615,624 research outputs found
Entanglement induced by a single-mode heat environment
A thermal field, which frequently appears in problems of decoherence,
provides us with minimal information about the field. We study the interaction
of the thermal field and a quantum system composed of two qubits and find that
such a chaotic field with minimal information can nevertheless entangle the
qubits which are prepared initially in a separable state. This simple model of
a quantum register interacting with a noisy environment allows us to understand
how memory of the environment affects the state of a quantum register.Comment: 13pages, 3 figure
Antiferromagnetic Order of Strongly Interacting Fermions in a Trap: Real-Space Dynamical Mean-Field Analysis
We apply Dynamical Mean-Field Theory to strongly interacting fermions in an
inhomogeneous environment. With the help of this Real-Space Dynamical
Mean-Field Theory (R-DMFT) we investigate antiferromagnetic states of
repulsively interacting fermions with spin 1/2 in a harmonic potential. Within
R-DMFT, antiferromagnetic order is found to be stable in spatial regions with
total particle density close to one, but persists also in parts of the system
where the local density significantly deviates from half filling. In systems
with spin imbalance, we find that antiferromagnetism is gradually suppressed
and phase separation emerges beyond a critical value of the spin imbalance.Comment: 4 pages 5 figures, published versio
Decoherence in an Interacting Quantum Field Theory: The Vacuum Case
We apply the decoherence formalism to an interacting scalar field theory. In
the spirit of the decoherence literature, we consider a "system field" and an
"environment field" that interact via a cubic coupling. We solve for the
propagator of the system field, where we include the self-energy corrections
due to the interaction with the environment field. In this paper, we consider
an environment in the vacuum state (T=0). We show that neglecting inaccessible
non-Gaussian correlators increases the entropy of the system as perceived by
the observer. Moreover, we consider the effect of a changing mass of the system
field in the adiabatic regime, and we find that at late times no additional
entropy has been generated.Comment: 40 pages, published versio
Control of the entanglement of a two-level atom in a dissipative cavity via a classical field
We investigate the entanglement dynamics and purity of a two-level atom,
which is additionally driven by a classical field, interacting with a coherent
field in a dissipative environment. It is shown that the amount of entanglement
and the purity of the system can be improved by controlling the classical
field.Comment: 5 pages, 4 figure
On the validity and breakdown of the Onsager symmetry in mesoscopic conductors interacting with environments
We investigate magnetic-field asymmetries in the linear transport of a
mesoscopic conductor interacting with its environment. Interestingly, we find
that the interaction between the two systems causes an asymmetry only when the
environment is out of equilibrium. We elucidate our general result with the
help of a quantum dot capacitively coupled to a quantum Hall conductor and
discuss the asymmetry dependence on the environment bias and induced dephasing.Comment: 4 pages, 4 figures; discussions clarified; published versio
Toroidal qubits: naturally-decoupled quiet artificial atoms
The requirements of quantum computations impose high demands on the level of
qubit protection from perturbations; in particular, from those produced by the
environment. Here we propose a superconducting flux qubit design that is
naturally protected from ambient noise. This decoupling is due to the qubit
interacting with the electromagnetic field only through its toroidal moment,
which provides an unusual qubit-field interaction
Decoherence-assisted transport and quantum criticalities
We study the dynamics of a two-level quantum system interacting with an
external environment that takes the form of an XY spin chain in the presence of
an external magnetic field. While the presence of the bath itself can enhance
the transition probability from the lower level to the upper level of the
system, we show that this noise-assisted phenomenon is sensitive to a change of
the quantum phase of the environment. The derivative of the transition
probability displays a maximum in correspondence with the critical value of the
applied field both in the case of isotropic and anisotropic chains
- …