15,452 research outputs found
Group theory for structural analysis and lattice vibrations in phosphorene systems
Group theory analysis for two-dimensional elemental systems related to
phosphorene is presented, including (i) graphene, silicene, germanene and
stanene, (ii) dependence on the number of layers and (iii) two stacking
arrangements. Departing from the most symmetric graphene space
group, the structures are found to have a group-subgroup relation, and analysis
of the irreducible representations of their lattice vibrations makes it
possible to distinguish between the different allotropes. The analysis can be
used to study the effect of strain, to understand structural phase transitions,
to characterize the number of layers, crystallographic orientation and
nonlinear phenomena.Comment: 24 pages, 3 figure
Entanglement and Bell's inequality violation above room temperature in metal carboxylates
In the present work we show that a special family of materials, the metal
carboxylates, may have entangled states up to very high temperatures. From
magnetic susceptibility measurements, we have estimated the critical
temperature below which entanglement exists in the cooper carboxylate
\{Cu(OCH)\}\{Cu(OCH)(2-methylpyridine)\}, and we have
found this to be above room temperature ( K). Furthermore, the
results show that the system remains maximally entangled until close to K and the Bell's inequality is violated up to nearly room temperature
( K)
Evidence for entanglement at high temperatures in an engineered molecular magnet
The molecular compound
[Fe(-oxo)(CHN)(CO)]
was designed and synthesized for the first time and its structure was
determined using single-crystal X-ray diffraction. The magnetic susceptibility
of this compound was measured from 2 to 300 K. The analysis of the
susceptibility data using protocols developed for other spin singlet
ground-state systems indicates that the quantum entanglement would remain at
temperatures up to 732 K, significantly above the highest entanglement
temperature reported to date. The large gap between the ground state and the
first-excited state (282 K) suggests that the spin system may be somewhat
immune to decohering mechanisms. Our measurements strongly suggest that
molecular magnets are promising candidate platforms for quantum information
processing
Experimental realization of the Yang-Baxter Equation via NMR interferometry
The Yang-Baxter equation is an important tool in theoretical physics, with
many applications in different domains that span from condensed matter to
string theory. Recently, the interest on the equation has increased due to its
connection to quantum information processing. It has been shown that the
Yang-Baxter equation is closely related to quantum entanglement and quantum
computation. Therefore, owing to the broad relevance of this equation, besides
theoretical studies, it also became significant to pursue its experimental
implementation. Here, we show an experimental realization of the Yang-Baxter
equation and verify its validity through a Nuclear Magnetic Resonance (NMR)
interferometric setup. Our experiment was performed on a liquid state
Iodotrifluoroethylene sample which contains molecules with three qubits. We use
Controlled-transfer gates that allow us to build a pseudo-pure state from which
we are able to apply a quantum information protocol that implements the
Yang-Baxter equation.Comment: 10 pages and 6 figure
Observation of environment-induced double sudden transitions in geometric quantum correlations
Correlations in quantum systems exhibit a rich phenomenology under the effect
of various sources of noise. We investigate theoretically and experimentally
the dynamics of quantum correlations and their classical counterparts in two
nuclear magnetic resonance setups, as measured by geometric quantifiers based
on trace-norm. We consider two-qubit systems prepared in Bell diagonal states,
and perform the experiments in decohering environments resulting from Bell
diagonal-preserving Markovian local noise. We then report the first observation
of environment-induced double sudden transitions in the geometric quantum
correlations, a genuinely nonclassical effect not observable in classical
correlations. The evolution of classical correlations in our physical
implementation reveals in turn the finite-time relaxation to a pointer basis
under nondissipative decoherence, which we characterize geometrically in full
analogy with predictions based on entropic measures.Comment: 5 pages, 2 figures. v2: Minor corrections. Published versio
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