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Search Results: 1 - 10 of 148141 matches for " Li Xi-Han "
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Efficient polarization qubit transmission assisted by frequency degree of freedom
Xi-Han Li
Physics , 2010, DOI: 10.1088/0953-4075/44/6/065503
Abstract: We present an efficient arbitrary polarization qubit transmission scheme against channel noise by utilizing frequency degree of freedom, which is more stable in transmission surroundings. The information of quantum state is encoded in frequency state during the transmission and transferred to polarization state later. Both the fidelity of quantum state transmitted and the success probability of this scheme are 1 in principle.
Multiparty-controlled teleportation of an arbitrary m-qudit state with pure entangled quantum channel
Ping Zhou,Xi-Han Li,Fu-Guo Deng,Hong-Yu Zhou
Physics , 2007,
Abstract: We present a general scheme for multiparty-controlled teleportation of an arbitrary m-qudit ($d$-dimensional quantum system) state by using non-maximally entangled states as the quantum channel. The sender performs m generalized Bell-state measurements on her 2$m$ particles, the controllers take some single-particle measurements with the measuring basis $X_{d}$ and the receiver only need to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if he cooperates with all the controllers. All the parties can use some decoy photons to set up their quantum channel securely, which will forbid some a dishonest party to eavesdrop freely. This scheme is optimal as the probability that the receiver obtains the originally unknown m-qudit state equals to the entanglement of the quantum channel.
Opaque Attack on Three-Party Quantum Secret Sharing Based on Entanglement
Fu-Guo Deng,Xi-Han Li,Hong-Yu Zhou
Physics , 2007,
Abstract: Security of the three-party quantum secret sharing (QSS) schemes based on entanglement and a collective eavesdropping check is analyzed in the case of considerable quantum channel losses. An opaque attack scheme is presented for the dishonest agent to eavesdrop the message obtained by the other agent freely, which reveals that these QSS schemes are insecure for transmission efficiencies lower than 50%, especially when they are used to share an unknown quantum state. Finally, we present a general way to improve the security of QSS schemes for sharing not only a private key but also an unknown quantum state.
Improving the security of secure direct communication based on secret transmitting order of particles
Xi-Han Li,Fu-Guo Deng,Hong-Yu Zhou
Physics , 2006, DOI: 10.1103/PhysRevA.74.054302
Abstract: We analyzed the security of the secure direct communication protocol based on secret transmitting order of particles recently proposed by Zhu, Xia, Fan, and Zhang [Phys. Rev. A 73, 022338 (2006)], and found that this scheme is insecure if an eavesdropper, say Eve, wants to steal the secret message with Trojan horse attack strategies. The vital loophole in this scheme is that the two authorized users check the security of their quantum channel only once. Eve can insert another spy photon, an invisible photon or a delay one in each photon which the sender Alice sends to the receiver Bob, and capture the spy photon when it returns from Bob to Alice. After the authorized users check the security, Eve can obtain the secret message according to the information about the transmitting order published by Bob. Finally, we present a possible improvement of this protocol.
Faithful qubit transmission against collective noise without ancillary qubits
Xi-Han Li,Fu-Guo Deng,Hong-Yu Zhou
Physics , 2007, DOI: 10.1063/1.2794433
Abstract: We present a faithful qubit transmission scheme with linear optics against collective noise, not resorting to ancillary qubits. Its set-up is composed of three unbalanced polarization interferometers, based on a polarizing beam splitter, a beam splitter and a half-wave plate, which makes this scheme more feasible than others with present technology. The fidelity of successful transmission is 1, independent of the parameters of the collective noise, and the success probability for obtaining an uncorrupted state can be improved to 100% with some time delayers. Moreover, this scheme has some good applications in one-way quantum communication for rejecting the errors caused by the collective noise in quantum channel.
Passively self-error-rejecting qubit transmission over a collective-noise channel
Fu-Guo Deng,Xi-Han Li,Hong-Yu Zhou
Physics , 2008,
Abstract: We propose a passively self-error-rejecting single-qubit transmission scheme for an arbitrary polarization state of a single qubit over a collective-noise channel, without resorting to additional qubits and entanglement. By splitting a single qubit into some wavepackets with some Mach-Zehnder interferometers, we can obtain an uncorrupted state with a success probability approaching 100% via postselection in different time bins, independent of the parameters of collective noise. It is simpler and more flexible than the schemes utilizing decoherence-free subspace and those with additional qubits. One can directly apply this scheme to almost all quantum communication protocols based on single photons or entangled photon systems against a collective noise.
Efficient quantum key distribution over a collective noise channel
Xi-Han Li,Fu-Guo Deng,Hong-Yu Zhou
Physics , 2008, DOI: 10.1103/PhysRevA.78.022321
Abstract: We present two efficient quantum key distribution schemes over two different collective-noise channels. The accepted hypothesis of collective noise is that photons travel inside a time window small compared to the variation of noise. Noiseless subspaces are made up of two Bell states and the spatial degree of freedom is introduced to form two nonorthogonal bases. Although these protocols resort to entangled states for encoding the key bit, the receiver is only required to perform single-particle product measurements and there is no basis mismatch. Moreover, the detection is passive as the receiver does not switch his measurements between two conjugate measurement bases to get the key.
Efficient high-capacity quantum secret sharing with two-photon entanglement
Fu-Guo Deng,Xi-Han Li,Hong-Yu Zhou
Physics , 2006, DOI: 10.1016/j.physleta.2007.10.066
Abstract: An efficient high-capacity quantum secret sharing scheme is proposed following some ideas in quantum dense coding with two-photon entanglement. The message sender, Alice prepares and measures the two-photon entangled states, and the two agents, Bob and Charlie code their information on their photons with four local unitary operations, which makes this scheme more convenient for the agents than others. This scheme has a high intrinsic efficiency for qubits and a high capacity.
Improving the security of multiparty quantum secret sharing against Trojan horse attack
Fu-Guo Deng,Xi-Han Li,Hong-Yu Zhou,Zhan-jun Zhang
Physics , 2005, DOI: 10.1103/PhysRevA.72.044302
Abstract: We analyzed the security of the multiparty quantum secret sharing (MQSS) protocol recently proposed by Zhang, Li and Man [Phys. Rev. A \textbf{71}, 044301 (2005)] and found that this protocol is secure for any other eavesdropper except for the agent Bob who prepares the quantum signals as he can attack the quantum communication with a Trojan horse. That is, Bob replaces the single-photon signal with a multi-photon one and the other agent Charlie cannot find this cheating as she does not measure the photons before they runs back from the boss Alice, which reveals that this MQSS protocol is not secure for Bob. Finally, we present a possible improvement of the MQSS protocol security with two single-photon measurements and six unitary operations.
Controlled Teleportation of an Arbitrary Multi-Qudit State in a General Form with d-Dimensional Greenberger-Horne-Zeilinger States
Xi-Han Li,Fu-Guo Deng,Hong-Yu Zhou
Physics , 2007, DOI: 10.1088/0256-307X/24/5/007
Abstract: A general scheme for controlled teleportation of an arbitrary multi-qudit state with d-dimensional Greenberger-Horne-Zeilinger (GHZ) states is proposed. For an arbitrary m-qudit state, the sender Alice performs m generalized Bell-state projective measurements on her 2m qudits and the controllers need only take some single-particle measurements. The receiver Charlie can reconstruct the unknown m-qudit state by performing some single-qudit unitary operations on her particles if she cooperates with all the controllers. As the quantum channel is a sequence of maximally entangled GHZ states, the intrinsic efficiency for qudits in this scheme approaches 100% in principle.
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