Quantum memory protocols for photonic solid-state devices

A photonic quantum memory (QM) is a device that has the capability of storing a quantum state of light and retrieving back after a controlled time. It is an important element in quantum information science and is, among other applications, a crucial device for quantum repeater architectures which have been proposed to overcome the loss and the decoherence issues in long distance transmission of photons. Rare earth ion doped solid state systems are promising candidates for QMs which combine the advantages of solid state systems, such as scalability and reduced experimental complexity, with the long coherence time typically found in atomic systems. In this thesis, I investigated three different QM protocols in a Pr3+:Y2SiO5 crystal. The first part describes here the first demonstration of the spectral hole memory (SHoMe) protocol which was proposed theoretically in 2009. This protocol relies on slowing down the light in a long-lived spectral hole and transferring the excitations to the spin state. We first prepare a spectral hole, then send an input pulse whose bandwidth is comparable with the hole and stop the compressed light in the crystal by transferring the off-resonant coherence to the spin state with an optical p pulse. Later a second p pulse transfers the coherence back and leads to the emission of the stored light. We reached a storage and retrieval efficiency of around 40% in the classical regime, and of 31% in the single photon level, with a signal-to-noise ratio of 33 ± 4 for a mean input photon number of 1. These results demonstrate the most efficient and noiseless spin-wave solid-state optical memory at the single photon level to date. The second part of the thesis describes new experiments using the well-known atomic frequency comb (AFC) protocol. It is based on tailoring the inhomogeneously broadened absorption profile of the rare earth with periodic absorptive peaks, which induces the re-emission of the absorbed light field after a certain time determined by the separation between the peaks. In this chapter I describe several AFC experiments. First I present the storage of frequency converted telecom photons into our crystal where we obtained a total efficiency of 1.9 ± 0.2 % for a storage time of 1.6 µs storage time and signal-to-noise ratio of more than 200 for a mean input photon number of 1. Then I discuss the results of improved excited state storage efficiency values for long storage times where we achieved 30% at short storage times and up to 17% at 10 µs storage time. And finally I present a spin-wave AFC experiment where we obtained a signal-to-noise ratio value of 28 ± 8 for a mean input photon number of 1, the highest value achieved so far for this kind of experiment. Finally, in the last part, I describe the first demonstration of a solid-state photon pair source with embedded multimode quantum memory. The aim of the protocol is to combine a single photon source and a QM in one ensemble as in the well-known Duan-Lukin-Zoller-Cirac (DLCZ) scheme however this time not in a cold atomic ensemble but in a solid-state crystal. The protocol takes advantage of the AFC protocol for rephasing the ions and obtaining efficient read-out. The use of AFC also makes the protocol temporally multi-mode. In the experiment, after the AFC preparation we send an on-resonant write pulse and detect the decayed Stokes photons which herald single spin excitations. At a later time a read pulse transfers the spin excitation back to the excited state and we detect the anti-Stokes photons. We show strong non-classical second order cross-correlations between the Stokes and anti-Stokes photons and demonstrate storage of 11 temporal modes. The results presented in this thesis represent a significant contribution to the field of solid-state quantum memories and an important steps towards the realization of scalable quantum network architectures with solid state systems.Una memòria quàntica (MQ) és un dispositiu que té la capacitat d'emmagatzemar l'estat quàntic de la llum i retornar-lo després d'un temps controlat.És un element important en la ciència de la informació quàntica i és un dispositiu crucial per a arquitectures de repetidors quàntica.Els sistemes d'estat sòlid basats en ions de terres rares són candidats prometedors per implementar MQs, ja que combinen els avantatges dels sistemes sòlids (escalabilitat i poca complexitat experimental) amb els llargs temps de coherència dels sistemes atòmics.En aquesta tesis he investigat tres protocols diferents de MQ en un cristall de Pr3+:Y2SiO5. La primera part descriu la primera demostració del protocol de memòria basat en forats espectrals (MFE), que va ser proposat teòricament el 2009. Aquest protocol es basa en disminuir la velocitat de la llum en un forat espectral de vida llarga i transferir les excitacions a un estat d'espín. Comencem preparant un forat espectral, després enviem un pols de llum amb una amplada espectral comparable a la del forat i aturem la llum comprimida en el cristall transferint la coherència fora de ressonància a l'estat d'espín amb un pols òptic.Seguidament un segon pols retorna la coherència i porta a l'emissió de la llum emmagatzemada. Aconseguim una eficiència d'emmagatzematge i recuperació de 40% en el règim clàssic i de 31% al nivell de fotons individuals, amb una relació senyal-soroll de 33 ±4 per un nombre mitjà de fotons incidents igual a 1. Aquests resultats demostren la memòria òtica operant al nivell de fotons individuals amb més eficiència i més lliure de soroll. La segona part de la tesis descriu nous experiments que utilitzen el protocol de pintes de freqüència atòmiques (PFA). Aquest està basat en modificar el perfil d'absorció eixamplat inhomogèniament dels ions de terres rares, creant pics d'absorció periòdics que indueixen la reemissió del camp de llum absorbit, després d'un cert temps que ve determinat per la separació dels pics. En aquest capítol descric varis experiments de PFA. Primer presento l'emmagatzematge en el nostre cristall de fotons amb freqüència convertida des de telecom, obtenint una eficiència total de 1.9 ± 0.2% per un temps d'emmagatzematge de 1.6us i una relació senyal-soroll de més de 200 per un nombre mitjà de fotons incidents igual a 1. Seguidament discuteixo els resultats obtinguts amb una millorada eficiència d'emmagatzematge en l'estat excitat per temps d'emmagatzematge llargs, on vam obtenir 30% per temps curts i 17% a 10us. I finalment presento un experiment de PFA amb ona d'espín on vam obtenir una relació senyal-soroll de 28 ± 8 per un nombre mitjà de fotons incidents igual a 1, el valor més alt assolit mai en un experiment d'aquest tipus. Finalment, en la última part, descric la primera demostració d'una font de parelles de fotons d'estat sòlid integrada amb una memòria quàntica multimodal. L'objectiu del protocol és combinar en un sol sistema una font de fotons individuals i una MQ, com té lloc en el conegut esquema de Duan-Lukin-Cirac-Zoller (DLCZ), però en aquest cas amb un cristall en lloc d'un sistema d'àtoms freds.El protocol agafa els avantatges del protocol PFA per refasar els ions i obtenir una recuperació eficient. Utilitzant PFA fa que el protocol sigui temporalment multimodal.En l'experiment, després de la preparació de la PFA, enviem un pols d'escriptura en ressonància i detectem un fotó Stokes que anuncia excitacions d'espín individuals. Un temps més tard, un pols de lectura transfereix l'excitació d'espín de tornada cap a l'estat excitat i detectem fotons anti-Stokes. Mostrem fortes correlacions de segon ordre no-clàssiques entre els fotons de Stokes i anti-Stokes i demostrem l'emmagatzematge de 11 modes temporals. Els resultats presentats en aquesta tesis representen una contribució significativa en el camp de les memòries quàntiques d'estat sòlid i un pas important cap a la realització d'arquitectures de xarxes quàntiques amb sistemes d'estat sòlidPostprint (published version

A solid state spin-wave quantum memory for time-bin qubits

We demonstrate the first solid-state spin-wave optical quantum memory with on-demand read-out. Using the full atomic frequency comb scheme in a \PrYSO crystal, we store weak coherent pulses at the single-photon level with a signal to noise ratio $> 10$. Narrow-band spectral filtering based on spectral hole burning in a second \PrYSO crystal is used to filter out the excess noise created by control pulses to reach an unconditional noise level of $(2.0 \pm 0.3) \times10^{-3}$ photons per pulse. We also report spin-wave storage of photonic time-bin qubits with conditional fidelities higher than a measure and prepare strategy, demonstrating that the spin-wave memory operates in the quantum regime. This makes our device the first demonstration of a quantum memory for time-bin qubits, with on demand read-out of the stored quantum information. These results represent an important step for the use of solid-state quantum memories in scalable quantum networks.Comment: 10 pages, 10 figure

Ganoderma lucidum (Fr.) karst (reishi)’nin miselyal özelliklerinin incelenmesi

Bu çalışmada, ölümsüzlük mantarı olarak bilinen Ganoderma lucidum-Reishi’un morfolojik ve anatomik yapısı incelendi. G. lucidum doku parçası patates dekstroz agar merkezine ekildi ve 28ºC’de 22 günlük bir süre için karanlık olarak inkübe edildi. Aşılama döneminin sonunda; misel beyaz renkli ve çok sağlam bir doku oluştu. G. lucidum’un spor ve misellerinin anatomik çalışmaları elektron mikroskobu (SEM) ve ışık mikroskobu (LM) ile ayrı ayrı tespit edildi ve fotoğrafları çekildi.In this study, morphological and anatomical structures of Ganoderma lucidum-Reishi known as immortality mushroom were examined. Part of the tissue of G. lucidum was inoculated potato dextrose agar center and they were incubated at 28ºC, the dark for a period of 22 days. At the end of the incubation period; mycelium formed white color and very solid tissue. Anatomical studies of spore and mycelium of G. lucidum were identified with scanning electron microscopy (SEM) and light microscopy (LM) separately and were micrographied

The ISIS Model and its Influence Over Global Terrorism

Counter-terrorism efforts against jihadist groups have been challenging for law enforcement and the military because terrorist organizations constantly update their tactics and mimic the successful strategies of popular and influential groups, such as ISIS, that have developed a specific model for carrying out their destructive acts. ISIS created its terrorism model in 2014 and has used it to control territory, spread its ideology, create provincial branches in different regions, inspire lone actors, and generate revenue. Terrorism databases are full of incidents that involve ISISstyle tactics, targets, and affiliated groups that act as provincial branches of ISIS. This paper examines how ISIS developed its model, what components that model involves, and how the model has influenced not only jihadist groups but also right-wing extremists and drug cartels around the world. The study uses a mixed method of quantative and qualitative research, and the proposed ISIS Model is developed through a rigorous literature review

New in vitro cellular model for molecular studies of retinitis pigmentosa

Retinitis pigmentosa (RP) is an inherited form of retinal degeneration characterized by primary rod photoreceptor cell death followed by cone loss. Mutations in several genes linked to the disease cause increased levels of cyclic guanosine monophosphate (cGMP) and calcium ion influxes. The purpose of this project was to develop a new in vitro photoreceptor degeneration model for molecular studies of RP. 661W cells were genetically modified to stably express the neural retina leucine zipper (NRL) transcription factor. One clone (661W-A11) was selected based on the expression of Nrl target genes. 661W-A11 showed a significant increase in expression of rod-specific genes but not of cone-specific genes, compared with 661W cells. Zaprinast was used to inhibit phosphodiesterase 6 (PDE6) activity to mimic photoreceptor degeneration in vitro. The activation of cell death pathways resulting from PDE6 inhibition was confirmed by detection of decreased viability and increased intracellular cGMP and calcium, as well as activation of protein kinase G (PKG) and calpains. In this new in vitro system, we validated the effects of previously published neuroprotective drugs. The 661W-A11 cells may serve as a new model for molecular studies of RP and for high-throughput drug screening

Quantum storage of heralded single photons in a praseodymium-doped crystal

We report on experiments demonstrating the reversible mapping of heralded single photons to long-lived collective optical atomic excitations stored in a Pr3+:Y2SiO5 crystal. A cavity-enhanced spontaneous down-conversion source is employed to produce widely nondegenerate narrow-band (≈2 MHz) photon pairs. The idler photons, whose frequency is compatible with telecommunication optical fibers, are used to herald the creation of the signal photons, compatible with the Pr3þ transition. The signal photons are stored and retrieved using the atomic frequency comb protocol. We demonstrate storage times up to 4.5 μs while preserving nonclassical correlations between the heralding and the retrieved photon. This is more than 20 times longer than in previous realizations in solid state devices, and implemented in a system ideally suited for the extension to spin-wave storage

Photonic quantum state transfer between a cold atomic gas and a crystal

Interfacing fundamentally different quantum systems is key to build future hybrid quantum networks. Such heterogeneous networks offer superior capabilities compared to their homogeneous counterparts as they merge individual advantages of disparate quantum nodes in a single network architecture. However, only very few investigations on optical hybrid-interconnections have been carried out due to the high fundamental and technological challenges, which involve e.g. wavelength and bandwidth matching of the interfacing photons. Here we report the first optical quantum interconnection between two disparate matter quantum systems with photon storage capabilities. We show that a quantum state can be faithfully transferred between a cold atomic ensemble and a rare-earth doped crystal via a single photon at telecommunication wavelength, using cascaded quantum frequency conversion. We first demonstrate that quantum correlations between a photon and a single collective spin excitation in the cold atomic ensemble can be transferred onto the solid-state system. We also show that single-photon time-bin qubits generated in the cold atomic ensemble can be converted, stored and retrieved from the crystal with a conditional qubit fidelity of more than $85\%$. Our results open prospects to optically connect quantum nodes with different capabilities and represent an important step towards the realization of large-scale hybrid quantum networks

Low-frequency noise behavior at reverse bias region in InAs/GaSb superlattice photodiodes on mid-wave infrared

We describe a relationship between the noise characterization and activation energy of InAs/GaSb superlattice Mid- Wavelength-Infrared photodiodes for different passivation materials applied to the device. The noise measurements exhibited a frequency dependent plateau (i.e. 1/f-noise characteristic) for unpassivated as well as Si3N4 passivated samples whereas 1/f-type low noise suppression (i.e. frequency independent plateau) with a noise current reduction of more than one order of magnitude was observed for SiO2 passivation. For reverse bias values below -0.15V, the classical Schottky-noise calculation alone did not appear to describe the noise mechanism in a SL noise behavior, which shows a divergence between theoretically and experimentally determined noise values. We identify that, the additional noise appears, with and without passivation, at the surface activation energy of < 60 meV and is inversely proportional to the reverse bias. This is believed to be caused by the surface dangling-bonds (as well as surface states) whose response is controlled by the applied reverse bias. The calculated noise characteristics showed a good agreement with the experimental data. © 2013 SPIE

Surgical Recovery of Intestinal Obstructions: Pre- and Postoperative Care and How Could it Be Prevented?

Although initial data on intestinal obstructions are based on Hippocrates, there is still no consensus on approaches today. However, parallel to the development of medical technology and the increasing experience of us surgeons, morbidity and mortality rates due to intestinal obstruction have decreased. Obstruction can occur at any point in the gastrointestinal tract. The main thing is to make a correct diagnosis and to treat the patient in the most correct way. Intestinal obstructions usually present with colic abdominal pain, nausea, vomiting, and constipation. Intestinal obstructions may be present due to various reasons. Surgeons have an important role in preventive mechanical obstructions due to adhesions. Patients must be hospitalized. If there is no emergency surgical indication, conservative methods can be applied. Patients should be mobilized early, and fluid-electrolyte balance should be adjusted and followed closely