Entanglement and swap of quantum states in two qubits

2015 ◽  
Vol 15 (11&12) ◽  
pp. 923-931
Author(s):  
Takaya Ikuto ◽  
Satoshi Ishizaka
Keyword(s):  
Quantum States ◽  
Entangled State ◽  
Classical Communication ◽  
Quantum Bits ◽  
Optimal Probability ◽  
Swap Operator

Suppose that two distant parties Alice and Bob share an entangled state $\rho_{AB}$, and they want to exchange the subsystems of $\rho_{AB}$ by local operations and classical communication (LOCC). In general, this LOCC task (i.e. the LOCC transformation of $\rho_{AB} \to V\rho_{AB} V$ with $V$ being a swap operator) is impossible deterministically, but becomes possible probabilistically. In this paper, we study how the optimal probability is related to the amount of entanglement in the framework of positive partial transposed (PPT) operations, and numerically show a remarkable class of states whose probability is the smallest among every state in two quantum bits.

Symmetric and asymmetric cyclic controlled quantum teleportation via nine-qubit entangled state

2021 ◽  
pp. 2150249
Author(s):  
Vikram Verma
Keyword(s):  
Quantum Channel ◽  
Quantum Teleportation ◽  
Quantum States ◽  
Entangled State ◽  
Controlled Quantum Teleportation ◽  
Intrinsic Efficiency ◽  
Qubit States ◽  
Generalized Scheme

In this paper, by utilizing a nine-qubit entangled state as a quantum channel, we propose new schemes for symmetric and asymmetric cyclic controlled quantum teleportation (CYCQT). In our proposed schemes, four participants Alice, Bob, Charlie and David teleport their unknown quantum states cyclically among themselves with the help of a controller Eve. No participants can reconstruct the original states sent from the respective senders without the permission of the controller. Also, by considering same nine-qubit entangled state as a quantum channel, we propose a generalized scheme for CYCQT of multi-qubit states. In contrast to the previous CYCQT schemes involving three communicators and a controller, there are four communicators and a controller in the proposed schemes. Also, compared with previous CYCQT schemes, our proposed CYCQT schemes require less consumption of quantum resource and the intrinsic efficiency of the generalized scheme increases with the increase of number of qubits in the information states.

scholarly journals Probabilistic Resumable Quantum Teleportation of a Two-Qubit Entangled State

Entropy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 352 ◽  
Author(s):  
Zhan-Yun Wang ◽  
Yi-Tao Gou ◽  
Jin-Xing Hou ◽  
Li-Ke Cao ◽  
Xiao-Hui Wang
Keyword(s):  
Quantum Channel ◽  
Quantum Teleportation ◽  
The State ◽  
Entangled States ◽  
Entangled State ◽  
Quantum Channels ◽  
Unknown State ◽  
Optimal Probability

We explicitly present a generalized quantum teleportation of a two-qubit entangled state protocol, which uses two pairs of partially entangled particles as quantum channel. We verify that the optimal probability of successful teleportation is determined by the smallest superposition coefficient of these partially entangled particles. However, the two-qubit entangled state to be teleported will be destroyed if teleportation fails. To solve this problem, we show a more sophisticated probabilistic resumable quantum teleportation scheme of a two-qubit entangled state, where the state to be teleported can be recovered by the sender when teleportation fails. Thus the information of the unknown state is retained during the process. Accordingly, we can repeat the teleportion process as many times as one has available quantum channels. Therefore, the quantum channels with weak entanglement can also be used to teleport unknown two-qubit entangled states successfully with a high number of repetitions, and for channels with strong entanglement only a small number of repetitions are required to guarantee successful teleportation.

MULTIPARTY REMOTELY PREPARING MULTIPARTITE EQUATORIAL ENTANGLED STATES IN HIGH DIMENSIONS

2011 ◽  
Vol 09 (06) ◽  
pp. 1437-1448
Author(s):  
YI-BAO LI ◽  
KUI HOU ◽  
SHOU-HUA SHI
Keyword(s):  
Quantum State ◽  
Quantum Channel ◽  
Success Probability ◽  
Quantum States ◽  
Remote State Preparation ◽  
Entangled States ◽  
Entangled State ◽  
High Dimensions ◽  
Original State ◽  
State Preparation

We propose two kinds of schemes for multiparty remote state preparation (MRSP) of the multiparticle d-dimensional equatorial quantum states by using partial entangled state as the quantum channel. Unlike more remote state preparation scheme which only one sender knows the original state to be remotely prepared, the quantum state is shared by two-party or multiparty in this scheme. We show that if and only if all the senders agree to collaborate with each other, the receiver can recover the original state with certain probability. It is found that the total success probability of MRSP is only by means of the smaller coefficients of the quantum channel and the dimension d.

scholarly journals Every entangled state provides an advantage in classical communication

2019 ◽  
Vol 60 (7) ◽  
pp. 072201 ◽  
Author(s):  
S. Bäuml ◽  
A. Winter ◽  
D. Yang
Keyword(s):  
Entangled State ◽  
Classical Communication

Generalized three-party sharing of operations on remote single qutrit

2014 ◽  
Vol 12 (03) ◽  
pp. 1450011 ◽  
Author(s):  
Pengfei Xing ◽  
Yimin Liu ◽  
Chuanmei Xie ◽  
Xiansong Liu ◽  
Zhanjun Zhang
Keyword(s):  
Success Probability ◽  
Entangled States ◽  
Entangled State ◽  
Quantum Channels ◽  
Channel State ◽  
Classical Communication ◽  
Maximally Entangled State ◽  
Quantum Operations ◽  
Local Operation ◽  
Maximally Entangled States

Two three-party schemes are put forward for sharing quantum operations on a remote qutrit with local operation and classical communication as well as shared entanglements. The first scheme uses a two-qutrit and three-qutrit non-maximally entangled states as quantum channels, while the second replaces the three-qutrit non-maximally entangled state with a two-qutrit. Both schemes are treated and compared from the four aspects of quantum and classical resource consumption, necessary-operation complexity, success probability and efficiency. It is found that the latter is overall more optimal than the former as far as a restricted set of operations is concerned. In addition, comparisons of both schemes with other four relevant ones are also made to show their two features, including degree generalization and channel-state generalization. Furthermore, some concrete discussions on both schemes are made to expose their important features of security, symmetry and experimental feasibility. Particularly, it is revealed that the success probabilities and intrinsic efficiencies in both schemes are completely determined by the shared entanglement.

scholarly journals Dc SQUID sensitivity for readout of entangled state quantum bits

2001 ◽  
Vol 14 (12) ◽  
pp. 1161-1165 ◽  
Author(s):  
H Tanaka ◽  
Y Sekine ◽  
S Saito ◽  
H Takayanagi
Keyword(s):  
Entangled State ◽  
Quantum Bits

LINEAR OPTICAL PROTOCOL FOR GENERATION OF W STATE WITHIN A NETWORK

2010 ◽  
Vol 08 (07) ◽  
pp. 1199-1206 ◽  
Author(s):  
PEI-MIN LU ◽  
YAN XIA ◽  
JIE SONG ◽  
HE-SHAN SONG
Keyword(s):  
Single Photon ◽  
W State ◽  
Entangled State ◽  
Photon Polarization ◽  
Photon Detectors ◽  
Optical Elements ◽  
Classical Communication ◽  
Linear Optical ◽  
Linear Optical Elements

We demonstrate a linear optical protocol to generate W state in terms of optical elements within a network. The proposed setup involves simple linear optical elements, N-photon polarization entangled state, and conventional photon detectors that only distinguish the vacuum and nonvacuum Fock number states. We show that with local operations, single-photon measurement, and one way classical communication, the protocol can be successfully realized with a certain probability.

scholarly journals Teleportation of entanglement over 143 km

2015 ◽  
Vol 112 (46) ◽  
pp. 14202-14205 ◽  
Author(s):  
Thomas Herbst ◽  
Thomas Scheidl ◽  
Matthias Fink ◽  
Johannes Handsteiner ◽  
Bernhard Wittmann ◽  
...  
Keyword(s):  
Direct Consequence ◽  
Building Blocks ◽  
Entanglement Swapping ◽  
Entangled State ◽  
Quantum Repeater ◽  
Long Distance ◽  
Entanglement Purification ◽  
Classical Communication ◽  
High Loss ◽  
La Palma

As a direct consequence of the no-cloning theorem, the deterministic amplification as in classical communication is impossible for unknown quantum states. This calls for more advanced techniques in a future global quantum network, e.g., for cloud quantum computing. A unique solution is the teleportation of an entangled state, i.e., entanglement swapping, representing the central resource to relay entanglement between distant nodes. Together with entanglement purification and a quantum memory it constitutes a so-called quantum repeater. Since the aforementioned building blocks have been individually demonstrated in laboratory setups only, the applicability of the required technology in real-world scenarios remained to be proven. Here we present a free-space entanglement-swapping experiment between the Canary Islands of La Palma and Tenerife, verifying the presence of quantum entanglement between two previously independent photons separated by 143 km. We obtained an expectation value for the entanglement-witness operator, more than 6 SDs beyond the classical limit. By consecutive generation of the two required photon pairs and space-like separation of the relevant measurement events, we also showed the feasibility of the swapping protocol in a long-distance scenario, where the independence of the nodes is highly demanded. Because our results already allow for efficient implementation of entanglement purification, we anticipate our research to lay the ground for a fully fledged quantum repeater over a realistic high-loss and even turbulent quantum channel.

scholarly journals QUANTUM HIERARCHIC MODELS FOR INFORMATION PROCESSING

2012 ◽  
Vol 10 (02) ◽  
pp. 1250026 ◽  
Author(s):  
MIKHAIL V. ALTAISKY ◽  
NATALIA E. KAPUTKINA
Keyword(s):  
Information Processing ◽  
Wavelet Transform ◽  
Memory Capacity ◽  
The State ◽  
Quantum States ◽  
Nanometer Scale ◽  
Information Compression ◽  
Quantum Bits ◽  
Quantum Register ◽  
Quantum Computations

Both classical and quantum computations operate with the registers of bits. At nanometer scale the quantum fluctuations at the position of a given bit, say, a quantum dot, not only lead to the decoherence of quantum state of this bit, but also affect the quantum states of the neighboring bits, and therefore affect the state of the whole register. That is why the requirement of reliable separate access to each bit poses the limit on miniaturization, i.e. constrains the memory capacity and the speed of computation. In the present paper we suggest an algorithmic way to tackle the problem of constructing reliable and compact registers of quantum bits. We suggest accessing the states of a quantum register hierarchically, descending from the state of the whole register to the states of its parts. Our method is similar to quantum wavelet transform, and can be applied to information compression, quantum memory, quantum computations.

scholarly journals Purification of two-qubit mixed states

2002 ◽  
Vol 2 (5) ◽  
pp. 348-354
Author(s):  
E. Jan\'e
Keyword(s):  
Qubit State ◽  
Entangled State ◽  
Sufficient Condition ◽  
Necessary And Sufficient Condition ◽  
Mixed States ◽  
Classical Communication ◽  
Maximally Entangled State ◽  
Optimal Protocol ◽  
Necessary And Sufficient

We find the necessary and sufficient condition under which two two-qubit mixed states can be purified into a pure maximally entangled state by local operations and classical communication. The optimal protocol for such transformation is obtained. This result leads to a necessary and sufficient condition for the exact purification of $n$ copies of a two-qubit state.

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