Papers by Marco Koschorreck
Bulletin of the American Physical Society, 2016
The subtle interplay between kinetic energy, interactions and dimensionality challenges our compr... more The subtle interplay between kinetic energy, interactions and dimensionality challenges our comprehension of strongly-correlated physics observed, for example, in the solid state. In this quest, the Hubbard model has emerged as a conceptually simple, yet rich model describing such physics. Here we present an experimental determination of the equation of state of the repulsive two-dimensional Hubbard model over a broad range of interactions, 0 ≤ U/t ≤ 20, and temperatures, down to k B T /t = 0.63(2) using high-resolution imaging of ultracold fermionic atoms in optical lattices. We show density profiles, compressibilities and double occupancies over the whole doping range, and hence our results constitute benchmarks for state-of-the-art theoretical approaches.
Tunable light-matter interactions with cold ensembles
2008 Conference on Lasers and Electro-Optics and 2008 Conference on Quantum Electronics and Laser Science, 2008
Effective interactions between a cold atomic ensemble and probe light can take the ldquoQND,rdquo... more Effective interactions between a cold atomic ensemble and probe light can take the ldquoQND,rdquo ldquobeamsplitter,rdquo and ldquotwo-mode squeezingrdquo forms, useful for quantum cloning and memory. We describe experiments with dipole-trapped 87Rb using these interactions.
Cold atomic ensembles for quantum interfaces: new interactions
Quantum-Atom Optics Downunder, 2007
ABSTRACT Cold, trapped atomic ensembles present new opportunities for light-matter interfaces, in... more ABSTRACT Cold, trapped atomic ensembles present new opportunities for light-matter interfaces, including tomographic measurements and new interactions. The tensor polarizability can be exploited to produce interactions useful for spin squeezing, measurement of atom number, and quantum cloning of light into matter. We describe experiments in a cold ensemble of dipole-trapped 87Rb to produce spin squeezing by quantum non-demolition measurement.
Better-than-Heisenberg scaling of sensitivity with light and cold atomic ensembles
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009
This work considers an atom-light interface consisting of pulses of polarized light that interact... more This work considers an atom-light interface consisting of pulses of polarized light that interacts with an ensemble of 106 cold 87Rb in dipole trap. Measurements of polarization changes in the light is used in probing the atomic state. In such polarization-based atom-light interface, a Hamiltonian nonlinear in the Stokes operators can be produced through optical nonlinearities. This work investigates the application of light and cold atomic ensembles to precision measurements with better-than-Heisenberg scaling. The effective nonlinear polarizability of atoms due to ns-duration illumination pulses and the resulting polarization rotation are also calculated in detail.
Ultrafast relaxation processes in organic molecular crystals of MePTCDI and PTCDA
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference and Photonic Applications Systems Technologies, 2004
ABSTRACT We observe a sub-30-fs intra-band relaxation in MePTCDI by pump-probe spectroscopy of th... more ABSTRACT We observe a sub-30-fs intra-band relaxation in MePTCDI by pump-probe spectroscopy of the excited state absorption. Furthermore, fluorescence and polarization anisotropies are determined to understand energy transfer processes between different molecules
Experimental light-squeezing-enhanced magnetometry
2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC), 2011
ABSTRACT We demonstrate a light-shot-noise-limited magnetometer based on the Faraday effect in a ... more ABSTRACT We demonstrate a light-shot-noise-limited magnetometer based on the Faraday effect in a hot unpolarized ensemble of rubidium atoms. By using off-resonant, polarization-squeezed probe light, we improve the sensitivity of the magnetometer by 3.2 dB.
Quantum Optics and the “Heisenberg Limit” of Measurement
Optics and Photonics News, 2011
Exciting work is being done in quantum information theory and the detection of low light levels.
Quantum-Light-Enhanced Optical Magnetometry
CLEO:2011 - Laser Applications to Photonic Applications, 2011
We demonstrate a lightshotnoiselimited magneto meter based on the Faraday effect in a hot unpolar... more We demonstrate a lightshotnoiselimited magneto meter based on the Faraday effect in a hot unpolarized ensemble of rubidium atoms. By using offresonant, polarizationsqueezed probe light, we improve the sensitivity of the magnetometer by 3.2 dB. ©2010 Optical Society of America OCIS codes: (270.0270) Quantum optics; (270.6570) Squeezed states.
Spin squeezing experiments in a cold ensemble of <sup>87</sup>Rb
2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
ABSTRACT Spin squeezed states can be used to improve the performance of atomic clocks and magneto... more ABSTRACT Spin squeezed states can be used to improve the performance of atomic clocks and magnetometers. Recently, atom-light interaction of a similar type has also been used to demonstrate quantum memory and quantum teleportation between light and matter. Furthermore, this interaction facilitates studies in the field of controlled quantum dynamics.
Quantum gases of interacting fermionic atoms in optical lattices promise to shed new light on the... more Quantum gases of interacting fermionic atoms in optical lattices promise to shed new light on the low-temperature phases of Hubbard-type models, such as spin-ordered phases or, in particular, on possible d-wave superconductivity. However, reaching the very low temperatures required necessitates the implementation of novel cooling schemes. As a first step towards this goal, we employ high-resolution imaging together with radio-frequency spectroscopy in order to spatially resolve the in-trap distributions of singly and doubly-occupied lattice sites after having loaded a quantum degenerate two-component Fermi gas of 40 K atoms into a three-dimensional optical lattice geometry. Here, I will report on our recent progress towards the observation and characterization of a fermionic Mott insulator, together with an outlook on future steps towards lowering the temperature in the lattice.
At the beginning of the 20th century measurement precision was related exclusively to the capabil... more At the beginning of the 20th century measurement precision was related exclusively to the capabilities of the experimenter and the apparatus. Any imprecision was attributed to imperfect devices for the measurement. Later on, when the quantumness of objects like photons, electrons, or atoms, was recognized, it became clear that the measurement and the object to be measured could no longer be separated. Both en un 3 dB, donde se mejora la sensibilidad metrológica en un 2 dB por encima del límite cuántico estándar de un estado de spin coherente. Abordamos la cuestión de cómo heterogeneidades espaciales y temporales tanto en la luz como en los átomos influyen en la preparación de los estados no-clásicos. Un método de la matriz de covarianza existente se amplió y aplicó al estudio de los efectos de la resolución del detector en tiempo, heterogeneidades espaciales y del movimiento atómico.
EPJ Web of Conferences, 2013
Quantum metrology uses quantum features such as entanglement and squeezing to improve the sensiti... more Quantum metrology uses quantum features such as entanglement and squeezing to improve the sensitivity of quantum-limited measurements. Long established as a valuable technique in optical measurements such as gravitational-wave detection, quantum metrology is increasingly being applied to atomic instruments such as matter-wave interferometers, atomic clocks, and atomic magnetometers. Several of these new applications involve dual optical/atomic quantum systems, presenting both new challenges and new opportunities. Here we describe an optical magnetometry system that achieves both shot-noise-limited and projectionnoise-limited performance, allowing study of optical magnetometry in a fully-quantum regime [1]. By near-resonant Faraday rotation probing, we demonstrate measurement-based spin squeezing in a magnetically-sensitive atomic ensemble [2-4]. The versatility of this system allows us also to design metrologically-relevant optical nonlinearities, and to perform quantum-noise-limited measurements with interacting photons. As a first interaction-based measurement [5], we implement a non-linear metrology scheme proposed by Boixo et al. with the surprising feature of precision scaling better than the 1/N "Heisenberg limit" [6].
Ultra-Sensitive Faraday Rotation Measurements from an Atom-Light Quantum Interface
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
Atomic ensembles have gained a lot of interest in the last decade for their prospective use as qu... more Atomic ensembles have gained a lot of interest in the last decade for their prospective use as quantum memories, in precision measurements and other applications in quantum information processing. The atomic part of the interface presented here is an all-optically trapped atomic ensemble of 87Rb at a temperature of 25 muK. The ensemble consists of 106 atoms and has an elongated shape with an aspect ratio of about 250:1. The resonant optical depth is around 50. The light part is an off-resonant polarized laser beam which dispersively probes the atomic state. The detection is a shot-noise limited polarization measurement of light pulses of a few mus and 3 x 105 photons.
Conference on Lasers and Electro-Optics 2012, 2012
We demonstrate spin squeezing and entanglement in a large-spin system via quantum nondemolition m... more We demonstrate spin squeezing and entanglement in a large-spin system via quantum nondemolition measurement. We make non-destructive, projection-noise-limited collective spin measurements on an ensemble of up to in 8.4 × 10 5 laser-cooled 87 Rb atoms in the f = 1 hyperfine ground state. A dynamically-decoupled probing scheme [Phys. Rev. Lett. 105, 093602 (2010)] prevents probe-induced decoherence, and techniques for compensation of magnetic field gradients [APL 98, 074101, (2011)] extend the lifetime of the coherent spin state to 290 µs. Repeated measurements show correlations beyond the standard quantum limit, indicating generation of a spin-squeezed state with up to −3.2 dB of noise reduction and −1.8 dB of metrologically-relevant squeezing.
Spin Squeezing of Large-Spin Ensembles via Quantum Non-demolition Measurement
Research in Optical Sciences, 2012
ABSTRACT We report the first demonstration of spin squeezing of a large-spin system via quantum n... more ABSTRACT We report the first demonstration of spin squeezing of a large-spin system via quantum non-demolition (QND) measurement. We observe 2 dB of metrological squeezing in an ensemble of ∼ 106 laser cooled 87Rb atoms in the F = 1 hyperfine ground state.
Quantum-Enhanced Measurements of Atomic Spin
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
Abstract We use narrow-band quantum light sources, tuned to the rubidium D1 resonance, to produce... more Abstract We use narrow-band quantum light sources, tuned to the rubidium D1 resonance, to produce polarization-squeezed and polarization-NooN states for Heisenberg-limited measurements on atoms. By paramagnetic Faraday rotation these states measure the ...
Spin Squeezing via Quantum Non-Demolition Measurements in Cold 87Rb Atomic Ensemble
Conference on Lasers and Electro-Optics 2010, 2010
... M. Koschorreck, M. Napolitano, B. Dubost, N. Behbood, R. Sewell, MW Mitchell ICFO-Institut de... more ... M. Koschorreck, M. Napolitano, B. Dubost, N. Behbood, R. Sewell, MW Mitchell ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain marco.koschorreck@icfo.es Abstract: We demonstrate spin ... OSA / CLEO/QELS 2010 ...
We report on an experiment for generating singlet states in a cold atomic ensemble. We use quantu... more We report on an experiment for generating singlet states in a cold atomic ensemble. We use quantum non-demolition measurement and feedback control to produce a macroscopic spin state with total spin zero and reduced spin fluctuations.
Spectroscopy on high-density mesoscopic atom samples
2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
In this paper trap-state spectroscopy on dense, cold optically trapped, micron sized atom clouds ... more In this paper trap-state spectroscopy on dense, cold optically trapped, micron sized atom clouds is performed and compared the results with model calculations based on a non-interacting, thermal Bose-gas confined in an anisotropic, 3-dimensional, Gaussian potential.
Inhomogeneities in atom-light interfaces and spin squeezing dynamics
2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
ABSTRACT This article proposes a model that provides important insights into the effect of inhomo... more ABSTRACT This article proposes a model that provides important insights into the effect of inhomogeneities in atom-light interactions. This model is able to handle all different kinds of inhomogeneities. Moreover, it simulates the influence of imperfect temporal detector resolution.
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Papers by Marco Koschorreck