Quantum Entanglement Swapping Research Articles

Novel two-party quantum private comparison via quantum walks on circle

The quantum private comparison aims to make the size comparison of two participants’ private information without leaking the private data of their own with quantum mechanism. In this paper, different from the current method of using single particle or entangled state as the information carrier, a novel two-party quantum private comparison protocol is firstly proposed via quantum walks on circle. In the protocol, a third party is assumed to be semi-honest and allowed to misbehave on his own, but cannot conspire with either of the two dishonest participants and obtain the participants’ private information. The protocol adopts the two-particle quantum walks state on circle rather than entangled state as the initial quantum resource and only needs measurement and quantum walks operator without the unitary operation and quantum entanglement swapping. The two-particle state is transferred as a whole among different parties, which reduces the protocol complexity and avoids the chance of being attacked. It can implement the equality comparison of private information, but also the size comparison. Security analyses show that this protocol is resistant to the external and internal malicious attacks, which can also determine the disputes over the judgment result of the third party. Compared with other quantum private comparison protocols, the proposed protocol has better flexibility and universality.

Feasible measurement-based entanglement purification in linear optics.

Entanglement purification is used to distill high quality entangled states from several noisy low quality entangled states, and it plays a key role in quantum repeater. The measurement-based entanglement purification protocol (MB-EPP) does not require local two-qubit gates or single-particle measurements on the noisy pairs and may offer significant advantages compared with the gate-based EPPs. We present an alternative MB-EPP in linear optics. Subsequently, we provide a detailed analysis on the realization of this MB-EPP using spontaneous parametric down conversion (SPDC) sources. By delicately designing the optical circuits, the double-pair emission noise caused by SPDC sources can be eliminated automatically. Combined with suitable quantum memory and entanglement swapping, this MB-EPP may have application potential in the implementation of a practical measurement-based quantum repeater.

A Novel Practical Quantum Secure Direct Communication Protocol

A novel practical quantum secure direct communication (QSDC) protocol is constructed by utilizing the evolution law of atom via cavity QED. It transmits the atoms from one communicant to the other communicant in a two-step manner. It adopts two-atom product states as the initial quantum resource and the decoy atom technique to guarantee the security against the outside attack. It only needs single-atom measurements, and neither the quantum entanglement swapping nor the unitary operations.

Quantum Secret Sharing via Cavity QED

A novel quantum secret sharing (QSS) protocol is suggested by utilizing the evolution law of atom via cavity quantum electrodynamics (QED) in this paper. It employs two-atom product states rather than entangled states as the initial quantum resource, and adopts single-atom measurements rather than two-atom or multiple-atom joint measurements. It needs neither the unitary operations nor the quantum entanglement swapping. It can resist both the outside attack and the participant attack.

A New Efficient Blind Quantum Signature Scheme Based on Entanglement Swapping

According to the principle of quantum entanglement swapping of GHZ states, this paper put forward a blind signature scheme based on quantum entanglement. Without performing any unitary operation, all participants just need to do Bell measurements on new entangled particles emerging from entanglement swapping of GHZ states to complete blind signature and verification. It is not difficult to prove that the proposed scheme processes the features of nonforgeability, non-disavowal and blindness. Furthermore, compared to some other blind signature schemes on entangled states, our scheme is more efficient because except a few decoy particles, only 2 GHZ states are required for signing each 3 bits in the message.

Quantum Gate-Based Quantum Private Comparison

Many existing protocols of quantum private comparison (QPC) are often made up of quantum part and classical part, because they employ quantum technology to provide security and use classical computation to perform the comparison. This could result in some lurking unfavourable effects such as insufficient security. To improve the QPC security, the paper presents a QPC protocol without the classical part, which uses Bell states as the quantum resource and substitutes the action of quantum gate for the classical computation. It needs no other complex quantum operations including quantum entanglement swapping technology. Except the phase of the eavesdropping check, quantum measurement isn’t required at one party either. The presented protocol is not only simple and efficient but also of better security. The analyses indicate its correctness so it could serve as an alternative way to implement QPC.

A Novel Pure Entangled State Based Two-Party Quantum Private Comparison Protocol

At present, the previous quantum private comparison (QPC) protocols always employ maximally entangled states as quantum resource, which are harder to prepare than pure entangled states. In this paper, by using two-particle pure entangled states as quantum resource, one novel QPC protocol is constructed, which is easy to implement in reality with present quantum technologies. The proposed protocol needs neither unitary operations nor quantum entanglement swapping but single-particle measurements. The proposed protocol is secure against both the outside attack and the participant attack.

A Novel Quantum Broadcasting Multiple Blind Signature Scheme Based on Multi-Particle Partial Entanglement

Recently, a quantum broadcasting multiple blind signature scheme has been proposed by using GHZ entanglement, which is claimed to have foreseeable application in E-bank system. However, its security is promised by the utilized hash function. In this paper, we have designed a novel quantum broadcasting multiple blind signature scheme by utilizing a three-particle partial entanglement state. In existed quantum broadcasting multiple blind signature schemes, the collector Charlie has to verify the individual signatures before aggregating them into a multi-signature. In this new scheme, Charlie is only acting as a signature collector. Specifically, Charlie only needs to collect all the individual signatures and aggregating them into a multi-signature, which indicates that Charlie has no need to verify the individual signature any more. All the verification are executed by the receiver Bob himself. Meanwhile, the signature is generated by quantum entanglement swapping rather than using hash function, which make its security is only based on quantum physics. It is showed that multi-particle partially entangled state can be efficiently used as a resource in quantum information processing with perfect performance.

Toward a quantum repeater protocol based on the coherent state approach

The aim of this paper is to swap the entanglement between two separate long-distant locations. The well-known entangled coherent states as two-mode continuous-variable states are very interesting in quantum teleportation and entanglement swapping processes. To make our investigation more realistic, by using such entangled states as the building blocks of our quantum repeater protocol, the effect of decoherence on the swapped entanglement is also considered. We explicitly establish our model for four locations; moreover, we find that our model can be extended to 2N locations, where . Consequently, we can introduce this model as a quantum repeater, which is helpful for entanglement swapping to long-enough distances.

Connecting two Gaussian cluster states by quantum entanglement swapping.

Cluster state is an important resource for one-way quantum computation and quantum network. In this paper, we present a scheme for connecting two Gaussian cluster states by entanglement swapping, which can be used to connect two local quantum networks composed by cluster states. The connection schemes between different types of four-mode cluster states are analyzed and we show that the structure of the output states after entanglement swapping may be not the same as that of the input states. The entanglement of the obtained new cluster states are presented when suitable feedforward schemes are applied in the entanglement swapping process. By using optimal gains in the classical channel and inseparability criteria, the requirement of squeezing parameters for obtaining entanglement of output states are reduced. The presented scheme provides a concrete reference for constructing quantum networks with cluster states.

Measure-Resend Semi-Quantum Private Comparison Without Entanglement

In this paper, we successfully design the semi-quantum private comparison (SQPC) protocol with the measure-resend characteristic by using two-particle product states as the initial prepared quantum resource which allows two classical users to compare the equality of their private secrets under the help of a quantum third party (TP). The quantum TP is semi-honest in the sense that he is allowed to misbehave on his own but cannot conspire with either of users. Both the output correctness and the security against the outside attack and the participant attack can be guaranteed. Compared with the previous SQPC protocols, the advantage of our protocol lies in that it only employs two-particle product states as the initial prepared quantum resource, only requires TP to perform single-photon measurements and does not need quantum entanglement swapping. Our protocol can be realized with current quantum technologies.

Semi-Quantum Private Comparison Using Single Photons

Recently, by using the BB84 quantum key distribution (QKD) protocol, Sun et al. put forward two quantum private comparison (QPC) protocols with a semi-honest third party (TP) and a malicious TP, respectively (Sun et al., Quantum Inf. Process. 14, 2125–2133, 2015). In this paper, we absorb the concept of semi-quantumness suggested by Boyer et al. (Phys. Rev. Lett. 99(14), 140501, 2007 and Phys. Rev. A 79(3), 032341, 2009) into Sun et al.’s QPC protocols and construct two corresponding SQPC protocols. The common interesting feature of the proposed SQPC protocols is that apart from the establishment of shared keys between different participants, the rest parts of the protocols are completely classical. The output correctness and the security of the proposed SQPC protocols are validated. Compared with the present SQPC protocols, the advantages of the proposed SQPC protocols lies in the following aspects: on the aspect of quantum resource, they employ single photons rather than Bell entangled states; with respect to quantum measurement for TP, they need single-photon measurements rather than Bell state measurements; as for quantum entanglement swapping, they do not need it at all; and the second proposed SQPC protocol takes effect under a malicious TP and makes TP know neither the genuine contents of secret inputs nor the comparison result.

Multiparty Quantum Direct Secret Sharing of Classical Information with Bell States and Bell Measurements

This paper proposed a new and efficient multiparty quantum direct secret sharing (QDSS) by using swapping quantum entanglement of Bell states. In the proposed scheme, the quantum correlation between the possible measurement results of the members (except dealer) and the original local unitary operation encoded by the dealer was presented. All agents only need to perform Bell measurements to share dealer’s secret by recovering dealer’s operation without performing any unitary operation. Our scheme has several advantages. The dealer is not required to retain any photons, and can further share a predetermined key instead of a random key to the agents. It has high capacity as two bits of secret messages can be transmitted by an EPR pair and the intrinsic efficiency approaches 100%, because no classical bit needs to be transmitted except those for detection. Without inserting any checking sets for detecting the eavesdropping, the scheme can resist not only the existing attacks, but also the cheating attack from the dishonest agent.

Quantum interference between autonomous single-photon sources from Doppler-broadened atomic ensembles

To realize a quantum network based on quantum entanglement swapping, bright and completely autonomous sources are essentially required. Here, we experimentally demonstrate Hong-Ou-Mandel (HOM) quantum interference between two independent bright photon pairs generated via the spontaneous four-wave mixing in Doppler-broadened ladder-type 87Rb atoms. Bright autonomous heralded single photons are operated in a continuous-wave (CW) mode with no synchronization or supplemental filters. The four-fold photon coincidence counts per hour correspond to 5000 events for a temporal range of 10 ns, one order higher than those of previously reported for autonomous single photons. We observe an HOM dip with 83% visibility with the two autonomous heralded single photons for an effective measurement time of 900 s. The achievement of the HOM interference between the two bright autonomous photon-pair sources has made an important step towards a practical scalable quantum network.

Quantum Private Comparison Based on χ-Type Entangled States

A two-party quantum private comparison (QPC) protocol is constructed with χ-type entangled states in this paper. The proposed protocol employs a semi-honest third party (TP) that is allowed to misbehave on his own but cannot conspire with the adversary. The proposed protocol need perform Bell basis measurements and single-particle measurements but neither unitary operations nor quantum entanglement swapping technology. The proposed protocol possesses good security toward both the outside attack and the participant attack. TP only knows the comparison result of the private information from two parties in the proposed protocol.

Construction of optimal resources for concatenated quantum protocols

We consider the explicit construction of resource states for measurement-based quantum information processing. We concentrate on special-purpose resource states that are capable to perform a certain operation or task, where we consider unitary Clifford circuits as well as non-trace preserving completely positive maps, more specifically probabilistic operations including Clifford operations and Pauli measurements. We concentrate on $1 \to m$ and $m \to 1$ operations, i.e. operations that map one input qubit to $m$ output qubits or vice versa. Examples of such operations include encoding and decoding in quantum error correction, entanglement purification or entanglement swapping. We provide a general framework to construct optimal resource states for complex tasks that are combinations of these elementary building blocks. All resource states only contain input and output qubits, and are hence of minimal size. We obtain a stabilizer description of the resulting resource states, which we also translate into a circuit pattern to experimentally generate these states. In particular, we derive recurrence relations at the level of stabilizers as key analytical tool to generate explicit (graph-) descriptions of families of resource states. This allows us to explicitly construct resource states for encoding, decoding and syndrome readout for concatenated quantum error correction codes, code switchers, multiple rounds of entanglement purification, quantum repeaters and combinations thereof (such as resource states for entanglement purification of encoded states).

Two-Party Quantum Private Comparison with Five-Qubit Entangled States

In this paper, a two-party quantum private comparison (QPC) protocol is proposed by using five-qubit entangled states as the quantum resource. The proposed protocol needs the help from a semi-honest third party (TP), who is allowed to misbehave on his own but not allowed to conspire with the adversary including the dishonest user. The proposed protocol has the following distinct features: (1) One five-qubit entangled state can be used to achieve the equality comparison of two bits in each round of comparison; (2) Neither unitary operations nor quantum entanglement swapping technology is needed, both of which may consume expensive quantum devices; (3) Only Bell measurements and single-particle measurements are employed, both of which can be realized with current quantum technologies; (4) The security toward both the outside attack and the participant attack can be guaranteed; (5) The private information of two parties is not leaked out to TP.

Quantum Entanglement Swapping between Two Multipartite Entangled States.

Quantum entanglement swapping is one of the most promising ways to realize the quantum connection among local quantum nodes. In this Letter, we present an experimental demonstration of the entanglement swapping between two independent multipartite entangled states, each of which involves a tripartite Greenberger-Horne-Zeilinger (GHZ) entangled state of an optical field. The entanglement swapping is implemented deterministically by means of a joint measurement on two optical modes coming from the two multipartite entangled states respectively and the classical feedforward of the measurement results. After entanglement swapping the two independent multipartite entangled states are merged into a large entangled state in which all unmeasured quantum modes are entangled. The entanglement swapping between a tripartite GHZ state and an Einstein-Podolsky-Rosen entangled state is also demonstrated and the dependence of the resultant entanglement on transmission loss is investigated. The presented experiment provides a feasible technical reference for constructing more complicated quantum networks.

A Quantum Multi-Proxy Weak Blind Signature Scheme Based on Entanglement Swapping

In this paper, we present a multi-proxy weak blind signature scheme based on quantum entanglement swapping of Bell states. In the scheme, proxy signers can finish the signature instead of original singer with his/her authority. It can be applied to the electronic voting system, electronic paying system, etc. The scheme uses the physical characteristics of quantum mechanics to implement delegation, signature and verification. It could guarantee not only the unconditionally security but also the anonymity of the message owner. The security analysis shows the scheme satisfies the security features of multi-proxy weak signature, singers cannot disavowal his/her signature while the signature cannot be forged by others, and the message owner can be traced.

Highly bright photon-pair generation in Doppler-broadened ladder-type atomic system.

We report a bright photon-pair source with a coincidence counting rate per input power (cps/mW) of tens of thousands, obtained via spontaneous four-wave mixing from a Doppler-broadened atomic ensemble of the 5S1/2-5P3/2-5D5/2 transition of 87Rb. The photon-pair generation rate is enhanced by the two-photon coherence contributions from almost all the atomic velocity groups in the Doppler-broadened ladder-type atomic system. We obtained the violation of the Cauchy-Schwarz inequality by a factor of 2370 ± 150. We believe that our scheme for highly bright paired photons is important as a useful quantum light source for quantum entanglement swapping between completely autonomous sources.