase transition

Armando Relaño, J. M. Arias, J. Dukelsky +2 more

We analyze the decoherence induced on a single qubit by the interaction with a two-level boson system with critical internal dynamics. We explore how the decoherence process is affected by the presence of quantum phase transitions in the environment. We conclude that the dynamics of the qubit changes dramatically when the environment passes through a continuous excited state quantum phase transition. If the system-environment coupling energy equals the energy at which the environment has a critical behavior, the decoherence induced on the qubit is maximal and the fidelity tends to zero with finite size scaling obeying a power law.We analyze the decoherence induced on a single qubit by the interaction with a two-level boson system with critical internal dynamics. We explore how the decoherence process is affected by the presence of quantum phase transitions in the environment. We conclude that the dynamics of the qubit changes dramatically when the environment passes through a continuous excited state quantum phase transition. If the system-environment coupling energy equals the energy at which the environment has a critical behavior, the decoherence induced on the qubit is maximal and the fidelity tends to zero with finite size scaling obeying a power law.

arXiv:1001.0397Physical Review ADec 16, 200877 citations

Quantum phase transitions for mixed-spin systems

昌久古賀, Akihisa Koga

Jan 1, 20000 citations

Decoherence as a Signature of an Excited State Quantum Phase Transition in Two Level Boson Systems

J. E. García-Ramos, J. M. Arias, J. Dukelsky +6 more

We analyze the decoherence induced on a single qubit by the interaction with a two-level boson system with critical internal dynamics.We explore how the decoherence process is affected by the presence of quantum phase transitions in the environment.We conclude that the dynamics of the qubit changes dramatically when the environment passes through a continuous excited state quantum phase transition.If the system-environment coupling energy equals the energy at which the environment has a critical behavior, the decoherence induced on the qubit is maximal and the fidelity tends to zero with finite size scaling obeying a power-law.We analyze the decoherence induced on a single qubit by the interaction with a two-level boson system with critical internal dynamics.We explore how the decoherence process is affected by the presence of quantum phase transitions in the environment.We conclude that the dynamics of the qubit changes dramatically when the environment passes through a continuous excited state quantum phase transition.If the system-environment coupling energy equals the energy at which the environment has a critical behavior, the decoherence induced on the qubit is maximal and the fidelity tends to zero with finite size scaling obeying a power-law.

AIP conference proceedingsJan 1, 20090 citations

Quantum Phase Transitions in Spin-Lattice Systems

Ristig, M L, Abu, Qasam K, DAMIAN J. J. FARNELL +1 more

Jan 1, 20010 citations

This paper analyzes the decoherence induced on a single qubit by the interaction with a spin chain with nontrivial internal dynamics (

XY

-type interactions). The aim of the paper is to study the existence and properties of the so-called universal regime, in which the decoherence time scale becomes independent of the strength of the coupling with the environment. It is shown that, although such a regime does exist, as previously established by Cucchietti et al. [Phys. Rev. A 75, 032337 (2007)], it is not a clear signature of a quantum phase transition in the environment. In fact, this kind of universality also exists in the absence of quantum phase transitions. A universal regime can be related to the existence of an energy scale separation between the Hamiltonian of the environment and the one characterizing the system-environment interaction. The results presented also indicate that in the strong-coupling regime the quantum phase transition does not produce an enhancement of decoherence (as opposed to what happens in the weak-coupling regime).