Demonstration of atomic frequency comb memory for light with spin-wave storage (2009)
Afzelius, Mikael, Usmani, Imam, Amari, Atia, Lauritzen, Björn, Walther, Andreas, Simon, Christoph, ...
We present a light-storage experiment where the light is mapped onto an inhomogeneously broadened optical transition in a praseodymium-doped crystal, which is shaped into an atomic frequency comb....
Solid state quantum memory for photons at telecommunication wavelengths (2009)
Lauritzen, Björn, Minář, Jiří, De Riedmatten, Hugues, Afzelius, Mikael, Sangouard, Nicolas, Simon, Christoph, ...
We demonstrate experimentally a solid-state quantum memory for photons at telecommunication wavelengths. Weak light fields at the single photon level are stored for a time up to 600 ns in an...
Conscious observers clarify many worlds (2009)
In this brief note I argue that putting conscious observers at the center of the considerations clarifies and strengthens the many-worlds interpretation. The basic assumption, which seems extremely...
Electric control of collective atomic coherence in an Erbium doped solid (2009)
Minář, Jiří, Lauritzen, Björn, De Riedmatten, Hugues, Afzelius, Mikael, Simon, Christoph, Gisin, Nicolas
We demonstrate fast and accurate control of the evolution of collective atomic coherences in an Erbium doped solid using external electric fields. This is achieved by controlling the inhomogeneous...
Quantum repeaters based on atomic ensembles and linear optics (2009)
Sangouard, Nicolas, Simon, Christoph, De Riedmatten, Hugues, Gisin, Nicolas
The distribution of quantum states over long distances is limited by photon loss. Straightforward amplification as in classical telecommunications is not an option in quantum communication because of...
Ottaviani, Carlo, Simon, Christoph, De Riedmatten, Hugues, Afzelius, Mikael, Lauritzen, Bjoern, Sangouard, Nicolas, ...
The creation of single collective excitations in atomic ensembles via spontaneous Raman emission plays a key role in several quantum communication protocols, starting with the seminal DLCZ protocol...
Quantum Repeaters based on Single Trapped Ions (2009)
Sangouard, Nicolas, Dubessy, Romain, Simon, Christoph
We analyze the performance of a quantum repeater protocol based on single trapped ions. At each node, single trapped ions embedded into high finesse cavities emit single photons whose polarization is...
Quantum experiments with human eyes as detectors based on cloning via stimulated emission (2009)
Sekatski, Pavel, Brunner, Nicolas, Branciard, Cyril, Gisin, Nicolas, Simon, Christoph
We show theoretically that the multi-photon states obtained by cloning single-photon qubits via stimulated emission can be distinguished with the naked human eye with high efficiency and fidelity....
Quantum Repeaters based on Single Trapped Ions (2009)
Sangouard, Nicolas, Dubessy, Romain, Simon, Christoph
We analyze the performance of a quantum repeater protocol based on single trapped ions. At each node, single trapped ions embedded into high finesse cavities emit single photons whose polarization is...
Quantum Repeaters based on Single Trapped Ions (2009)
Sangouard, Nicolas, Dubessy, Romain, Simon, Christoph
We analyze the performance of a quantum repeater protocol based on single trapped ions. At each node, single trapped ions embedded into high finesse cavities emit single photons whose polarization is...
Quantum Repeaters based on Single Trapped Ions (2009)
Sangouard, Nicolas, Dubessy, Romain, Simon, Christoph
We analyze the performance of a quantum repeater protocol based on single trapped ions. At each node, single trapped ions embedded into high finesse cavities emit single photons whose polarization is...
Quantum Repeaters based on Single Trapped Ions (2009)
Sangouard, Nicolas, Dubessy, Romain, Simon, Christoph
We analyze the performance of a quantum repeater protocol based on single trapped ions. At each node, single trapped ions embedded into high finesse cavities emit single photons whose polarization is...
Purification of single-photon entanglement with linear optics (2008)
Sangouard, Nicolas, Simon, Christoph, Coudreau, Thomas, Gisin, Nicolas
We show that single-photon entangled states of the form |0>|1>+|1>|0> can be purified with a simple linear-optics based protocol, which is eminently feasible with current technology. Besides its...
Testing a Bell inequality in multi-pair scenarios (2008)
Bancal, Jean-Daniel, Branciard, Cyril, Brunner, Nicolas, Gisin, Nicolas, Popescu, Sandu, Simon, Christoph
To date, most efforts to demonstrate quantum nonlocality have concentrated on systems of two (or very few) particles. It is however difficult in many experiments to address individual particles,...
A solid state light-matter interface at the single photon level (2008)
De Riedmatten, Hugues, Afzelius, Mikael, Staudt, Matthias, Simon, Christoph, Gisin, Nicolas
Coherent and reversible mapping of quantum information between light and matter is an important experimental challenge in quantum information science. In particular, it is a decisive milestone for...
Why the two-pulse photon echo is not a good quantum memory protocol (2008)
Ruggiero, Jérôme, Gouët, Jean-Louis Le, Simon, Christoph, Chanelière, Thierry
We consider in this paper a two-pulse photon echo sequence as a potential quantum light storage protocol. It is widely believed that a two-pulse scheme should lead to very low efficiency and is then...
Multi-Mode Quantum Memory based on Atomic Frequency Combs (2008)
Afzelius, Mikael, Simon, Christoph, De Riedmatten, Hugues, Gisin, Nicolas
An efficient multi-mode quantum memory is a crucial resource for long-distance quantum communication based on quantum repeaters. We propose a quantum memory based on spectral shaping of an...
Robust and Efficient Quantum Repeaters with Atomic Ensembles and Linear Optics (2008)
Sangouard, Nicolas, Simon, Christoph, Zhao, Bo, Chen, Yu-Ao, De Riedmatten, Hugues, Pan, Jian-Wei, ...
In the last few years there has been a lot of interest in quantum repeater protocols using only atomic ensembles and linear optics. Here we show that the local generation of high-fidelity entangled...
Phase noise measurements in long fiber interferometers for quantum repeaters applications (2007)
Minář, Jiří, De Riedmatten, Hugues, Simon, Christoph, Zbinden, Hugo, Gisin, Nicolas
Many protocols for long distance quantum communication require interferometric phase stability over long distances of optical fibers. In this paper we investigate the phase noise in long optical...
Long-Distance Entanglement Distribution with Single-Photon Sources (2007)
Sangouard, Nicolas, Simon, Christoph, Minar, Jiri, Zbinden, Hugo, De Riedmatten, Hugues, Gisin, Nicolas
We present an efficient architecture for quantum repeaters based on single-photon sources in combination with quantum memories for photons. Errors inherent to previous repeater protocols using...
Entangling Independent Photons by Time Measurement (2007)
Halder, Matthaeus, Beveratos, Alexios, Gisin, Nicolas, Scarani, Valerio, Simon, Christoph, Zbinden, Hugo
A quantum system composed of two or more subsystems can be in an entangled state, i.e. a state in which the properties of the global system are well defined but the properties of each subsystem are...
Detection loophole in asymmetric Bell experiments (2007)
Brunner, Nicolas, Gisin, Nicolas, Scarani, Valerio, Simon, Christoph
The problem of closing the detection loophole with asymmetric systems, such as entangled atom-photon pairs, is addressed. We show that, for the Bell inequality I_3322, a minimal detection efficiency...
Quantum Repeaters with Photon Pair Sources and Multi-Mode Memories (2007)
Simon, Christoph, De Riedmatten, Hugues, Afzelius, Mikael, Sangouard, Nicolas, Zbinden, Hugo, Gisin, Nicolas
We propose a quantum repeater protocol which builds on the well-known DLCZ protocol [L.M. Duan, M.D. Lukin, J.I. Cirac, and P. Zoller, Nature 414, 413 (2001)], but which uses photon pair sources in...
Comment on "Separability of quantum states and the violation of Bell-type inequalities" (2006)
The statement of E.R. Loubenets, Phys. Rev. A 69, 042102 (2004), that separable states can violate classical probabilistic constraints is based on a misleading definition of classicality, which is...
Creating single time-bin entangled photon pairs (2006)
Simon, Christoph, Poizat, Jean-Philippe
When a single emitter is excited by two phase-coherent pulses with a time delay, each of the pulses can lead to the emission of a photon pair, thus creating a ``time-bin entangled'' state. Double...
Could Energy Decoherence due to Quantum Gravity be observed? (2006)
Simon, Christoph, Jaksch, Dieter
It has recently been proposed that quantum gravity might lead to the decoherence of superpositions in energy, corresponding to a discretization of time at the Planck scale. At first sight the...
Sangouard, Nicolas, Simon, Christoph, Afzelius, Mikael, Gisin, Nicolas
We present a detailed analysis of a quantum memory for photons based on controlled and reversible inhomogeneous broadening (CRIB). The explicit solution of the equations of motion is obtained in the...
Auffeves-Garnier, Alexia, Simon, Christoph, Gerard, Jean-Michel, Poizat, Jean-Philippe
A two-level system that is coupled to a high-finesse cavity in the Purcell regime exhibits a giant optical non-linearity due to the saturation of the two-level system at very low intensities, of the...
Quantum Communication with Quantum Dot Spins (2006)
Simon, Christoph, Niquet, Yann-Michel, Caillet, Xavier, Eymery, Joel, Poizat, Jean-Philippe, Gerard, Jean-Michel
Single electron spins in quantum dots are attractive for quantum communication because of their expected long coherence times. We propose a method to create entanglement between two remote spins...
Precision of single-qubit gates based on Raman transitions (2005)
Caillet, Xavier, Simon, Christoph
We analyze the achievable precision for single-qubit gates that are based on Raman transitions between two near-degenerate ground states via a virtually excited state. In particular, we study the...
Multi-Partite Entanglement Inequalities via Spin Vector Geometry (2005)
Durkin, Gabriel A., Simon, Christoph
We introduce inequalities for multi-partite entanglement, derived from the geometry of spin vectors. The criteria are constructed iteratively from cross and dot products between the spins of...
Realisation of Hardy's Thought Experiment (2004)
Irvine, William T. M., Hodelin, Juan F., Simon, Christoph, Bouwmeester, Dirk
We present an experimental realisation of Hardy's thought experiment [Phys. Rev. Lett. {\bf 68}, 2981 (1992)], using photons. The experiment consists of a pair of Mach-Zehnder interferometers that...
Comment on "Separability of quantum states and the violation of Bell-type inequalities" (2004)
The statement of E.R. Loubenets, Phys. Rev. A 69, 042102 (2004), that separable states can violate classical probabilistic constraints is based on a misleading definition of classicality, which is...
Creating single time-bin entangled photon pairs (2004)
Simon, Christoph, Poizat, Jean-Philippe
When a single emitter is excited by two phase-coherent pulses with a time delay, each of the pulses can lead to the emission of a photon pair, thus creating a ``time-bin entangled'' state. Double...
Could Energy Decoherence due to Quantum Gravity be observed? (2004)
Simon, Christoph, Jaksch, Dieter
It has recently been proposed that quantum gravity might lead to the decoherence of superpositions in energy, corresponding to a discretization of time at the Planck scale. At first sight the...
Entanglement Detection Based on Interference and Particle Counting (2003)
Toth, Geza, Simon, Christoph, Cirac, Juan Ignacio
A sufficient condition for entanglement in two-mode continuous systems is constructed based on interference visibility and the uncertainty of the total particle number. The observables to be measured...
Robust long-distance entanglement and a loophole-free Bell test with ions and photons (2003)
Simon, Christoph, Irvine, William T. M.
Two trapped ions that are kilometers apart can be entangled by the joint detection of two photons, each coming from one of the ions, in a basis of entangled states. Such a detection is possible with...
Theory of an Entanglement Laser (2003)
Simon, Christoph, Bouwmeester, Dik
We consider the creation of polarization entangled light from parametric down- conversion driven by an intense pulsed pump inside a cavity. The multi-photon states produced are close approximations...
Towards quantum superpositions of a mirror (2002)
Marshall, William, Simon, Christoph, Penrose, Roger, Bouwmeester, Dik
We propose a scheme for creating quantum superposition states involving of order $10^{14}$ atoms via the interaction of a single photon with a tiny mirror. This mirror, mounted on a high-quality...
Experimental Quantum Cloning of Single Photons (2002)
Lamas-Linares, Antia, Simon, Christoph, Howell, John C., Bouwmeester, Dik
Although perfect copying of unknown quantum systems is forbidden by the laws of quantum mechanics, approximate cloning is possible. A natural way of realizing quantum cloning of photons is by...
On the effective size of certain "Schr\"{o}dinger cat'' like states (2002)
Dür, Wolfgang, Simon, Christoph, Cirac, J. Ignacio
Several experiments and experimental proposals for the production of macroscopic superpositions naturally lead to states of the general form $|\phi_1>^{\otimes N}+|\phi_2>^{\otimes N}$, where the...
On the quantification of entanglement in infinite-dimensional quantum systems (2001)
Eisert, Jens, Simon, Christoph, Plenio, Martin B.
We investigate entanglement measures in the infinite-dimensional regime. First, we discuss the peculiarities that may occur if the Hilbert space of a bi-partite system is infinite-dimensional, most...
Natural Entanglement in Bose-Einstein Condensates (2001)
Every Bose-Einstein condensate is in a highly entangled state, as a consequence of the fact that the particles in a condensate are distributed over space in a coherent way. It is proved that any two...
Multi-Photon Entanglement Concentration and Quantum Cryptography (2001)
Durkin, Gabriel A., Simon, Christoph, Bouwmeester, Dik
Multi-photon states from parametric down-conversion can be entangled both in polarization and photon number. Maximal high-dimensional entanglement can be concentrated from these states via photon...
Robustness of Multi-Party Entanglement (2001)
Simon, Christoph, Kempe, Julia
How common is large-scale entanglement in nature? As a first step towards addressing this question, we study the robustness of multi-party entanglement under local decoherence, modeled by partially...
Probabilistic instantaneous quantum computation (2001)
Brukner, Caslav, Pan, Jian-Wei, Simon, Christoph, Weihs, Gregor, Zeilinger, Anton
The principle of teleportation can be used to perform a quantum computation even before its quantum input is defined. The basic idea is to perform the quantum computation at some earlier time with...
Polarization Entanglement Purification using Spatial Entanglement (2001)
Simon, Christoph, Pan, Jian-Wei
Parametric down-conversion can produce photons that are entangled both in polarization and in space. Here we show how the spatial entanglement can be used to purify the polarization entanglement...
The Foundations of Quantum Information and Feasible Experiments (2001)
This thesis consists of four parts. In the first part it is shown that optimal universal cloning of photons can be realized with the help of stimulated emission. Possible schemes based on three-level...
Carollo, Angelo, Palma, G. Massimo, Simon, Christoph, Zeilinger, Anton
In a recent paper Bennett et al.[Phys. Rev.A 59, 1070 (1999)] have shown the existence of a basis of product states of a bipartite system with manifest non-local properties. In particular these...
The no-signaling condition and quantum dynamics (2001)
Simon, Christoph, Buzek, Vladimir, Gisin, Nicolas
We show that the basic dynamical rules of quantum physics can be derived from its static properties and the condition that superluminal communication is forbidden. More precisely, the fact that the...
Feasible Entanglement Purification for Quantum Communication (2000)
Pan, Jian-Wei, Simon, Christoph, Brukner, Caslav, Zeilinger, Anton
The distribution of entangled states between distant locations will be essential for the future large scale realization of quantum communication schemes such as quantum cryptography and quantum...
A feasible "Kochen-Specker" experiment with single particles (2000)
Simon, Christoph, Zukowski, Marek, Weinfurter, Harald, Zeilinger, Anton
We present a simple experimental scheme which can be used to demonstrate an all-or-nothing type contradiction between non-contextual hidden variables and quantum mechanics. The scheme, which is...
Hidden-variable theorems for real experiments (2000)
Simon, Christoph, Brukner, Caslav, Zeilinger, Anton
It has recently been questioned whether the Kochen-Specker theorem is relevant to real experiments, which by necessity only have finite precision. We give an affirmative answer to this question by...
Lambda's, V's and optimal cloning with stimulated emission (2000)
Kempe, Julia, Simon, Christoph, Weihs, Gregor
We show that optimal universal cloning of the polarization state of photons can be achieved via stimulated emission in three-level systems, both of the Lambda and the V type. We establish the...
Quantum Cryptography with Entangled Photons (1999)
Jennewein, Thomas, Simon, Christoph, Weihs, Gregor, WeinfurterD, Harald, Zeilinger, Anton
By realizing a quantum cryptography system based on polarization entangled photon pairs we establish highly secure keys, because a single photon source is approximated and the inherent randomness of...
Optimal Quantum Cloning via Stimulated Emission (1999)
Simon, Christoph, Weihs, Gregor, Zeilinger, Anton
We show that optimal universal quantum cloning can be realized via stimulated emission. Universality of the cloning procedure is achieved by choosing systems that have appropriate symmetries. We...
Violation of Bell's inequality under strict Einstein locality conditions (1998)
Weihs, Gregor, Jennewein, Thomas, Simon, Christoph, Weinfurter, Harald, Zeilinger, Anton
We observe strong violation of Bell's inequality in an Einstein, Podolsky and Rosen type experiment with independent observers. Our experiment definitely implements the ideas behind the well known...