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Optical microtraps provide a strong spatial confinement for laser-cooled atoms. They can, e.g., be realized with strongly focused trapping light beams or the optical near fields of nano-scale waveguides and photonic nanostructures. Atoms in such traps often experience strongly spatially varying AC Stark shifts which are proportional to the magnetic quantum number of the respective energy level. These...
Reversible light-matter interfaces are crucial elements in quantum optics and quantum information networks. In particular, the coupling of one-dimensional bosonic nanoscale waveguides and cold atoms appears as a promising pathway to build strong light-matter interaction thanks to the tight transverse confinement of light.
One efficient approach for generating single photons is based on using a two-level atom, which inherently cannot emit more than one photon at the time. As early as the 1980s, this quantum feature was identified as the gateway to creating single photon sources (SPS's), where a regular excitation sequence would produce a stream of photons with photon number fluctuations below the shot noise. Such an...
Neutral atoms trapped inside an optical cavity provide an ideal platform for the implementation of quantum networks [1]. In such a network, nodes containing multiple atomic qubits are essential for the construction of a quantum repeater as they allow for entanglement swapping and thus the generation of entanglement between qubits over long distances. Here we will show the realisation of such a multi-qubit...
Achieving photon-photon interactions is one of the main objectives of the quantum information technology community, since these interactions provide the basis for deterministic quantum gates with high fidelity. In the last few years new milestones in creating phase-shifts [1] and quantum gates[2] have been achieved. Researching resource-moderate experimental realizations for the future development...
Complete control of individual atoms trapped in far-off resonance optical tweezers is vital for gaining a better understanding of the microscopic world. It will provide a platform with unprecedented flexibility for studying few-body physics, and might lead to new quantum technologies.
The remarkably-high intrinsic optical nonlinearity of graphene can be pushed even further when the optical frequency is tuned to plasmon resonances hosted by the material when it is doped [1-4]. Atomistic simulations provide an accurate description of these phenomena, although their computational cost is prohibitive for large graphene nanostructures [3, 4]. An alternative formalism consists in relying...
For memory applications and optical control of qubits ultrafast manipulation and high coupling efficiencies are desirable. Ultrafast coherent control can be achieved by the off-resonant Raman scheme [1]. There exist several colour centres with an optically accessible lambda-type energy structure which offer a level splitting large enough for broadband laser pulses.
Strong interaction between two single photons [1], is a long standing and important goal in quantum photonics. This would enable a new regime of nonlinear optics and unlock several applications in quantum information science, including photon-photon gates and deterministic Bell-state measurements for quantum networking. In the context of quantum networks [2], a particularly important case is to achieve...
Controlling the interaction of light and matter is the basis for diverse applications ranging from light technology to quantum information processing. Nowadays, many of these applications are based on nanophotonic structures. It turns out that the confinement of light in such nanostructures imposes an inherent link between its local polarization and its propagation direction, also referred to as spin-momentum...
Entangled photon pair is key factor for realization of quantum communication, quantum information, etc. For long distance quantum communication, it is necessary to generate narrow band biphoton for interaction with atomic based quantum memory. In recent years, generation of time-frequency entangled photon pairs based on spontaneous four-wave mixing (SFWM) process in atomic ensemble have been reported...
Optical vortex or orbital angular momentum (OAM) of light are a subject of active research and have been employed for novel applications such as optical manipulation, quantum information and control of cold atoms [1]. For decades, it has been discussed if OAM of light could affect the state of a bound system of charges such as an atom or a molecule, an exchange should arise between light and matter,...
In this work, we present a model that describes the atomic reaction to a periodic excitation in a general case. Starting with a holeburning material, we aim at computing the steady state of the atoms of interest within the whole bulk material. This work is composed of three steps. In the first one, we generalize the optical Bloch equations to any atomic structure, keeping as long as possible the Bloch...
Reliable long-term operation of integrated quantum sensors employing atom interferometry in space imposes challenging requirements on the utilized technology and materials. In the last decade, the progress in miniaturization of each experimental subsystem (e.g., vacuum chamber with atom source, laser system and optics) greatly benefited from atom chip technology [1], micro integrated diode laser modules...
Quantum memories for light are important resources as quantum interfaces between light and matter in future quantum information networks. In particular, solid state optical memories based on rare earth ion doped (REID) crystals are of great interest due to their unique physical properties. They provide large number of atoms naturally trapped in a solid with narrow optical and spin transitions. They...
In our experiments, we generate arrays of up to 50 optical tweezers arranged in arbitrary two-dimensional geometries, each containing a single cold atom, and separated by distances of a few micrometers (Fig. 1). This is achieved by active sorting of atoms in larger arrays that are initially loaded stochastically [1]. By exciting the atoms to Rydberg states (with principal quantum numbers in the range...
Integrated optical circuits for information processing promise to outperform their electronic counterparts in terms of bandwidth and energy consumption. However, such circuits require components that control the flow of light. In our group we employ micro- and nanophotonic components such as optical nanofibers to confine light at the wavelength scale and to control its flow in integrated optical environments...
The development of atom interferometry in the last few decades has led to high precision measurements of inertial effects and tests of fundamental physics [1]. New methods for higher sensitivity atom interferometers (AIs) are being explored, in particular the interrogation of atoms with optical cavities. The benefits of optical cavities would be higher optical power allowing large momentum transfer...
Quantum storage of flying optical qubits, namely coherently mapping photonic states into and out of an optically controlled memory on demand, constitutes an essential component in the optical quantum information processing science, with applications to long-distance optical communication [1]. In this context, practical protocols require sufficiently large storage efficiency to achieve a performance...
Quantum memories are very important in quantum communication and information as they provide a quantum interface between photons, used for long distance communication, and matter, in which stationary qubits can be stored. Moreover they are fundamental building blocks in quantum repeaters. Rare-earth doped crystals (REDC) are promising candidates for the implementation of quantum memories because of...
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