%0 Journal Article
%J Physical Review B
%D 2016
%T Autonomous {Quantum} {Refrigerator} in a {Circuit}-{QED} {Architecture} {Based} on a {Josephson} {Junction}
%A Hofer, Patrick P.
%A Perarnau-Llobet, Marti
%A Brask, Jonatan Bohr
%A Silva, Ralph
%A Huber, Marcus
%A Brunner, Nicolas
%K Condensed Matter - Mesoscale and Nanoscale Physics
%K Quantum Physics
%X An implementation of a small quantum absorption refrigerator in a circuit QED architecture is proposed. The setup consists of three harmonic oscillators coupled to a Josephson unction. The refrigerator is autonomous in the sense that it does not require any external control for cooling, but only thermal contact between the oscillators and heat baths at different temperatures. In addition, the setup features a built-in switch, which allows the cooling to be turned on and off. If timing control is available, this enables the possibility for coherence-enhanced cooling. Finally, we show that significant cooling can be achieved with experimentally realistic parameters and that our setup should be within reach of current technology.
%B Physical Review B
%V 94
%U http://arxiv.org/abs/1607.05218
%R 10.1103/PhysRevB.94.235420
%0 Journal Article
%J Phys. Rev. A
%D 2011
%T Disordered spinor Bose-Hubbard model
%A Ł{\k a}cki, M.
%A Paganelli, Simone
%A Ahufinger, V.
%A Sanpera, Anna
%A Zakrzewski, J.
%K Condensed Matter - Other Condensed Matter
%K Quantum Physics
%X We study the zero-temperature phase diagram of the disordered spin-1 Bose-Hubbard model in a two-dimensional square lattice. To this aim, we use a mean-field Gutzwiller ansatz and a probabilistic mean-field perturbation theory. The spin interaction induces two different regimes, corresponding to a ferromagnetic and antiferromagnetic order. In the ferromagnetic case, the introduction of disorder reproduces analogous features of the disordered scalar Bose-Hubbard model, consisting in the formation of a Bose glass phase between Mott insulator lobes. In the antiferromagnetic regime, the phase diagram differs more from the scalar case. Disorder in the chemical potential can lead to the disappearance of Mott insulator lobes with an odd-integer filling factor and, for sufficiently strong spin coupling, to Bose glass of singlets between even-filling Mott insulator lobes. Disorder in the spinor coupling parameter results in the appearance of a Bose glass phase only between the n and the n+1 lobes for n odd. Disorder in the scalar Hubbard interaction inhibits Mott insulator regions for occupation larger than a critical value.
%B Phys. Rev. A
%V 83
%P 013605
%G eng
%U http://link.aps.org/doi/10.1103/PhysRevA.83.013605
%R 10.1103/PhysRevA.83.013605
%0 Journal Article
%J Phys. Rev. Lett.
%D 2010
%T Adiabatic Markovian Dynamics
%A Oreshkov, Ognyan
%A Calsamiglia, John
%K Quantum Physics
%X We propose a theory of adiabaticity in quantum Markovian dynamics based on a structural decomposition of the Hilbert space induced by the asymptotic behavior of the Lindblad semigroup. A central idea of our approach is that the natural generalization of the concept of eigenspace of the Hamiltonian in the case of Markovian dynamics is a noiseless subsystem with a minimal noisy cofactor. Unlike previous attempts to define adiabaticity for open systems, our approach deals exclusively with physical entities and provides a simple, intuitive picture at the underlying Hilbert-space level, linking the notion of adiabaticity to the theory of noiseless subsystems. As an application of our theory, we propose a framework for decoherence-assisted computation in noiseless codes under general Markovian noise. We also formulate a dissipation-driven approach to holonomic computation based on adiabatic dragging of subsystems that is generally not achievable by non-dissipative means.
%B Phys. Rev. Lett.
%V 105
%P 050503
%U http://arxiv.org/abs/1002.2219
%R 10.1103/PhysRevLett.105.050503
%0 Journal Article
%J Phys. Rev. A
%D 2010
%T Ion-trap simulation of the quantum phase transition in an exactly solvable model of spins coupled to bosons
%A Giorgi, Gian Luca
%A Paganelli, Simone
%A Galve, Fernando
%K Quantum Physics
%X It is known that arrays of trapped ions can be used to efficiently simulate a variety of many-body quantum systems. Here we show how it is possible to build a model representing a spin chain interacting with bosons that is exactly solvable. The exact spectrum of the model at zero temperature and the ground-state properties are studied. We show that a quantum phase transition occurs when the coupling between spins and bosons reaches a critical value, which corresponds to a level crossing in the energy spectrum. Once the critical point is reached, the number of bosonic excitations in the ground state, which can be assumed as an order parameter, starts to be different from zero. The population of the bosonic mode is accompanied by a macroscopic magnetization of the spins. This double effect could represent a useful resource for phase transition detection since a measure of the phonon can give information about the phase of the spin system. A finite-temperature phase diagram is also given in the adiabatic regime.
%B Phys. Rev. A
%V 81
%P 052118
%8 2010
%G eng
%R 10.1103/PhysRevA.81.052118
%0 Journal Article
%J arXiv
%D 2006
%T Kaonic Quantum Erasers at KLOE 2: "Erasing the Present, changing the Past''
%A Bramon, Albert
%A Garbarino, G.
%A Hiesmayr, B. H
%K Quantum Physics
%X Neutral kaons are unique quantum systems to show some of the most puzzling peculiarities of quantum mechanics. Here we focus on a quantitative version of Bohr's complementary principle and on quantum marking and eraser concepts. In detail we show that neutral kaons (1) are kind of double slit devices encapsulating Bohr's complementarity principle in a simple and transparent way, and (2) offer marking and eraser options which are not afforded by other quantum systems and which can be performed at the DAPHNE machine.
%B arXiv
%8 11/2006
%G eng
%U http://www.arxiv.org/pdf/hep-ph/0609314.pdf http://arxiv.org/abs/hep-ph/0609314