scholarly journals BELL'S INEQUALITIES DETECT EFFICIENT ENTANGLEMENT

2004 ◽  
Vol 02 (01) ◽  
pp. 23-31 ◽  
Author(s):  
ANTONIO ACÍN ◽  
NICOLAS GISIN ◽  
LLUIS MASANES ◽  
VALERIO SCARANI
Keyword(s):  
Quantum Key Distribution ◽  
Bell Inequality ◽  
Entangled State ◽  
Secret Key ◽  
Bell’S Inequalities ◽  
Maximally Entangled State ◽  
The Status ◽  
Bell's Inequalities ◽  
Key Extraction ◽  
Secret Key Extraction

We review the status of Bell's inequalities in quantum information, stressing mainly the links with quantum key distribution and distillation of entanglement. We also prove that for all the eavesdropping attacks using one qubit, and for a family of attacks of two qubits, acting on half of a maximally entangled state of two qubits, the violation of a Bell inequality implies the possibility of an efficient secret-key extraction.

SPIN-PARITY EFFECT IN VIOLATION OF BELL'S INEQUALITIES

2013 ◽  
Vol 28 (01) ◽  
pp. 1450004 ◽  
Author(s):  
ZHIGANG SONG ◽  
J.-Q. LIANG ◽  
L.-F. WEI
Keyword(s):  
Berry Phase ◽  
Quantum Probability ◽  
Quantum Nonlocality ◽  
Entangled State ◽  
Bell’S Inequalities ◽  
Bipartite Entanglement ◽  
Spin Parity ◽  
Parity Effect ◽  
Bell's Inequalities ◽  
Spin Parity Effect

Analytic formulas of Bell correlations are derived in terms of quantum probability statistics under the assumption of measuring outcome-independence and the Bell's inequalities (BIs) are extended to general bipartite-entanglement macroscopic quantum-states (MQS) of arbitrary spins. For a spin-½ entangled state we find analytically that the violations of BIs really resulted from the quantum nonlocal correlations. However, the BIs are always satisfied for the spin-1 entangled MQS. More generally the quantum nonlocality does not lead to the violation for the integer spins since the nonlocal interference effects cancel each other by the quantum statistical-average. Such a cancellation no longer exists for the half-integer spins due to the nontrivial Berry phase, and thus the violation of BIs is understood remarkably as an effect of geometric phase. Specifically, our generic observation of the spin-parity effect can be experimentally tested with the entangled photon-pairs.

Bell inequality for quNits with binary measurements

2003 ◽  
Vol 3 (2) ◽  
pp. 157-164
Author(s):  
H. Bechmann-Pasquinucci ◽  
N. Gisin
Keyword(s):  
Quantum Cryptography ◽  
Bell Inequality ◽  
The Other ◽  
Entangled State ◽  
Maximally Entangled State ◽  
Von Neumann ◽  
Chsh Inequality ◽  
Intermediate States ◽  
Von Neumann Measurements

We present a generalized Bell inequality for two entangled quNits. On one quNit the choice is between two standard von Neumann measurements, whereas for the other quNit there are N^2 different binary measurements. These binary measurements are related to the intermediate states known from eavesdropping in quantum cryptography. The maximum violation by \sqrt{N} is reached for the maximally entangled state. Moreover, for N=2 it coincides with the familiar CHSH-inequality.

Secret Key Extraction from Wireless Signal Strength in Real Environments

2013 ◽  
Vol 12 (5) ◽  
pp. 917-930 ◽  
Author(s):  
Sriram Nandha Premnath ◽  
Suman Jana ◽  
Jessica Croft ◽  
Prarthana Lakshmane Gowda ◽  
Mike Clark ◽  
...  
Keyword(s):  
Signal Strength ◽  
Secret Key ◽  
Wireless Signal ◽  
Key Extraction ◽  
Secret Key Extraction ◽  
Wireless Signal Strength

scholarly journals A practical trojan horse for Bell-inequality-based quantum cryptography

2002 ◽  
Vol 2 (6) ◽  
pp. 434-442
Author(s):  
J. Larsson
Keyword(s):  
Quantum Cryptography ◽  
Quantum Channel ◽  
Quantum Key Distribution ◽  
Bell Inequality ◽  
Trojan Horse ◽  
Unconditional Security ◽  
Single Photons ◽  
Secret Key ◽  
Photon Polarization ◽  
At Will

Quantum Cryptography, or more accurately, Quantum Key Distribution (QKD) is based on using an unconditionally secure ``quantum channel'' to share a secret key among two users. A manufacturer of QKD devices could, intentionally or not, use a (semi-)classical channel instead of the quantum channel, which would remove the supposedly unconditional security. One example is the BB84 protocol, where the quantum channel can be implemented in polarization of single photons. Here, use of several photons instead of one to encode each bit of the key provides a similar but insecure system. For protocols based on violation of a Bell inequality (e.g., the Ekert protocol) the situation is somewhat different. While the possibility is mentioned by some authors, it is generally thought that an implementation of a (semi-)classical channel will differ significantly from that of a quantum channel. Here, a counterexample will be given using an identical physical setup as is used in photon-polarization Ekert QKD. Since the physical implementation is identical, a manufacturer may include this modification as a Trojan Horse in manufactured systems, to be activated at will by an eavesdropper. Thus, the old truth of cryptography still holds: you have to trust the manufacturer of your cryptographic device. Even when you do violate the Bell inequality.

Wireless Transceiver Aided Run-Time Secret Key Extraction for IoT Device Security

2020 ◽  
Vol 66 (1) ◽  
pp. 11-21 ◽  
Author(s):  
Mi-Kyung Oh ◽  
Sangjae Lee ◽  
Yousung Kang ◽  
Dooho Choi
Keyword(s):  
Secret Key ◽  
Wireless Transceiver ◽  
Run Time ◽  
Key Extraction ◽  
Secret Key Extraction
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