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Quantum Private Information Retrieval (QPIR) allows a user (Alice) to retrieve a database item from the database owned by the database holder (Bob) in such a way that Alice can query only the database item she wants, but cannot get other items, and Bob does not know which item Alice queries. However, the real quantum channel between Alice and Bob is noisy, and the noise may result in not only the chance that Alice obtains a false item, but also that both parties may cheat by camouflaging themselves with noise. In this paper, we use the decoherence-free subspace (DFS) for QPIR, which we call DFS-QPIR. The DFS-QPIR protocol removes the effect of the channel noise on the errors in the retrieved item so that two parties cannot cheat by replacing the noisy channel with a noiseless one. It can work over a collective noisy channel while retaining high reliability, database security and user privacy simultaneously. While only the collective unitary noise is taken into account, the proposed DFS-QPIR protocol can be straightforwardly extended to more general collective noise channel.

In this paper, we introduce a novel model for collective-dephasing noise in $d$-dimensional space. After that, we construct a multi-particle entangled state to resist the given collective-dephasing noise. Based on the measurement laws of multi-particle entangled state under two different bases, we propose a multipartite quantum key agreement protocol. In this protocol, multiple participants would obtain $d$-dimensional secret key even if the quantum channel is influenced by collective-dephasing noise. The security analysis indicates that this protocol can resist both dishonest participant attack and the outsider attacks which include intercept-resend attack and entangle-measure attack. By comparing with the existing QKA protocols, it is clear that our protocol has greater universality from the perspective of dimensionality and number of participants.

Unconditional security in Quantum Key Distribution (QKD) relies on authenticating the identities of users involved in key distribution. While classical identity authentication schemes were initially utilized in QKD implementations, concerns regarding their vulnerability have prompted the exploration of Quantum Identity Authentication (QIA) protocols. In this study, we introduce a new protocol for QIA, derived from the concept of controlled secure direct quantum communication. Our proposed scheme facilitates simultaneous authentication between two users, Alice and Bob, leveraging Bell states with the assistance of a third party, Charlie. Through rigorous security analysis, we demonstrate that the proposed protocol withstands various known attacks, including impersonation, intercept and resend and impersonated fraudulent attacks. Additionally, we establish the relevance of the proposed protocol by comparing it with the existing protocols of similar type.

We propose two symmetrically-private information retrieval protocols based on quantum key distribution, which provide a good degree of database and user privacy while being flexible, loss-resistant and easily generalized to a large database similar to the precedent works. Furthermore, one protocol is robust to a collective-dephasing noise, and the other is robust to a collective-rotation noise.

Based on logical GHZ states and logical Bell states, two robust quantum key agreement protocols are proposed, which can be immune to the collective-dephasing noise and the collective-rotation noise, respectively. The delayed measurement technique ensures that two participants can fairly negotiate a shared key and any one of them cannot successfully perform the participant attacks. The two protocols are congenitally free from the Trojan horse attacks and they can resist against other outsider attacks with the help of the decoy state technology. Moreover, they have no information leakage problem and achieve high qubit efficiency.

In order to eliminate the influence of the channel noise, two new measurement-device-independent quantum key distribution (MDI-QKD) protocols are proposed with logical quantum states. They can resist collective-dephasing noise and collective-rotation noise, respectively. This paper produces logical quantum states by adding the auxiliary light sources, the CNOT operations and the Hadamard transforms in the system model. The main light sources and auxiliary light sources are flexible and easily implemented, since they can be weak coherent state (WCS) sources, heralded single-photon sources (HSPSs) or heralded pair coherent state (HPCS) sources. To generate one key bit, the new MDI-QKD protocols only need one logical qubit with two particles so that they have high qubit efficiency. Moreover, the new protocols also use partial Bell-state measurement (BSM) which is very easily implemented with existing technologies.

In this paper, we discussed the local preparation methods of two types of multi-qubit logical GHZ-type states using controlled quantum gates, and drew the corresponding quantum circuits. Subsequently, we investigated the measurement-related properties of logical GHZ-type state and thus proposed two multi-party quantum secret sharing schemes against collective-dephasing and collective-rotation noise, respectively. Further, we demonstrated that the schemes can effectively resist some familiar attack strategies. Finally, we analyzed the quantum efficiency of our schemes and made a comprehensive comparison with previous similar schemes.

This work proposes two kinds of fault tolerant quantum blind dual-signature (QBDS) protocols with photon quartets, which are robust against the collective-dephasing noise and collective-rotation noise, respectively. In the protocols, the initial information needs to be signed by the message owner in addition to the signer, which will be well suitable for application in some E-payment and E-government systems that require the message owner to provide authentication information. Both QBDS protocols are constructed with logical qubits which are immune to the collective noise, thereby the protocols can provide higher communication fidelity with respect to the existing quantum signature protocols. Furthermore, the protocols had been proved to be secure against some individual eavesdropping attacks. Meanwhile, the protocols satisfy the characteristics of quantum blind signature (QBS) protocols such as unforgeability, undeniability and blindness.

We present two robust quantum key distribution protocols against two kinds of collective noise, following some ideas in quantum dense coding. Three-qubit entangled states are used as quantum information carriers, two of which form the logical qubit, which is invariant with a special type of collective noise. The information is encoded on logical qubits with four unitary operations, which can be read out faithfully with Bell-state analysis on two physical qubits and a single-photon measurement on the other physical qubit, not three-photon joint measurements. Two bits of information are exchanged faithfully and securely by transmitting two physical qubits through a noisy channel. When the losses in the noisy channel is low, these protocols can be used to transmit a secret message directly in principle.

We present two quantum key distribution (QKD) schemes over a collective-noise channel. Each logical qubit, composed of two physical qubits with a decoherence-free subspace, is immune to a collective noise and can carry one bit of information in theory. Although the receiver should prepare entangled two-photon quantum systems, he can read out the information encoded by the sender with two unitary operations on two photons, resorting to only two single-photon measurements, not Bell-state measurements, which makes these protocols simpler than others in experiment. These two QKD protocols are deterministic, not random, which makes the classical information exchanged be reduced largely. Also, they have a high intrinsic efficiency.

Quantum entanglement is an important element of quantum information processing. Sharing entangled quantum states between two remote parties is a precondition of most quantum communication schemes. We will show that the protocol proposed by Yamamoto et al. (Phys. Rev. Lett.95 (2005) 040503) for transmitting single quantum qubit against collective noise with linear optics is also suitable for distributing the components of entanglements with some modifications. An additional qubit is introduced to reduce the effect of collective noise, and the receiver can take advantage of the time discrimination and the measurement results of the assistant qubit to reconstruct a pure entanglement with the sender. Although the scheme succeeds probabilistically, the fidelity of the entangled state is almost unity in principle. The resource used in our protocol to get a pure entangled state is finite, which establishes entanglement more easily in practice than quantum entanglement purification. Also, we discuss its application in quantum key distribution over a collective channel in detail.

Based on the quantum key distribution protocol [X. H. Li, F. G. Deng and H. Y. Zhou, Phys. Rev. A78 (2008) 022321], we proposed two efficient fault-tolerant quantum secret sharing schemes over two collective-noise channels, in which the sharers can establish a key with the sender only if all the sharers collaborate together. Noiseless subspaces are composed of two Bell states based on the hypothesis of collective noise and the spatial degree of freedom is introduced to insure the security. Although entangled states are used to encode the key bits, the sharers are only required to perform single-particle product operations or single-particle product measurement, making the schemes convenient with current technique. As there is no basis mismatch during the measurement, almost all of the samples can be used to share the key.

In this article, we first review some general mathematical framework for operator quantum error correction. Then implementation of these schemes on collective noise was discussed.