Entanglement gauge and the non-Abelian geometric phase with two photonic qubits University of Calgary | Publication | 2003-02-01 | K. Marzlin, S. D. Bartlett, B. C. Sanders |

Inconsistency in the Application of the Adiabatic Theorem University of Calgary | Publication | 2004-10-01 | K. Marzlin, B. C. Sanders |

State independence in atom interferometry and insensitivity to acceleration and rotation University of Calgary | Publication | 1996-01-01 | K. Marzlin, J. Audretsch |

Decoherence of atomic gases in largely detuned laser fields University of Calgary | Publication | 2001-06-01 | K. Marzlin |

Photonic band gaps and defect states induced by excitations of Bose-Einstein condensates in optical lattices University of Calgary | Publication | 1999-04-01 | K. Marzlin, W. Zhang |

States insensitive to the Unruh effect in multilevel detectors University of Calgary | Publication | 1998-01-01 | K. Marzlin, J. Audretsch |

Atom optics and quantum groups University of Calgary | Publication | 1997-04-01 | K. Marzlin |

Dipole coupling of atoms and light in gravitational fields University of Calgary | Publication | 1995-01-01 | K. Marzlin |

The physical meaning of Fermi coordinates University of Calgary | Publication | 1994-06-01 | K. Marzlin |

Geometric phase of a system coupled to a reservoir, University of Calgary | Presentation | 2004-06-14 | K. Marzlin, S. Ghose, B. C. Sanders |

Quantum information with atoms and photonsAtomic gases and single photons are among the most promising candidates to implement quantum information technology because they can be well isolated from their environment. Despite this advantage it is challenging to design controllable interaction between these particles and to store or manipulate quantum information in a reliable way. We have explored how electromagnetically induced transparency can be used to create a large nonlinear interaction between single-photon pulses, to transfer optical states between different photon modes, and to create an unusual interaction between light fields. Furthermore, we have found new results on the physical limitations of decoherence-free states. The nature of these limitations points towards new directions in the search for decoherence-free subspaces.
University of Calgary | Presentation | 2006-05-08 | K. Marzlin |

Applications of electromagnetically induced transparency in quantum information University of Calgary | Presentation | 2005-02-28 | K. Marzlin |

Transverse excitations and triple gap solitons in Bose-Einstein condensates University of Calgary | Presentation | 2004-07-12 | K. Marzlin, I. V. Yukalov |

Quantum information with photons and atoms University of Calgary | Presentation | 2006-06-29 | K. Marzlin |

Slow photons as charged Quasi-Particles, and photonic Aharonov-Bohm effectOver the past few years several proposals have been made how to realize artificial Abelian and non-Abelian gauge potentials for ultracold atoms. I will give a pedagogical introduction to this field and present our own proposal to achieve an analogous effect for quantized light (photons) propagating through an atomic gas. In this case, the dynamical equation for photons is equivalent to the Schroedinger equation for charged particles in two dimensions. The corresponding vector potential is completely determined by a set of classical light fields that are used to manipulate the atomic state. We suggest classical field configurations that generate potentials corresponding to a constant electric and a constant magnetic field. Furthermore we devise a scheme of fields that generates a vector potential of Aharonov-Bohm type which induces a topological phase shift for slow photons. University of Calgary | Presentation | 2007-07-17 | K. Marzlin |

Slow photons as charged quasi-particles, and photonic Aharonov-Bohm effectOver the past few years several proposals have been made how to realize
artifical Abelian and non-Abelian gauge potentials for ultracold atoms. I
will give a pedagical introduction to this field and present our own proposal
to achieve an analogous effect for quantized light (photons) propagating
through an atomic gas.
In this case, the dynamical equation for photons is equivalent to the
Schroedinger equation for charged particles in two dimensions. The
corresponding vector potential is completely determined by a set of classical
light fields that are used to manipulate the atomic state.
We suggest classical field configurations that generate potentials
corresponding to a constant electric and a constant magnetic field.
Furthermore we devise a scheme of fields that generates a vector
potential of Aharonov-Bohm type which induces a topological phase shift
for slow photons. University of Calgary | Presentation | 2007-09-06 | K. Marzlin |

Slow photons as charged Quasi-ParticlesRecently we have proposed the method of Raman Adiabatic Transfer of Optical States (RATOS)
to manipulate the optical state of light. A four-level atomic medium in double-Lambda configuration
is interacting with two pump fields and a signal photon with very slow group velocity. An
adiabatic change in time of the pump fields can then generate a slow photon in a superposition
of different frequencies. Here we theoretically analyze the influence of an adiabatic change in
the spatial form of the pump fields. We demonstrate that the signal photon then behaves like a
charged quasi-particle: in paraxial approximation its dynamics is governed by a Schroedingerlike
equation that includes a scalar and a vector potential whose form is determined by the
shape of the pump fields. We suggest pump field configurations that generate potentials corresponding
to a constant electric and a constant magnetic field. In both cases the center of a
Gaussian signal pulse follows the trajectory of corresponding classical point particles. In the
case of a quasi-magnetic field the dispersion of the pulse is reduced. We give an intuitive interpretation
of this effect, which may have application as a waveguide of light inside an atomic
vapor. Furthermore, we devise a scheme of pump fields that generates a vector University of Calgary | Presentation | 2007-09-04 | K. Marzlin, J. Appel, A. Lvovsky |

Slow light and its application in quantum informationOver the last decade tremendous progress has been made
in slowing and stopping of light. In specially prepared
atomic gases the velocity of light has been reduced to
that of a bicyclist, and it is now possible to reversibly
store even the tiniest amount of light, a single photon,
in such a gas. This effect may be used in quantum information
to build a quantum memory, an essential tool for long-distance
quantum communication.
In this talk I will give a review of the basic mechanisms
to store light and describe our recent contributions to this
field, including routing of quantum information, the design
of a photon-controlled light switch, and "charged" photons.
University of Calgary | Presentation | 2008-03-28 | K. Marzlin |

Slow light and its application in quantum informationOver the last decade tremendous progress has been made
in slowing and stopping of light. In specially prepared
atomic gases the velocity of light has been reduced to
that of a bicyclist, and it is now possible to reversibly
store even the tiniest amount of light, a single photon,
in such a gas. This effect may be used in quantum information,
for instance to build a quantum memory which is an essential
tool for long-distance quantum communication.
In this talk I will give a review of the basic mechanisms
to store light and describe our recent contributions to this
field, including routing of quantum information, the design
of a photon-controlled light switch, and "charged" photons. University of Calgary | Presentation | 2008-06-02 | K. Marzlin |

Decoherence-free subspaces and spontaneous emission cancellation: necessity of Dicke limitDecoherence-free subspaces (DFS) of an open quantum system are states for which the coupling to the environment is canceled by destructive interference. DFS are usually studied for states involving two or more particles and are considered a prominent candidate for quantum memory and quantum information processing. Experiments with ions indicate that partial cancellation is possible, but a demonstration of significant cancellation is challenging. \\ We prove that a perfect physical DFS requires co-located particles, i.e., the Dicke limit. The assumptions made are very general and invoke a homogeneous environment with energy-conserving coupling to the particles. We indicate when a DFS outside the Dicke limit may be possible; this includes molecular and confined systems. Furthermore, we establish a connection between DFS and spontaneous emission cancelation and refine the conditions for one of the important theorems on DFS to hold. University of Calgary | Presentation | 2006-05-20 | K. Marzlin, R. Karasik, B. C. Sanders, B. K. Whaley |

Decoherence-free subspaces: necessity of Dicke limitDecoherence-free subspaces (DFS) consist of quantum states of a system S that are immune to the effect of the environment E on the system. In practise, because of symmetry restrictions, S is usually composed of more than one particle to realize a DFS. We outline a proof that, under very general assumptions about the system, the environment, and the coupling between S and E, a DFS can only be obtained in the Dicke limit when the particles are located at the same position. The nature of the proof points towards new directions in the search for realizable DFS.
University of Calgary | Presentation | 2006-06-09 | K. Marzlin |

Criteria for the existence of decoherence-free subspacesDecoherence-free subspaces (DFS) are spanned by such states of an open quantum system that are insensitive to the decoherence induced by the reservoir to which the system is coupled. DFS are immune to this coupling because of different physical effects, including destructive interference between different transition amplitudes or energy conservation.
We compare different definitions of DFS and explore rigorous criteria for the existence of DFS in finite-dimensional systems coupled to Markovian reservoirs. The advantages and disadvantages of various approaches are compared and a geometrical interpretation for DFS in qubit-systems is given.
University of Calgary | Presentation | 2007-06-01 | K. Marzlin, R. Karasik, B. C. Sanders, B. K. Whaley |

Slow photons as charged quasi-particles, and photonic Aharonov-Bohm effectRecently we have proposed the method of Raman Adiabatic
Transfer of Optical States (RATOS) to manipulate the
optical state of light [1]. In this method a four-level atomic
medium in double-Lambda configuration is interacting with two pump
fields and a signal photon, which can be in a superposition of
two modes with different frequencies. Depending on the
intensity of the pump fields, only a particular superposition
will experience electromagnetically induced transparency and thus
can be slowed down. An adiabatic change in time of the pump fields can
then change this superposition dynamically.
Here we theoretically analyze the influence of an adiabatic change
in the spatial form of the pump fields. We demonstrate that the
signal photon then behaves like a charged quasi-particle: in
paraxial approximation its dynamics is governed by a Schroedinger-like
equation that includes a scalar and a vector quasi-potential whose
form is determined by the shape of the pump fields. We suggest
pump field configurations that generate potentials corresponding
to a constant electric and a constant magnetic quasi-field and show
that the magnetic quasi-field suppresses spatial dispersion
of the signal photon. Furthermore we devise a scheme of pump fields
that generates a vector potential of Aharonov-Bohm type.
This induces a topological phase shift on the signal field.
[1] J. Appel, K.-P. Marzlin and A.I. Lvovsky, Phys. Rev. A 73, 013804 (2006). University of Calgary | Presentation | 2007-06-19 | K. Marzlin, J. Appel, A. Lvovsky |

Slow photons as charged quasi-particles, and photonic Aharonov-Bohm effectRecently we have proposed the method of Raman Adiabatic
Transfer of Optical States (RATOS) to manipulate the
optical state of light. A four-level atomic medium in
double-$\Lambda$ configuration is interacting with two pump
fields and a signal photon with very slow group velocity.
An adiabatic change in time of the pump fields can then
generate a slow photon in a superposition of different frequencies.
Here we theoretically analyze the influence of an adiabatic change
in the spatial form of the pump fields. We demonstrate that the
signal photon then behaves like a charged quasi-particle: in
paraxial approximation its dynamics is governed by a
Schr\"odinger-like equation that includes a scalar and a vector
potential whose form is determined by the shape of the pump fields.
We suggest pump field configurations that generate potentials
corresponding to a constant electric and a constant magnetic field.
Furthermore we devise a scheme of pump fields that generates a vector
potential of Aharonov-Bohm type which induces a topological phase shift
for slow photons. University of Calgary | Presentation | 2007-06-09 | K. Marzlin, J. Appel, A. Lvovsky |

Atom interferometry, microscopy, complementarity, and the perfect lensDevelopment of the `perfect lens' poses an interesting challenge to standard concepts of complementarity manifested in interferometric which-way vs fringe visibility experiments. We show that a `microscope' with a `perfect lens' provides the extremal point of maximum which-way information in atom interferometry, and our theory rigorously connects complementarity in interferometry with the standard position-momentum Heisenberg uncertainty relation. University of Calgary | Presentation | 2007-06-09 | K. Marzlin, B. C. Sanders, L. P. Knight |

Atomic many-body effects in the propagation of slow light through atomic gasesA quantum memory for photonic qubits is an essential tool
for quantum information processing because it would be vital
for long-distance quantum communication. A strong candidate
for quantum memories are atomic gases that exhibit electromagnetically
induced transparency (EIT). In such a medium the information about a
photon can be reversibly stored in form of a spin-wave.
The common quantum optical calculations suggest that ultracold gases
of high density would be most suitable for this task, but these theories
ignore the dipole-dipole interaction (DDI) between atoms that become
relevant at high densities. We have investigated the effect of DDI on
EIT and found significant differences between hot and ultracold atomic
gases. In a dense gas bosonic atoms close to condensation, DDI changes
the refractive index more significantly and also leads to collective
decoherence effects. Our theoretical approach combines dressed-states
of quantum optics with non-equilibrium many-body techniques
(Keldysh diagrams). University of Calgary | Presentation | 2008-04-20 | K. Marzlin, I. Mahmoud, B. C. Sanders |

Entanglement gauge and non-abelian geometric phase for photonic qubits University of Calgary | Presentation | 2003-03-01 | K. Marzlin, D. S. Bartlett, B. C. Sanders |

Erzeugung von skyrmionen in einem drei-komponentigen Bose-Einstein-Kondensat University of Calgary | Presentation | 2000-04-01 | K. Marzlin, P. W. Zhang, B. C. Sanders |

Momentum spread of spontaneously decaying cold gas in thermal radiation University of Calgary | Publication | 2002-12-01 | C. H. Ooi, K. Marzlin, J. Audretsch |

Ramsey fringes in atomic interferometry: Measurability of the influence of space-time curvature University of Calgary | Publication | 1994-09-01 | J. Audretsch, K. Marzlin |

Influence of external potentials on optical Ramsey fringes in atomic interferometry University of Calgary | Publication | 1993-05-01 | J. Audretsch, K. Marzlin |

Double electromagnetically induced transparency and its application in quantum information University of Calgary | Publication | 2006-08-01 | Z. Wang, K. Marzlin, B. C. Sanders |

FERMI–FRENET COORDINATES FOR SPACELIKE CURVES University of Calgary | Publication | 2010-03-01 | U. N. MICHAEL, K. Marzlin |

Moyal phase-space analysis of nonlinear optical Kerr media University of Calgary | Publication | 2009-09-01 | T. A. Osborn, K. Marzlin |

Giant nonlinearities and double electromagnetically induced transparency in Rb University of Calgary | Presentation | 2006-02-25 | Z. Wang, K. Marzlin, B. C. Sanders |

Fermi-Frenet coordinates for space-like curves We generalize Fermi coordinates, which correspond to an adapted set of coordinates describing the vicinity of an observer's world line, to a coordinate system in a neighbourhood of the worldsheet of an arbitrary spatial curve in a static spacetime. The spatial coordinate axes are fixed using a covariant Frenet triad, analogous to that of classical differential geometry, so that the metric can be expressed in terms of the curvature and torsion of the spatial curve. This construction is used to analyze the covariant definition of inertial forces felt by an observer constrained to motion upon the worldsheet. We also consider the application of these coordinates to examining photon propagation in arbitrarily-curved optical fibres. University of Calgary | Presentation | 2007-06-18 | M. Underwood, K. Marzlin |

Manipulation and storage of qubits via CRIB We present a new technique for using a quantum memory device to perform arbitrary rotations of qubits living in the two-dimensional Hilbert space spanned by the time-bin states |early〉 and |late〉. The CRIB protocol [1, 2, 3, 4] (controlled and reversible inhomogeneous broadening) allows the quantum information encoded in a photon state to be stored in the atomic coherences of a collection of rare-earth ions in a doped crystal or optical ﬁbre. This is achieved by artificially broadening the inhomogeneous line width of an atomic transition within the medium in a reversible manner such that all Fourier components of the input light ﬁeld can be absorbed. When this is the case one can show that later reversing the applied detuning (i.e. letting Δ→−Δ) and applying a phase-matching operation allows the equations of motion for a forward-propagating pulse to be transformed into a time-reversed copy of the equations of motion for a backward-moving pulse. When done correctly this causes the atomic coherences to evolve back to their initial state and the input pulse to be re-emitted in the opposite direction. A modification to this protocol allows an input pulse in a well-defined time bin to be recalled in a superposition of |early> and |late>, or more than two different states. We have numerically simulated the Maxwell-Bloch equations describing the interaction of a classical electric ﬁeld with an ensemble of two-level systems. In the modified version of the CRIB protocol we perform the rephasing operation on the absorbing medium at different times for two spatially distinct sections. This results in two output pulses. By modifying the relative size of the two spatial sections being rephased we are able to tailor the ratio of the amplitudes of the output pulses. The time difference between the pulses is easily controlled, so by associating the ﬁrst (second) pulse with the early (late) time bin we have eﬀectively rotated the initial pulse into a superposition state with coefficients that depend on the amplitudes of the output pulses. We investigate a number of variations on this theme including different input pulse shapes and detuning proﬁles. We look at different coherence times and temporal separations of the output pulses, and consider output in both the forward and backward directions. In each case the recall efficiency provides a ﬁgure of merit.
**References** [1] S. A. Moiseev and S. Kröll, Phys. Rev. Lett. **87**, 173601 (2001) [2] M. Nilsson and S. Kröll, Opt. Commun. **247** 292 (2005) [3] B. Kraus, W. Tittel, N. Gisin, M. Nilsson, S. Kröll, and J. I. Cirac, Phys. Rev. A. **73**,\\r\\n020302(R) (2006) [4] A. L. Alexander, J. J. Longdell, N. B. Manson, and M. J. Sellars, Phys. Rev. Lett. **96**, 043602 (2006) University of Calgary, The University of Calgary | Presentation | 2008-01-26 | M. Underwood, K. Marzlin, W. Tittel |

Refractive index of driven dense atomic gasesThe optical properties of an atomic gas, including
the dramatic reduction of the group velocity
of light associated with electromagnetically induced
transparency (EIT), usually grow with the density
of atoms in the medium. However, in high density
atomic gases, the resonant dipole-dipole interaction
(DDI) generates atomic correlations. These correlations
could significantly modify both linear and nonlinear
optical properties of the medium [1, 2, 3], which
may be beneficial for quantum information processing.
We develop a theory that describes the influence
of DDI on the optical properties of a dense gas
driven by classical control fields. Our method combines
dressed-states of quantum optics with nonequilibrium
many-body theory based on Feynman diagrams
and includes the effect of the atomic centerof-
mass-motion, which is relevant for the study of
different temperature regimes. This approach has
the advantage that the control fields are treated nonperturbatively. University of Calgary | Presentation | 2008-08-23 | I. Mahmoud, K. Marzlin, B. C. Sanders |

Adapting CRIB-based memories to photon state manipulation University of Calgary, The University of Calgary | Presentation | 2008-08-21 | M. Underwood, K. Marzlin, S. Moiseev, W. Tittel |

Cooperative emission into surface plasmons University of Calgary | Presentation | 2008-08-21 | J. Choquette, K. Marzlin, R. Stock, B. C. Sanders |

Giant cross-phase modulation in double electromagnetically induced transparency and its applications University of Calgary | Presentation | 2008-08-23 | Z. Wang, K. Marzlin, S. Moiseev, B. C. Sanders |

Criteria for dynamically stable decoherence-free subspacesA decoherence-free subspace (DFS) is a collection of states for a system that is impervious to dominant noise effects created by the environment. The DFS approach provides an important strategy for quantum information processing because it would allow quantum circuit simplification by reducing the need for quantum error correction and providing stable quantum memory. Experimental demonstrations of DFSs show the efficacy of this approach. We analyze similarities and differences between various approaches to DFSs present in the literature and show that an excessively restrictive assumption on immunity from decoherence for an arbitrary initial environment state can be relaxed for practical DFS cases. In the important class of systems whose dynamics is described by Markovian master equations, we provide necessary and sufficient conditions for the existence of a dynamically stable DFS. We also present examples that show why previous work in this direction was not sufficient. University of Calgary | Presentation | 2007-06-07 | R. Karasik, K. Marzlin, B. C. Sanders, B. K. Whaley |

QED of surface plasmonsA full quantum description of photons and surface plasmons near an interface between lossy dielectrics is given, allowing estimation of SP-induced noise. The emitted radiation of a decaying atom near the interface is characterized. University of Calgary | Presentation | 2007-06-14 | J. Choquette, K. Marzlin, R. Stock, B. C. Sanders |

Collective excitation of surface plasmons by a linear dipole arraySurface plasmons are electromagnetically induced charge-density waves that appear at the interface between dielectrics and a thin metal film and can enhance optical field intensities by two to three orders of magnitude. Optical dipoles placed near the metal interface have their radiative properties significantly affected by the presence of surface plasmon modes. The spontaneous emission rate is heavily modified and an optical emitter can decay both radiatively and into a surface plasmon. We consider a linear (pencil-like) arrangement of $N$ dipoles in vacuum near a metal film on the surface of a prism. In free space this arrangement would predominantly emit radiation along the axis of this pencil with an intensity that increases like $N^2$. We show that this gain persists in the presence of the metal film and an additional enhancement of the intensity can be achieved by the narrow characteristic of the radiation field emitted by the induced surface plasmon modes. This effect is rather insensitive to the alignment of the pencil due to the evanescent nature of surface plasmon fields.
University of Calgary | Presentation | 2008-05-30 | J. Choquette, K. Marzlin, B. C. Sanders |

Multi-particle decoherence free subspaces in extended systemsA decoherence-free subspace (DFS) is a collection of states that are immune to the noise derived from interactions with the environment. DFS is especially of interest for states involving two or more particles and is considered a prominent candidate for quantum memory and quantum information processing. We develop a method for finding DFS in real quantum systems. For systems with a homogeneous environment and energy-conserving coupling to the particles in 3D space, our methods show that perfect DFS exists for co-located particles only . This restriction does not exist for confined systems, such as atoms embedded in an optical fiber.
University of Calgary | Presentation | 2008-05-29 | R. Karasik, K. Marzlin, B. C. Sanders, B. K. Whaley |

Quantum logic in a decoherence-suppressed subspace with atomic qubits University of Calgary | Presentation | 2005-01-31 | G. P. Brooke, K. Marzlin, B. C. Sanders |

Stability of gap solitons in a Bose-Einstein condensate University of Calgary | Publication | 2002-12-01 | K. M. Hilligsøe, M. K. Oberthaler, K. Marzlin |

Giant optical nonlinearities using double electromagnetically induced transparency in Rubidium University of Calgary | Presentation | 2007-09-26 | A. MacRae, Z. Wang, K. Marzlin, A. Lvovsky |

Few-photon all-optical switching University of Calgary | Presentation | 2010-07-13 | B. C. Sanders, A. Kamli, K. Marzlin, S. Moiseev, Z. Wang |

Large cross-phase modulation between slow co-propagating weak pulse in rubidium University of Calgary | Presentation | 2006-08-13 | B. C. Sanders, Z. Wang, K. Marzlin |

Incoherently generated coherence and immunity to decoherenceThe decoherence free subspace is important as states in this subspace are immune to the decohering effects of open system dynamics. We introduce a new kind of state, which, for certain open system dynamics, can be made immune to decoherence by driving the system with an appropriate driving field: we refer to these states as incoherently generated coherent states, and they are pure states that evolve unitarily despite coupling to the open system. The seemingly non-unitary open system driving term becomes essential as a partner with the driving field to generate coherences that stabilize these special states. We prove that such states cannot exist for most open system models with finite-dimensional systems but are readily found for infinite-dimensional systems, and we present examples of such states for suitable open systems. University of Calgary | Presentation | 2008-05-29 | B. C. Sanders, R. Karasik, K. Marzlin, B. K. Whaley |

Escaping decoherenceDecoherence is the bane of quantum information, and putting states into decoherence-free subspaces is one strategy to avoid this destruction of quantum information. The bad news is that we have found that decoherence-free subspaces do not exist for extended systems in more than one dimension for a broad class of realistic reservoirs, but the good news is that we have discovered that in some cases the environment protects certain states by disallowing them from decohering via a nudging process from the unitary part of the open system dynamics. Examples given from cavity quantum electrodynamics and squeezed light. University of Calgary | Presentation | 2008-06-10 | B. C. Sanders, R. Karasik, K. Marzlin, B. K. Whaley |

Double electromagnetically-induced transparency in rubidium vaporWe report demonstration of double electromagnetically-induced transparency in a hot rubidium-87 vapor: two transparency windows appear simultaneously on | 5S_{1/2},F=1> to | 5P_{1/2},F=2> and |5S_{1/2},F=2> to |5P_{1/2},F=2> when a single control field is applied. We have been able to simultaneously slow down two optical pulses resonant with these transitions. By switching the control field, we have demonstrated simultaneous storage of these pulses. This scheme can be applied to achieve optical nonlinearities in the pulsed regime at light levels as low as a few photons per atomic cross section.
University of Calgary | Presentation | 2008-06-11 | A. MacRae, G. Campbell, K. Marzlin, A. Lvovsky |

Giant cross-phase modulation for two slowed co-propagating pulses University of Calgary | Presentation | 2008-07-01 | B. C. Sanders, Z. Wang, K. Marzlin, S. Moiseev |

Giant nonlinearity with double-EIT in rubidium University of Calgary | Presentation | 2005-10-16 | B. C. Sanders, Z. Wang, K. Marzlin |

Giant optical nonlinearities between two matched pulsesOne of the primary limitations of nonlinear optics is that relatively high intensities are needed to produce a noticeable effect. However, in an atomic system with electromagnetically induced transparency (EIT) it is possible to observe nonlinearities at light levels as low as a few photons per atomic cross section [1]. Implementation of the EIT-based nonlinearity with pulsed light may however be challenging as it requires the interacting pulses to propagate at equal group velocities. Recently, a scheme satisfying this requirement was proposed which employs double EIT in atomic Rubidium-87 [2]. We report on our recent progress towards experimentally realizing this scheme. We have successfully demonstrated a double EIT system in which two separate pulses may be simultaneously slowed or stored. By applying a large, homogenous magnetic field across the atomic vapor, thus splitting the atomic levels, we create a large nonlinear interaction in the form of XPM. *References: [1]: H. Schmidt, and V. Imamoglu, Optics Letters 21 23 1996 [2]: Z.B. Wang, K.P. Marzlin, B.C. Sanders, Phys. Rev. Lett. 97 06, 2006 University of Calgary | Presentation | 2008-05-30 | A. MacRae, G. Campbell, Z. Wang, K. Marzlin, B. C. Sanders, A. Lvovsky |

Routing of optical states by atomic mediaElectromagnetically induced transparency (EIT) is a quantum interference
effect, in which a weak signal light field and a stronger control field
drive atomic transitions with a common excited state. The quantum
interference between both light-atom interactions leads to strong
dispersion which causes phenomena such as slowdown and stopping of
light and can be used for enhanced nonlinear interaction.
We extended the standard quantum theory of EIT to accommodate for
multiple excited levels and show experimentally that a transfer of
optical quantum states between different signal modes can be
implemented by an adiabatic change of the control fields.
Raman adiabatic transfer of optical states resembles stimulated Raman
adiabatic passage (STIRAP) but applies to optical rather than atomic
states. It can be used to route and distribute optically encoded
information in classical and quantum communication.
We performed experiments using the hyperfine levels of Rb87 atoms
at the D1 line: First, a signal pulse (resonant to the F=1,
F'=1 transition) was placed into the cell under EIT conditions created
by a control laser (resonant to F=2, F'=1). Then adiabatically this
laser is switched off while another control laser (resonant to F=2,
F'=2) is switched on. This procedure transfers the information carried
by the state of the original signal pulse to the optical mode resonant
with the F=1, F'=2 transition. University of Calgary | Presentation | 2006-05-02 | J. Appel, E. Figueroa, F. Vewinger, K. Marzlin, A. Lvovsky |

Polarization squeezing in atomic Rubidium vapourRecently there has been debate regarding the possibility of using polarization self-rotation (PSR) in a thermal vapour cell as a mechanism for generating a squeezed vacuum state [1,2]. It has been claimed that the squeezing produced by this method is overwhelmed by atomic noise in the thermal vapour [2]. We present a new experimental study on the possibility to generate squeezing in this system and theoretical results that highlight the importance of the atomic ground state decoherence. \newline \newline [1] J. Ries, B. Brezger and A. I. Lvovsky, Pys. Rev. A 68, 025801 (2003). \newline [2] M. T. L. Hsu, G. Hetet, A. Peng, C. C. Harb, H.-A. Bachor, M. T. Johnsson, J. J. Hope, P. K. Lam, A. Dantan, J. Cviklinski, A. Bramati and M. Pinard, Phys. Rev. A 73, 023806 (2006). University of Calgary | Presentation | 2007-06-08 | G. Campbell, C. Healey, J. Appel, K. Marzlin, A. Lvovsky |

Experimental Raman adiabatic transfer of optical states in rubidiumAn essential element of a quantum optical communication network is a tool for transferring and/or distributing quantum information between optical modes (possibly of different frequencies) in a loss- and decoherence-free fashion. We present a theory [1] and an experimental demonstration [2] of a protocol for routing and frequency conversion of optical quantum information via electromagnetically-induced transparency in an atomic system with multiple excited levels. Transfer of optical states between different signal modes is implemented by adiabatically changing the control fields. The proof-of-principle experiment is performed using the hyperfine levels of the rubidium D1 line. [1] F. Vewinger, J. Appel, E. Figueroa, A. I. Lvovsky, quant-ph/0611181 [2] J. Appel, K.-P. Marzlin, A. I. Lvovsky, Phys. Rev. A \\textbf{73}, 013804 (2006) University of Calgary | Presentation | 2007-06-08 | J. Appel, E. Figueroa, F. Vewinger, K. Marzlin, A. Lvovsky |

Relaxing symmetry in CRIB: Combining quantum state storage with data transformationRelaxing symmetry in CRIB: Combining quantum state storage with data
transformation
A. Delfan1, C. La Mela1, M. S. Underwood1, K.-P. Marzlin1, S. Moiseev1,2, and W. Tittel1
1Institute for Quantum Information Science, University of Calgary, Canada
2Kazan Physical-Technical Institute, Russian Academy of Science, Russia
Quantum repeater [1], based on sources of entangled photons, quantum memory, and
single and two qubit gates plus measurements, promise overcoming the distance barrier
of quantum communication protocols. We investigate extensions of a recent quantum
memory protocol based on controlled, reversible, inhomogeneous broadening (CRIB) [2-
5] for combining quantum state storage with transformation of the absorbed quantum
data. More precisely, we relax the symmetry requirement between inhomogeneous
broadening during quantum state absorption and recall, as required for perfectly timereversed
quantum dynamics. We will discuss possibilities for single qubit rotations based
on sequential rephrasing [3], and propose an experiment based on stimulated photon
echoes [4], which serves as a test-bed for the more efficient, CRIB based realization.
Other types of quantum (or classical) data transformation arise from asymmetry in the
rate of de-and rephasing, leading to data compression or decompression [5].
[1] H. Briegel, W. DÃ¼r, I. Cirac, P. Zoller, Phys. Rev. Lett. 81, 5932(1998)
[2] S. A. Moiseev and S. KrÃ¶ll, Phys Rev Lett. 87, 173601(2001),
[3] M. Nilsson and S. KrÃ¶ll, Opt. Commun. 247, 292 (2005),
[4]} A. L. Alexander, J. J. Longdell, N. B. Manson, and M. J. Sellars Phys. Rev. Lett. 96,
043602 (2006).
[5] B. Kraus, W. Tittel, N. Gisin, M. Nilsson, S. Kroll, and J. I. Cirac, Phys. Rev. A. 73,
020302(R) (2006).
[6] see contribution by M.S.Underwood et al.
[7] see contribution by A. Delfan et al.
[8] see contribution by S. Moiseev et al. University of Calgary, The University of Calgary | Presentation | 2008-01-25 | A. Delfan, C. La Mela, M. Underwood, K. Marzlin, S. Moiseev, W. Tittel |

Beyond CRIB-based memory: combining storage with data manipulation University of Calgary, The University of Calgary | Presentation | 2008-03-18 | A. Delfan, C. La Mela, M. Underwood, K. Marzlin, S. Moiseev, W. Tittel |

Combining quantum memory with state manipulation University of Calgary, The University of Calgary | Presentation | 2008-07-02 | A. Delfan, C. La Mela, M. Underwood, K. Marzlin, S. Moiseev, W. Tittel |

Raman adiabatic transfer of optical statesElectromagnetically induced transparency (EIT) is a quantum interference effect occurring when a weak signal light field and a stronger control field interact in atomic ensembles with a lambda-shaped energy level configuration. This effect attracts great interest due to its possible applications in non-linear optics and quantum information processing.
The range of possible applications of EIT extends further in lambda-systems with multiple excited levels. In this work, we show experimentally that by an adiabatic change of the control fields, a transfer of optical states between different signal modes can be implemented [1]. This procedure resembles stimulated Raman adiabatic passage (STIRAP) but applies to optical rather than atomic states. It can be useful for routing and distribution of optically encoded information in classical and quantum communication.
The experiments were performed using the hyperfine levels of Rb 87 atoms at the D1 line. First, we placed a signal pulse (resonant to the F=1, F’=1 transition) into the cell under EIT conditions created by a control laser (resonant to F=2, F’=1). This laser is adiabatically switched off while another control laser (resonant to F=2, F’=2) is switched on. The information carried by the state of the original signal pulse is transferred to the optical mode resonant with the F=1, F’=2 transition. Transfer efficiencies above 50 % have been achieved.
While the experiment was conducted with classical light pulses, the implemented procedure can be extended to nonclassical light [1] and thus can be used for a variety of applications in quantum information processing.
1. J. Appel, K. –P. Marzlin and A. I. Lvovsky. PRA 73, 013804 (2006)
* This work is being supported by NSERC, CFI, AIF, CIAR
University of Calgary | Presentation | 2006-06-12 | E. Figueroa, J. Appel, G. Günter, K. Marzlin, A. Lvovsky |

Decoherence in electromagnetically-induced transparency University of Calgary | Presentation | 2006-02-25 | J. Appel, E. Figueroa, F. Vewinger, G. Günter, K. Marzlin, A. Lvovsky |

Controlling light by electromagnetically-induced transparency University of Calgary | Presentation | 2006-05-07 | J. Appel, E. Figueroa, F. Vewinger, G. Günter, K. Marzlin, A. Lvovsky |

Adiabatic transfer of quantum optical information by means of electromagnetically-induced transparency University of Calgary | Presentation | 2006-07-25 | J. Appel, F. Vewinger, E. Figueroa, G. Günter, K. Marzlin, A. Lvovsky |

Raman adiabatic transfer of optical statesWir pr¨asentieren ein Protokoll zum Transfer von Quantenzust¨anden
zwischen zwei optischenModen basierend auf elektromagnetisch induzierter
Transparenz. Wird ein metastabiler Zustand durch zwei (klassische)
Kontrollfelder an zwei angeregte Zust¨ande gekoppelt, welche wiederum
mittels zweier (quantisierter) Signalfelder an einen weiteren metastabilen
Zustand gekoppelt sind (Multi- Konfiguration), so laesst sich durch
die geeignete Wahl der Kontrollelder der Quantenzustand eines Signalfeldes
adiabatisch auf die zweite Signalmode ¨ubertragen. Wir pr¨asentieren
ein theoretisches Modell, welches den Transfer beschreibt, sowie erste
Ergebnisse auf dem Weg zur experimentellen Implementierung in Rubidiumdampf. University of Calgary | Presentation | 2006-03-13 | F. Vewinger, J. Appel, E. Figueroa, G. Günter, K. Marzlin, A. Lvovsky |

Electromagnetically-induced transparency in systems with multiple excited levels University of Calgary | Presentation | 2006-11-30 | A. Lvovsky, J. Appel, E. Figueroa, G. Günter, F. Vewinger, K. Marzlin |