Multi Photon Entanglement From Parametric Downconversion
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Multi Photon Entanglement From Parametric Downconversion
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Author : George Khoury
language : en
Publisher:
Release Date : 2006
Multi Photon Entanglement From Parametric Downconversion written by George Khoury and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
Several optics experiments at the few-photon level are presented. First, we demonstrate the production of entangled states of up to 100 photons and methods to analyze their entanglement with single photon detectors. We then develop a method to generate path entangled states of light from the output of a parametric downconverter without postselection. We observe the bunching of composite states of photons, and show that they can exhibit bosonic or fermionic behavior depending on their internal phase. We demonstrate a novel way to produce entangled photon pairs that provides unmatched quantum interference visibility when using an ultrafast pump source. We then theoretically analyze the multi-photon state produced with such a source. By using the Schmidt decomposition of the state, we obtain intuitive expressions for four-fold correlation functions and also the non-perturbative solution to the downconversion interaction Hamiltonian. Finally, we present two measurements of the output of a Mach-Zehnder interferometer using a novel multiphoton detector. We show that the individual photon absorption probabilities vary on a subwavelength scale. We also show, using a Bayesian analysis of the detection results, that the phase sensitivity of an interferometer is in fact independent of phase angle, in contrast to the widely used standard theory.
Multi Photon Quantum Interference
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Author : Zhe-Yu Jeff Ou
language : en
Publisher: Springer Science & Business Media
Release Date : 2007-06-08
Multi Photon Quantum Interference written by Zhe-Yu Jeff Ou and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007-06-08 with Technology & Engineering categories.
This book details parametric down-conversion for the generation of non-classical state of light and its applications in generating various kinds of quantum entanglement among multiple photons from parametric down-conversion. It presents applications of the principle of quantum interference to multi-photon systems. The book also details continuous variable entanglement and various types of multi-photon interference effects.
Multi Photon Entanglements From Pulsed Pump Spontaneous Parametric Down Conversion
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Author : Timothy E. Keller
language : en
Publisher:
Release Date : 1999
Multi Photon Entanglements From Pulsed Pump Spontaneous Parametric Down Conversion written by Timothy E. Keller and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with Photons categories.
Direct Generation Of Three Photon Entanglement Using Cascaded Downconversion
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Author : Deny R. Hamel
language : en
Publisher:
Release Date : 2013
Direct Generation Of Three Photon Entanglement Using Cascaded Downconversion written by Deny R. Hamel and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
High quality entangled photon sources are a key requirement for many promising quantum optical technologies. However, the production of multi-photon entangled states with good fidelity is challenging. Current sources of multi-photon entanglement require the use of post-selection, which limits their usefulness for some applications. It has been an open challenge to create a source capable of directly producing three-photon entanglement. An important step in this direction was achieved with the demonstration of photon triplets produced by a new process called cascaded downconversion, but these previous measurements were not sufficient to show whether these photons were in an entangled state and only had detection rates of five triplets per hour. In this thesis, we show the first demonstration of a direct source of three-photon entanglement. Our source is based on cascaded downconversion, and we verify that it produces genuine tripartite entanglement in two degrees of freedom: energy-time and polarization. The energy-time entanglement is similar to a three-particle generalization of an Einstein-Podolski-Rosen state; the three photons are created simultaneously, yet the sum of their energies is well defined, which is an indication of energy-time entanglement. To prove it, we use time-bandwidth inequalities which check for genuine tripartite entanglement. Our measurements show that the state violates the inequalities with what constitute, to the best of our knowledge, the strongest violation of time-bandwidth inequalities in a tripartite continuous-variable system to date. We create polarization entanglement by modifying our experimental setup so that two downconversion processes producing orthogonally polarized triplets interfere to create Greenberger-Horne-Zeilinger states. By using highly efficient superconducting nanowire single photon detectors, we improve the detected triplet rate by 2 orders of magnitude to 660 triplets per hour. We characterize the state using quantum state tomography, and find a fidelity of 86\% with the ideal state, beating the previous best value for a three-photon entangled state fidelity measured by tomography. We also use the state to perform two tests of local realism. We violate the Mermin and Svetlichny inequalities by 10 and 5 standard deviations respectively, the latter being the strongest violation to date. Finally, we show that, unlike previous sources of tree-photon entanglement, our source can be used as a source of heralded Bell pairs. We demonstrate this by measuring a CHSH inequality with the heralded Bell pairs, and by reconstructing their state using quantum state tomography.
Towards On Demand Generation Of Entangled Photons With Quantum Dots
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Author : Arash Ahmadi
language : en
Publisher:
Release Date : 2020
Towards On Demand Generation Of Entangled Photons With Quantum Dots written by Arash Ahmadi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
The biexciton-exciton cascade in quantum dots (QDs) yields entangled photon pairs, and recent developments in engineering photonic structures around the dot for efficient light extraction and proper control of the fine-structure splitting, has led to significant breakthroughs in achieving an ideal entangled photon source -- exhibiting properties such as high extraction efficiency, low multi-photon emission and high entanglement fidelity. This thesis presents our development in enhancing the performance of entangled photon generation of QDs towards near-unity efficiency and fidelity. We study InAsP quantum dots in photonic nanowires for efficient light extraction and to reveal the effect of a quantum dot with high nuclear spin on the entanglement fidelity. Revealing the ultimate limit of entanglement in QDs is still a challenge, and it is generally believed that a sample made of atoms possessing high nuclear spins exhibits limited entanglement due to the dephasing caused by spin-spin interactions. Moreover, it is assumed that the fine-structure splitting of QDs degrades the entanglement fidelity, as it introduces a which-path information in the biexciton-exciton cascade. We have performed two-photon state tomography on InAsP QDs in InP nanowires, comprising of nuclear spin 9/2, and have realized that such a source is capable of generating entangled photon pairs with negligible dephasing during the emission lifetime, with a peak concurrence C = 77% and a count-weighted average concurrence 62%. This result was obtained by comparing the outcome of our measurements with a theoretical model that assumes no dephasing, however, takes into account the details of the detection system, i.e., dark-count rates and timing resolution, as well as, specific features of the QD, e.g., emission lifetime, fine-structure splitting, multi-photon emission probability, etc. Proper engineering of tapered nanowires allows for extraction of the emitted photons with high efficiency, which makes it possible to perform a complete two-photon state tomography and monitoring the evolution of the exciton state, as well as, the entanglement fidelity of the photon-pair, during the emission lifetime. This enabled us to reveal the effect of an imperfect detection system, as well as, multi-photon emission in recording low values for entanglement fidelity. Moreover, our calculations show that proper analysis of the time-energy uncertainty relation provides the necessary means to measure a high entanglement fidelity even in the presence of fine-structure splitting; since, a detection system with high timing resolution can overlook the which-path information, as the uncertainty in measuring the energy of the photons will be larger than the fine-structure splitting. Therefore, realizing near-unity entanglement fidelity using QDs is merely a technical challenge, i.e., resonant excitation of the QD, in order to suppress multi-photon emission, and use of a detection system with low timing jitter and dark-count rates. As a next step to achieve this goal, we have performed the resonant two-photon excitation scheme for the first time on a QD in a photonic nanowire, which resulted in an enhancement of the performance of our source. We managed to improve the single-photon purity of the source, g^(2)(0), by two orders of magnitude; moreover, analysis of the emission spectrum reveals that this scheme increases the pair-production efficiency to values above 93% for the biexciton-exciton cascade. Taking the efficiency of our experimental setup into consideration, the results indicate an approximately eight-fold enhancement of the pair-extraction efficiency as compared to the quasi-resonant excitation scheme (12.55% vs. 1.6%). Based on these results, two-photon state tomography on our source, under resonant two-photon excitation and performed by a detection system with high timing resolution and low dark-count rates, yields near-unity entanglement fidelity. By considering the enhancement in pair-extraction efficiency that we obtained, QDs in photonic nanowires can surpass the performance of spontaneous parametric down conversion sources in terms of entanglement fidelity and pair-extraction efficiency. Even though we have shown a finite fine-structure splitting does not degrade the entanglement fidelity in QDs, for various application in quantum information removing the fine-structure splitting is beneficial. Therefore, we have proposed a universal all-optical approach for removing the fine-structure splitting. In this scheme, the energy of the photons are shifted by using a pair of quarter-wave plates and fast-rotating half-wave plates after they have been emitted; and as a result, the energy difference between the two decay paths in the biexciton-exciton cascade is erased. This method is applicable to any QD source and can be easily implemented using the currently available technology; moreover, no further sample processing will be required in order to achieve zero fine-structure splitting.
Two Photon Quantum Entanglement From Type Ii Spontaneous Parametric Down Conversion
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Author : Todd B. Pittman
language : en
Publisher:
Release Date : 1996
Two Photon Quantum Entanglement From Type Ii Spontaneous Parametric Down Conversion written by Todd B. Pittman and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with Photons categories.
Coherence Properties Of The Entangled Two Photon Field Produced By Parametric Down Conversion
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Author : Anand Kumar Jha
language : en
Publisher:
Release Date : 2009
Coherence Properties Of The Entangled Two Photon Field Produced By Parametric Down Conversion written by Anand Kumar Jha and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
"Parametric down-conversion is a second-order nonlinear optical process in which a pump photon breaks up into two separate photons known as the signal photon and the idler photon. The constraints of energy and momentum conservation render the signal and idler photons entangled in several different variables including time and energy, position and transverse momentum, and angular position and orbital angular momentum. Because of these correlations, the down-converted signal and idler photons can be described adequately only as a single, two-photon system. In this thesis, we present our theoretical and experimental studies of the coherence properties of the down-converted, entangled two-photon fields, through two-photon interference effects in temporal, spatial and angular domains. First of all, we study the temporal coherence properties of the down-converted two-photon fields, in the limit in which the frequency bandwidth of the pump field is much narrower than that of the down-converted field. We present a formalism to completely characterize temporal two-photon interference effects in terms of the variations of two length parameters--called the two-photon path length difference and the two-photon path-asymmetry length difference--which we construct using the six different length parameters that a general two-photon interference experiment involves. Next, we extend this formalism to describe also the spatial coherence properties of the two-photon field. By explicitly treating the case of a partially spatially coherent pump beam of Gaussian Schell-model type, we show that in parametric down-conversion the spatial coherence properties of the pump field get entirely transferred to the spatial coherence properties of the down-converted two-photon field. As an important consequence of this study, we find that for two-qubit states that are based on the spatial correlations of the down-converted photons, the maximum achievable entanglement is bounded by the degree of spatial coherence of the pump field. In the last part of this thesis, we study the coherence properties of the entangled two-photon field in the angular domain, by investigating two-photon angular interference effects in situations in which the down-converted photons are made to pass through apertures in the form of double angular-slits"--Leaves vii-viii.
Spontaneous Parametric Down Conversion And Quantum Entanglement
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Author :
language : en
Publisher:
Release Date : 2014
Spontaneous Parametric Down Conversion And Quantum Entanglement written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Quantum entanglement categories.
Quantum entanglement has been a topic of much research in modern physics, and an application in quantum computing is envisioned. This thesis addresses the use of polarization entangled photon pairs produced by spontaneous parametric down-conversion (SPDC) in entanglement transfer process and quantum computing. The simplicity of SPDC entanglement relative to other quantum phenomena is first emphasized by developing a complete classical theory of the photon-crystal interactions characteristic of SPDC. The methods of achieving polarization superposition via the Type-I and Type-II SPDC are described. A combination of superposition and polarization correlation between down-converted photons is shown to violate Bell's inequality, thus revealing the entangled nature of the photon pairs. Finally, the possibility of controlling entangled photons through the manipulation of surface plasmons is highlighted as a way to transfer entanglement from photons to material particles.
On The Squeezing And Over Squeezing Of Photons
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Author : Lynden Krister Shalm
language : en
Publisher:
Release Date : 2011
On The Squeezing And Over Squeezing Of Photons written by Lynden Krister Shalm and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Quantum mechanics allows us to use nonclassical states of light to make measurements with a greater precision than comparable classical states. Here an experiment is presented that squeezes the polarization state of three photons. We demonstrate the deep connection that exists between squeezing and entanglement, unifying the squeezed state and multi-photon entangled state approaches to quantum metrology. For the first time we observe the phenomenon of over-squeezing where a system is squeezed to the point that further squeezing leads to a counter-intuitive increase in measurement uncertainty. Quasi-probability distributions on the surface of a Poincare sphere are the most natural way to represent the topology of our polarization states. Using this representation it is easy to observe the squeezing and over-squeezing behaviour of our photon states.Work is also presented on two different technologies for generating nonclassical states of light. The first is based on the nonlinear process of spontaneous parametric downconversion to produce pairs of photons. With this source up to 200,000 pairs of photons/s have been collected into single-mode fibre, and over 100 double pairs/s have been detected. This downconversion source is suitable for use in a wide variety of multi-qubit quantum information applications. The second source presented is a single-photon source based on semiconductor quantum dots. The single-photon character of the source is verified using a Hanbury Brown-Twiss interferometer.
Photonic Entanglement New Sources And New Applications
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Author : Jiŕí Svozilík
language : en
Publisher:
Release Date : 2014
Photonic Entanglement New Sources And New Applications written by Jiŕí Svozilík and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Non-classical correlations, usually referred as entanglement, are ones of the most studied and discussed features of Quantum Mechanics, since the initial introduction of the concept in the decade of 1930s. Even nowadays, a lot of efforts, both theoretical and experimental, are devoted in this topic, that covers many distinct areas of physics, such as a quantum computing, quantum measurement, quantum communications, solid state physics, chemistry and even biology. The fundamental tasks that one should consider related to the entanglement are: -How to create quantum entangled states. -How to maintain entanglement during propagation against sources of decoherence. -How to effectively detect it. -How to employ the benefits that entanglement offers. This thesis, divided into four chapters, concentrates on the first and last tasks considered above. In Chapter 1, a brief introduction and overview of what it is entanglement is given, starting with the famous paper of Einstein, Podolsky and Rosen, and continuing with John Bell's formulation of the so-called Bell's inequalities. We define here general concepts about entangled quantum states and introduce important entanglement measures, that are later used all over the thesis. In this chapter, sources of entangled particles (namely photons) are also mentioned. The importance is put on sources based on the nonlinear process of spontaneous parametric down-conversion. The last part of this chapter is then dedicated to a list of applications that benefit from the use of engangled states. Chapter 2 is devoted to the systematic study of the generation of entangled and non-entangled photon pairs in semiconductor Bragg reflection waveguides. Firstly, we present a source of photon pairs with a spectrally uncorrelated two-photon amplitude, achieved by a proper tailoring of the geometrical and material dispersions via structural design of waveguides. Secondly, Bragg reflection waveguides are designed in a scuh way, that results in the generation of spectrally broadband paired photons entangled in the polarization degree of freedom. Finally, we present experimental results of entangled photon pairs generation in this type of structures. In Chapter 3, we explore the feasibility of the generation of photon pairs entangled in the spatial degree of freedom, i.e. in the orbital angular momentum (OAM). Firstly, we examine how to create a highly multidimensional Hilbert space using OAM modes obtained in a chipred-poled nonlinear bulk crystals. Here, we show, how an increase of the chirp of the poling can effectively increase the Schmidt number by several orders of magnitude. Secondly, we investigate periodically poled silica glass fibres with a ring-shpaed core, that are capable to support the generation of simple OAM modes. The final Chapter 4 is dedicated to the Anderson localization and quantum random walks. At the beginning of this chapter, we present an experimental proposal for the realization of a discrete quantum random walks using the multi-path Mach-Zehnder interferometer with a spatial light modulator, that allows us to introduce different types of statistical or dynamical disorders. And secondly, we show how the transverse Anderson localization of partially coherent light, with a variable first-order degree of coherence, can be studied making use of entangled photon pairs.