scholarly journals Decoherence-free subspaces and spontaneous emission cancellation

2007 ◽  
Vol 85 (6) ◽  
pp. 641-645 ◽  
Author(s):  
K -P Marzlin ◽  
R Karasik ◽  
B C Sanders ◽  
K B Whaley
Keyword(s):  
Quantum Information ◽  
Quantum Optics ◽  
Spontaneous Emission ◽  
Destructive Interference ◽  
Target State ◽  
Initial States ◽  
Transition Amplitudes ◽  
Common Target ◽  
Decoherence Free Subspaces

We establish the connection between decoherence-free subspaces of quantum information and spontaneous emission cancellation in quantum optics with molecules. Both phenomena rely on the destructive interference of transition amplitudes from two initial states to a common target state. We discuss physical similarities, differences, and limitations of both phenomena. PACS Nos.: 03.65.Yz, 42.50.–p, 03.67.Pp

Quantum optics with nitrogen-vacancy centres in diamond

2017 ◽  
Author(s):  
Yiwen Chu ◽  
Mikhail D. Lukin
Keyword(s):  
Optical Properties ◽  
Quantum Information ◽  
Solid State ◽  
Quantum Optics ◽  
Quantum States ◽  
Nitrogen Vacancy ◽  
Common Theme ◽  
External Effects ◽  
Promising Candidate ◽  
Optical Photons

A common theme in the implementation of quantum technologies involves addressing the seemingly contradictory needs for controllability and isolation from external effects. Undesirable effects of the environment must be minimized, while at the same time techniques and tools must be developed that enable interaction with the system in a controllable and well-defined manner. This chapter addresses several aspects of this theme with regard to a particularly promising candidate for developing applications in both metrology and quantum information, namely the nitrogen-vacancy (NV) centre in diamond. The chapter describes how the quantum states of NV centres can be manipulated, probed, and efficiently coupled with optical photons. It also discusses ways of tackling the challenges of controlling the optical properties of these emitters inside a complex solid state environment.

scholarly journals Transforming graph states using single-qubit operations

2018 ◽  
Vol 376 (2123) ◽  
pp. 20170325 ◽  
Author(s):  
Axel Dahlberg ◽  
Stephanie Wehner
Keyword(s):  
Quantum Information ◽  
Error Correcting Codes ◽  
Graph States ◽  
Target State ◽  
Single Qubit ◽  
Minor Problem ◽  
Fixed Parameter ◽  
Source State ◽  
Quantum Error ◽  
Stabilizer States

Stabilizer states form an important class of states in quantum information, and are of central importance in quantum error correction. Here, we provide an algorithm for deciding whether one stabilizer (target) state can be obtained from another stabilizer (source) state by single-qubit Clifford operations (LC), single-qubit Pauli measurements (LPM) and classical communication (CC) between sites holding the individual qubits. What is more, we provide a recipe to obtain the sequence of LC+LPM+CC operations which prepare the desired target state from the source state, and show how these operations can be applied in parallel to reach the target state in constant time. Our algorithm has applications in quantum networks, quantum computing, and can also serve as a design tool—for example, to find transformations between quantum error correcting codes. We provide a software implementation of our algorithm that makes this tool easier to apply. A key insight leading to our algorithm is to show that the problem is equivalent to one in graph theory, which is to decide whether some graph G ′ is a vertex-minor of another graph G . The vertex-minor problem is, in general, -Complete, but can be solved efficiently on graphs which are not too complex. A measure of the complexity of a graph is the rank-width which equals the Schmidt-rank width of a subclass of stabilizer states called graph states, and thus intuitively is a measure of entanglement. Here, we show that the vertex-minor problem can be solved in time O (| G | 3 ), where | G | is the size of the graph G , whenever the rank-width of G and the size of G ′ are bounded. Our algorithm is based on techniques by Courcelle for solving fixed parameter tractable problems, where here the relevant fixed parameter is the rank width. The second half of this paper serves as an accessible but far from exhausting introduction to these concepts, that could be useful for many other problems in quantum information. This article is part of a discussion meeting issue ‘Foundations of quantum mechanics and their impact on contemporary society’.

scholarly journals Quantum optics and cavity QED with quantum dots in photonic crystals

2017 ◽  
Author(s):  
Jelena Vučković
Keyword(s):  
Quantum Dots ◽  
Information Processing ◽  
Quantum Information ◽  
Quantum Optics ◽  
Quantum Electrodynamics ◽  
Cavity Qed ◽  
Cavity Quantum Electrodynamics ◽  
Test Bed ◽  
Matter Interaction ◽  
Light Matter Interaction

Quantum dots in optical nanocavities are interesting as a test-bed for fundamental studies of light–matter interaction (cavity quantum electrodynamics, QED), as well as an integrated platform for information processing. As a result of the strong field localization inside sub-cubic-wavelength volumes, these dots enable very large emitter–field interaction strengths. In addition to their use in the study of new regimes of cavity QED, they can also be employed to build devices for quantum information processing, such as ultrafast quantum gates, non-classical light sources, and spin–photon interfaces. Beside quantum information systems, many classical information processing devices, such as lasers and modulators, benefit greatly from the enhanced light–matter interaction in such structures. This chapter gives an introduction to quantum dots, photonic crystal resonators, cavity QED, and quantum optics on this platform, as well as possible device applications.

scholarly journals Measuring Nonclassicality of Mesoscopic Twin-Beam States with Silicon Photomultipliers †

Proceedings ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 48
Author(s):  
Giovanni Chesi ◽  
Luca Malinverno ◽  
Alessia Allevi ◽  
Romualdo Santoro ◽  
Massimo Caccia ◽  
...  
Keyword(s):  
Quantum Information ◽  
Quantum Optics ◽  
Output Signal ◽  
Photon Number ◽  
Quantum States ◽  
Silicon Photomultipliers ◽  
Nonclassical Properties ◽  
Relevant Topic ◽  
Twin Beam ◽  
Proper Analysis

The study of nonclassical properties of quantum states is a relevant topic for fundamental Quantum Optics and Quantum Information applications. In the mesoscopic domain, promising results have been obtained using photon-number-resolving detectors. Here we show recent results achieved with the class of Silicon Photomultipliers: by a proper analysis of the output signal, the nonclassicality of twin-beam states can be detected and exploited.

scholarly journals Enhancement of and interference among higher order multipole transitions in molecules near a plasmonic nanoantenna

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Evgenia Rusak ◽  
Jakob Straubel ◽  
Piotr Gładysz ◽  
Mirko Göddel ◽  
Andrzej Kędziorski ◽  
...  
Keyword(s):  
Spontaneous Emission ◽  
Electric Dipole ◽  
Electric Quadrupole ◽  
Coherence Time ◽  
Dipole Approximation ◽  
Higher Order ◽  
Destructive Interference ◽  
Interference Effects ◽  
Matter Coupling ◽  
Molecular Transition

AbstractSpontaneous emission of quantum emitters can be modified by their optical environment, such as a resonant nanoantenna. This impact is usually evaluated under assumption that each molecular transition is dominated only by one multipolar channel, commonly the electric dipole. In this article, we go beyond the electric dipole approximation and take light-matter coupling through higher-order multipoles into account. We investigate a strong enhancement of the magnetic dipole and electric quadrupole emission channels of a molecule adjacent to a plasmonic nanoantenna. Additionally, we introduce a framework to study interference effects between various transition channels in molecules by rigorous quantum-chemical calculations of their multipolar moments and a consecutive investigation of the transition rate upon coupling to a nanoantenna. We predict interference effects between these transition channels, which allow in principle for a full suppression of radiation by exploiting destructive interference, waiving limitations imposed on the emitter’s coherence time by spontaneous emission.

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