569 research outputs found
Experimental Quantum Error-Free Transmission
Error-free transmission (EFT) of quantum information is a crucial ingredient
in quantum communication network. To overcome the unavoidable decoherence in
noisy channel, to date, many efforts have focused on faithfully transmitting
one state by consuming large numbers of synchronized ancillary states. However,
huge demands of quantum resources are hard to meet with current technology,
thus restrict practical applications. Here we propose and demonstrate an
economical method of reliably transmitting quantum information. An arbitrary
unknown quantum state is converted into time bins deterministically in terms of
its own polarization using a modified Franson interferometer. Any arisen noise
in channel will induce an associated error to the reference frame of the time
bins, which can be utilized to reject errors and recover the initial state. By
virtue of state-independent feature, our method can be applied to entanglement
distribution. After passing through 0.8 km randomly twisted optical fiber, the
entanglement still survives and is verified. Our approach significantly
simplifies the implementation of quantum EFT and enables a general quantum
state even entanglement to be protected by feedback, thus can be used as a
basic building block in practical long-distance quantum communication network.Comment: 18 pages, 3 figures, Submitted to Nature Communications, Under revie
Implications for Ediacaran biological evolution from the ca. 602 Ma Lantian biota in China
The morphologically differentiated benthic macrofossils of algae and putative animal affinities of the Lantian biota in China represents the oldest known Ediacaran macroscopic eukaryotic assemblage. Although the biota provides remarkable insights into the early evolution of complex macroeukaryotes in the Ediacaran, the uncertainty in its age has hampered any robust biological evaluation. We resolve this issue by applying a petrographic-guided rhenium-osmium (Re-Os) organic-bearing sedimentary unit study on the Lantian biota. This work confines a minimum age for the first appearance of the Lantian biota to 602 ± 7 Ma (2σ, including decay constant uncertainty). This new Re-Os date confirms that the Lantian biota is of early–mid Ediacaran age and temporally distinct from the typical Ediacaran macrobiotas. Our results indicate that the differentiation and radiation of macroscopic eukaryotes, and the evolution of the primitive, erect epibenthic ecosystem, occurred in the early–mid Ediacaran and were associated with highly fluctuating oceanic redox conditions. The radiogenic initial 187Os/188Os ratios derived from the Lantian (1.14 ± 0.02) and other Ediacaran shales invoke oxidative weathering of upper continental crust in the early–middle Ediacaran, which may have stimulated the evolution of life and oceanic-atmospheric oxygenation. Integrated with published Ediacaran chronological and geochemical data, our new Re-Os geochemical study of the Lantian black shale provides a refined, time-calibrated record of environment and eukaryote evolution during the Ediacaran
Kosterlitz-Thouless melting of magnetic order in the triangular quantum Ising material TmMgGaO4
Frustrated magnets hold the promise of material realizations of exotic phases of quantum matter, but direct comparisons of unbiased model calculations with experimental measurements remain very challenging. Here we design and implement a protocol of employing many-body computation methodologies for accurate model calculations-of both equilibrium and dynamical properties-for a frustrated rare-earth magnet TmMgGaO4 (TMGO), which explains the corresponding experimental findings. Our results confirm TMGO is an ideal realization of triangular-lattice Ising model with an intrinsic transverse field. The magnetic order of TMGO is predicted to melt through two successive Kosterlitz-Thouless (KT) phase transitions, with a floating KT phase in between. The dynamical spectra calculated suggest remnant images of a vanishing magnetic stripe order that represent vortex-antivortex pairs, resembling rotons in a superfluid helium film. TMGO therefore constitutes a rare quantum magnet for realizing KT physics, and we further propose experimental detection of its intriguing properties. TmMgGaO4 is one of a number of recently-synthesized quantum magnets that are proposed to realize important theoretical models. Here the authors demonstrate the agreement between detailed experimental measurements and state-of-the-art predictions based on the 2D transverse-field triangular lattice Ising model
A possible Macronova in the late afterglow of the `long-short' burst GRB 060614
Long-duration ( s) -ray bursts that are believed to originate
from the death of massive stars are expected to be accompanied by supernovae.
GRB 060614, that lasted 102 s, lacks a supernova-like emission down to very
stringent limits and its physical origin is still debated. Here we report the
discovery of near-infrared bump that is significantly above the regular
decaying afterglow. This red bump is inconsistent with even the weakest known
supernova. However, it can arise from a Li-Paczy\'{n}ski macronova the
radioactive decay of debris following a compact binary merger. If this
interpretation is correct GRB 060614 arose from a compact binary merger rather
than from the death of a massive star and it was a site of a significant
production of heavy r-process elements. The significant ejected mass favors a
black hole-neutron star merger but a double neutron star merger cannot be ruled
out.Comment: Minor revision; The version published in Nature Communication
Experimental Quantum Communication without a Shared Reference Frame
We present an experimental realization of a robust quantum communication
scheme [Phys. Rev. Lett. 93, 220501 (2004)] using pairs of photons entangled in
polarization and time. Our method overcomes errors due to collective rotation
of the polarization modes (e.g., birefringence in optical fiber or
misalignment), is insensitive to the phase's fluctuation of the interferometer,
and does not require any shared reference frame including time reference,
except the need to label different photons. The practical robustness of the
scheme is further shown by implementing a variation of the Bennett-Brassard
1984 quantum key distribution protocol over 1 km optical fiber.Comment: 4 pages, 4 figure
Experimental Free-Space Distribution of Entangled Photon Pairs over a Noisy Ground Atmosphere of 13km
We report free-space distribution of entangled photon pairs over a noisy
ground atmosphere of 13km. It is shown that the desired entanglement can still
survive after the two entangled photons have passed through the noisy ground
atmosphere. This is confirmed by observing a space-like separated violation of
Bell inequality of . On this basis, we exploit the distributed
entangled photon source to demonstrate the BB84 quantum cryptography scheme.
The distribution distance of entangled photon pairs achieved in the experiment
is for the first time well beyond the effective thickness of the aerosphere,
hence presenting a significant step towards satellite-based global quantum
communication.Comment: 4 pages, 3 figure
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