57 research outputs found
Dynamics of a two-state system through a real level crossing
The dynamics of a two-state system whose energies undergo a real crossing at
some instant of time is studied. At this instant, both the coupling and the
detuning vanish simultaneously, which leads to an exact degeneracy of the
eigenenergies of the system. It is found that the dynamics of the system is
primarily determined by the manner in which the degeneracy occurs. This
interesting behavior is reminiscent of a symmetry breaking process, since the
totally symmetric situation occurring at the crossing is significantly altered
by infinitesimal quantities, which remove the degeneracy, with very important
dynamical implications from there on. A very simple analytical formula is
derived, which is found to describe the population changes very accurately
Star network synchronization led by strong coupling-induced frequency squeezing
We consider a star network consisting of N oscillators coupled to a central
one which in turn is coupled to an infinite set of oscillators (reservoir),
which makes it leaking. Two of the N + 1 normal modes are dissipating, while
the remaining N - 1 lie in a frequency range which is more and more squeezed as
the coupling strengths increase, which realizes synchronization of the single
parts of the system
Interaction-free evolution in the presence of time-dependent Hamiltonians
The generalization of the concept of interaction-free evolutions (IFE) [A.
Napoli, {\it et al.}, Phys. Rev. A {\bf 89}, 062104 (2014)] to the case of
time-dependent Hamiltonians is discussed. It turns out that the time-dependent
case allows for much more rich structures of interaction-free states and
interaction-free subspaces. The general condition for the occurrence of IFE is
found and exploited to analyze specific situations. Several examples are
presented, each one associated to a class of Hamiltonians with specific
features.Comment: 6 pahes, no figure
Extraction of Work via a Thermalization Protocol
This extended abstract contains an outline of the work reported at the conference IQIS2018. We show that it is possible to exploit a thermalization process to extract work from a resource system R to a bipartite system S. To do this, we propose a simple protocol in a general setting in the presence of a single bath at temperature T and then examine it when S is described by the quantum Rabi model at T = 0 . We find the theoretical bounds of the protocol in the general case and we show that when applied to the Rabi model it gives rise to a satisfactory extraction of work and efficiency
Extraction of Work via a Thermalization Protocol
This extended abstract contains an outline of the work reported at the
conference IQIS2018. We show that it is possible to exploit a thermalization
process to extract work from a resource system to a bipartite system .
To do this, we propose a simple protocol in a general setting in the presence
of a single bath at temperature and then examine it when is described
by the quantum Rabi model at . We find the theoretical bounds of the
protocol in the general case and we show that when applied to the Rabi model it
gives rise to a satisfactory extraction of work and efficiency.Comment: 4 pages, 2 figures. Proceedings (extended abstract) for the
conference IQIS 2018, special issue of Proceedings (MDPI). Version close to
the published on
Work extraction exploiting thermalization with a single bath
We propose a protocol which exploits the collective thermalisation of a
bipartite system to extract work from another system. The protocol is based on
a recently proposed work definition not requiring measurements and involving
the presence of a single bath. A general description of the protocol is
provided without specifying the characteristics of the bipartite system. We
quantify both the extracted work and the ideal efficiency of the process also
giving a maximum bound to the extracted work. Then, we apply the protocol to
the case when the bipartite system is governed by the Rabi Hamiltonian while
using a zero temperature bath. For very strong couplings, an extraction of work
comparable with the typical energies of the subsystems and an efficiency
greater than one half can be obtained.Comment: 11 pages, 5 figure
A quantum particle in a box with moving walls
We analyze the non-relativistic problem of a quantum particle that bounces
back and forth between two moving walls. We recast this problem into the
equivalent one of a quantum particle in a fixed box whose dynamics is governed
by an appropriate time-dependent Schroedinger operator.Comment: 12 pages, 0 figure
Quantum correlations beyond entanglement in a classical-channel model of gravity
A direct quantization of the Newtonian interaction between two masses is known to establish entanglement, which if detected would witness the quantum nature of the gravitational field. Gravitational interaction is yet compatible also with gravitational decoherence models relying on classical channels, hence unable to create entanglement. Here, we show in paradigmatic cases that, despite the absence of entanglement, a classical-channel model of gravity can still establish quantum correlations in the form of quantum discord between two masses. This is demonstrated for the Kafri-Taylor-Milburn (KTM) model and a recently proposed dissipative extension of this. In both cases, starting from an uncorrelated state, a significant amount of discord is generally created. This eventually decays in the KTM model, while it converges to a small stationary value in its dissipative extension. We also find that initial local squeezing on the state of the masses can significanlty enhance the generated discord
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