Quantum Teleportation Protocol Research Articles

Quantum Teleportation in Thermal Fluctuating Electromagnetic Field

In this paper, we study the quantum teleportation protocol in fluctuating electromagnetic field. The noisy model of quantum teleportation is constructed and the master equation that governs the evolution is solved. We analyze the effect of temperature and noisy parameter on fidelity and quantum coherence, which give us more freedom in controlling the quantum teleportation. We find that the fidelity has some relations with quantum coherence. Fidelity decay rate is dependent on the atom spontaneous emission rate and temperature. When teleporting a non-maximally coherent state, for different ranges of noisy parameter, fidelity has different variations with temperature, and evolves to different values, higher temperature leading to higher fidelity at last; when teleporting a maximally coherent state, fidelity decays to a fixed value with increasing noisy parameter and temperature.

Quantumness of quantum channels

Quantum coherence is a fundamental aspect of quantum physics and plays a central role in quantum information science. This essential property of the quantum states could be fragile under the influence of the quantum operations. The extent to which quantum coherence is diminished depends both on the channel and the incoherent basis. Motivated by this, we propose a measure of nonclassicality of a quantum channel as the average quantum coherence of the state space after the channel acts on, minimized over all orthonormal basis sets of the state space. Utilizing the squared $l_1$-norm of coherence for the qubit channels, the minimization can be treated analytically and the proposed measure takes a closed form of expression. If we allow the channels to act locally on a maximally entangled state, the quantum correlation is diminished making the states more classical. We show that the extent to which quantum correlation is preserved under local action of the channel cannot exceed the quantumness of the underlying channel. We further apply our measure to the quantum teleportation protocol and show that a nonzero quantumness for the underlying channel provides a necessary condition to overcome the best classical protocols.

Quantum teleportation through time-shifted AdS wormholes

Based on the work of Gao-Jafferis-Wall and Maldacena-Stanford-Yang, we observe that the time-shifted thermofield states of two entangled CFTs can be made traversable by an appropriate coupling of the two CFTs, or alternatively by the application of a modified quantum teleportation protocol. This provides evidence for the smoothness of the horizon for a large class of entangled states related to the thermofield by time-translations. The smoothness of these states has some relevance for the firewall paradox and the proposal that some observables in quantum gravity may be state-dependent. We notice that quantum teleportation through these entangled states could be used in a laboratory setup to implement a “time-machine”, which allows the observer to travel far in the future.

Quantum teleportation protocol with an assistant who prepares amplitude modulated unknown qubits

We consider implementation of a quantum teleportation protocol of an unknown qubit with an entangled hybrid state. Coherent components of the entangled hybrid state displace the teleported qubit at the same absolute but opposite in sign values, so that any information about the amount by which the qubit is displaced is lost despite the fact that one of these events has definitely occurred. Alice unambiguously distinguishes her measurement outcomes and Bob obtains at his disposal states of a single photon in superposition of two modes with controllable amplitude distortions. We consider the implementation of this protocol with a third participant who off-line prepares amplitude modulated (AM) unknown qubits and hands them to Alice for teleportation. In particular, highly unbalanced unknown qubits can be teleported with success probability close to 1. We also consider some ways of demodulating AM states by the receiver in order to increase the success probability of the teleportation of unknown qubits.

Bidirectional Teleportation Protocol in Quantum Wireless Multi-hop Network

We propose a bidirectional quantum teleportation protocol based on a composite GHZ-Bell state. In this protocol, the composite GHZ-Bell state channel is transformed into two-Bell state channel through gate operations and single qubit measurements. The channel transformation will lead to different kinds of quantum channel states, so a method is proposed to help determine the unitary matrices effectively under different quantum channels. Furthermore, we discuss the bidirectional teleportation protocol in the quantum wireless multi-hop network. This paper is aimed to provide a bidirectional teleportation protocol and study the bidirectional multi-hop teleportation in the quantum wireless communication network.

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.

Simplified Protocol of Quantum Teleportation

A simplified version of the quantum teleportation protocol is presented in here. Its experimental confirmation will have deep implications for a better understanding of Quantum Entanglement with a particular projection on Quantum Communications.

Quantum Teleportation of Eight-Qubit State via Six-Qubit Cluster State

A novel quantum teleportation protocol for certain class of eight-qubit state is proposed. We utilize a six-qubit cluster state as quantum channel. In our scheme, the sender performs four controlled-NOT operations and a six-qubit von-Neumann projective measurement, the original state with deterministic probability can be reconstructed by the receiver. Higher efficiency can be achieved based on our results.

Bidirectional Quantum Teleportation of a Class of n-Qubit States by Using (2n + 2)-Qubit Entangled States as Quantum Channel

A new protocol of bidirectional quantum teleportation (BQT) is proposed in which the users can transmit a class of n-qubit state to each other simultaneously, by using (2n + 2)-qubit entangled states as quantum channel. The state of the art approaches can only transmit two-qubit states in each round. This scheme is based on control-not operation, single-qubit measurements and appropriate single-qubit unitary operations. It is shown that the protocol is secure in preparation phase.

Probabilistic resumable bidirectional quantum teleportation

In order to effectively use partially entangled pairs, we consider two kinds of generalized bidirectional quantum teleportation (GBQT) protocols in the different cases: (I) Alice and Bob send messages to each other, and (II) Bob replays Alice after he received Alice’s message, where partially entangled pairs are utilized as the quantum channels. However, the states to be teleported will be destroyed if GBQT fails. To solve this problem, we show an improved project, probabilistic resumable bidirectional quantum teleportation (RBQT), where the states to be teleported can be rebuilt exactly by senders when RBQT has not been successfully achieved. Thus, we are able to carry out RBQT many times until it succeeds, although there are no other copies of the initial states. In RBQT, weak entanglement can also be utilized to bidirectionally teleport unknown states successfully.

Optimal Continuous Variable Quantum Teleportation with Limited Resources.

Given a certain amount of entanglement available as a resource, what is the most efficient way to accomplish a quantum task? We address this question in the relevant case of continuous variable quantum teleportation protocols implemented using two-mode Gaussian states with a limited degree of entanglement and energy. We first characterize the class of single-mode phase-insensitive Gaussian channels that can be simulated via a Braunstein-Kimble protocol with nonunit gain and minimum shared entanglement, showing that infinite energy is not necessary apart from the special case of the quantum limited attenuator. We also find that apart from the identity, all phase-insensitive Gaussian channels can be simulated through a two-mode squeezed state with finite energy, albeit with a larger entanglement. We then consider the problem of teleporting single-mode coherent states with Gaussian-distributed displacement in phase space. Performing a geometrical optimization over phase-insensitive Gaussian channels, we determine the maximum average teleportation fidelity achievable with any finite entanglement and for any realistically finite variance of the input distribution.

Port-based teleportation in arbitrary dimension

Port-based teleportation (PBT), introduced in 2008, is a type of quantum teleportation protocol which transmits the state to the receiver without requiring any corrections on the receiver’s side. Evaluating the performance of PBT was computationally intractable and previous attempts succeeded only with small systems. We study PBT protocols and fully characterize their performance for arbitrary dimensions and number of ports. We develop new mathematical tools to study the symmetries of the measurement operators that arise in these protocols and belong to the algebra of partially transposed permutation operators. First, we develop the representation theory of the mentioned algebra which provides an elegant way of understanding the properties of subsystems of a large system with general symmetries. In particular, we introduce the theory of the partially reduced irreducible representations which we use to obtain a simpler representation of the algebra of partially transposed permutation operators and thus explicitly determine the properties of any port-based teleportation scheme for fixed dimension in polynomial time.

Open quantum systems with delayed coherent feedback

We present an elementary derivation and generalisation of a recently reported method of simulating feedback in open quantum systems. We use our generalised method to simulate systems with multiple delays, as well as cascaded systems with delayed backscatter. In addition, we derive a generalisation of the quantum regression formula that applies to systems with delayed feedback, and show how to use the formula to compute two-time correlation functions of the system as well as output field properties. Finally, we show that delayed coherent feedback can be simulated as a quantum teleportation protocol that requires only Markovian resources, pre-shared entanglement, and time travel. The requirement for time travel can be avoided by using a probabilistic protocol.

Protected State Transfer via an Approximate Quantum Adder

We propose a decoherence protected protocol for sending single photon quantum states through depolarizing channels. This protocol is implemented via an approximate quantum adder engineered through spontaneous parametric down converters, and shows higher success probability than distilled quantum teleportation protocols for distances below a threshold depending on the properties of the channel.

Quantum Teleportation of Five-qubit State

We propose a novel quantum teleportation protocol for certain class of five-qubit state with a seven-qubit cluster state as quantum channel. In our scheme, the sender merely needs to perform a seven-qubit von-Neumann projective measurement, the original state with deterministic probability can be reconstructed by the receiver after a series corresponding unitary transformations. Compared with other schemes proposed before, our scheme has the distinct advantages of requiring fewer quantum channels, possessing higher intrinsic efficiency, and transmitting more quantum information bits.

Adiabatic transport of qubits around a black hole

We consider localized qubits evolving around a black hole following a quantum adiabatic dynamics. We develop a geometric structure (based on fibre bundles) permitting to describe the quantum states of a qubit and the spacetime geometry in a single framework. The quantum decoherence induced by the black hole on the qubit is analysed in this framework (the role of the dynamical and geometric phases in this decoherence is treated), especially for the quantum teleportation protocol when one qubit falls to the event horizon. A simple formula to compute the fidelity of the teleportation is derived. The case of a Schwarzschild black hole is analysed.

A noise immunity controlled quantum teleportation protocol

With the advent of the Internet and information and communication technology, quantum teleportation has become an important field in information security and its application areas. This is because quantum teleportation has the ability to attain a timely secret information delivery and offers unconditional security. And as such, the field of quantum teleportation has become a hot research topic in recent years. However, noise has serious effect on the safety of quantum teleportation within the aspects of information fidelity, channel capacity and information transfer. Therefore, the main purpose of this paper is to address these problems of quantum teleportation. Firstly, in order to resist collective noise, we construct a decoherence-free subspace under different noise scenarios to establish a two-dimensional fidelity quantum teleportation models. And also create quantum teleportation of multiple degree of freedom, and these models ensure the accuracy and availability of the exchange of information and in multiple degree of freedom. Secondly, for easy preparation, measurement and implementation, we use super dense coding features to build an entangled quantum secret exchange channel. To improve the channel utilization and capacity, an efficient super dense coding method based on ultra-entanglement exchange is used. Thirdly, continuous variables of the controlled quantum key distribution were designed for quantum teleportation; in addition, we perform Bell-basis measurement under the collective noise and also prepare the storage technology of quantum states to achieve one-bit key by three-photon encoding to improve its security and efficiency. We use these two methods because they conceal information, resist a third party attack and can detect eavesdropping. Our proposed methods, according to the security analysis, are able to solve the problems associated with the quantum teleportation under various noise environments.

Secure quantum communication using classical correlated channel

We propose a secure protocol to send quantum information from one part to another without a quantum channel. In our protocol, which resembles quantum teleportation, a sender (Alice) and a receiver (Bob) share classical correlated states instead of EPR ones, with Alice performing measurements in two different bases and then communicating her results to Bob through a classical channel. Our secure quantum communication protocol requires the same amount of classical bits as the standard quantum teleportation protocol. In our scheme, as in the usual quantum teleportation protocol, once the classical channel is established in a secure way, a spy (Eve) will never be able to recover the information of the unknown quantum state, even if she is aware of Alice's measurement results. Security, advantages, and limitations of our protocol are discussed and compared with the standard quantum teleportation protocol.

Displacement of Propagating Squeezed Microwave States.

Displacement of propagating quantum states of light is a fundamental operation for quantum communication. It enables fundamental studies on macroscopic quantum coherence and plays an important role in quantum teleportation protocols with continuous variables. In our experiments, we have successfully implemented this operation for propagating squeezed microwave states. We demonstrate that, even for strong displacement amplitudes, there is no degradation of the squeezing level in the reconstructed quantum states. Furthermore, we confirm that path entanglement generated by using displaced squeezed states remains constant over a wide range of the displacement power.

High teleportation rates using cold-atom-ensemble-based quantum repeaters with Rydberg blockade

We present a simplified version of a repeater protocol in a cold neutral-atom ensemble with Rydberg excitations optimized for two-node entanglement generation and describe a protocol for quantum teleportation. Our proposal draws from previous proposals [Zhao, {\sl et al.}, Phys. Rev. A {\bf 81}, 052329 (2010)] and [Han, {\sl et al.} Phys. Rev. A {\bf 81}, 052311 (2010)] who described efficient and robust protocols for long-distance entanglement with many nodes. Using realistic experimental values we predict an entanglement generation rate of $\sim$25 Hz and teleportation rate of $\sim$ 5 Hz. Our predicted rates match the current state of the art experiments for entanglement generation and teleportation between quantum memories. With improved efficiencies we predict entanglement generation and teleportation rates of $\sim$7.8 kHz and $\sim$3.6 kHz respectively, representing a two order of magnitude improvement over the currently realized values. Cold-atom ensembles with Rydberg excitations are promising candidates for repeater nodes because collective effects in the ensemble can be used to deterministically generate a long-lived ground state memory which may be efficiently mapped onto a directionally emitted single photon.