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1.
We present a generation proposal of three-photon polarization-entangled decoherence-free states, which are immune to the collective decoherence. Based on weak cross-Kerr nonlinearities, the polarization and spacial entanglement gates are realized, and thus three-photon polarization-entangled decoherence-free states can be produced. According to the outcomes of Homodyne measurement performed in the spacial entanglement gate, one Swap gate is inserted into two paths of the photon 1 to swap its spacial modes, by means of classical feed forward. In addition, in the process for realizing two entanglement gates, unitary transformation operations are performed on the appropriate photons conditioned on the different phase shifts occurred on the coherent states, aiming to obtain the same state under two scenarios of the different path compositions of photons. At the output ports of the circuit, three-photon polarization-entangled decoherence-free states which can be utilized to represent two logical qubits, |0〉L and |1〉L are achieved. Apart from Kerr media, only simple linear optical elements and the classical feed forward techniques are necessary in this proposal, facilitating its practical implementation. 相似文献
2.
Either collective-dephasing noise or collective-rotation noise is considered, two efficient quantum key distribution protocols are presented. With eight product states of three EPR pairs, two bits of secret key can be distributed successfully in each six-photon state. Comparing with the four-photon secret key distribution protocols, the security is also enhanced by using three sets (or more) of measurement bases. 相似文献
3.
We suggest a protocol for quantum key distribution—a technology allowing two distant parties to create an unconditionally
secure cryptographic key. For the creation of the key we suggest to use laser pulses weakened to the single-photon level of
duration T, the pulse carrying the value “1” being shifted in time by T/2 compared to the pulse carrying the value “0”. The overlap of the pulses provides their non-orthogonality and, therefore,
impossibility to discriminate between them with certainty. Besides the signal pulses the protocol uses coherent decoy pulses,
having longer duration than the signal ones and providing a more effective protection from a wide class of attacks. Security
of the protocol is based on interferometric control of the pulse coherence at the receiving station. We analyze the security
of the protocol against a number of intercept-resend attacks and on the basis of this analysis substantiate the necessity
of decoy state implementation. 相似文献
4.
To increase dramatically the distance and the secure key generation rate of quantum key distribution (QKD), the idea of quantum decoys--signals of different intensities--has recently been proposed. Here, we present the first experimental implementation of decoy state QKD. By making simple modifications to a commercial quantum key distribution system, we show that a secure key generation rate of 165 bit/s, which is 1/4 of the theoretical limit, can be obtained over 15 km of a telecommunication fiber. We also show that with the same experimental parameters, not even a single bit of secure key can be extracted with a non-decoy-state protocol. Compared to building single photon sources, decoy state QKD is a much simpler method for increasing the distance and key generation rate of unconditionally secure QKD. 相似文献
5.
Gu-hao Zhao Shang-hong Zhao Zhou-shi Yao Chen-Lu Hao Wen Meng Xiang Wang Zhi-hang Zhu Feng Liu 《Optik》2014
An improved quantum key distribution scheme via single-photon two-qubit states is proposed. The input–output model of the polarization state is established. And the influence of the interferometers to the polarization state is analyzed. Quantum bit error rate of polarization coding caused by birefringent and coordinate system difference between incident light and the fast and slow axes in fiber interferometer is simulated. Furthermore, maintaining conditions of polarization state are given on this basis. 相似文献
6.
Multi-user quantum key distribution with collective eavesdropping detection over collective-noise channels
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《中国物理 B》2015,(7)
A multi-user quantum key distribution protocol is proposed with single particles and the collective eavesdropping detection strategy on a star network. By utilizing this protocol, any two users of the network can accomplish quantum key distribution with the help of a serving center. Due to the utilization of the collective eavesdropping detection strategy, the users of the protocol just need to have the ability of performing certain unitary operations. Furthermore, we present three fault-tolerant versions of the proposed protocol, which can combat with the errors over different collective-noise channels.The security of all the proposed protocols is guaranteed by the theorems on quantum operation discrimination. 相似文献
7.
An efficient quantum key distribution (QKD) protocol with orthogonal
product states in the 3 \otimes 3 Hilbert space is presented. The
sender, Alice, disorders the orthogonal product state sequence and
sends it to Bob. After Alice has published the matching information
of the particle sequence, Bob recovers the correct correspondences
and makes an orthogonal measurement on the orthogonal product states
to obtain the information sent by Alice. Finally, security analysis
is also made. 相似文献
8.
S. N. Molotkov 《JETP Letters》2010,91(1):48-53
A new deterministic optical scheme has been proposed for preparing and detecting quantum states in quantum cryptography. This
scheme makes it possible to quadruple the efficiency of the existing systems under the other conditions being equal. Thus,
the efficiency of the optical part is increased to the maximum for the preparation and detection of quantum states. 相似文献
9.
An efficient two-step quantum key distribution (QKD) protocol with
orthogonal product states in the n\otimes n(n\geq3)Hilbert space
is presented. In this protocol, the particles in the orthogonal
product states form two particle sequences. The sender, Alice, first
sends one sequence to the receiver, Bob. After Bob receives the first
particle sequence, Alice and Bob check eavesdropping by measuring a
fraction of particles randomly chosen. After ensuring the security of
the quantum channel, Alice sends the other particle sequence to Bob.
By making an orthogonal measurement on the two particle sequences,
Bob can obtain the information of the orthogonal product states sent
by Alice. This protocol has many distinct features such as great
capacity, high efficiency in that it uses all orthogonal product
states in distributing the key except those chosen for checking
eavesdroppers. 相似文献
10.
We assess the security of a quantum key distribution protocol relying on the transmission of Gaussian-modulated coherent states and homodyne detection. This protocol is shown to be equivalent to an entanglement purification protocol using CSS codes followed by key extraction, and is thus secure against any eavesdropping strategy. 相似文献
11.
12.
基于连续变量GHZ态的纠缠特性,提出一种三方量子确定性密钥分配协议,其中密钥由GHZ态的振幅产生,而相位可以用来验证信道的安全性.现有的量子确定性密钥分配协议一次只能向一个接收方传送密钥,现实生活中经常要向多个接收方发送确定性密钥.信息论分析结果表明,当信道传输效率大于0.5时,该协议可以同时向两个接收方安全传送确定性密钥,制备多重纠缠态后,该协议还能够扩展成多方量子确定性密钥分配协议,这极大提高了密钥的整体传送效率,而且连续变量量子GHZ态信道容量较高,因此该协议具有重要的现实意义. 相似文献
13.
We study the possible application of the decoy state method on a basic two way quantum key distribution (QKD) scheme to extend its distance. Noting the obvious advantage of such a QKD scheme in allowing for single as well as double photon contributions, we derive relevant lower bounds on the corresponding gains in a practical decoy state implementation using two intensities for decoy states. We work with two different approaches in this vein and compare these with an ideal infinite decoy state case as well as the simulation of the original. 相似文献
14.
S. N. Molotkov 《JETP Letters》2004,80(8):563-567
A “collective” attack on the key is considered, and its connection with the classical capacity of a quantum communication channel is analyzed. It has been shown that the allowable error probability for legitimate users to which the secure key can be extracted is less than half the value for “translucent” eavesdropping and individual measurements. 相似文献
15.
We propose a new scheme for controlled quantum teleportation with Bell states in which classical keys for controllers’ portion are used. We also discuss the security of the proposed scheme and show that it can satisfy the requirements for controlled quantum teleportation. The comparison between this scheme and the previous ones shows that it is more economical and efficient. 相似文献
16.
We present two polarization-based protocols for quantum key distribution. The protocols encode key bits in noiseless subspaces or subsystems and so can function over a quantum channel subjected to an arbitrary degree of collective noise, as occurs, for instance, due to rotation of polarizations in an optical fiber. These protocols can be implemented using only entangled photon-pair sources, single-photon rotations, and single-photon detectors. Thus, our proposals offer practical and realistic alternatives to existing schemes for quantum key distribution over optical fibers without resorting to interferometry or two-way quantum communication, thereby circumventing, respectively, the need for high precision timing and the threat of Trojan horse attacks. 相似文献
17.
Fault tolerant deterministic secure quantum communication using logical Bell states against collective noise
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This study proposes two novel fault tolerant deterministic secure quantum communication(DSQC) schemes resistant to collective noise using logical Bell states. Either DSQC scheme is constructed based on a new coding function, which is designed by exploiting the property of the corresponding logical Bell states immune to collective-dephasing noise and collective-rotation noise, respectively. The secret message can be encoded by two simple unitary operations and decoded by merely performing Bell measurements, which can make the proposed scheme more convenient in practical applications.Moreover, the strategy of one-step quanta transmission, together with the technique of decoy logical qubits checking not only reduces the influence of other noise existing in a quantum channel, but also guarantees the security of the communication between two legitimate users. The final analysis shows that the proposed schemes are feasible and robust against various well-known attacks over the collective noise channel. 相似文献
18.
S. A. Podoshvedov 《Journal of Experimental and Theoretical Physics》2010,110(4):576-583
We propose a scheme for a quantum key distribution (QKD) protocol with dual-rail displaced photon states. Displaced single-photon
states with different amplitudes carry bit values of code that may be extracted, while coherent states carry nothing and only
provide an inconclusive outcome. A real resource of single photons is used, involving imperfections associated with experimental
technique that result in a photon state with an admixture of the vacuum state. The protocol is robust against the loss of
a single photon and the inefficiency of the detectors. Pulses with large amplitudes, unlike the conventional QKD relying on
faint laser pulses, are used that may approximate it to standard telecommunication and may show resistance to eaves-dropping
even in settings with high attenuation. Information leakage to the eavesdropper is determined from comparison of the output
distributions of the outcomes with ideal ones that are defined by two additional parameters accessible to only those send
the pulses. Robustness to some possible eavesdropping attacks is shown. 相似文献
19.
《Physics letters. A》2020,384(12):126340
How to lengthen the maximum transmission of continuous variable quantum key distribution (CVQKD) has been a notorious hard problem in quantum communications. Here, we propose a simple solution to this problem, i.e., quantum catalyzing CVQKD for discrete modulation with eight states. The quantum catalysis, which can facilitate the conversion of the target ensemble, is used for not only tolerating more excess noise but also lengthening the maximum transmission distance. Security analysis shows that the zero-photon catalysis (ZPC), which is actually seen as a noiseless attenuation can be used as an elegant candidate for the performance improvement of discrete modulation (DM)-CVQKD. The numerical simulations show the ZPC-involved DM-CVQKD protocol outperforms the original DM-CVQKD in terms of maximum transmission distance as well as tolerable noise. Moreover, the ZPC-involved DM-CVQKD protocol can tolerate lower reconciliation efficiency and allow the lower detection efficiency to achieve the same performance. 相似文献
20.
Security of a practical semi-device-independent quantum key distribution protocol against collective attacks
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Similar to device-independent quantum key distribution(DI-QKD), semi-device-independent quantum key distribution(SDI-QKD) provides secure key distribution without any assumptions about the internal workings of the QKD devices.The only assumption is that the dimension of the Hilbert space is bounded. But SDI-QKD can be implemented in a oneway prepare-and-measure configuration without entanglement compared with DI-QKD. We propose a practical SDI-QKD protocol with four preparation states and three measurement bases by considering the maximal violation of dimension witnesses and specific processes of a QKD protocol. Moreover, we prove the security of the SDI-QKD protocol against collective attacks based on the min-entropy and dimension witnesses. We also show a comparison of the secret key rate between the SDI-QKD protocol and the standard QKD. 相似文献