A5043245879- Quantum optics and atomic interactions
- Quantum Information and Cryptography
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Subatomic Physics Research
- Quantum Mechanics and Applications
- Advanced Frequency and Time Standards
- Mechanical and Optical Resonators
- Photonic and Optical Devices
- Spectroscopy and Quantum Chemical Studies
- Random lasers and scattering media
- Quantum Computing Algorithms and Architecture
- Advanced Fiber Optic Sensors
- Ultrasound and Cavitation Phenomena
- Quantum and electron transport phenomena
- Photonic Crystal and Fiber Optics
- Advanced MEMS and NEMS Technologies
- Electrostatics and Colloid Interactions
- Microfluidic and Bio-sensing Technologies
- Advanced Optical Sensing Technologies
- Optical Coherence Tomography Applications
- Molecular spectroscopy and chirality
- Image Enhancement Techniques
- Integrated Circuits and Semiconductor Failure Analysis
- Fire Detection and Safety Systems
- Neural Networks and Reservoir Computing
University of Copenhagen
2008-2020
Danish National Research Foundation
2009-2012
University of Calgary
2005-2009
Max Planck Institute of Quantum Optics
2009
National Research Foundation
2008
Frederiksberg Hospital
2005
University of Konstanz
1989-2004
University of Göttingen
2002-2003
Squeezing of quantum fluctuations by means entanglement is a well-recognized goal in the field information science and precision measurements. In particular, squeezing via between 2-level atoms can improve sensing, clocks, metrology, spectroscopy. Here, we demonstrate 3.4 dB metrologically relevant for ≳ 10 5 cold caesium nondemolition (QND) measurement on atom clock levels. We show that there an optimal degree decoherence induced which maximizes generated entanglement. A 2-color QND scheme...
We produce a 600-ns pulse of 1.86-dB squeezed vacuum at 795 nm in an optical parametric amplifier and store it rubidium vapor cell for $1\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ using electromagnetically induced transparency. The recovered pulse, analyzed time-domain homodyne tomography, exhibits up to $0.21\ifmmode\pm\else\textpm\fi{}0.04\text{ }\mathrm{dB}$ squeezing. identify the factors leading degradation squeezing investigate phase evolution atomic coherence during storage interval.
We use a quantum non-demolition measurement to generate spin squeezed state and create entanglement in cloud of 10^5 cold cesium atoms, for the first time operate an atomic clock improved by squeezing beyond projection noise limit proof-of-principle experiment. For clock-interrogation 10 \mu\s experiments show improvement 1.1 dB signal-to-noise ratio, compared limit.
We present the first experimental realization of coherent Bragg scattering off a one-dimensional system—two strings atoms strongly coupled to single photonic mode—realized by trapping in evanescent field tapered optical fiber, which also guides probe light. report nearly 12% power reflection from containing only about 1000 cesium atoms, an enhancement 2 orders magnitude compared randomly positioned atoms. This result paves road towards collective strong coupling 1D atom-photon systems. Our...
We demonstrate preparation and detection of an atom number distribution in a one-dimensional atomic lattice with the variance $-14$ dB below Poissonian noise level. A mesoscopic ensemble containing few thousand atoms is trapped evanescent field nanofiber. The measured through dual-color homodyne interferometry pW-power shot limited probe. Strong coupling probe guided by nanofiber allows for real-time measurement precision $\pm 8$ on some $10^3$ trap. method very well suited generating...
A single photon, delocalized over two optical modes, is characterized by means of quantum homodyne tomography. The reconstructed four-dimensional density matrix extends the entire Hilbert space and thus reveals, for first time, complete information about dual-rail bit as a state electromagnetic field. experimental data violate Bell inequality albeit with loophole similar to detection in photon counting experiments.
We report characterization of electromagnetically induced transparency (EIT) resonances in the D1 line 87Rb under various experimental conditions. The dependence EIT linewidth on power pump field was investigated at temperatures for ground states lambda system associated with different hyperfine levels atomic 5S1/2 state as well magnetic sublevels same level. Strictly linear behavior observed all cases. A theoretical analysis our results shows that dephasing is main source decoherence,...
The effect of the detector electronic noise in an optical homodyne tomography experiment is shown to be equivalent loss if calibrated by measuring quadrature vacuum state. An explicit relation between level and efficiency obtained confirmed with a narrowband squeezed source operating at atomic rubidium wavelength.
We present a versatile, inexpensive and simple optical phase lock for applications in atomic physics experiments. Thanks to all-digital detection implementation of beat frequency pre-scaling, the apparatus requires no microwave-range reference input, permits locking at differences ranging from sub-MHz 7 GHz (and with minor extension, 12 GHz). The range thus covers ground state hyperfine splittings all alkali metals, which makes this system universal tool many experiments on coherent...
We report on the nondestructive observation of Rabi oscillations Cs clock transition. The internal atomic state evolution a dipole-trapped ensemble cold atoms is inferred from phase shift probe laser beam as measured using Mach-Zehnder interferometer. describe single color well two-color probing scheme. Using latter, measurements collective pseudospin projection in superposition states are performed and observed spin fluctuations shown to be close standard quantum limit.
We analyze the creation of spin squeezed atomic ensembles by simultaneous dispersive interactions with several optical frequencies. A judicious choice parameters enables optimization an interferometric detection scheme that suppresses inhomogeneous light shifts and keeps interferometer operating in a balanced mode minimizes technical noise. show when atoms interact two-frequency tuned to cycling transitions degree squeezing ${\ensuremath{\xi}}^{2}$ scales as...
We experimentally demonstrate a communication protocol that enables frequency conversion and routing of quantum information in an adiabatic thus robust way. The is based on electromagnetically induced transparency (EIT) systems with multiple excited levels: transfer and/or distribution optical states between different signal modes implemented by adiabatically changing the control fields. proof-of-principle experiment performed using hyperfine levels rubidium D1 line.
We report on the observation of quantum interference a collective single spin excitation with ensemble ${N}_{\mathrm{a}}\ensuremath{\approx}{10}^{5}$ atoms. Detection photon scattered from atoms creates excitation, Fock state embedded in ensemble. The atomic is then detected by nondemolition measurement spin. A macroscopic difference order ${\sqrt{N}}_{\mathrm{a}}$ marginal distribution arises between excited and ${N}_{\mathrm{a}}$ These hybrid discrete-continuous manipulation procedures...
Although nonclassical quantum states are important both conceptually and as a resource for technology, it is often difficult to test whether given system displays nonclassicality. A simple method certify nonclassicality introduced, based on easily accessible collective atomic quadrature measurements, without the need of full state tomography. The statistics analyzed beyond ground-state noise level by direct sampling regularized quasiprobability. Nonclassicality squeezed ensemble...
We analyze electromagnetically induced transparency and light storage in an ensemble of atoms with multiple excited levels (multi-$\ensuremath{\Lambda}$ configuration) which are coupled to one the ground states by quantized signal fields other via classical control fields. present a basis transformation atomic optical reduces analysis system that regular three-level configuration. demonstrate existence dark state polaritons propose protocol transfer quantum information from mode another adiabatic
We present a proposal and feasibility study for the creation quantum state tomography of single polariton an atomic ensemble. The collective non-classical non-Gaussian ensemble is generated by detection forward scattered photon. subsequently characterized performed using strong dispersive light-atoms interaction followed homodyne measurement on transmitted light. backed preliminary experimental results showing projection noise limited sensitivity simulation demonstrating proposed method...
We analyze the transmission of continuous-wave and pulsed squeezed vacuum through rubidium vapor under conditions electromagnetically induced transparency. Our analysis is based on a full theoretical treatment for state light propagating temporal spectral filters detected using time frequency-domain homodyne tomography. A model three-level atom allows us to evaluate linear losses extra noise that degrade nonclassical properties during atomic interaction eventually predict quantum states...
In the production of tapered optical fibers, it is important to control fiber shape according application-dependent requirements and ensure adiabatic tapers. Especially in transition regions, depends on heater properties. The axial viscosity profile within can, however, be hard access therefore often approximated by assuming a uniform temperature distribution. We present method for easy experimental calibration heater. This allows determination resultant arbitrary pulling procedures, using...
The evanescent field surrounding nanoscale optical waveguides offers an efficient interface between light and mesoscopic ensembles of neutral atoms. However, the thermal motion trapped atoms, combined with strong radial gradients guided light, leads to a time-modulated coupling atoms mode, thus giving rise additional noise motional dephasing collective states. Here, we present dipole force free scheme for states, utilizing intensity gradient mode demonstrate all-optical cesium hyperfine...