16 research outputs found
State transfer in dissipative and dephasing environments
By diagonalization of a generalized superoperator for solving the master
equation, we investigated effects of dissipative and dephasing environments on
quantum state transfer, as well as entanglement distribution and creation in
spin networks. Our results revealed that under the condition of the same
decoherence rate , the detrimental effects of the dissipative
environment are more severe than that of the dephasing environment. Beside
this, the critical time at which the transfer fidelity and the
concurrence attain their maxima arrives at the asymptotic value
quickly as the spin chain length increases. The transfer
fidelity of an excitation at time is independent of when the system
subjects to dissipative environment, while it decreases as increases when
the system subjects to dephasing environment. The average fidelity displays
three different patterns corresponding to , and . For
each pattern, the average fidelity at time is independent of when the
system subjects to dissipative environment, and decreases as increases when
the system subjects to dephasing environment. The maximum concurrence also
decreases as increases, and when , it arrives at an
asymptotic value determined by the decoherence rate and the structure
of the spin network.Comment: 12 pages, 6 figure
State transfer in intrinsic decoherence spin channels
By analytically solving the master equation, we investigate quantum state
transfer, creation and distribution of entanglement in the model of Milburn's
intrinsic decoherence. Our results reveal that the ideal spin channels will be
destroyed by the intrinsic decoherence environment, and the detrimental effects
become severe as the decoherence rate and the spin chain length
increase. For infinite evolution time, both the state transfer fidelity and the
concurrence of the created and distributed entanglement approach steady state
values, which are independent of the decoherence rate and decrease as
the spin chain length increases. Finally, we present two modified spin
chains which may serve as near perfect spin channels for long distance state
transfer even in the presence of intrinsic decoherence environments .Comment: 11 pages, 11 figure
The genetic history of the Southern Arc: a bridge between West Asia and Europe
By sequencing 727 ancient individuals from the Southern Arc (Anatolia and its neighbors in Southeastern Europe and West Asia) over 10,000 years, we contextualize its Chalcolithic period and Bronze Age (about 5000 to 1000 BCE), when extensive gene flow entangled it with the Eurasian steppe. Two streams of migration transmitted Caucasus and Anatolian/Levantine ancestry northward, and the Yamnaya pastoralists, formed on the steppe, then spread southward into the Balkans and across the Caucasus into Armenia, where they left numerous patrilineal descendants. Anatolia was transformed by intra?West Asian gene flow, with negligible impact of the later Yamnaya migrations. This contrasts with all other regions where Indo-European languages were spoken, suggesting that the homeland of the Indo-Anatolian language family was in West Asia, with only secondary dispersals of non-Anatolian Indo-Europeans from the steppe. Stories about the peopling?and people?of Southern Europe and West Asia have been passed down for thousands of years, and these stories have contributed to our historical understanding of populations. Genomic data provide the opportunity to truly understand these patterns independently from written history. In a trio of papers, Lazaridis et al. examined more than 700 ancient genomes from across this region, the Southern Arc, spanning 11,000 years, from the earliest farming cultures to post-Medieval times (see the Perspective by Arbuckle and Schwandt). On the basis of these results, the authors suggest that earlier reliance on modern phenotypes and ancient writings and artistic depictions provided an inaccurate picture of early Indo-Europeans, and they provide a revised history of the complex migrations and population integrations that shaped these cultures. ?SNV A web of migrations between Anatolia, its neighbors, and the Steppe suggests a West Asian origin of Indo-Anatolian languages
Ancient DNA from Mesopotamia suggests distinct Pre-Pottery and Pottery Neolithic migrations into Anatolia
We present the first ancient DNA data from the Pre-Pottery Neolithic of Mesopotamia (Southeastern Turkey and Northern Iraq), Cyprus, and the Northwestern Zagros, along with the first data from Neolithic Armenia. We show that these and neighboring populations were formed through admixture of pre-Neolithic sources related to Anatolian, Caucasus, and Levantine hunter-gatherers, forming a Neolithic continuum of ancestry mirroring the geography of West Asia. By analyzing Pre-Pottery and Pottery Neolithic populations of Anatolia, we show that the former were derived from admixture between Mesopotamian-related and local Epipaleolithic-related sources, but the latter experienced additional Levantine-related gene flow, thus documenting at least two pulses of migration from the Fertile Crescent heartland to the early farmers of Anatolia