21 research outputs found
Manipulating quantum entanglement with atomic ensembles and with atoms in optical superlattices : towards scalable quantum information processing
Quantum information science possesses promising potentialities for developing new secure and efficient ways to transfer and process information. Prodigious efforts have been and are being devoted, however, a scalable architecture is still a considerable challenge. Among the potential candidates, photons are assumed to be good carriers, and neutral atoms good hosts. In this thesis, photon-matter entanglement sources, which exploit the advantages of both, are employed to demonstrate a teleportation between two atomic-ensemble quantum memory nodes and an efficient entanglement swapping, which are essential for scalable quantum networks. Later, the entanglement source is further developed, and an active feedforward one-way quantum computation is presented
with stationary quantum memories, which are necessary for scalable quantum computers. To fulfill another feature of scalability, the ease of integration, ultracold atoms in
two-dimensional optical superlattices are studied and an experiment is designed to generate four-qubit entangled states. With the help of the photon-matter entanglement
sources, serving as quantum memories and nodes of quantum networks, realization of large-scale quantum networks is foreseeable. Meanwhile, by applying controllable interactions, large entangled states could be generated in optical superlattices, which might help to construct quantum processors that outperform the classical counterparts
TESTING THE QUANTUM-CLASSICAL BOUNDARY AND DIMENSIONALITY OF QUANTUM SYSTEMS
Ph.DDOCTOR OF PHILOSOPH
Quantum interferometers: principles and applications
Interference, which refers to the phenomenon associated with the
superposition of waves, has played a crucial role in the advancement of physics
and finds a wide range of applications in physical and engineering
measurements. Interferometers are experimental setups designed to observe and
manipulate interference. With the development of technology, many quantum
interferometers have been discovered and have become cornerstone tools in the
field of quantum physics. Quantum interferometers not only explore the nature
of the quantum world but also have extensive applications in quantum
information technology, such as quantum communication, quantum computing, and
quantum measurement. In this review, we analyze and summarize three typical
quantum interferometers: the Hong-Ou-Mandel (HOM) interferometer, the N00N
state interferometer, and the Franson interferometer. We focus on the
principles and applications of these three interferometers. In the principles
section, we present the theoretical models for these interferometers, including
single-mode theory and multi-mode theory. In the applications section, we
review the applications of these interferometers in quantum communication,
computation, and measurement. We hope that this review article will promote the
development of quantum interference in both fundamental science and practical
engineering applications.Comment: 64 pages, 40 figures. Comments are welcom
Quantum manipulation of photons and atoms : the application in quantum information processing
Quantum information has been witnessing great science value and latent application since 1980's. The research work presented here consist of mainly two important parts: manipulations of multiphoton entanglement and atomic ensembles based quantum memory. In first part, the experimental technique multi-photon entanglement is further developed to study fundamental issues in quantum mechanics, remarkable applications to quantum communication and quantum computation. Specifically, we have demonstrated a bit-flip error-free transfer of quantum information, violation of Bell's inequality beyond Tsirelson's bound, teleportation of a two-qubit composite system, as well as the one-way computing by two-photon-four-qubit cluster state. To overcome un-scalability problem due to probabilistic feature in linear optical quantum information processing, we investigated in the second part the physics of atomic ensembles based quantum memory. We show that theoretically, entanglement between distant locations can be deterministically generated. The experimental work has thoroughly developed the necessary techniques and we have achieved deterministic single photon source, and interference of the photons from independent atomic ensembles, teleportation between photonic and atomic qubits, a novel way to create a robust entanglement between an atomic and a photonic qubit, and memory based entanglement swapping. We believe, the developed techniques here would dramatically facilitate progresses in many fields including global quantum communication, linear optical quantum computation and the foundations of quantum mechanics etc
On the nature and decay of quantum relative entropy
Historically at the core of thermodynamics and information theory, entropy's use in quantum information extends to diverse topics including high-energy physics and operator algebras. Entropy can gauge the extent to which a quantum system departs from classicality, including by measuring entanglement and coherence, and in the form of entropic uncertainty relations between incompatible measurements. The theme of this dissertation is the quantum nature of entropy, and how exposure to a noisy environment limits and degrades non-classical features.
An especially useful and general form of entropy is the quantum relative entropy, of which special cases include the von Neumann and Shannon entropies, coherent and mutual information, and a broad range of resource-theoretic measures. We use mathematical results on relative entropy to connect and unify features that distinguish quantum from classical information. We present generalizations of the strong subadditivity inequality and uncertainty-like entropy inequalities to subalgebras of operators on quantum systems for which usual independence assumptions fail. We construct new measures of non-classicality that simultaneously quantify entanglement and uncertainty, leading to a new resource theory of operations under which these forms of non-classicalty become interchangeable. Physically, our results deepen our understanding of how quantum entanglement relates to quantum uncertainty.
We show how properties of entanglement limit the advantages of quantum superadditivity for information transmission through channels with high but detectable loss. Our method, based on the monogamy and faithfulness of the squashed entanglement, suggests a broader paradigm for bounding non-classical effects in lossy processes. We also propose an experiment to demonstrate superadditivity.
Finally, we estimate decay rates in the form of modified logarithmic Sobolev inequalities for a variety of quantum channels, and in many cases we obtain the stronger, tensor-stable form known as a complete logarithmic Sobolev inequality. We compare these with our earlier results that bound relative entropy of the outputs of a particular class of quantum channels
Multi-photon entanglement and interferometry
Multi-photon interference reveals strictly non-classical phenomena. Its
applications range from fundamental tests of quantum mechanics to photonic
quantum information processing, where a significant fraction of key experiments
achieved so far comes from multi-photon state manipulation. We review the
progress, both theoretical and experimental, of this rapidly advancing
research. The emphasis is given to the creation of photonic entanglement of
various forms, tests of the completeness of quantum mechanics (in particular,
violations of local realism), quantum information protocols for quantum
communication (e.g., quantum teleportation, entanglement purification and
quantum repeater), and quantum computation with linear optics. We shall limit
the scope of our review to "few photon" phenomena involving measurements of
discrete observables.Comment: 71 pages, 38 figures; updated version accepted by Rev. Mod. Phy
2022 Roadmap on integrated quantum photonics
AbstractIntegrated photonics will play a key role in quantum systems as they grow from few-qubit prototypes to tens of thousands of qubits. The underlying optical quantum technologies can only be realized through the integration of these components onto quantum photonic integrated circuits (QPICs) with accompanying electronics. In the last decade, remarkable advances in quantum photonic integration have enabled table-top experiments to be scaled down to prototype chips with improvements in efficiency, robustness, and key performance metrics. These advances have enabled integrated quantum photonic technologies combining up to 650 optical and electrical components onto a single chip that are capable of programmable quantum information processing, chip-to-chip networking, hybrid quantum system integration, and high-speed communications. In this roadmap article, we highlight the status, current and future challenges, and emerging technologies in several key research areas in integrated quantum photonics, including photonic platforms, quantum and classical light sources, quantum frequency conversion, integrated detectors, and applications in computing, communications, and sensing. With advances in materials, photonic design architectures, fabrication and integration processes, packaging, and testing and benchmarking, in the next decade we can expect a transition from single- and few-function prototypes to large-scale integration of multi-functional and reconfigurable devices that will have a transformative impact on quantum information science and engineering