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Search Results: 1 - 10 of 85950 matches for " Qing-yu Cai "
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Deterministic secure communication protocol without using entanglement
Qing-yu Cai
Physics , 2003, DOI: 10.1088/0256-307X/21/4/003
Abstract: We show a deterministic secure direct communication protocol using single qubit in mixed state. The security of this protocol is based on the security proof of BB84 protocol. It can be realized with current technologies.
Deterministic Secure Direct Communication Using Mixed state
Qing-yu Cai
Physics , 2003,
Abstract: 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.
Eavesdropping on the "ping-pong" type quantum communication protocols with invisible photon
Qing-yu Cai
Physics , 2005, DOI: 10.1016/j.physleta.2005.10.050
Abstract: The crucial issue of quantum communication protocol is its security. In this paper, we show that all the deterministic and direct two-way quantum communication protocols, sometimes called ping-pong (PP) protocols, are insecure when an eavesdropper uses the invisible photon to eavesdrop on the communication. With our invisible photon eavesdropping (IPE) scheme, the eavesdropper can obtain full information of the communication with zero risk of being detected. We show that this IPE scheme can be implemented experimentally with current technology. Finally, a possible improvement of PP communication protocols security is proposed. PACS:03.67.Hk
Deterministic Secure Direct Communication Using Ping-pong protocol without public channel
Qing-yu Cai
Physics , 2003,
Abstract: 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.
An one-time-pad key communication protocol with entanglement
Qing-yu Cai
Physics , 2003,
Abstract: 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.
Optimal Experimental Scheme for Bennett-Brassard 1984 Quantum Key Distribution Protocol with Weak Coherent Sources, Noisy and Lossy Channel
Qing-yu Cai
Physics , 2005,
Abstract: 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 $\mu $, which is independent of the channel loss and the intensity of the decoy source. Such upper bound is $inherent$ 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.Dd
The ping-pong protocol can be attacked without eavesdropping
Qing-yu Cai
Physics , 2004, DOI: 10.1103/PhysRevLett.91.109801
Abstract: Attack the ping-pong protocol without eavesdropping.
Measurement, Trace, Information Erasure and Entropy
Qing-Yu Cai
Physics , 2003,
Abstract: 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.
Secure direct communication using step-split Einstein-Podolsky-Rosen pair
Qing-yu Cai
Physics , 2003,
Abstract: 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.
Accessible Information and Quantum operations
Qing-yu Cai
Physics , 2003,
Abstract: The accessible information decreases under quantum operations. We analyzed the connection between quantum operations and accessible information. We show that a general quantum process cannot be operated accurately. Futhermore, an unknown state of a closed quantum system can not be operated arbitrarily by a unitary quantum operation.
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