Zobrazeno 1 - 10
of 219
pro vyhledávání: '"Mäkelä H"'
Publikováno v:
Phys. Rev. A 93, 033638 (2016)
We study numerically the detailed structure and decay dynamics of isolated monopoles in conditions similar to those of their recent experimental discovery. We find that the core of a monopole in the polar phase of a spin-1 Bose-Einstein condensate co
Externí odkaz:
http://arxiv.org/abs/1504.07770
Autor:
Mäkelä, H.
Publikováno v:
Phys. Rev. A 91, 012108 (2015)
We derive an upper bound for the distinguishability-based non-Markovianity measure of a two-level system and prove that for certain master equations the exact value of the measure achieves this bound. Furthermore, we obtain an easily calculable lower
Externí odkaz:
http://arxiv.org/abs/1411.7671
Autor:
Mäkelä, H., Möttönen, M.
Publikováno v:
Phys. Rev. A 88, 052111 (2013)
We study the effect of the rotating-wave approximation (RWA) and the secular approximation (SA) on the non-Markovian behavior in the spin-boson model at zero-temperature. We find that both the RWA and SA lead to a dramatic reduction in the observed n
Externí odkaz:
http://arxiv.org/abs/1306.6301
Autor:
Mäkelä, H., Lundh, E.
Publikováno v:
Phys. Rev. A 88, 033622 (2013)
We calculate analytically the Bogoliubov excitation spectrum of a toroidal spin-1 Bose-Einstein condensate that is subjected to a homogeneous magnetic field and contains vortices with arbitrary winding numbers in the $m_F=\pm 1$ components of the hyp
Externí odkaz:
http://arxiv.org/abs/1301.7260
Autor:
Mäkelä, H., Lundh, E.
Publikováno v:
Phys. Rev. A 85, 053622 (2012)
The dynamical stability of nonstationary states of homogeneous spin-2 rubidium Bose-Einstein condensates is studied. The states considered are such that the spin vector remains parallel to the magnetic field throughout the time evolution, making it p
Externí odkaz:
http://arxiv.org/abs/1202.3658
Publikováno v:
Phys. Rev. A 84, 043646 (2011)
The stability of nonstationary states of homogeneous spin-1 Bose-Einstein condensates is studied by performing Bogoliubov analysis in a frame of reference where the state is stationary. In particular, the effect of an external magnetic field is exami
Externí odkaz:
http://arxiv.org/abs/1109.1723
Publikováno v:
J. Mod. Opt. 59, 1-20 (2012)
This article gives a brief overview of some recent progress in the characterization and parametrization of density matrices of finite dimensional systems. We discuss in some detail the Bloch-vector and Jarlskog parametrizations and mention briefly th
Externí odkaz:
http://arxiv.org/abs/1103.4542
Autor:
Mäkelä, H., Messina, A.
Publikováno v:
Physica Scripta T140, 014054 (2010)
We show how the Majorana representation can be used to express the pure states of an N-qubit system as points on the Bloch sphere. We compare this geometrical representation of N-qubit states with an alternative one, proposed recently by the present
Externí odkaz:
http://arxiv.org/abs/0910.0630
Autor:
Mäkelä, H., Messina, A.
Publikováno v:
Phys. Rev. A 81, 012326 (2010)
We present a mapping which associates pure N-qubit states with a polynomial. The roots of the polynomial characterize the state completely. Using the properties of the polynomial we construct a way to determine the separability and the number of unen
Externí odkaz:
http://arxiv.org/abs/0908.1727
Autor:
Mäkelä, H., Suominen, K. -A.
Publikováno v:
Phys. Rev. Lett. 99, 190408 (2007)
We present a simple but efficient geometrical method for determining the inert states of spin-S systems. It can be used if the system is described by a spin vector of a spin-S particle and its energy is invariant in spin rotations and phase changes.
Externí odkaz:
http://arxiv.org/abs/0706.2505