Three-particle Entanglement Research Articles

Partial orbits of quantum gates and full three-particle entanglement

Partial orbits of quantum gates and full three-particle entanglement

A One-Round Quantum Mutual Authenticated Key Agreement Protocol with Semi-Honest Server Using Three-Particle Entangled States

In this paper, we propose a mutual authenticated quantum key agreement scheme based on three-particle entangled states, which can achieve both completely secure and more efficient. In our scheme, the pre-shared keys are classical bit strings between the semi-honest server (SHS) and the client (Alice or Bob), so they are kept and use to authenticate each other easily. More important, by the SHS’s helping with three-particle entangled states, SHS and Alice/Bob can authenticate each other, and at the same time anyone else cannot get the session key between Alice and Bob even for SHS. The proposed scheme has the properties of completeness, information theoretic security, non-repudiation and unforgeability. Its information-theoretic security is ensured by quantum indistinguishability mechanics. Compared with the related works, our proposed scheme can increase efficiency factors η1 and η2 to 50% and 80% respectively in one communication round.

An Authenticated Quantum Dialog Protocol with Three-Particle Entangled States Using Subset of Intersection Method

In this paper, we propose a mutual authenticated quantum key agreement scheme based on three-particle entangled states, which can achieve both completely secure and more efficient. In our scheme, the shared keys are classical bit strings between the trusted third party Charlie and the client (Alice or Bob), so they are kept and use to authenticate each other easily. More important, by the Charlie’s helping with three-particle entangled states using subset of intersection method, Charlie and Alice/Bob can authenticate each other, and at the same time anyone else cannot get the session key between Alice and Bob even Charlie. The proposed scheme has the properties of completeness, information theoretic security, non-repudiation and unforgeability. Its information-theoretic security is ensured by quantum indistinguishability mechanics. On the other hand, our scheme is more efficient than the similar schemes.

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.

Quantum broadcasting multiple blind signature protocol based on three-particle partial entanglement

<sec>Recently, a quantum broadcasting multiple blind signature scheme based on GHZ state has been proposed, which could be used to settle the problem that a message is so important that it needs to be signed by multiple signatories, in order to guarantee the message privacy: none of signatories can acquire the content of the message they have signed. Maybe it can be applied to an E-bank system. For example, a large amount of money has to be transferred through E-bank system on the internet. The E-bank system operator submits the request to the bank after filling the application form including payment amount, bank transfer account and some other information. When the request arrives, the bank clerk signs to approve. However, it is not enough, it has to ask the manager for authority, and then it needs to be signed by the manager. In the whole process, all the signatories cannot learn what they have signed, but the application form has been recorded in the E-bank system. So, once disagreement takes place, the bank can track the message sender. </sec><sec>In this paper, we present a new quantum broadcasting multiple blind signature scheme which is based on a three-particle partial entanglement state. Comparing with the original scheme, the partial entanglement state is utilized in our new scheme in place of the GHZ state, and this does not bring down the security of the scheme. Particularly, using the partial entanglement state can not only save the entanglement resource to some extent, but also make the scheme much easier to be realized. As is well known, It is not easy to keep the maximum entanglement state shared among the participants in the whole quantum communication process. By using the partial entanglement in place of the maximum entanglement can improve the new scheme applicability to make it more practical. It is also indicated that multi-qubit entangled systems which are partially entangled can be efficiently used as a resource in quantum information processing with perfect performance.</sec>

Scaling of genuine multiparticle entanglement close to a quantum phase transition

We investigate the scaling and spatial distribution of genuine multiparticle entanglement in three- and four-spin reduced states of the one-dimensional $XY$ model at the quantum phase transition. We observe a logarithmic divergence, show that genuine three- and four-particle entanglement obeys finite-size scaling of the $XY$ model and demonstrate that the genuine three-particle entanglement has a finite spatial range.

Three-particle entanglement swapping in an imperfect channel

Extending our previous work [J. Korean Phys. Soc. 58, 1708 (2011)], we analyze the noise effects of an imperfect channel on three-particle entanglement swapping by calculating the fidelity F of a three-qubit state after a GHZ measurement. In contrast to other kinds of noise, the bit flip noise and the phase flip noise do not cause the fidelity to decay exponentially to 0.25 but to 0.5, which shows the presence of genuine entanglement.

Tripartite interactions between two phase qubits and a resonant cavity

Micrometre-scale superconducting circuits are at present explored as the building blocks for scalable quantum information processors. In a system where two such qubits are coupled to a resonant cavity, tripartite interactions and controlled coherent dynamics have now been demonstrated. This platform should allow for a fuller exploration of multipartite quantum states and their deterministic preparation. Multipartite entanglement is essential for quantum computation1 and communication2,3,4, and for fundamental tests of quantum mechanics5 and precision measurements6. It has been achieved with various forms of quantum bits (qubits), such as trapped ions7,8, photons9 and atoms passing through microwave cavities10. Quantum systems based on superconducting circuits, which are potentially more scalable, have been used to control pair-wise interactions of qubits11,12,13,14,15,16 and spectroscopic evidence for three-particle entanglement was observed17,18. Here, we report the demonstration of coherent interactions in the time domain for three directly coupled superconducting quantum systems, two phase qubits and one resonant cavity. We provide evidence for the deterministic evolution from a simple product state, through a tripartite W state, into a (bipartite) Bell state. The cavity can be thought of as a multiphoton register or an entanglement bus, and arbitrary preparation of multiphoton states in this cavity using one of the qubits19 and subsequent interactions for entanglement distribution should allow for the deterministic creation of another class of entanglement, a Greenberger–Horne–Zeilinger state.

Teleportation of an unknown two-particle entangled state via an asymmetric three-particle entanglement state

In this article, a protocol for the teleportation of an unknown two-particle entanglement is proposed. The feature of the present protocol is that we utilize an asymmetric three-particle entangled state as the quantum channel. The optimal discrimination between two nonorthogonal quantum states is adopted. It is shown that an unknown two-particle entangled state can be probabilistically teleported from the sender to the remote receiver on condition that the co-sender successfully collaborates. The fidelity in this protocol is one. In addition, the probability of the successful teleportation is calculated and all kinds of transformations performed by the sender and the receiver are provided in detail.

Discussion on building the net of quantum teleportation using three-particle entangled states

We may make three-particle entanglement using the source of three-particle W states. Put this particle entanglement down as quantum channel, and transfer information of Bell states measurement and von Neumann measurement using classical channel, the quantum teleportation net may then be realized. Based on this idea, we investigate the physical principle for building the quantum teleportation net using three-particle W states, find out the unitary transformation matrix for quantum teleportation of three-particle W states, and design a quantum teleportation net. We propose a scheme for quantum communications net and its protocol. If all stations work as schemed, quantum communications between any two stations may be realized.

Entanglement Criterion of N-Qubit State

In this paper, we shall develop a generic scheme to construct thecriterion that an N-qubit state has true N-particle entanglement.For the N = 3 case, we show that violation of the Mermin'sinequality |ELHV(σ̂x⊗σ̂y⊗σ̂y+σ̂y⊗σ̂x⊗σ̂y+σ̂y⊗σ̂y⊗σ̂x−σ̂x⊗σ̂x⊗σ̂x)|⩽2, is sufficient to confirm three-particle entanglement.

Fault-tolerant quantum computing with coded spins using the conditional Faraday rotation in quantum dots

We propose a scalable fault-tolerant scheme for deterministic quantum computing with spins that is based on a three-particle entanglement produced by the conditional Faraday rotation of the polarization of single photons due to the nonresonant interaction with spins of quantum dots, embedded in microcavities inside a photonic crystal. The resulting conditional phase gate yields switching times of $50\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$. We show that it acts fault-tolerantly not only on the Calderbank-Shor-Steane quantum error correction codes, but also on Shor's code in a single shot. Single-qubit operations on Shor's logical qubits can be implemented by means of the optical Stark effect combined with the optical Ruderman-Kittel-Kasuya-Yosida interaction in a single shot.

W STATE GENERATION AND EFFECT OF CAVITY PHOTONS ON THE PURIFICATION OF DOT-LIKE SINGLE QUANTUM WELL EXCITONS

A scheme of three-particle entanglement purification is presented in this work. The physical system undertaken for investigation is dot-like single quantum well excitons independently coupled through a single microcavity mode. The theoretical framework for the proposed scheme is based on the quantum jump approach for analyzing the progress of the trible-exciton entanglement as a series of conditional measurement has been taken on the cavity field state. We first investigate how cavity photon affects the purity of the double-exciton state and the purification efficiency in two-particle protocol. Then we extend the two-particle case and conclude that the three-exciton state can be purified into W state, which involves the one-photon-trapping phenomenon, with a high yield. Finally, an achievable setup for purification using only modest and presently feasible technologies is also proposed.

Addendum to “Sufficient conditions for three-particle entanglement and their tests in recent experiments”

A recent paper [] presented a bound for the three-qubit Mermin inequality such that the violation of this bound indicates genuine three-qubit entanglement. We show that this bound can be improved for a specific choice of observables. In particular, if spin observables corresponding to orthogonal directions are measured at the qubits (e.g., $X$ and $Y$ spin coordinates), then the bound is the same as the bound for states with a local hidden variable model. As a consequence, it can straightforwardly be shown that in the experiment described by ], genuine three-qubit entanglement was detected.

Spectroscopy of Three-Particle Entanglement in a Macroscopic Superconducting Circuit

We study the quantum mechanical behavior of a macroscopic, three-body, superconducting circuit. Microwave spectroscopy on our system, a resonator coupling two large Josephson junctions, produced complex energy spectra well explained by quantum theory over a large frequency range. By tuning each junction separately into resonance with the resonator, we first observe strong coupling between each junction and the resonator. Bringing both junctions together into resonance with the resonator, we find spectroscopic evidence for entanglement between all 3 degrees of freedom and suggest a new method for controllable coupling of distant qubits, a key step toward quantum computation.

Patient–practitioner–remedy (PPR) entanglement. Part 5. Can homeopathic remedy reactions be outcomes of PPR entanglement?

The possibility that well-documented types of reaction to the prescribed homeopathic medicine may be outcomes of PPR entanglement is discussed within the context of a previously described model for homeopathy that incorporates GHZ three-particle entanglement and Weak Quantum Theory.

Patient–practitioner–remedy (PPR) entanglement Part 4.: Towards classification and unification of the different entanglement models for homeopathy

The possibility of classifying and unifying some of the recent entanglement models for homeopathy is discussed. Unification involves combining the previous GHZ/WQT-based entanglement model, itself a fusion of Greenberger–Horne–Zeilinger (GHZ) three-particle entanglement and a generalised version of quantum theory, called Weak Quantum Theory (WQT), with Walach's semiotic model involving double entanglement. The new combined model invokes a ‘geometry’ of patient–practitioner–remedy (PPR) entanglement embedded in a therapeutic state space.

Patient–practitioner–remedy (PPR) entanglement. Part 3. Refining the quantum metaphor for homeopathy

The notion of patient–practitioner–remedy (PPR) entanglement, previously proposed for homeopathy, is refined by adapting concepts derived from Greenberger, Horne, and Zeilinger's treatment of three-particle entanglement (GHZ states), and a generalised version of quantum theory, called weak quantum theory (WQT). These suggest that for maximum PPR entanglement during the therapeutic encounter, the practitioner's awareness needs to be directed inward as well as outward toward the patient, and that health and disease are mirror images of each other, similar to and represented by, the relationship of complex numbers to their complex conjugates.

Three-particle entanglement versus three-particle nonlocality

The notions of three-particle entanglement and three-particle nonlocality are discussed in the light of Svetlichny's inequality [Phys. Rev. D 35, 3066 (1987)]. It is shown that there exist sets of measurements which can be used to prove three-particle entanglement, but which are nevertheless useless at proving three-particle nonlocality. In particular, it is shown that the quantum predictions giving a maximal violation of Mermin's three-particle Bell inequality [Phys. Rev. Lett. 65, 1838 (1990)] can be reproduced by a hybrid hidden variables model in which nonlocal correlations are present only between two of the particles. It should be possible, however, to test the existence of both three-particle entanglement and three-particle nonlocality for any given quantum state via Svetlichny's inequality.

Sufficient conditions for three-particle entanglement and their tests in recent experiments

We point out a loophole problem in some recent experimental claims to produce three-particle entanglement. The problem consists in the question whether mixtures of two-particle entangled states might suffice to explain the experimental data. In an attempt to close this loophole, we review two sufficient conditions that distinguish between N-particle states in which all N particles are entangled to each other and states in which only M particles are entangled (with M<N). It is shown that three recent experiments to obtain three-particle entangled states (Bouwmeester et al., Pan et al., and Rauschenbeutel et al.) do not meet these conditions. We conclude that the question whether these experiments provide confirmation of three-particle entanglement remains unresolved. We also propose modifications of the experiments that would make such confirmation feasible.