31 research outputs found
Information-Theoretic Meaning of Quantum Information Flow and Its Applications to Amplitude Amplification Algorithms
The advantages of quantum information processing are in many cases obtained
as consequences of quantum interactions, especially for computational tasks
where two-qubit interactions are essential. In this work, we establish the
framework of analyzing and quantifying loss or gain of information on a quantum
system when the system interacts with its environment. We show that the
information flow, the theoretical method of characterizing (non-)Markovianity
of quantum dynamics, corresponds to the rate of the minimum uncertainty about
the system given quantum side information. Thereafter, we analyze the
information exchange among subsystems that are under the performance of quantum
algorithms, in particular, the amplitude amplification algorithms where the
computational process relies fully on quantum evolution. Different realizations
of the algorithm are considered, such as i)quantum circuits, ii) analog
computation, and iii) adiabatic computation. It is shown that, in all the
cases, our formalism provides insights about the process of amplifying the
amplitude from the information flow or leakage on the subsystems.Comment: 7 pages, 5 figures, close to the published versio
Trends of information backflow in disordered spin chains
We investigate the trends of information backflow associated with the
dynamics of a sub-part of a disordered spin-1/2 transverse field Heisenberg
chain for different regimes of the Hamiltonian. Towards this aim, the decay
profile of bipartite entanglement shared between a probe-qubit and a
system-qubit (sub-part) of the chain is monitored in time. A clear shift in the
trends of the decay profiles of the bipartite entanglement from monotonic in
the low-disorder limit to non-monotonic in the moderately large disorder limit
occurs due to strong information backflow from the environment
(complementary-part) to the system-qubit. A connection between environmental
interruption caused by the information backflow and the disorder strength is
established by examining the entanglement revival frequencies. The growth
patterns of the revival frequencies in the localized phase play an instrumental
role to effectively distinguish an interacting system (many-body localized)
from its non-interacting (Anderson localized) counterpart.Comment: 7 pages, 4 figures, close to the published versio
Genuine multipartite entanglement in 1D Bose-Hubbard model with frustrated hopping
Frustration and quantum entanglement are two exotic quantum properties in
quantum many-body systems. However, despite several efforts, an exact relation
between them remains elusive. In this work, we explore the relationship between
frustration and quantum entanglement in a physical model describing strongly
correlated ultracold bosonic atoms in optical lattices. In particular, we
consider the one-dimensional Bose-Hubbard model comprising both
nearest-neighbor () and frustrated next-nearest neighbor ()
hoppings and examine how the interplay of onsite interaction () and hoppings
results in different quantum correlations dominating in the ground state of the
system. We then analyze the behavior of quantum entanglement in the model. In
particular, we compute genuine multipartite entanglement as quantified through
the generalized geometric measure and make a comparative study with bipartite
entanglement and other relevant order parameters. We observe that genuine
multipartite entanglement has a very rich behavior throughout the considered
parameter regime and frustration does not necessarily favor generating a high
amount of it. Moreover, we show that in the region with strong quantum
fluctuations, the particles remain highly delocalized in all momentum modes and
share a very low amount of both bipartite and multipartite entanglement. Our
work illustrates the necessity to give separate attention to dominating
ordering behavior and quantum entanglement in the ground state of strongly
correlated systems.Comment: 14 pages, 9 figure
Beating no-go theorems by engineering defects in quantum spin models
There exist diverse no-go theorems, ranging from no-cloning to monogamies of
quantum correlations and Bell inequality violations, which restrict the
processing of information in the quantum world. In a multipartite scenario,
monogamy of Bell inequality violation and exclusion principle of dense coding
are such theorems, which impede the ability of the system to have quantum
advantage between all its parts. In ordered spin systems, the twin restrictions
of translation invariance and monogamy of quantum correlations, in general,
enforce the bipartite states to be neither Bell inequality violating nor
dense-codeable. We show that these quantum characteristics, viz. Bell
inequality violation and dense-codeability, can be resurrected, and thereby the
no-go theorems overcome, by having quenched disorder in the system parameters
leading to quantum spin glass or quantum random field models. We show that the
quantum characteristics are regained even though the quenched averaging keeps
the disordered spin chains translationally invariant at the physically relevant
level of observables. The results show that it is possible to conquer
constraints imposed by quantum mechanics in ordered systems by introducing
impurities.Comment: 9 pages, 6 figures, RevTeX 4.
Growth of genuine multipartite entanglement in random unitary circuits
We study the growth of genuine multipartite entanglement in random quantum
circuit models, which include random unitary circuit models and the random
Clifford circuit. We find that for the random Clifford circuit, the growth of
multipartite entanglement remains slower in comparison to the random unitary
case. However, the final saturation value of multipartite entanglement is
almost the same in both cases. The behavior is then compared to the genuine
multipartite entanglement obtained in random matrix product states with a
moderately high bond dimension. We then relate the behavior of multipartite
entanglement to other global properties of the system, viz. the delocalization
of the many-body wavefunctions in Hilbert space. Along with this, we analyze
the robustness of such highly entangled quantum states obtained through random
unitary dynamics under weak measurements.Comment: 11 pages, 10 figures, close to the published versio