1,658 research outputs found
Secure direct communication using step-split Einstein-Podolsky-Rosen pair
We presen a secure direct communication protocol by using step-split
Einstein-Podolsky-Rosen (EPR) pair. In this communication protocol, Alice first
sends one qubit of an EPR pair to Bob. Bob sends a receipt signal to Alice
through public channel when he receives Alice's first qubit. Alice performs her
encoding operations on the second qubit and sends this qubit to Bob. Bob
performs a Bell-basis measurement to draw Alice's information. The security of
this protocol is based on `High fidelity implies low entropy'. If Eve want to
eavesdrop Alice's information, she has to attack both qubits of the EPR pair,
which results in that any effective eavesdropping attack can be detected. Bob's
receipt signal can protect this protocol against the eavesdropping hiding in
the quantum channel losses. And this protocol is strictly secure to perform a
quantum key distribution by using Calderbank-Shor-Steane codes.Comment: PACS:03.67.Hk,03.65.U
Measurement, Trace, Information Erasure and Entropy
We show that both information erasure process and trace process can be
realized by projective measurement. And a partial trace operation consists to a
projective measurement on a subsystem. We show that a nonunitary operation will
destroy the wave-behavior of a particle. We give a quantum manifestation of
Maxwell's demon and give a quantum manifestation of the second law of
therodynamics. We show that, considering the law of memontum-energy
conversation, the evolution of a closed system should be unitary and the von
Neumann entropy of the closed quantum system should be least.Comment: 8pages. Reported on the Conference of Chinese Physics Society (2003
autumn):Quantum information conncil hous
Eavesdropping on the Bostroem-Filbinger Communication Protocol in Noisy Quantum Channel
We show an eavesdropping scheme on Bostr\UNICODE{0xf6}m-Felbinger
communication protocol (called ping-pong protocol) [Phys. Rev. Lett. 89, 187902
(2002)] in an ideal quantum channel. A measurement attack can be perfectly used
to eavesdrop Alice's information instead of a most general quantum operation
attack. In a noisy quantum channel, the direct communication is forbidden. We
present a quantum key distribution protocol based on the ping-pong protocol,
which can be used in a low noisy quantum channel. And we give a weak upper
bound on the bit-error ratio that the detection probability should be lower
than 0.11, which is a requirement criterion when we utilize the ping-pong
protocol in a real communication.Comment: 4 pages; PSCA, 03.67.Hk, 03.65.U
Optimal Experimental Scheme for Bennett-Brassard 1984 Quantum Key Distribution Protocol with Weak Coherent Sources, Noisy and Lossy Channel
It is the first scheme which allows the detection apparatus to achieve both
the photon number of arriving signals and quantum bit error rate of the
multiphoton pulses precisely. We show that the upper bound of the fraction of
the tagged multiphoton pulses counts is , which is independent of the
channel loss and the intensity of the decoy source. Such upper bound is
and cannot be reduced any longer as long as the weak coherent
scouces and high lossy channel are used. We show that our scheme can be
implemented even if the channel loss is very high. A stronger intensity of the
pulse source is allowable to improve the rate of quantum key distribution. Both
the signal pulses and decoy pulses can be used to generate the raw key after
verified the security of the communication. We analyze that our scheme is
optimal under today's technology.
PACS: 03.67.DdComment: RevTex, 2figures, submitted for publication on 30 March 200
Deterministic Secure Direct Communication Using Ping-pong protocol without public channel
Based on an EPR pair of qubits and allowing asymptotically secure key
distribution, a secure communication protocol is presented. Bob sends either of
the EPR pair qubits to Alice. Alice receives the travel qubit. Then she can
encode classical information by local unitary operations on this travel qubit.
Alice send the qubit back to Bob. Bob can get Alice's information by
measurement on the two photons in Bell operator basis. If Eve in line, she has
no access to Bob's home qubit. All her operations are restricted to the travel
qubit. In order to find out which opeartion Alice performs, Eve's operation
must include measurements. The EPR pair qubits are destroyed. Bob's measurement
on the two photons in Bell operator basis can help him to judge whether Eve
exist in line or not. In this protocal, a public channel is not necessary.Comment: 3 figure
Deterministic Secure Direct Communication Using Mixed state
We show an improved ping-pong protocol which is based on the protocol showed
by Kim Bostrom and Timo Felbinger [Phys. Rev. Lett. 89, 187902 (2002);
quant-ph/0209040]. We show that our protocol is asymptotically secure key
distribution and quasisecure direct communication using a single photon
resource. And this protocol can be can be carried out with great efficiency and
speed using today's technology
An one-time-pad key communication protocol with entanglement
We present an one-time-pad key communication protocol that allows secure
direct communication with entanglement. Alice can send message to Bob in a
deterministic manner by using local measurements and public communication. The
theoretical efficiency of this protocol is double compared with BB84 protocol.
We show this protocol is unconditional secure under arbitrary quantum attack.
And we discuss that this protocol can be perfectly implemented with current
technologies.Comment: 4 pages;PACS: 03.67.Hk, 03.65.U
N-Partner Secure Direct Communication Based on Quantum Nonlocality
A multipartner secure direct communication protocol is presented, using
quantum nonlocality. Security of this protocol is based on `High fidelity
implies low entropy'. When the entanglement was successfully distributed,
anyone of the multipartner can send message secretly by using local operation
and reliable public channel. Since message transfered only by using local
operation and public channel after entanglement successfully distributed, so
this protocol can protect the communication against
destroying-travel-qubit-type attack.Comment: PACS: 03.67.Hk, 03.65.U
Gravitational baryogenesis of vacuum Inflation
We show that in the vacuum inflation model, the gravitational baryogenesis
mechanism will produce the baryon asymmetry. We analyze the evolution of
entropy and baryon number in the vacuum inflation model. The comparison between
dilution speed and the chemical potential may give a natural interpretation for
decouple temperature of the gravitational baryogenesis interaction. From the
result, the mechanism can give acceptable baryon-to-entropy ratio in the vacuum
inflation model
Hidden Messenger from Quantum Geometry: Towards Information Conservation in Quantum Gravity
The back reactions of Hawking radiation allow nontrivial correlations between
consecutive Hawking quanta, which gives a possible way of resolving the paradox
of black hole information loss known as the hidden messenger method. In a
recent work of Ma {\it et al} [arXiv:1711.10704], this method is enhanced by a
general derivation using small deviations of the states of Hawking quanta off
canonical typicality. In this paper, we use this typicality argument to study
the effects of generic back reactions on the quantum geometries described by
spin network states, and discuss the viability of entropy conservation in loop
quantum gravity. We find that such back reactions lead to small area
deformations of quantum geometries including those of quantum black holes. This
shows that the hidden-messenger method is still viable in loop quantum gravity,
which is a first step towards resolving the paradox of black hole information
loss in quantum gravity.Comment: 13 page
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