Two Ways of Robust Quantum Dialogue by Using Four-Qubit Cluster State

We propose a feasible scheme for implementing bidirectional quantum direct communication protocol using four-qubit cluster states. In this scheme, the quantum channel between the sender Alice and the receiver Bob consists of an ordered sequence of cluster states which are prepared by Alice. After ensuring the security of quantum channel, according to the secret messages, the sender will perform the unitary operation and the receiver can obtain different secret messages in a deterministic way.

A new application of the four-qubit cluster state is investigated for quantum information splitting (QIS) of an arbitrary N-qubit GHZ-type state among three parties. We demonstrate that a four-qubit cluster state can be used to realize the deterministic QIS of an arbitrary N-qubit GHZ-type state by introducing N−1 ancillary qubits and performing N−1 controlled-NOT operations. The presented protocols considered here are secure against certain eavesdropping attacks.

A scheme of quantum state sharing(QSTS) an arbitrary three-qubit state is presented using two particular four-qubit cluster state as the quantum channel. With four Bell pairs state measurements and the local unitary operation, any one of the two agents has the access to reconstruct the original if he/she collaborates with the other one. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2566 Full Text: PDF

A new two-party quantum key agreement (QKA) protocol is proposed based on four-qubit cluster states. Encoded four-qubit cluster states can be transmitted directly by means of order rearrangement operation. In contrast to existing QKA protocols based on four-qubit cluster states, it is unnecessary to perform two-way quantum communication. We analyze the security of this protocol and prove that it is secure in ideal conditions. We also propose the method to ensure the security of this protocol in noisy channel. Finally, we analyze the expansibility of the proposed QKA protocol and propose a three-party QKA protocol based on four-qubit cluster states.

In this paper, we propose a mesh-topology-based multi-hop teleportation scheme for a quantum network. By using the proposed scheme, quantum communication can be realized between two arbitrary nodes, even when they do not share a direct quantum channel. Einstein–Podolsky–Rosen pairs are used as quantum channels. The source node (initial sender) and all intermediate nodes make Bell measurements independently. They send the results to the destination node (final receiver) by classical channels. The quantum state can be determined from the Bell measurement result, and only the destination node is required for simple unitary transformation. This method of simultaneous measurement contributes significantly to quantum network by reducing the hop-by-hop transmission delay.

A scheme is proposed for quantum information splitting of a two-qubit Bell state by using a four-qubit entangled state as a quantum channel. In the scenario, it is supposed that there are three legitimate parties, say Alice, Bob and Charlie. Alice is the sender of quantum information. Bob and Charlie are two agents. Alice first performs GHZ state measurement and tells Bob and Charlie the measurement results via a classical channel. It is impossible for Bob to reconstruct the original state with local operations unless help is obtained from Charlie. If Charlie allows Bob to reconstruct the original state information, he needs to perform a single-qubit measurement and tell Bob the measurement result. Using the measurement results from Alice and Charlie, Bob can reconstruct the original state. We also consider the problem of security attacks. This protocol is considered to be secure.

The high-dimensional quantum system greatly improve the quantum channel capacity and information storage space, and achieve high-dimensional quantum information transmission, which enhance the speed of quantum computing and quantum information processing. In this paper, a high-dimensional quantum teleportation protocol without information loss is proposed. We consider pre-sharing a high-dimensional non-maximum entangled state as a quantum channel between sender and receiver. By adding auxiliary particle and performing high-dimensional local operations, it is possible to achieve high-dimensional quantum teleportation without information loss. Simultaneously, we apply the protocol to butterfly network, and propose a novel high-dimensional quantum network coding based on prediction mechanism. In our scheme, we use Z-{|0⟩, |1⟩} basis to predict the transmission of high dimensional states over the butterfly network. When the prediction is successful, the deterministic transmission of high-dimensional quantum states can be realized over the butterfly network. Our scheme greatly saves the usage of quantum and classical channels, which improves the utilization efficiency of both channels.

In this paper, we introduce an improved spontaneous Raman scattering (SRS) model to accurately determine the quantum communication channel's quality when integrated into a Dense Wavelength Division Multiplexing (DWDM) network. To assess the degradational effect of counter‐propagating SRS, we carried out laboratory experiments to analyse the impact of different variables, namely the input power, fibre length and channel arrangement. Based on the measurement results, we developed a new model for defining SRS within the C‐band, which provides more precision in describing the impact of SRS compared to the previously used simplified V‐shape model. A 96‐channel DWDM use case, including one quantum and 90 classical channels, is modelled to identify the optimal channel wavelength allocation strategy. Using the revised model, we concluded that the optimal channel layout, where the channel numbering is based on the ITU‐T standard, is with the quantum channel being the 88th (1533.4 nm), or the 96th (1530.2 nm) if we consider the classical capacity. In contrast, if the V‐shape model is used for defining the optimal channel allocation, the quantum channel would be the 59th (1545 nm). The results show the importance of accurately modelling SRS, as determining the right channel placement is essential for the coexistence of quantum and classical channels.

A novel scheme for remote preparation of an arbitrary three-qubit state using four-qubit cluster state and Bell state is proposed.The three-particle state can be perfectly prepared if the sender(Alice) performs the orthogonal complete measurement on her particles and the receiver(Bob) introduces an appropriate unitary transformation on his particles.For the two cases of remote state preparation,two different projective measurement bases are constructed at sender′s side and the corresponding success probabilities are calculated.The probability of success regarding this preparation scheme is calculated in both general and some particular cases.It is that in general such remote state preparation can be realized with a probability of 1/8.But in several special cases,the probability of success can be improved to 1/4,1/2 or even 1.

In this paper, we propose two kinds of fault tolerant quantum dialogue (QD) protocols against collective-dephasing noise and collective-rotation noise, respectively. For resisting the collective noise in quantum channels, decoherence-free subspace (DFS) has been constructed with two logical qubits. The combinations of two logical qubits form four kinds of photon quartets depending on the spatial degree of freedom. Both protocols are constructed with photon quartets, which are immune to the collective noise, thereby the protocols can provide higher communication fidelity with respect to the existing QD protocols. Furthermore, we had demonstrated that the protocols can withstand the problem of information leakage and Eve’s active eavesdropping attacks.

In the emerging field of quantum information technology the two basic subfields are quantum communication and quantum computation. Photonic qubits are considered as most promising information carriers for this new technology due to the immense advantage of suffering negligible decoherence. Additionally, the very small photon-photon interactions can be replaced by inducing effective nonlinearities via measurements which allow for the implementation of crucial two-qubit gate operations. Although the spontaneous parametric down-conversion gives access to the generation of highly entangled few-photon states, such as four-qubit cluster states which allow to demonstrate the new concept of the one-way quantum computer, its applicability is highly limited due to the poor scaling of the simultaneous emission of more than one-entangled photon pair. Therefore of particular interest is the reversible mapping of qubits from photon states to atomic states. This might allow the implementation of photonic quantum repeaters for long-distance quantum communication or the generation of arbitrary multi-photon states as required for linear-optics quantum computing. Thus for the realization of such a quantum network several approaches for achieving the required quantum control between matter and photons have been studied during the past few years. Recent experiments demonstrating the generation of narrow-bandwidth single photons using a room-temperature ensemble of ⁸⁷Rb atoms and electromagnetically induced transparency should emphasize the progress towards such a quantum network.

The feasibility of transmitting discrete-variable quantum key distribution channels with carrier-grade classical optical channels over multicore fibers is experimentally explored in terms of achievable quantum bit error rates, secret key rates as well as classical signal bit error rates. A coexistence transmission record of 11.2 Tb/s is achieved for the classical channels simultaneously with a DV-QKD channel over a 1 km-long 7-core multicore fiber. Coexistence over the same multicore fiber core is identified as a dominant factor for the performance of the quantum channel requiring optical bandpass filtering of 17 nm for the quantum channel to avoid the effect of Raman noise. Also, counter-propagation of classical channels and quantum channels probe more tolerance to noise proliferation than co-propagation. In addition, the performance of the quantum channel is maintained when more than three cores are used for the classical channels. Furthermore, by adding a second DV-QKD channel in the multicore fiber, the simultaneous transmission of classical channels as well as the generation of quantum-secured keys of two QKD channels is achieved with an operational range of 10 dB of launched power into the MCF.

This paper presents theoretical analysis of Quantum Bit Error Rate (QBER) for Quantum Key Distribution (QKD) in mobile networks (5G/6G). The considered configuration of the underlying optical fiber network that is available for the establishment of the QKD in multi-site 5G networks assumes that the 5G sites are connected by a single optical fiber. Thus, multiplexing of both quantum and classical channels in a single optical fiber is thus necessary. This, in turn, results in a cross talk between classical and quantum channels, which increases QBER and imposes limitations on the maximum distance that can be reached. The approach followed in this paper provides an estimate of the maximum quantum link budget for the targeted QBER. The results of the analysis show that the QKD solution considered here can be potentially deployed using current Operators’ 5G infrastructures to replace currently used asymmetric key exchange algorithms if needed.

In this paper we analyze the impact of the spontaneous Raman scattered noise\ngenerated from multiple optical classical channels on a single quantum key\ndistribution channel, all within the telecom C-band. We experimentally measure\nthe noise generated from up to 14 continuous lasers with different wavelengths\nusing the dense wavelength division multiplexing (DWDM) standard, in both\npropagation directions in respect to the QKD channel, over different standard\nSMF-28 fiber lengths. We then simulate the expected secure key generation rate\nfor a decoy-states-based system as a function of distance under the presence of\nsimultaneous telecom traffic with different modulation techniques, and show a\nsevere penalty growing with the number of classical channels present. Our\nresults show that, for in-band coexistence, the telecom channels should be\ndistributed as close as possible from the quantum channel to avoid the Raman\nnoise peaks. Operation far from the zero dispersion wavelength of the fiber is\nalso beneficial as it greatly reduces the generation of four-wave mixing inside\nthe quantum channel. Furthermore, narrow spectral filtering on the quantum\nchannels is required due to the harsh limitations of performing QKD under real\ntelecom environments, with the quantum and several classical channels\ncoexisting in the same ITU-T C-band.\n

Various protocols exist by which a referee can be convinced that two observers share an entangled resource. Such protocols typically specify the types of communication allowed, and the degrees of trust required, between the referee and each observer. Here it is shown that the need for any degree of trust of the observers by the referee can be completely removed via the referee using classical and quantum communication channels appropriately. In particular, trust-free verification of Bell nonlocality, EPR-steering, and entanglement, respectively, requires two classical channels, one classical and one quantum channel, and two quantum channels. These channels correspond to suitable inputs of quantum randomness by the referee, which prevent the observers from mimicking entanglement using shared classical randomness. Our results generalize recent work by Buscemi [Phys. Rev. Lett. 108, 200401 (2012)], and offer a perspective on the operational significance of that work. They also offer the possibility of simpler experimental demonstrations of the basic idea of quantum-refereed nonlocality tests.