scholarly journals Describing and Simulating Concurrent Quantum Systems

2020 ◽  
pp. 271-277
Author(s):  
Richard Bornat ◽  
Jaap Boender ◽  
Florian Kammueller ◽  
Guillaume Poly ◽  
Rajagopal Nagarajan
Keyword(s):  
Programming Language ◽  
Quantum Communication ◽  
Quantum Systems

Abstract We present a programming language for describing and analysing concurrent quantum systems. We have an interpreter for programs in the language, using a symbolic rather than a numeric calculator, and we give its performance on examples from quantum communication and cryptography.

scholarly journals Fundamental limitations on distillation of quantum channel resources

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Bartosz Regula ◽  
Ryuji Takagi
Keyword(s):  
Lower Bounds ◽  
Quantum Channel ◽  
Quantum Communication ◽  
Fault Tolerant ◽  
State Of The Art ◽  
Quantum Systems ◽  
Noisy Channels ◽  
General Transformation ◽  
Fundamental Limitations ◽  
Strong Converse

AbstractQuantum channels underlie the dynamics of quantum systems, but in many practical settings it is the channels themselves that require processing. We establish universal limitations on the processing of both quantum states and channels, expressed in the form of no-go theorems and quantitative bounds for the manipulation of general quantum channel resources under the most general transformation protocols. Focusing on the class of distillation tasks — which can be understood either as the purification of noisy channels into unitary ones, or the extraction of state-based resources from channels — we develop fundamental restrictions on the error incurred in such transformations, and comprehensive lower bounds for the overhead of any distillation protocol. In the asymptotic setting, our results yield broadly applicable bounds for rates of distillation. We demonstrate our results through applications to fault-tolerant quantum computation, where we obtain state-of-the-art lower bounds for the overhead cost of magic state distillation, as well as to quantum communication, where we recover a number of strong converse bounds for quantum channel capacity.

scholarly journals Quantum stochastic dynamics in multi-photon optics

2014 ◽  
Vol 17 (01) ◽  
pp. 1450007
Author(s):  
Ricardo Castro Santis
Keyword(s):  
Quantum Communication ◽  
Stochastic Dynamics ◽  
Continuous Measurement ◽  
Open Quantum Systems ◽  
Measurement Theory ◽  
Quantum Systems ◽  
Generic Model ◽  
Unbounded Coefficients ◽  
Squeezed Light ◽  
Relevant Role

Multi-photon models are theoretically and experimentally important because in them quantum properly phenomena are verified; as well as squeezed light and quantum entanglement also play a relevant role in quantum information and quantum communication (see Refs. 18–20).In this paper we study a generic model of a multi-photon system with an arbitrary number of pumping and subharmonics fields. This model includes measurement on the system, as could be direct or homodyne detection and we demonstrate the existence of dynamics in the context of Continuous Measurement Theory of Open Quantum Systems (see Refs. 1–11) using Quantum Stochastic Differential Equations with unbounded coefficients (see Refs. 10–15).

Heralded Entanglement Between Widely Separated Atoms

Science ◽  
2012 ◽  
Vol 337 (6090) ◽  
pp. 72-75 ◽  
Author(s):  
Julian Hofmann ◽  
Michael Krug ◽  
Norbert Ortegel ◽  
Lea Gérard ◽  
Markus Weber ◽  
...  
Keyword(s):  
Quantum Mechanics ◽  
Quantum Communication ◽  
Information Science ◽  
Essential Feature ◽  
Quantum Systems ◽  
Long Distance ◽  
Quantum Information Science ◽  
Classical Statistics ◽  
Measurement Results ◽  
Generation Of Entanglement

Entanglement is the essential feature of quantum mechanics. Notably, observers of two or more entangled particles will find correlations in their measurement results that cannot be explained by classical statistics. To make it a useful resource, particularly for scalable long-distance quantum communication, the heralded generation of entanglement between distant massive quantum systems is necessary. We report on the creation and analysis of heralded entanglement between spins of two single rubidium-87 atoms trapped independently 20 meters apart. Our results illustrate the viability of an integral resource for quantum information science, as well as for fundamental tests of quantum mechanics.

scholarly journals From Single Atoms to Engineered “Super-Atoms”: Interfacing Photons and Atoms in Free Space

2014 ◽  
Vol 2014 ◽  
pp. 1-28 ◽  
Author(s):  
Yevhen Miroshnychenko
Keyword(s):  
Laser Cooling ◽  
Quantum Communication ◽  
Single Photon ◽  
Experimental Methods ◽  
Quantum Systems ◽  
Single Atom ◽  
Laser Cooling And Trapping ◽  
Single Atoms ◽  
Quantum Properties ◽  
Collective Levels

During the last decades the development of laser cooling and trapping has revolutionized the field of quantum optics. Now we master techniques to control the quantum properties of atoms and light, even at a single atom and single photon level. Understanding and controlling interactions of atoms and light both on the microscopic single particle and on the macroscopic collective levels, are two of the very active directions of the current research in this field. The goal is to engineer quantum systems with tailored properties designed for specific applications. One of the ambitious applications on this way is interfacing quantum information for quantum communication and quantum computing. We summarize here theoretical ideas and experimental methods for interfacing atom-based quantum memories with single flying photons.

scholarly journals Experimental realization of entangled qutrits for quantum communication

2004 ◽  
Vol 4 (2) ◽  
pp. 93-101
Author(s):  
R. Thew ◽  
A. Acin ◽  
H. Zbinden ◽  
N. Gisin
Keyword(s):  
Quantum Communication ◽  
Fiber Optic ◽  
Quantum Systems ◽  
Entangled States ◽  
Fringe Visibility ◽  
Long Distance ◽  
Experimental Realization ◽  
3 Dimensional ◽  
Higher Dimensional ◽  
Maximally Entangled States

We have experimentally realized a technique to generate, control and measure entangled qutrits, 3-dimensional quantum systems. This scheme uses spontaneous parametric down converted photons and unbalanced 3-arm fiber optic interferometers in a scheme analogous to the Franson interferometric arrangement for qubits. The results reveal a source capable of generating maximally entangled states with a net state fidelity, F = 0.985 $\pm$ 0.018. Further the control over the system reveals a high, net, 2-photon interference fringe visibility, V = 0.919 $\pm$ 0.026. This has all been done at telecom wavelengths thus facilitating the advancement towards long distance higher dimensional quantum communication.

scholarly journals Degradation and Protection of Entanglement in Open Quantum Systems †

Proceedings ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 40
Author(s):  
Antonella Pasquale
Keyword(s):  
System Dynamics ◽  
Quantum Computation ◽  
Continuous Time ◽  
Noise Level ◽  
Quantum Communication ◽  
Open Quantum Systems ◽  
Quantum Systems ◽  
Post Processing ◽  
Open Quantum ◽  
Time Description

The distribution of entangled quantum systems among the nodes of a network is a key task at the basis of the development of quantum technologies, e.g., quantum communication, quantum computation, etc. Many efforts have been devoted to identify strategies, based on pre- and post-processing operations or decoherence-free subspaces, to prevent the deterioration of such exotic correlations. However, all these approaches loose their usefulness when the noise level affecting the system surpasses a certain minimal threshold that leads to an entanglement-breaking dynamics. Here we attack this problem in the context of discrete- and continuous-time description of the system dynamics, providing some explicit examples in the context of qubit channels.

scholarly journals Optomechanical interfaces for hybrid quantum networks

2015 ◽  
Vol 2 (4) ◽  
pp. 510-519 ◽  
Author(s):  
Chunhua Dong ◽  
Yingdan Wang ◽  
Hailin Wang
Keyword(s):  
Degrees Of Freedom ◽  
Quantum Communication ◽  
Quantum Information Processing ◽  
Quantum Systems ◽  
Optical Control ◽  
Special Role ◽  
Mechanical Motion ◽  
Optical Fields ◽  
Quantum Networks ◽  
Optical Resonances

Abstract Recent advances on optical control of mechanical motion in an optomechanical resonator have stimulated strong interests in exploring quantum behaviors of otherwise classical, macroscopic mechanical systems and especially in exploiting mechanical degrees of freedom for applications in quantum information processing. In an optomechanical resonator, an optically- active mechanical mode can couple to any of the optical resonances supported by the resonator via radiation pressure. This unique property leads to a remarkable phenomenon: mechanically-mediated conversion of optical fields between vastly different wavelengths. The resulting optomechanical interfaces can play a special role in a hybrid quantum network, enabling quantum communication between disparate quantum systems. In this review, we introduce the basic concepts of optomechanical interactions and discuss recent theoretical and experimental progresses in this field. A particular emphasis is on taking advantage of mechanical degrees of freedom, while avoiding detrimental effects of thermal mechanical motion.

scholarly journals Quantum communication with itinerant surface acoustic wave phonons

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
É. Dumur ◽  
K. J. Satzinger ◽  
G. A. Peairs ◽  
M.-H. Chou ◽  
A. Bienfait ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Surface Acoustic Wave ◽  
Acoustic Waves ◽  
Quantum Communication ◽  
Surface Acoustic Waves ◽  
Bell State ◽  
Quantum Systems ◽  
High Fidelity ◽  
Superconducting Qubit ◽  
Fabry Perot

AbstractSurface acoustic waves are commonly used in classical electronics applications, and their use in quantum systems is beginning to be explored, as evidenced by recent experiments using acoustic Fabry–Pérot resonators. Here we explore their use for quantum communication, where we demonstrate a single-phonon surface acoustic wave transmission line, which links two physically separated qubit nodes. Each node comprises a microwave phonon transducer, an externally controlled superconducting variable coupler, and a superconducting qubit. Using this system, precisely shaped individual itinerant phonons are used to coherently transfer quantum information between the two physically distinct quantum nodes, enabling the high-fidelity node-to-node transfer of quantum states as well as the generation of a two-node Bell state. We further explore the dispersive interactions between an itinerant phonon emitted from one node and interacting with the superconducting qubit in the remote node. The observed interactions between the phonon and the remote qubit promise future quantum-optics-style experiments with itinerant phonons.

scholarly journals Hamiltonians for one-way quantum repeaters

Quantum ◽  
2018 ◽  
Vol 2 ◽  
pp. 75 ◽  
Author(s):  
Filippo M. Miatto ◽  
Michael Epping ◽  
Norbert Lütkenhaus
Keyword(s):  
Quantum Information ◽  
Quantum Communication ◽  
Quantum Systems ◽  
Coupling Loss ◽  
Natural Evolution ◽  
Simple Fact ◽  
Optical Elements ◽  
Quantum Repeaters ◽  
Lossy Channel ◽  
Additional Coupling

Quantum information degrades over distance due to the unavoidable imperfections of the transmission channels, with loss as the leading factor. This simple fact hinders quantum communication, as it relies on propagating quantum systems. A solution to this issue is to introduce quantum repeaters at regular intervals along a lossy channel, to revive the quantum signal. In this work we study unitary one-way quantum repeaters, which do not need to perform measurements and do not require quantum memories, and are therefore considerably simpler than other schemes. We introduce and analyze two methods to construct Hamiltonians that generate a repeater interaction that can beat the fundamental repeaterless key rate bound even in the presence of an additional coupling loss, with signals that contain only a handful of photons. The natural evolution of this work will be to approximate a repeater interaction by combining simple optical elements.

scholarly journals Electrically driven optical interferometry with spins in silicon carbide

2019 ◽  
Vol 5 (11) ◽  
pp. eaay0527 ◽  
Author(s):  
Kevin C. Miao ◽  
Alexandre Bourassa ◽  
Christopher P. Anderson ◽  
Samuel J. Whiteley ◽  
Alexander L. Crook ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Excited State ◽  
Electric Fields ◽  
Quantum Interference ◽  
Degrees Of Freedom ◽  
Quantum Communication ◽  
Optical Transition ◽  
Microwave Frequency ◽  
Quantum Systems ◽  
Simultaneous Control

Interfacing solid-state defect electron spins to other quantum systems is an ongoing challenge. The ground-state spin’s weak coupling to its environment not only bestows excellent coherence properties but also limits desired drive fields. The excited-state orbitals of these electrons, however, can exhibit stronger coupling to phononic and electric fields. Here, we demonstrate electrically driven coherent quantum interference in the optical transition of single, basally oriented divacancies in commercially available 4H silicon carbide. By applying microwave frequency electric fields, we coherently drive the divacancy’s excited-state orbitals and induce Landau-Zener-Stückelberg interference fringes in the resonant optical absorption spectrum. In addition, we find remarkably coherent optical and spin subsystems enabled by the basal divacancy’s symmetry. These properties establish divacancies as strong candidates for quantum communication and hybrid system applications, where simultaneous control over optical and spin degrees of freedom is paramount.

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