3,275 research outputs found
Composite quantum collision models
A collision model (CM) is a framework to describe open quantum dynamics. In
its {\it memoryless} version, it models the reservoir as
consisting of a large collection of elementary ancillas: the dynamics of the
open system results from successive "collisions" of
with the ancillas of . Here, we present a general formulation of
memoryless {\it composite} CMs, where is partitioned into the very
open system under study coupled to one or more auxiliary systems .
Their composite dynamics occurs through internal - collisions
interspersed with external ones involving and the reservoir . We show that important known instances of quantum {\it non-Markovian}
dynamics of -- such as the emission of an atom into a reservoir featuring a
Lorentzian, or multi-Lorentzian, spectral density or a qubit subject to random
telegraph noise -- can be mapped on to such {\it memoryless} composite CMs.Comment: 12 pages, 4 figure
Class of exact memory-kernel master equations
A well-known situation in which a non-Markovian dynamics of an open quantum
system arises is when this is coherently coupled to an auxiliary system
in contact with a Markovian bath. In such cases, while the joint dynamics of
- is Markovian and obeys a standard (bipartite) Lindblad-type master
equation (ME), this is in general not true for the reduced dynamics of .
Furthermore, there are several instances (\eg the dissipative Jaynes-Cummings
model) in which a {\it closed} ME for the 's state {\it cannot} even be
worked out. Here, we find a class of bipartite Lindblad-type MEs such that the
reduced ME of can be derived exactly and in a closed form for any initial
product state of -. We provide a detailed microscopic derivation of our
result in terms of a mapping between two collision modelsComment: 9 pages, 1 figur
Quantum non-Markovian piecewise dynamics from collision models
Recently, a large class of quantum non-Markovian piecewise dynamics for an
open quantum system obeying closed evolution equations has been introduced [B.
Vacchini, Phys. Rev. Lett. 117, 230401 (2016)]. These dynamics have been
defined in terms of a waiting-time distribution between quantum jumps, along
with quantum maps describing the effect of jumps and the system's evolution
between them. Here, we present a quantum collision model with memory, whose
reduced dynamics in the continuous-time limit reproduces the above class of
non-Markovian piecewise dynamics, thus providing an explicit microscopic
realization.Comment: 18 pages, 1 figures. Submitted to "Open Systems and Information
Dynamics" as a contribution to the upcoming special issue titled "40 years of
the GKLS equation
Landauer's principle in multipartite open quantum system dynamics
We investigate the link between information and thermodynamics embodied by
Landauer's principle in the open dynamics of a multipartite quantum system.
Such irreversible dynamics is described in terms of a collisional model with a
finite temperature reservoir. We demonstrate that Landauer's principle holds,
for such a configuration, in a form that involves the flow of heat dissipated
into the environment and the rate of change of the entropy of the system. Quite
remarkably, such a principle for {\it heat and entropy power} can be explicitly
linked to the rate of creation of correlations among the elements of the
multipartite system and, in turn, the non-Markovian nature of their reduced
evolution. Such features are illustrated in two exemplary cases.Comment: 5 pages, 3 figures, RevTeX4-1; Accepted for publication in Phys. Rev.
Let
Heat flux dynamics in dissipative cascaded systems
We study the dynamics of heat flux in the thermalization process of a pair of
identical quantum system that interact dissipatively with a reservoir in a {\it
cascaded} fashion. Despite the open dynamics of the bipartite system S is
globally Lindbladian, one of the subsystems "sees" the reservoir in a state
modified by the interaction with the other subsystem and hence it undergoes a
non-Markovian dynamics. As a consequence, the heat flow exhibits a
non-exponential time behaviour which can greatly deviate from the case where
each party is independently coupled to the reservoir. We investigate both
thermal and correlated initial states of and show that the presence of
correlations at the beginning can considerably affect the heat flux rate. We
carry out our study in two paradigmatic cases -- a pair of harmonic oscillators
with a reservoir of bosonic modes and two qubits with a reservoir of fermionic
modes -- and compare the corresponding behaviours. In the case of qubits and
for initial thermal states, we find that the trace distance discord is at any
time interpretable as the correlated contribution to the total heat flux.Comment: Final accepted versio
Quantum Critical Scaling under Periodic Driving
Universality is key to the theory of phase transition stating that the
equilibrium properties of observables near a phase transition can be classified
according to few critical exponents. These exponents rule an universal scaling
behaviour that witnesses the irrelevance of the model's microscopic details at
criticality. Here we discuss the persistence of such a scaling in a
one-dimensional quantum Ising model under sinusoidal modulation in time of its
transverse magnetic field. We show that scaling of various quantities
(concurrence, entanglement entropy, magnetic and fidelity susceptibility)
endures up to a stroboscopic time , proportional to the size of the
system. This behaviour is explained by noticing that the low-energy modes,
responsible for the scaling properties, are resilient to the absorption of
energy. Our results suggest that relevant features of the universality do hold
also when the system is brought out-of-equilibrium by a periodic driving.Comment: 11 pages, 7 figure
Non-Markovian dynamics from band edge effects and static disorder
It was recently shown [S. Lorenzo, F. Lombardo, F. Ciccarello and M. Palma, Sci. Rep. 7 (2017) 42729] that the presence of static disorder in a bosonic bath \ue2\u80\u94 whose normal modes thus become all Anderson-localized \ue2\u80\u94 leads to non-Markovianity in the emission of an atom weakly coupled to it (a process which in absence of disorder is fully Markovian). Here, we extend the above analysis beyond the weak-coupling regime for a finite-band bath so as to account for band edge effects. We study the interplay of these with static disorder in the emergence of non-Markovian behavior in terms of a suitable non-Markovianity measure
Epidemic Management via Imperfect Testing: A Multi-criterial Perspective
Diagnostic testing may represent a key component in response to an ongoing epidemic, especially if coupled with containment measures, such as mandatory self-isolation, aimed to prevent infectious individuals from furthering onward transmission while allowing non-infected individuals to go about their lives. However, by its own nature as an imperfect binary classifier, testing can produce false negative or false positive results. Both types of misclassification are problematic: while the former may exacerbate the spread of disease, the latter may result in unnecessary isolation mandates and socioeconomic burden. As clearly shown by the COVID-19 pandemic, achieving adequate protection for both people and society is a crucial, yet highly challenging task that needs to be addressed in managing large-scale epidemic transmission. To explore the trade-offs imposed by diagnostic testing and mandatory isolation as tools for epidemic containment, here we present an extension of the classical Susceptible-Infected-Recovered model that accounts for an additional stratification of the population based on the results of diagnostic testing. We show that, under suitable epidemiological conditions, a careful assessment of testing and isolation protocols can contribute to epidemic containment, even in the presence of false negative/positive results. Also, using a multi-criterial framework, we identify simple, yet Pareto-efficient testing and isolation scenarios that can minimize case count, isolation time, or seek a trade-off solution for these often contrasting epidemic management objectives
Temperature gradient and asymmetric steady state correlations in dissipatively coupled cascaded optomechanical systems
The interaction between a light mode and a mechanical oscillator via radiation pressure in optomechanical systems is an excellent platform for a multitude of applications in quantum technologies. In this work we study the dynamics of a pair of optomechanical systems interacting dissipatively with a wave guide in a unidirectional way. Focusing on the regime where the cavity modes can be adiabatically eliminated, we derive an effective coupling between the two mechanical modes and explore the classical and quantum correlations established between the modes in both the transient and the stationary regime, highlighting their asymmmetrical nature due to the unidirectional coupling. Noteworthy, we find that a constant amount of steady correlations can exist at long times. Furthermore we show that this unidirectional coupling establishes a temperature gradient between the mirrors, depending on the frequencies' detuning. We additionally analyze the power spectrum of the output guide field and we show how, thanks to the chiral coupling, from such spectrum it is possible to reconstruct the spectra of each single mirror
Temperature gradient and asymmetric steady state correlations in dissipatively coupled cascaded optomechanical systems
The interaction between a light mode and a mechanical oscillator via
radiation pressure in optomechanical systems is an excellent platform for a
multitude of applications in quantum technologies. In this work we study the
dynamics of a pair of optomechanical systems interacting dissipatively with a
wave guide in a unidirectional way. Focusing on the regime where the cavity
modes can be adiabatically eliminated we derive an effective coupling between
the two mechanical modes and we explore both classical and quantum correlations
established between the modes in both in the transient and in the stationary
regime, highlighting their asymmmetrical nature due to the unidirectional
coupling, and we find that a constant amount of steady correlations can exist
at long times. Furthermore we show that this unidirectional coupling
establishes a temperature gradient between the mirrors, depending on the
frequencies' detuning. We additionally analyze the power spectrum of the output
guide field and we show how, thanks to the chiral coupling, from such spectrum
it is possible to reconstruct the spectra of each single mirror.Comment: 27 pages, 10 figure
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