Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Quantum-Atom Optics Downunder (QAO)

Cold atomic ensembles for quantum interfaces: new interactions.

Marcin Kubasik, Marco Koschorreck, M. Napolitano, S.R. de Echaniz, Morgan W. Mitchell

Published Jan 1, 2007• 0 citations
Publisher

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.

DOI
10.1364/qao.2007.qwd3

Related papers

Quantum Light - Matter Interactions with Cold Ensembles

Marcin Kubasik, S.R. de Echaniz, Marco Koschorreck +2 more

Cold, trapped atomic ensembles present new opportunities for light-matter interfaces, including tomographic measurements and new light-matter interactions. By way of illustration, we describe spinsqueezing experiments in a dipole-trapped 87Rb ensemble.

The Rochester Conferences on Coherence and Quantum Optics and the Quantum Information and Measurement meeting•Jan 1, 2007•0 citations

Tunable light-matter interactions with cold ensembles

Marcin Kubasik, S.R. de Echaniz, Marco Koschorreck +3 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.

•May 4, 2008•0 citations

Cold 87 Rb ensembles: non-Gaussian state detection and spin tomography

Morgan W. Mitchell, S.R. de Echaniz, Marcin Kubasik +1 more

Light interacting with atomic ensembles allows the possibility of strong, and thus deterministic, quantum interface processes. Recently demonstrated processes of interest for quantum networking include quantum memory for light and teleportation of a quantum state from light to matter. Many important results have been accomplished with room temperature ensembles, which has thus far limited the experiments to relatively long interaction times, ~ ms, large numbers of atoms ~1012, and far-detuned interactions. In contrast, a cold, trapped atomic ensemble can have the same optical depth with far fewer atoms ~106, simultaneous with faster ~mus interaction times. For a combination of technical and fundamental reasons, this allows for new types of experiments using light-ensemble interfaces. Here we describe methods to detect non-gaussian states and perform spin-state tomography.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2007•0 citations

Towards spin squeezing in cold atomic ensembles

Marcin Kubasik

The subject of this thesis is the construction and characterization of an experimental setup for studying the interaction of an ensemble of 10^5 - 10^6 cold 87 Rb atoms held in a far off-resonance optical dipole trap with a probe detuned by about 100 natural line widths, a regime in which refractive effects are resonantly enhanced but absorption is small. An important feature of this type of atom-light interface is that it facilitates quantum non-demolition measurements which in turn have numerous applications in quantum information technology, as well as in the field of ultra-precise metrology where they allow the measurements to overcome the so-called standard quantum limit. The use of a dipole trap has several advantages over more conventional approaches in which vapor cells or magneto-optical traps (MOT) have been used. Most importantly interaction strength of comparable magnitude can be achieved with a far lower number of atoms and with longer coherence times. The elongated geometry that can be realized in a dipole trap maximizes the interaction strength. One of the complications that arise is that the achievable interaction strength is highly sensitive to the mode-matching between the trapped ensemble and the probe beam. The theoretical description of the interaction between a trapped ensemble and a freely-propagating probe beam is provided in the framework of continuous variables. The relevant quantities are a pseudo-spin, defined for an ensemble of atoms in their ground state, and the Stokes vector that characterizes the polarization state of light. In practice the experiment consists of four main blocks: the atom traps, the optical pumping setup, the probe laser setup, and the photodetection. Before loading into the dipole trap, atoms are cooled in a MOT. An existing MOT setup has been improved by implementing a new, more powerful laser system. A dedicated dipole trap, which had been constructed in collaboration with another project, has been thoroughly characterized and the results are presented in this thesis. Setups for optical pumping and for the probe have been built, characterized and incorporated into the apparatus. Several experimental techniques have been developed and tested in order to optimize the alignment of the probe with the trapped ensemble. The effect of the geometrical overlap on the achievable signal to noise ratio is discussed and illustrated using simple, intuitive models. Photo-detection is a critical part of the setup. In order to facilitate detection of non-classical (squeezed) states of the atomic (pseudo-) spin, the detection system must be shot-noise limited within the range of photon numbers used in the experiments. Such a system has been constructed and tested, and is described in detail. It employs a charge-sensitive amplifier (CSA) but, unlike earlier implementations, it does not use a pulse-shaping stage. Instead, an algorithm has been devised and implemented that derives the quantities of interest directly from the output signal of the CSA. This novel approach avoids the technical problems that arise in systems using hardware-based pulse shaping. It also makes the detector more flexible in terms of the shape and timing of the probe pulses that can be used. The atomic states produced in the setup are intrinsically sensitive to stray magnetic fields. Therefore an efficient cancellation of stray fields is essential. On the other hand having the possibility to apply a fully controlled, external magnetic field makes the experimental setup more versatile. Both goals can be achieved with a magnetic field control unit that has been built during this project. It facilitates active cancellation of stray magnetic fields at the frequency of the mains and in addition allows to apply an arbitrary waveform magnetic fields along all three axes. One of the main results reported in this thesis is the observation of polarization rotation caused by population imbalance created in the process of optical pumping and, in a separate series of measurements, due to an applied magnetic field. These measurements have allowed us to assess the strength of the atom-light interaction available in the current setup. They indicate that with the necessary modifications to the optical pumping scheme the system should prove successful in implementing quantum information protocols, in particular quantum memory for light. An interesting off-shoot has been the spectroscopic characterization of the atomic state in the dipole trap. In these measurements Doppler free spectra are recorded in a very simple setup without the need to use nonlinear techniques. Apart from providing a method to characterize the efficiency of the optical pumping into the hyperfine level of interest, the acquired spectra are a very direct illustration of the power of the laser cooling techniques developed in the recent years and without which this work would not have been possible.

•Jan 1, 2009•5 citations

Hamiltonian design in atom-light interactions with rubidium ensembles: A quantum-information toolbox

S.R. de Echaniz, Marco Koschorreck, M. Napolitano +2 more

We study the coupling between collective variables of atomic spin and light polarization in an ensemble of cold $^{87}\text{R}\text{b}$ probed with polarized light. The effects of multiple hyperfine levels manifest themselves as a rank-2 tensor polarizability, whose irreducible components can be selected by means of probe detuning. The ${D}_{1}$ and ${D}_{2}$ lines of Rb are explored and we identify different detunings which lead to Hamiltonians with different symmetries for rotations. As possible applications of these Hamiltonians, we describe schemes for spin squeezing, quantum cloning, quantum memory, and measuring atom number.

arXiv:0712.0256•Physical Review A•Mar 11, 2008•40 citations

Generation of planar quantum squeezing in an atomic ensemble

Giorgio Colangelo, N. Behbood, Ferran Martin Ciurana +3 more

We extend the covariance-matrix description of atom-light quantum interfaces to spin-1 systems including technical noise and decoherences. We use this description to predict and produce a planar squeezed state in a cold 87Rb ensemble.

•Jan 1, 2013•0 citations
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.
Light interacting with atomic ensembles allows the possibility of strong, and thus deterministic, quantum interface processes. Recently demonstrated processes of interest for quantum networking include quantum memory for light and teleportation of a quantum state from light to matter. Many important results have been accomplished with room temperature ensembles, which has thus far limited the experiments to relatively long interaction times, ~ ms, large numbers of atoms ~1012, and far-detuned interactions. In contrast, a cold, trapped atomic ensemble can have the same optical depth with far fewer atoms ~106, simultaneous with faster ~mus interaction times. For a combination of technical and fundamental reasons, this allows for new types of experiments using light-ensemble interfaces. Here we describe methods to detect non-gaussian states and perform spin-state tomography.
The subject of this thesis is the construction and characterization of an experimental setup for studying the interaction of an ensemble of 10^5 - 10^6 cold 87 Rb atoms held in a far off-resonance optical dipole trap with a probe detuned by about 100 natural line widths, a regime in which refractive effects are resonantly enhanced but absorption is small. An important feature of this type of atom-light interface is that it facilitates quantum non-demolition measurements which in turn have numerous applications in quantum information technology, as well as in the field of ultra-precise metrology where they allow the measurements to overcome the so-called standard quantum limit. The use of a dipole trap has several advantages over more conventional approaches in which vapor cells or magneto-optical traps (MOT) have been used. Most importantly interaction strength of comparable magnitude can be achieved with a far lower number of atoms and with longer coherence times. The elongated geometry that can be realized in a dipole trap maximizes the interaction strength. One of the complications that arise is that the achievable interaction strength is highly sensitive to the mode-matching between the trapped ensemble and the probe beam. The theoretical description of the interaction between a trapped ensemble and a freely-propagating probe beam is provided in the framework of continuous variables. The relevant quantities are a pseudo-spin, defined for an ensemble of atoms in their ground state, and the Stokes vector that characterizes the polarization state of light. In practice the experiment consists of four main blocks: the atom traps, the optical pumping setup, the probe laser setup, and the photodetection. Before loading into the dipole trap, atoms are cooled in a MOT. An existing MOT setup has been improved by implementing a new, more powerful laser system. A dedicated dipole trap, which had been constructed in collaboration with another project, has been thoroughly characterized and the results are presented in this thesis. Setups for optical pumping and for the probe have been built, characterized and incorporated into the apparatus. Several experimental techniques have been developed and tested in order to optimize the alignment of the probe with the trapped ensemble. The effect of the geometrical overlap on the achievable signal to noise ratio is discussed and illustrated using simple, intuitive models. Photo-detection is a critical part of the setup. In order to facilitate detection of non-classical (squeezed) states of the atomic (pseudo-) spin, the detection system must be shot-noise limited within the range of photon numbers used in the experiments. Such a system has been constructed and tested, and is described in detail. It employs a charge-sensitive amplifier (CSA) but, unlike earlier implementations, it does not use a pulse-shaping stage. Instead, an algorithm has been devised and implemented that derives the quantities of interest directly from the output signal of the CSA. This novel approach avoids the technical problems that arise in systems using hardware-based pulse shaping. It also makes the detector more flexible in terms of the shape and timing of the probe pulses that can be used. The atomic states produced in the setup are intrinsically sensitive to stray magnetic fields. Therefore an efficient cancellation of stray fields is essential. On the other hand having the possibility to apply a fully controlled, external magnetic field makes the experimental setup more versatile. Both goals can be achieved with a magnetic field control unit that has been built during this project. It facilitates active cancellation of stray magnetic fields at the frequency of the mains and in addition allows to apply an arbitrary waveform magnetic fields along all three axes. One of the main results reported in this thesis is the observation of polarization rotation caused by population imbalance created in the process of optical pumping and, in a separate series of measurements, due to an applied magnetic field. These measurements have allowed us to assess the strength of the atom-light interaction available in the current setup. They indicate that with the necessary modifications to the optical pumping scheme the system should prove successful in implementing quantum information protocols, in particular quantum memory for light. An interesting off-shoot has been the spectroscopic characterization of the atomic state in the dipole trap. In these measurements Doppler free spectra are recorded in a very simple setup without the need to use nonlinear techniques. Apart from providing a method to characterize the efficiency of the optical pumping into the hyperfine level of interest, the acquired spectra are a very direct illustration of the power of the laser cooling techniques developed in the recent years and without which this work would not have been possible.
We study the coupling between collective variables of atomic spin and light polarization in an ensemble of cold 87Rb^{87}\text{R}\text{b}87Rb probed with polarized light. The effects of multiple hyperfine levels manifest themselves as a rank-2 tensor polarizability, whose irreducible components can be selected by means of probe detuning. The D1{D}_{1}D1​ and D2{D}_{2}D2​ lines of Rb are explored and we identify different detunings which lead to Hamiltonians with different symmetries for rotations. As possible applications of these Hamiltonians, we describe schemes for spin squeezing, quantum cloning, quantum memory, and measuring atom number.