scholarly journals Generation and robustness of quantum entanglement in spin graphs

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Jan Riegelmeyer ◽  
Dan Wignall ◽  
Marta P. Estarellas ◽  
Irene D’Amico ◽  
Timothy P. Spiller
Keyword(s):  
Quantum Information Processing ◽  
Bell State ◽  
Spin Chains ◽  
Coupling Scheme ◽  
High Fidelity ◽  
Coupling Ratio ◽  
Entanglement Generation ◽  
Fabrication Errors ◽  
Coupling Strengths ◽  
Hardware Platforms

AbstractEntanglement is a crucial resource for quantum information processing, and so protocols to generate high-fidelity entangled states on various hardware platforms are in demand. While spin chains have been extensively studied to generate entanglement, graph structures also have such potential; however, only a few classes of graphs have been explored for this specific task. In this paper, we apply a particular coupling scheme involving two different coupling strengths to a graph of two interconnected $$3\times 3$$ 3 × 3 square graphs such that it effectively contains three defects. We show how this structure allows generation of a Bell state whose fidelity depends on the chosen coupling ratio. We apply partitioned graph theory in order to reduce the dimension of the graph and show that, using a reduced graph or a reduced chain, we can still simulate the same protocol with identical dynamics. Finally, we investigate how fabrication errors affect the entanglement generation protocol and how the different equivalent structures are affected, finding that for some specific coupling ratios they are extremely robust.

scholarly journals Rapid and robust generation of Einstein-–Podolsky–-Rosen pairs with spin chains

2018 ◽  
Vol 18 (3&4) ◽  
pp. 247-264
Author(s):  
Kieran N. Wilkinson ◽  
Marta P. Estarellas ◽  
Timothy P. Spiller ◽  
Irene D'Amico
Keyword(s):  
Quantum Information Processing ◽  
Bell State ◽  
Spin Chains ◽  
High Fidelity ◽  
Coupling Ratio ◽  
Einstein Podolsky Rosen ◽  
Characteristic Values ◽  
Natural Dynamics ◽  
Diagonal Disorder ◽  
Very High

We investigate the ability of dimerized spin chains with defects to generate EPR pairs to very high fidelity through their natural dynamics. We propose two protocols based on different initializations of the system, which yield the same maximally entangled Bell state after a characteristic time. This entangling time can be varied through engineering the weak/strong couplings' ratio of the chain, with larger values giving rise to an exponentially faster quantum entangling operation. We demonstrate that there is a set of characteristic values of the coupling, for which the entanglement generated remains extremely high. We investigate the robustness of both protocols to diagonal and off-diagonal disorder. Our results demonstrate extremely strong robustness to both perturbation types, up to strength of 50\% of the weak coupling. Robustness to disorder can be further enhanced by increasing the coupling ratio. The combination of these properties makes the use of our proposed device suitable for the rapid and robust generation of Bell states in quantum information processing applications.

scholarly journals Entanglement generation between distant parties via disordered spin chains

2019 ◽  
Vol 18 (2) ◽  
Author(s):  
Guilherme M. A. Almeida ◽  
Francisco A. B. F. de Moura ◽  
Marcelo L. Lyra
Keyword(s):  
Spin Chains ◽  
Entanglement Generation

ENTANGLEMENT DYNAMICS OF TRANSFERRING BELL STATES IN SPIN CHAINS

2010 ◽  
Vol 24 (17) ◽  
pp. 3341-3349 ◽  
Author(s):  
JIE REN ◽  
SHIQUN ZHU
Keyword(s):  
Quantum Wire ◽  
Bell State ◽  
Spin Chains ◽  
Bell States ◽  
Entanglement Dynamics ◽  
State Formula ◽  
Better Than

A teleportation scheme between two arbitrary locations is introduced. The locations only need to establish a quantum wire to a super-location. The super-location can create and transfer Bell states by two unmodulated and coupled spin chains or by two engineered spin chains. The entanglement of transferring the Bell state of [Formula: see text] is better than that of transferring state [Formula: see text].

Towards quantum networks of single spins: analysis of a quantum memory with an optical interface in diamond

2015 ◽  
Vol 184 ◽  
pp. 173-182 ◽  
Author(s):  
M. S. Blok ◽  
N. Kalb ◽  
A. Reiserer ◽  
T. H. Taminiau ◽  
R. Hanson
Keyword(s):  
Quantum Information Processing ◽  
Quantum States ◽  
Nitrogen Vacancy ◽  
Nuclear Spins ◽  
Quantum Repeater ◽  
Quantum Networks ◽  
Entanglement Generation ◽  
Quantum Bit ◽  
Single Defect ◽  
Coupling Parameters

Single defect centers in diamond have emerged as a powerful platform for quantum optics experiments and quantum information processing tasks. Connecting spatially separated nodes via optical photons into a quantum network will enable distributed quantum computing and long-range quantum communication. Initial experiments on trapped atoms and ions as well as defects in diamond have demonstrated entanglement between two nodes over several meters. To realize multi-node networks, additional quantum bit systems that store quantum states while new entanglement links are established are highly desirable. Such memories allow for entanglement distillation, purification and quantum repeater protocols that extend the size, speed and distance of the network. However, to be effective, the memory must be robust against the entanglement generation protocol, which typically must be repeated many times. Here we evaluate the prospects of using carbon nuclear spins in diamond as quantum memories that are compatible with quantum networks based on single nitrogen vacancy (NV) defects in diamond. We present a theoretical framework to describe the dephasing of the nuclear spins under repeated generation of NV spin-photon entanglement and show that quantum states can be stored during hundreds of repetitions using typical experimental coupling parameters. This result demonstrates that nuclear spins with weak hyperfine couplings are promising quantum memories for quantum networks.

Quantum-entanglement storage and extraction in quantum network node

2018 ◽  
Vol 16 (01) ◽  
pp. 1850009 ◽  
Author(s):  
ZhuoYu Shan ◽  
Yong Zhang
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Entanglement ◽  
Information Technologies ◽  
Quantum Information Processing ◽  
Bell State ◽  
Nitrogen Vacancy ◽  
Quantum Network ◽  
Nuclear Spins ◽  
Nv Centers

Quantum computing and quantum communication have become the most popular research topic. Nitrogen-vacancy (NV) centers in diamond have been shown the great advantage of implementing quantum information processing. The generation of entanglement between NV centers represents a fundamental prerequisite for all quantum information technologies. In this paper, we propose a scheme to realize the high-fidelity storage and extraction of quantum entanglement information based on the NV centers at room temperature. We store the entangled information of a pair of entangled photons in the Bell state into the nuclear spins of two NV centers, which can make these two NV centers entangled. And then we illuminate how to extract the entangled information from NV centers to prepare on-demand entangled states for optical quantum information processing. The strategy of engineering entanglement demonstrated here maybe pave the way towards a NV center-based quantum network.

scholarly journals Parallel single-shot measurement and coherent control of solid-state spins below the diffraction limit

Science ◽  
2020 ◽  
Vol 370 (6516) ◽  
pp. 592-595
Author(s):  
Songtao Chen ◽  
Mouktik Raha ◽  
Christopher M. Phenicie ◽  
Salim Ourari ◽  
Jeff D. Thompson
Keyword(s):  
Solid State ◽  
Coherent Control ◽  
Quantum Information Processing ◽  
High Fidelity ◽  
Single Shot ◽  
Frequency Domain Multiplexing ◽  
Spin Interactions ◽  
Quantum Science ◽  
Logic Operations ◽  
State Spin

Solid-state spin defects are a promising platform for quantum science and technology. The realization of larger-scale quantum systems with solid-state defects will require high-fidelity control over multiple defects with nanoscale separations, with strong spin-spin interactions for multi-qubit logic operations and the creation of entangled states. We demonstrate an optical frequency-domain multiplexing technique, allowing high-fidelity initialization and single-shot spin measurement of six rare-earth (Er3+) ions, within the subwavelength volume of a single, silicon photonic crystal cavity. We also demonstrate subwavelength control over coherent spin rotations by using an optical AC Stark shift. Our approach may be scaled to large numbers of ions with arbitrarily small separation and is a step toward realizing strongly interacting atomic defect ensembles with applications to quantum information processing and fundamental studies of many-body dynamics.

Practical one-step synthesis of multipartite entangled states on superconducting circuits

2019 ◽  
Vol 17 (07) ◽  
pp. 1950051
Author(s):  
Rui Tao ◽  
Xiao-Tao Mo ◽  
Zheng-Yuan Xue ◽  
Jian Zhou
Keyword(s):  
Quantum Information Processing ◽  
Single Step ◽  
Entangled States ◽  
Entangled State ◽  
Many Body ◽  
Entanglement Generation ◽  
Superconducting Circuits ◽  
Transmission Line Resonator ◽  
One Step ◽  
Microwave Control

Quantum entanglement is an important resource for quantum information processing tasks. However, realistic multipartite entangled state production is very difficult. In this paper, we propose an efficient single-step scheme for generating many body Greenberger–Horne–Zeilinger (GHZ) states on superconducting circuits by using a superconducting transmission-line resonator (TLR) interact with [Formula: see text] superconducting transmon qubits. The distinct merit of our proposal is that it does not require the qubit-resonator coupling strengths to be the same, which is usually impractical experimentally, and thus is one of the main reasons for entanglement generation infidelity in previous single-step schemes. The removing of the uniform interaction requirement is achieved by modulating the qubits splitting frequencies with ac microwave fields, which results in tunable individual qubit-resonator coupling strength, and thus effective uniform qubit–qubit interaction Hamiltonian can be obtained. Since microwave control is conventional nowadays, our proposal can be directly tested experimentally, which makes previous multipartite entangled states generation schemes more efficient.

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