3 research outputs found
The quantum cryptographic switch
No full textWe illustrate using a quantum system the principle of a cryptographic switch,
in which a third party (Charlie) can control to a continuously varying degree
the amount of information the receiver (Bob) receives, after the sender (Alice)
has sent her information. Suppose Charlie transmits a Bell state to Alice and
Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit
information corresponding to choice of Bell state is made available by Charlie
to Bob can the latter recover Alice's information. By varying the information
he gives, Charlie can continuously vary the information recovered by Bob. The
performance of the protocol subjected to the squeezed generalized amplitude
damping channel is considered. We also present a number of practical situations
where a cryptographic switch would be of use.Comment: 7 pages, 4 Figure
Analysing QBER and secure key rate under various losses for satellite based free space QKD
No full textQuantum Key Distribution is a key distribution method that uses the qubits to
safely distribute one-time use encryption keys between two or more authorised
participants in a way that ensures the identification of any eavesdropper. In
this paper, we have done a comparison between the BB84 and B92 protocols and
BBM92 and E91 entanglement based protocols for satellite based uplink and
downlink in low Earth orbit. The expressions for the quantum bit error rate and
the keyrate are given for all four protocols. The results indicate that, when
compared to the B92 protocol, the BB84 protocol guarantees the distribution of
a higher secure keyrate for a specific distance. Similarly, it is observed that
BBM92 ensures higher keyrate in comparison with E91 protocol.Comment: arXiv admin note: text overlap with arXiv:1906.08115 by other author
Longitudinal wave-breaking limits in a unified geometric model of relativistic warm plasmas
No full textThe covariant Vlasov–Maxwell system is used to study the breaking of relativistic warm plasma waves. The well-known theory of relativistic warm plasmas due to Katsouleas and Mori (KM) is subsumed within a unified geometric formulation of the 'waterbag' paradigm over spacetime. We calculate the maximum amplitude Emax of nonlinear longitudinal electric waves for a particular class of waterbags whose geometry is a simple three-dimensional generalization (in velocity) of the one-dimensional KM waterbag (in velocity). It has been shown previously that the value of limv → cEmax (with the effective temperature of the plasma electrons held fixed) diverges for the KM model; however, we show that a certain class of simple three-dimensional waterbags exhibit a finite value for limv → cEmax, where v is the phase velocity of the wave and c is the speed of light
