Arbitrary Two-qubit Entangled State Research Articles

Role of Steering Inequality in Quantum Key Distribution Protocol

Violation of Bell's inequality has been the mainspring for secure key generation in an entanglement assisted Quantum Key Distribution (QKD) protocol. Various contributions have relied on the violation of Bell inequalities to build an appropriate QKD protocol. Residing between Bell nonlocality and entanglement, there exists a hybrid trait of correlations, namely correlations exhibited through the violation of steering inequalities. However, such correlations have not been put to use in QKD protocols as much as their stronger counterpart, the Bell violations. In the present work, we show that the violations of the Cavalcanti–Jones–Wiseman–Reid (CJWR) steering inequalities can act as key ingredients in an entanglement assisted QKD protocol. We work with arbitrary two-qubit entangled states, and characterize them by their utility in such protocols. The characterization is based on the quantum bit error rate and violation of the CJWR inequality. Furthermore, we show that subsequent applications of local filtering operations on initially entangled states exhibiting no violation, lead to violations necessary for the successful implementation of the protocol. An additional vindication of our protocol is provided by the use of absolutely Bell–Clauser–Horne–Shimony–Holt (Bell–CHSH) local states, states which remain Bell–CHSH local even under global unitary operations.Quanta 2023; 12: 1–21.

A secure deterministic remote state preparation via a seven-qubit entangled channel of a two-qubit entangled state under the impact of quantum noise

In this study, a deterministic remote state preparation protocol is presented for the preparation of arbitrary two-qubit entangled states through a seven-qubit entangled channel prepared from the state proposed by Borras et al. (2007). The implementation of any protocol for quantum communication is inherently susceptible to quantum noise, presenting a challenge to the reliability and security of quantum communication systems. The introduction of noise results in a transition from a pure to a mixed quantum state. This paper examines six distinct noise models, including bit-flip noise, phase-flip noise, bit-phase-flip noise, amplitude damping, phase damping, and depolarizing noise, and analyzes their impact on the entangled channel. The alterations to the density matrices resulting from the introduction of noise are evaluated. The fidelity between the original and remotely prepared quantum states is also analyzed and visually represented. Additionally, a thorough security analysis is conducted to demonstrate the robustness of the protocol against both internal and external attacks.

Probabilistic resumable quantum teleportation for an arbitrary two-qubit entangled state with different quantum channels

We propose two probabilistic resumable quantum teleportation schemes for an arbitrary two-qubit entangled state with different quantum channels. The characteristic of our schemes is that the initial state in the sender’s hand can be recovered instead of being destroyed when teleportation fails, so we can improve the success probabilities by repeating the teleportation process more times. The analysis results show that the number of repetitions required for successful teleportation depends on the entanglement strength of the quantum channels, and even weak entanglement enables a high probability of success.

Asymmetric cyclic controlled quantum teleportation by using a quantum channel composed of six G states

In the existing research on cyclic teleportation protocols, it is generally discussed that the teleportation of single particle, two particle unknown quantum states with symmetrical structure or asymmetric special unknown quantum states (such as GHZ state) with three or four participants. In contrast, the scheme proposed in this paper has universality and stronger practicability. In this paper, we propose a novel scheme of asymmetric cyclic controlled teleportation. In our scheme, Alice can teleport an arbitrary single-qubit entangled state to Charlie, Charlie can teleport an arbitrary three-qubit entangled state to Bob and at the same time Bob can teleport an arbitrary two-qubit entangled state to Alice under the control of a controller David. It only needs Bell measurement and local unitary operation, and can realize three-party cyclic transmission with probability 1 by using a quantum channel composed of any six of the 16 G states.

Asymmetric bidirectional quantum state exchange between Alice and Bob through a third party

In this paper we present a quantum communication protocol which utilizes a multipartite multi-qubit entangled channel for mutual transfer of three-qubit generalized W-state and arbitrary two-qubit entangled state between two parties. The protocol is perfect with no cases of failure and is supervised by a third party. The work is in the direction of the recently initiated line of research on exploring the possibility of simultaneous quantum multitasking using multipartite entanglement.

Enhancing remote state preparation via five-qubit cluster state in noisy environments

This study proposes a remote state preparation scheme using a five-qubit cluster state as the quantum channel. In this scheme, Alice can prepare an arbitrary two-qubit entangled state on Bob’s side using only some local operations and classical communications. The scheme is first described in an ideal environment, and the corresponding quantum circuit is given. An investigation of the scheme in the amplitude-damping noise and collective-dephasing noise, and an analysis of their influence on the scheme are carried out by calculating the fidelity of the output state. Moreover, the study takes full advantage of the weak measurement and reversing measurement to enhance the fidelity in the amplitude-damping noise, and constructing a decoherence-free subspace to suppress the collective-dephasing noise. The findings indicate that the schemes can provide higher fidelity in the amplitude-damping noise and collective-dephasing noise.

A reinforcement learning approach for quantum state engineering

Machine learning (ML) has become an attractive tool for solving various problems in different fields of physics, including the quantum domain. Here, we show how classical reinforcement learning (RL) could be used as a tool for quantum state engineering (QSE). We employ a measurement based control for QSE where the action sequences are determined by the choice of the measurement basis and the reward through the fidelity of obtaining the target state. Our analysis clearly displays a learning feature in QSE, for example in preparing arbitrary two-qubit entangled states and delivers successful action sequences that generalise previously found human solutions from exact quantum dynamics. We provide a systematic algorithmic approach for using RL for quantum protocols that deal with a non-trivial continuous state space, and discuss the scaling of these approaches for the preparation of larger entangled (cluster) states.

On the Controlled Cyclic Quantum Teleportation of an Arbitrary Two-Qubit Entangled State by Using a Ten-Qubit Entangled State

Recently, Li et al. (Int J Theor Phys: 58:1541–1545, 2019) proposed a controlled cyclic quantum teleportation method of the arbitrary two-qubit entangled states. They claimed that their method can help each of three involved participants to teleport an arbitrary two-qubit entangled state to the next participant, and at the same time, none of the involved participants can obtain the teleported state without the controller’s permission. However, this study shows that two involved participants can reconstruct the teleported states without the controller’s permission. To solve this problem, a modification is proposed here.

Controlled Cyclic Quantum Teleportation of an Arbitrary Two-Qubit Entangled State by Using a Ten-Qubit Entangled State

We propose a scheme of controlled cyclic quantum teleportation of an arbitrary two-qubit entangled state by using a ten-qubit entangled state. In our scheme, Alice can teleport an arbitrary two-qubit entangled state to Bob, Bob can teleport an arbitrary two-qubit entangled state to Charlie and at the same time Charlie can teleport an arbitrary two-qubit entangled state to Alice with the help of the controller David.

Scheme for Asymmetric and Deterministic Controlled Bidirectional Joint Remote State Preparation**Supported by the National Natural Science Foundation of China under Grant No. 11604115

The scheme for asymmetric and deterministic controlled bidirectional joint remote state preparation by using one ten-qubit entangled state as the quantum channel is proposed. In this scheme, Alice and David want to remotely prepare an arbitrary single-qubit state at Bob’s site, at the same time, Bob and Eve wish to help Alice remotely prepare an arbitrary two-qubit entangled state. Alice and Bob can simultaneously prepare the desired states with the cooperation of David and Eve under the control of Charlie.

Symmetric bidirectional quantum teleportation via five-qubit cluster state

We propose a protocol of symmetric bidirectional quantum teleportation via five-qubit cluster state. Based on the Bell-state measurements, introduces an auxiliary particle and perform joint unitary transformation, Alice wants to transmit an arbitrary two-qubit entangled state to Bob and Bob wants to transmit an arbitrary two-qubit state to Alice.

Asymmetric Controlled Bidirectional Remote State Preparation by Using a Ten-qubit Entangled State

We present a novel scheme for asymmetric controlled bidirectional remote state preparation (ACBRSP) with complex coefficients via a ten-qubit entangled state as the quantum channel. In this scheme, two distant parties, Alice and Bob are not only senders but also receivers, and Alice wants to remotely prepare a single-qubit state at Bob’s site, at the same time, Bob wishes to help Alice remotely prepares an arbitrary two-qubit entangled state. It is shown that, only if the two senders and the controller collaborate with each other, the ACBRSP can be completed successfully. We demonstrate that the total success probability of the ACBRSP in this scheme can reach 1, that is, the scheme is deterministic.

Asymmetric Bidirectional Controlled Teleportation by Using Six-qubit Cluster State

We propose a scheme for asymmetric bidirectional controlled teleportation by using a six-qubit cluster state as quantum channel. In our scheme, Alice can transmit an arbitrary two-qubit entangled state to Bob and at the same time Bob can teleport an arbitrary single-qubit state to Alice under the control of the supervisor Charlie.

Bidirectional Quantum Teleportation by Using Five-qubit Cluster State

We propose a scheme for bidirectional quantum teleportation by using a five-qubit cluster state. In our scheme, Alice can transmit an arbitrary two-qubit entangled state to Bob and at the same time Bob can teleport an arbitrary single-qubit state to Alice.

Schemes for Splitting Quantum Information via Tripartite Entangled States

In this paper we propose two schemes for quantum information splitting via tripartite entangled states. Explicit protocols for the quantum information splitting of a single qubit state and an arbitrary two-qubit entangled state are illustrated. We also consider the security against certain eavesdropping attacks. Moreover, a generalization of the scheme to multi-particle case is also outlined.

Entanglement and the Berry phase in a new Yang–Baxter system

We present a new S-matrix, a solution of the braid relation and obtain a unitary solution of the Yang–Baxter equation (YBE) via Yang-Baxterization acting on the solution. We show that arbitrary two-qubit entangled states can be achieved by relating the unitary matrix to entanglement. An oscillator Hamiltonian can be constructed from the matrix. The Berry phase of the Yang–Baxter system is investigated.

Novel Schemes for Directly Measuring Entanglement of General States

An intrinsic relation between maximally entangled states and entanglement measures is revealed, which plays a role in establishing connections for different entanglement quantifiers. We exploit the basic idea and propose a framework to construct schemes for directly measuring entanglement of general states. In particular, we demonstrate that rank-1 local factorizable projective measurements, which are achievable with only one copy of an entangled state involved at a time in a sequential way, are sufficient to directly determine the concurrence of an arbitrary two-qubit entangled state.

Generation of arbitrary two-qubit entangled states in cavity QED

We present a scheme for the generation of arbitrary two-qubit entangled states between two cavity fields via interaction of an atom resonantly interacting with classical and quantized cavity fields. The controlling parameters are the interaction times with these fields.