We demonstrate a light-shot-noise-limited magnetometer based on the Faraday effect in hot unpolarized ensemble of rubidium atoms. By using off-resonant, polarization-squeezed probe light, we improve sensitivity by 3.2 dB. The technique could most advanced magnetometers and quantum nondemolition measurements atomic spin ensembles.

The strong confinement of semiconductor excitons in a quantum dot gives rise to atom-like behavior. full benefit such structure is best observed resonant excitation where the excited state can be deterministically populated and coherently manipulated. Due large refractive index device geometry it remains challenging observe resonantly emission that free from laser scattering III/V self-assembled dots. Here we exploit biexciton binding energy create an extremely clean single photon source via...

In this Letter, we present entanglement generated from a novel structure: single InAsP quantum dot embedded in an InP nanowire. These structures can grow site-controlled way and exhibit high collection efficiency; detect 0.5 million biexciton counts per second coupled into mode fiber with standard commercial avalanche photo diode. If correct for the known setup losses detector efficiency, get extraction efficiency of 15(3) %. For measured polarization entanglement, observe fidelity 0.76(2)...

The quantification of the entanglement present in a physical system is paramount importance for fundamental research and many cutting-edge applications. Now, achieving this goal requires either priori knowledge on or very demanding experimental procedures such as full state tomography collective measurements. Here, we demonstrate that, by using neural networks, can quantify degree without need to know description quantum state. Our method allows direct correlations an incomplete set local...

Emitter dephasing is one of the key issues in performance solid-state single-photon sources. Among various sources dephasing, acoustic phonons play a central role adding decoherence to emission. Here, we demonstrate that it possible tune and engineer coherence photons emitted from single WSe2 monolayer quantum dot via selectively coupling spectral cavity resonance. We utilize an open enhancement, leveling, suppression highly asymmetric phonon sideband, finding excellent agreement with...

We demonstrate a high-brightness source of pairs indistinguishable photons based on type-II phase-matched doubly-resonant optical parametric oscillator operated far below threshold. The cavity-enhanced down-conversion output PPKTP crystal is coupled into two single-mode fibers with mode coupling efficiency 58%. high degree indistinguishability between the pair demonstrated by Hong-Ou-Mandel interference visibility higher than 90% without any filtering at an instantaneous coincidence rate 450...

We introduce and experimentally explore the concept of quantum non-Gaussian depth single-photon states with a positive Wigner function. The measures robustness state against optical losses. directly witnessed non-Gaussianity withstands significant attenuation, exhibiting 18 dB, while nonclassicality remains unchanged. Quantum is an approachable quantity that much more robust than negativity Furthermore, we use it to reveal differences between otherwise strongly nonclassical sources.

A hyperentangled state of light represents a valuable tool capable reducing the experimental requirements and resource overheads, it can improve success rate quantum information protocols. Here, we report on demonstration polarization time-bin photon pairs emitted from single dot. We achieved this result by applying resonant coherent excitation dot system with marginal fine structure splitting. Our results yield fidelities to maximally entangled 0.81(6) 0.87(4) in time bin, respectively.

The generation of photon pairs in single quantum dots is based on a process that is, its nature, deterministic. However, an efficient extraction these from high-index semiconductor host material requires engineering the photonic environment. We report micropillar-based device featuring efficiency 69.4(10)$\%$ achieved by harnessing broadband operation suitable for emitted dot. Opposing approaches rely solely Purcell enhancement to realize efficiency, our solution exploits suppression...

We demonstrate a tunable narrowband filter based on optical-pumping-induced circular dichroism in rubidium vapor. The achieves peak transmission of 14.6%, linewidth 80 MHz, and an out-of-band extinction ⩾35 dB. can be tuned within the range Doppler D1 line atomic at 795 nm. While other filters work frequencies far from absorption, presented technique provides light resonant with media, useful for atom-photon interaction experiments. could readily extended to alkali atoms.

The development of linear quantum computing within integrated circuits demands high quality semiconductor single photon sources. In particular, for a reliable source it is not sufficient to have low multi-photon component, but also possess efficiency. We investigate the statistics emission from dot with method that able sensitively detect trade-off between efficiency and contribution. Our measurements show, light emitted when resonantly excited very content. Additionally, we demonstrated,...

Abstract Producing advanced quantum states of light is a priority in information technologies. In this context, experimental realizations multipartite photon would enable improved tests the foundations mechanics as well implementations complex optical networks and protocols. It favourable to directly generate these using solid state systems, for simpler handling promise reversible transfer between stationary flying qubits. Here we use ground two optically active coupled dots produce...

Two-photon interference is an indispensable resource in quantum photonics, but it not straightforward to achieve. The cascaded generation of photon pairs contains intrinsic temporal correlations that negatively affect the ability such sources perform two-photon interference, thus hindering applications. We report on how correlation interplays with decoherence and postselection, under which conditions postselection could improve visibility. Our study identifies crucial parameters points way a...

Photonic quantum information experiments demand bright and highly entangled photon pair sources. The combination of periodic poling collinear excitation geometry allows the use considerably longer crystals for parametric down-conversion. We demonstrate a picosecond-pulsed laser pumped source high quality polarization pairs. phase output biphoton state is affected by relative two-color interferometer nonlinearly interacting Gaussian beams. measure influence these onto state. presented...

We report on the generation of time-bin entangled photon pairs from a semiconductor quantum dot via pulsed resonant biexciton generation. Based theoretical modeling we optimized duration excitation pulse to minimize laser-induced dephasing and increase biexciton-to-background single exciton occupation probability. This results in high degree entanglement with concurrence up 0.78(6) 0.88(3) overlap maximally state. Theoretical simulations also indicate power dependent nature during laser that...

Device-independent quantum key distribution (DI-QKD) offers the strongest form of security against eavesdroppers bounded by laws mechanics. However, a practical implementation is still pending due to requirement combinations visibility and detection efficiency that are beyond those possible with current technology. This mismatch motivates search for DI-QKD protocols can close gap between theoretical security. In this work, we present two whose relies on Bell inequalities more than inputs...

We propose a scheme to dissipatively produce steady-state entanglement in two-qubit system, via an interaction with bosonic mode. The system is driven into stationary entangled state, while we compensate the mode dissipation by injecting energy coherent pump field. also present which allows us adiabatically transfer all population desired state. dynamics leading state these schemes can be understood analogy electromagnetically induced transparency and stimulated Raman adiabatic passage, respectively.

Two fundamental quantum resources, nonlocality and contextuality, can be connected through Bell inequalities that are violated by state-independent contextuality (SI-C) sets. These allow for applications require simultaneous contextuality. However, existing inequalities, the produced SI-C sets is very sensitive to noise. This precludes experimental implementation. Here we identify which optimal, i.e., maximally robust either noise or detection inefficiency, simplest [S. Yu C. H. Oh, Phys....

We demonstrate a diode-laser-pumped system for generation of quadrature squeezing and polarization squeezing. Due to their excess phase noise, diode lasers are challenging use in phase-sensitive quantum optics experiments such as The we present overcomes the noise laser through combination active stabilization appropriate delays local oscillator beam. generated light is resonant rubidium $D1$ transition at $795\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ thus can be readily used memory experiments.

Photons which are generated in a two-photon cascade process have an underlying time correlation since the spontaneous emission of upper level populates intermediate state. This leads to reduction purity photon emitted from Here we characterize this for biexciton-exciton InAs/GaAs quantum dot. We show that can be reduced by tuning biexciton transition resonance planar distributed Bragg reflector cavity. The enhanced and inhibited into cavity accelerates slows down exciton thus reduces...

In this paper, we present a detailed, all optical study of the influence different excitation schemes on indistinguishability single photons from InAs quantum dot. For study, measure Hong–Ou–Mandel interference consecutive spontaneous emission an dot state under various and conditions give comparison.

We study the optical properties of coupled quantum dot-microcavity systems with elliptical cross section. First, we develop an analytic model that describes spectrum cavity modes are split due to reduced symmetry resonator. By coupling QD emission polarized fundamental modes, observe vectorial nature Purcell enhancement, which depends on intrinsic polarization dot and its relative alignment respect axis. The variable interaction strength leads observation strong weak coupling. Finally,...