7,499 research outputs found
Itinerant chiral ferromagnetism in a trapped Rashba spin-orbit coupled Fermi gas
How ferromagnetic phases emerge in itinerant systems is an outstanding
problem in quantum magnetism. Here we consider a repulsive two-component Fermi
gas confined in a two dimensional isotropic harmonic potential and subject to a
large Rashba spin-orbit (SO) coupling, whose single-particle dispersion can be
tailored by adjusting the SO coupling strength. We show that the interplay
among SO coupling, correlation effects and mean-field repulsion leads to a
competition between ferromagnetic and non-magnetic phases. At intermediate
interaction strengths, ferromagnetic phase emerges which can be well described
by the mean-field Hartree-Fock theory; whereas at strong interaction strengths,
a strongly correlated non-magnetic phase is favored due to the
beyond-mean-field quantum correlation effects. Furthermore, the ferromagnetic
phase of this system possesses a chiral current density induced by the Rashba
spin-orbit coupling, whose experimental signature is investigated.Comment: Main text: 5 pages, 6 figures; Supplement: 4 pages, 2 figure
Like-sign Di-lepton Signals in Higgsless Models at the LHC
We study the potential LHC discovery of the Z1 KK gauge boson unitarizing
longitudinal W+W- scattering amplitude. In particular, we explore the decay
mode Z1->t tbar along with Z1-> W+W- without specifying the branching
fractions. We propose to exploit the associated production pp-> W Z1, and
select the final state of like-sign dileptons plus multijets and large missing
energy. We conclude that it is possible to observe the Z1 resonance at a 5
sigma level with an integrated luminosity of 100 inverse fb at the LHC upto 650
GeV for a dominant WW channel, and 560 GeV for a dominant ttbar channel.Comment: 13 pages, 7 figure
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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