18 research outputs found
Integrated AlGaAs source of highly indistinguishable and energy-time entangled photons
The generation of nonclassical states of light in miniature chips is a
crucial step towards practical implementations of future quantum technologies.
Semiconductor materials are ideal to achieve extremely compact and massively
parallel systems and several platforms are currently under development. In this
context, spontaneous parametric down conversion in AlGaAs devices combines the
advantages of room temperature operation, possibility of electrical injection
and emission in the telecom band. Here we report on a chip-based AlGaAs source,
producing indistinguishable and energy-time entangled photons with a brightness
of pairs/s and a signal-to-noise ratio of .
Indistinguishability between the photons is demonstrated via a Hong-Ou-Mandel
experiment with a visibility of , while energy-time entanglement is
tested via a Franson interferometer leading to a value for the Bell parameter
High-detection efficiency and low-timing jitter with amorphous superconducting nanowire single-photon detectors
Recent progress in the development of superconducting nanowire single-photon
detectors (SNSPDs) made of amorphous material has delivered excellent
performances, and has had a great impact on a range of research fields. Despite
showing the highest system detection efficiency (SDE) ever reported with
SNSPDs, amorphous materials typically lead to lower critical currents, which
impacts on their jitter performance. Combining a very low jitter and a high SDE
remains a challenge. Here, we report on highly efficient superconducting
nanowire single-photon detectors based on amorphous MoSi, combining system
jitters as low as 26 ps and a SDE of 80% at 1550 nm. We also report detailed
observations on the jitter behaviour, which hints at intrinsic limitations and
leads to practical implications for SNSPD performance
Dispositifs photoniques en AlGaAs : de la génération d'etats quantiques aux communications quantiques
Un des plus grands challenges dans le domaine de lâinformation quantique est la gĂ©nĂ©ration, manipulation et dĂ©tection de plusieurs qubits sur des micro-puces. On assiste ainsi Ă un vĂ©ritable essor des technologies pour lâinformation quantique et pour transmettre lâinformation, les photons ont un grand avantage sur les autres systĂšmes, grĂące Ă leur grande vitesse et leur immunitĂ© contre la dĂ©cohĂ©rence.Mon travail de thĂšse porte sur la conception, fabrication et caractĂ©risation dâune source de photons intriquĂ©s en matĂ©riaux semiconducteurs dâune trĂšs grande compacitĂ©. Ce dispositif fonctionne Ă tempĂ©rature ambiante, et Ă©met dans la bande de longueurs dâonde tĂ©lĂ©com. AprĂšs une prĂ©sentation des concepts fondamentaux (chap. 1), le chap. 2 explique la conception et la fabrication des dispositifs.Le chap. 3 prĂ©sente les caractĂ©risations opto-Ă©lectroniques des Ă©chantillons pompĂ©s Ă©lectriquement, et le chap. 4 les rĂ©sultats des mesures de pertes et des caractĂ©risations non-linĂ©aires optiques (gĂ©nĂ©ration de seconde harmonique, conversion paramĂ©trique spontanĂ©e et reconstruction de lâintensitĂ© spectrale jointe). Les chap. 5 et 6 se concentrent sur la caractĂ©risation des Ă©tats quantiques gĂ©nĂ©rĂ©s par un dispositif passif (dĂ©monstration de lâindiscernabilitĂ© et de lâintrication en Ă©nergie-temps) et leur utilisation dans un protocole de distribution de clĂ©s quantiques multi-utilisateurs (intrication en polarisation). Finalement le travail sur le premier dispositif produisant des pairs de photons dansles longueurs dâonde tĂ©lĂ©coms, injectĂ© Ă©lectriquement et fonctionnant Ă tempĂ©rature ambiante est prĂ©sentĂ© (chap. 7).One of the main issues in the domain of quantum information and communication is the generation,manipulation and detection of several qubits on a single chip. Several approaches are currentlyinvestigated for the implementation of qubits on different types of physical supports and a varietyof quantum information technologies are under development: for quantum memories, spectacularadvances have been done on trapped atoms and ions, while to transmit information, photons arethe ideal support thanks to their high speed of propagation and their almost immunity againstdecoherence. My thesis work has been focused on the conception, fabrication and characterization ofa miniaturized semiconductor source of entangled photons, working at room temperature and telecomwavelengths. First the theoretical concepts relevant to understand the work are described (chapter1). Then the conception and fabrication procedures are given (chapter 2). Chapter 3 presents theoptoelectronics characterization of the device under electrical pumping, and chapter 4 the resultson the optical losses measurements and the nonlinear optical characterization (second harmonicgeneration, spontaneous parametric down conversion and joint spectral intensity reconstruction).Chapters 5 and 6 focus on the characterization of the quantum state generated by a passive sample(demonstration of indistinguishability and energy-time entanglement) and its utilization in a multiuserquantum key distribution protocol (polarization entanglement). Finally the work on the firstelectrically driven photon pairs source emitting in the telecom range and working at room temperatureis presented (chapter 7)
Dispositifs photoniques en AlGaAs : de la génération d'états quantiques aux communications quantiques
One of the main issues in the domain of quantum information and communication is the generation, manipulation and detection of several qubits on a single chip. Several approaches are currently investigated for the implementation of qubits on different types of physical supports and a variety of quantum information technologies are under development: for quantum memories, spectacular advances have been done on trapped atoms and ions, while to transmit information, photons are the ideal support thanks to their high speed of propagation and their almost immunity against decoherence. My thesis work has been focused on the conception, fabrication and characterization of a miniaturized semiconductor source of entangled photons, working at room temperature and telecom wavelengths. First the theoretical concepts relevant to understand the work are described (chapter 1). Then the conception and fabrication procedures are given (chapter 2). Chapter 3 presents the optoelectronics characterization of the device under electrical pumping, and chapter 4 the results on the optical losses measurements and the nonlinear optical characterization (second harmonic generation, spontaneous parametric down conversion and joint spectral intensity reconstruction). Chapters 5 and 6 focus on the characterization of the quantum state generated by a passive sample (demonstration of indistinguishability and energy-time entanglement) and its utilization in a multi- user quantum key distribution protocol (polarization entanglement). Finally the work on the first electrically driven photon pairs source emitting in the telecom range and working at room temperature is presented (chapter 7).Un des plus grands challenges dans le domaine de lâinformation quantique est la geÌneÌration, manipulation et deÌtection de plusieurs qubits sur des micro-puces. On assiste ainsi aÌ un veÌritable essor des technologies pour lâinformation quantique et pour transmettre lâinformation, les photons ont un grand avantage sur les autres systeÌmes, graÌce aÌ leur grande vitesse et leur immuniteÌ contre la deÌcoheÌrence. Mon travail de theÌse porte sur la conception, fabrication et caracteÌrisation dâune source de photons intriqueÌs en mateÌriaux semiconducteurs dâune treÌs grande compaciteÌ. Ce dispositif fonctionne aÌ tempeÌrature ambiante, et eÌmet dans la bande de longueurs dâonde teÌleÌcom. ApreÌs une preÌsentation des concepts fondamentaux (chap. 1), le chap. 2 explique la conception et la fabrication des dispositifs. Le chap. 3 preÌsente les caracteÌrisations opto-eÌlectroniques des eÌchantillons pompeÌs eÌlectriquement, et le chap. 4 les reÌsultats des mesures de pertes et des caracteÌrisations non-lineÌaires optiques (geÌneÌration de seconde harmonique, conversion parameÌtrique spontaneÌe et reconstruction de lâintensiteÌ spectrale jointe). Les chap. 5 et 6 se concentrent sur la caracteÌrisation des eÌtats quantiques geÌneÌreÌs par un dispositif passif (deÌmonstration de lâindiscernabiliteÌ et de lâintrication en eÌnergie-temps) et leur utilisation dans un protocole de distribution de cleÌs quantiques multi-utilisateurs (intrication en polarisation). Finalement le travail sur le premier dispositif produisant des pairs de photons dans les longueurs dâonde teÌleÌcoms, injecteÌ eÌlectriquement et fonctionnant aÌ tempeÌrature ambiante est preÌsenteÌ (chap. 7)
Direct measurement of the recovery time of superconducting nanowire single-photon detectors
One of the key properties of single-photon detectors is their recovery time, i.e. the time required for the detector to recover its nominal efficiency. In the case of superconducting nanowire single-photon detectors (SNSPDs), which can feature extremely short recovery times in free-running mode, a precise characterization of this recovery time and its time dynamics is essential for many quantum optics or quantum communication experiments. We introduce a fast and simple method to characterize precisely the recovery time of SNSPDs. It provides full information about the recovery of the efficiency in time for a single or several consecutive detections. We also show how the method can be used to gain insight into the behavior of the bias current inside the nanowire after a detection, which allows predicting the behavior of the detector and its efficiency in any practical experiment using these detectors
Operation of parallel SNSPDs at high detection rates
Recent progress in the development of superconducting nanowire single-photon detectors (SNSPD) has delivered excellent performance, and their increased adoption has had a great impact on a range of applications. One of the key characteristic of SNSPDs is their detection rate, which is typically higher than other types of free-running single-photon detectors. The maximum achievable rate is limited by the detector recovery time after a detection, which itself is linked to the superconducting material properties and to the geometry of the meandered SNSPD. Arrays of detectors biased individually can be used to solve this issue, but this approach significantly increases both the thermal load in the cryostat and the need for time processing of the many signals, and this scales unfavorably with a large number of detectors. One potential scalable approach to increase the detection rate of individual detectors further is based on parallelizing smaller meander sections. In this way, a single detection temporarily disables only one subsection of the whole active area, thereby leaving the overall detection efficiency mostly unaffected. In practice however, cross-talk between parallel nanowires typically leads to latching, which prevents high detection rates. Here we show how this problem can be avoided through a careful design of the whole SNSPD structure. Using the same electronic readout as with conventional SNSPDs and a single coaxial line, we demonstrate detection rates over 200 MHz without any latching, and a fibre-coupled SDE as high as 77%, and more than 50% average SDE per photon at 50 MHz detection rate under continuous wave illumination
High-rate photon pairs and sequential Time-Bin entanglement with Si<sub>3</sub>N<sub>4</sub> microring resonators
Integrated photonics is increasing in importance for compact, robust, and scalable enabling quantum technologies. This is particularly interesting for developing quantum communication networks, where resources need to be deployed in the field. We exploit photonic chip-based Si3N4 microring resonators to realise a photon pair source with low-loss, high-noise suppression and coincidence rates of 80Ă103 sâ1. A simple photonic noise characterisation technique is presented that distinguishes linear and nonlinear contributions useful for system design and optimisation. We then demonstrate an all-fiber 750 MHz clock-rate sequential Time-Bin entanglement scheme with raw interference visibilities > 98 %