scholarly journals Experimental realization of entangled qutrits for quantum communication

2004 ◽  
Vol 4 (2) ◽  
pp. 93-101
Author(s):  
R. Thew ◽  
A. Acin ◽  
H. Zbinden ◽  
N. Gisin
Keyword(s):  
Quantum Communication ◽  
Fiber Optic ◽  
Quantum Systems ◽  
Entangled States ◽  
Fringe Visibility ◽  
Long Distance ◽  
Experimental Realization ◽  
3 Dimensional ◽  
Higher Dimensional ◽  
Maximally Entangled States

We have experimentally realized a technique to generate, control and measure entangled qutrits, 3-dimensional quantum systems. This scheme uses spontaneous parametric down converted photons and unbalanced 3-arm fiber optic interferometers in a scheme analogous to the Franson interferometric arrangement for qubits. The results reveal a source capable of generating maximally entangled states with a net state fidelity, F = 0.985 $\pm$ 0.018. Further the control over the system reveals a high, net, 2-photon interference fringe visibility, V = 0.919 $\pm$ 0.026. This has all been done at telecom wavelengths thus facilitating the advancement towards long distance higher dimensional quantum communication.

scholarly journals Twisted photon entanglement through turbulent air across Vienna

2015 ◽  
Vol 112 (46) ◽  
pp. 14197-14201 ◽  
Author(s):  
Mario Krenn ◽  
Johannes Handsteiner ◽  
Matthias Fink ◽  
Robert Fickler ◽  
Anton Zeilinger
Keyword(s):  
Angular Momentum ◽  
Quantum Entanglement ◽  
Quantum Communication ◽  
Entangled States ◽  
Phase Front ◽  
Quantum Channels ◽  
Long Distance ◽  
Large Alphabet ◽  
Large State Space ◽  
Promising Application

Photons with a twisted phase front can carry a discrete, in principle, unbounded amount of orbital angular momentum (OAM). The large state space allows for complex types of entanglement, interesting both for quantum communication and for fundamental tests of quantum theory. However, the distribution of such entangled states over large distances was thought to be infeasible due to influence of atmospheric turbulence, indicating a serious limitation on their usefulness. Here we show that it is possible to distribute quantum entanglement encoded in OAM over a turbulent intracity link of 3 km. We confirm quantum entanglement of the first two higher-order levels (with OAM=± 1ℏ and ± 2ℏ). They correspond to four additional quantum channels orthogonal to all that have been used in long-distance quantum experiments so far. Therefore, a promising application would be quantum communication with a large alphabet. We also demonstrate that our link allows access to up to 11 quantum channels of OAM. The restrictive factors toward higher numbers are technical limitations that can be circumvented with readily available technologies.

TWO-PHOTON HIGH-DIMENSIONAL SPATIAL ENTANGLEMENT: THEORY AND EXPERIMENT

2006 ◽  
Vol 20 (01) ◽  
pp. 1-23 ◽  
Author(s):  
LEONARDO NEVES ◽  
G. LIMA ◽  
J. G. AGUIRRE GÓMEZ ◽  
C. H. MONKEN ◽  
C. SAAVEDRA ◽  
...  
Keyword(s):  
Quantum Systems ◽  
High Dimensional ◽  
Entangled States ◽  
Type Ii ◽  
Opaque Screen ◽  
Two Photon ◽  
Parametric Down Conversion ◽  
Experimental Works ◽  
Maximally Entangled States ◽  
Down Conversion

We review recent theoretical and experimental works where are proposed and demonstrated how to use photon pairs created by spontaneous parametric down-conversion to generate entangled states of D-dimensional quantum systems, or qudits. This is the first demonstration of high-dimensional entanglement based on the intrinsic transverse momentum entanglement of the type-II down-converted photons. The qudit space is defined by an aperture made up of an opaque screen with D slits (paths), placed in the arms of the twin photons. By manipulating the pump beam profile we can prepare different entangled states of these possible paths. We focus our attention on an important case for applications in quantum information: the maximally entangled states. Experimental results for qudits with D=4 and D=8 are shown and measuring a two-photon conditional interference, we also demonstrate the nonclassical character of the correlations.

scholarly journals Parameter regimes for surpassing the PLOB bound with error-corrected qudit repeaters

Quantum ◽  
2019 ◽  
Vol 3 ◽  
pp. 216 ◽  
Author(s):  
Daniel Miller ◽  
Timo Holz ◽  
Hermann Kampermann ◽  
Dagmar Bruß
Keyword(s):  
Secure Communication ◽  
Quantum Communication ◽  
Quantum Repeater ◽  
Long Distance ◽  
Quantum Networks ◽  
Quantum Capacity ◽  
Higher Dimensional ◽  
Quantum Repeaters ◽  
New Applications ◽  
Provably Secure

A potential quantum internet would open up the possibility of realizing numerous new applications, including provably secure communication. Since losses of photons limit long-distance, direct quantum communication and wide-spread quantum networks, quantum repeaters are needed. The so-called PLOB-repeaterless bound [Pirandola et al., Nat. Commun. 8, 15043 (2017)] is a fundamental limit on the quantum capacity of direct quantum communication. Here, we analytically derive the quantum-repeater gain for error-corrected, one-way quantum repeaters based on higher-dimensional qudits for two different physical encodings: Fock and multimode qudits. We identify parameter regimes in which such quantum repeaters can surpass the PLOB-repeaterless bound and systematically analyze how typical parameters manifest themselves in the quantum-repeater gain. This benchmarking provides a guideline for the implementation of error-corrected qudit repeaters.

Heralded Entanglement Between Widely Separated Atoms

Science ◽  
2012 ◽  
Vol 337 (6090) ◽  
pp. 72-75 ◽  
Author(s):  
Julian Hofmann ◽  
Michael Krug ◽  
Norbert Ortegel ◽  
Lea Gérard ◽  
Markus Weber ◽  
...  
Keyword(s):  
Quantum Mechanics ◽  
Quantum Communication ◽  
Information Science ◽  
Essential Feature ◽  
Quantum Systems ◽  
Long Distance ◽  
Quantum Information Science ◽  
Classical Statistics ◽  
Measurement Results ◽  
Generation Of Entanglement

Entanglement is the essential feature of quantum mechanics. Notably, observers of two or more entangled particles will find correlations in their measurement results that cannot be explained by classical statistics. To make it a useful resource, particularly for scalable long-distance quantum communication, the heralded generation of entanglement between distant massive quantum systems is necessary. We report on the creation and analysis of heralded entanglement between spins of two single rubidium-87 atoms trapped independently 20 meters apart. Our results illustrate the viability of an integral resource for quantum information science, as well as for fundamental tests of quantum mechanics.

scholarly journals Single-photon entanglement concentration for long-distance quantum communication

2010 ◽  
Vol 10 (3&4) ◽  
pp. 272-281
Author(s):  
Y.-B. Sheng ◽  
F.-G. Deng ◽  
H.-Y. Zhou
Keyword(s):  
Quantum Communication ◽  
Single Photon ◽  
Entanglement Concentration ◽  
Entangled States ◽  
Accurate Information ◽  
Photon Detectors ◽  
Long Distance ◽  
Practical Applications ◽  
Single Photon Detectors ◽  
Quantum Internet

We present a single-photon entanglement concentration protocol for long-distance quantum communication with quantum nondemolition detector. It is the first concentration protocol for single-photon entangled states and it dose not require the two parties of quantum communication to know the accurate information about the coefficient $\alpha$ and $\beta$ of the less entangled states. Also, it does not resort to sophisticated single-photon detectors, which makes this protocol more feasible in current experiments. Moreover, it can be iterated to get a higher efficiency and yield. All these advantages maybe make this protocol have more practical applications in long-distance quantum communication and quantum internet.

scholarly journals Fundamental limitations on distillation of quantum channel resources

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Bartosz Regula ◽  
Ryuji Takagi
Keyword(s):  
Lower Bounds ◽  
Quantum Channel ◽  
Quantum Communication ◽  
Fault Tolerant ◽  
State Of The Art ◽  
Quantum Systems ◽  
Noisy Channels ◽  
General Transformation ◽  
Fundamental Limitations ◽  
Strong Converse

AbstractQuantum channels underlie the dynamics of quantum systems, but in many practical settings it is the channels themselves that require processing. We establish universal limitations on the processing of both quantum states and channels, expressed in the form of no-go theorems and quantitative bounds for the manipulation of general quantum channel resources under the most general transformation protocols. Focusing on the class of distillation tasks — which can be understood either as the purification of noisy channels into unitary ones, or the extraction of state-based resources from channels — we develop fundamental restrictions on the error incurred in such transformations, and comprehensive lower bounds for the overhead of any distillation protocol. In the asymptotic setting, our results yield broadly applicable bounds for rates of distillation. We demonstrate our results through applications to fault-tolerant quantum computation, where we obtain state-of-the-art lower bounds for the overhead cost of magic state distillation, as well as to quantum communication, where we recover a number of strong converse bounds for quantum channel capacity.

Entanglement concentration for non-maximally entangled states of qudits

2009 ◽  
Vol 282 (7) ◽  
pp. 1482-1487 ◽  
Author(s):  
M. Yang ◽  
A. Delgado ◽  
L. Roa ◽  
C. Saavedra
Keyword(s):  
Entanglement Concentration ◽  
Entangled States ◽  
Maximally Entangled States
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