Publications by Alexander Lvovsky


Teleportation and nonlocality by means of a single photon

2003 European Quantum Electronics Conference, EQEC 2003 (2003) 412-

SA Babichev, J Ries, AI Lvovsky

Generation of single-photon pulses by means of conditional measurements on photon pairs generated in spontaneous parametric down-conversion is reported. Positive measurement results by Alice's Bell-state analyzer triggered Bob's balanced homodyne detector, which is used for characterizing the teleported state. Optical phase of the source state is varied to demonstrate the nonclassical nature of the teleportation and teleportation fidelity for various a's is evaluated and find it close to unity for α蠐1. A homodyne tomography characterization of the state is presented and whether local hidden variable theory can explain these measurements is also discussed.


Cabello’s Nonlocality and Linear Optics

Physical Review Letters 88 (2002) 1-

AI Lvovsky


Quantum-Optical Catalysis: Generating Nonclassical States of Light by Means of Linear Optics

Physical Review Letters 88 (2002) 4-

AI Lvovsky, J Mlynek

We report preparation and characterization of coherent superposition states [Formula presented] of the electromagnetic field by conditional measurements on a beam splitter. This state is generated in one of the beam splitter output channels if a coherent state [Formula presented] and a single-photon Fock state [Formula presented] are present in the two input ports and a single photon is registered in the other beam splitter output. The single photon thus plays a role of a “catalyst:” it is explicitly present in both the input and the output channels of the interaction yet facilitates generation of a nonclassical state of light. © 2002 The American Physical Society.


Nonclassical character of statistical mixtures of the single-photon and vacuum optical states

Physical Review A - Atomic, Molecular, and Optical Physics 65 (2002) 1-6

AI Lvovsky, JH Shapiro

The electric-field-quadrature statistics of the ensembles of the vacuum state 0> are nonclassical according to the Vogel criterion. These states were synthesized and measured with an improved pair-production rate achieved by the pulse picking method. The Vogel criterion is generalized to apply to quadrature distributions obtained in interferometrically unstable settings. In addition, a quantitative analysis of statistical errors is given.


Synthesis and tomographic characterization of the displaced Fock state of light

Physical Review A - Atomic, Molecular, and Optical Physics 66 (2002) 4-

AI Lvovsky, SA Babichev

Displaced Fock states of the electromagnetic field have been synthesized by overlapping the pulsed optical single-photon Fock state [Formula Presented] with coherent states on a high-reflection beam splitter and completely characterized by means of quantum homodyne tomography. The reconstruction reveals nonclassical properties of displaced Fock states, such as negativity of the Wigner function and photon number oscillations. To our knowledge, this is the first time complete tomographic reconstruction has been performed on a highly nonclassical optical state. 5555 2002 The American Physical Society.


Bulk contribution from isotropic media in surface sum-frequency generation

Physical Review B - Condensed Matter and Materials Physics 66 (2002) 1-7

H Held, AI Lvovsky, X Wei, YR Shen

We present systematic conceptual and experimental investigations of the bulk contribution to surface sum-frequency generation (SFG) from an isotropic medium. A practical method for the analysis of spectra obtained in a transmission geometry is presented which allows to estimate the bulk contribution in any future application. A systematic degeneracy due to the molecular nature of the material is found which makes a subtle interpretation of transmission experiments necessary. Practical consequences for the analysis of typical SFG spectra are discussed. © 2002 The American Physical Society.


Bulk contribution from isotropic media in surface sum-frequency generation

Physical Review B - Condensed Matter and Materials Physics 66 (2002) 2051101-2051107

H Held, AI Lvovsky, X Wei, YR Shen

We present systematic conceptual and experimental investigations of the bulk contribution to surface sum-frequency generation (SFG) from an isotropic medium. A practical method for the analysis of spectra obtained in a transmission geometry is presented which allows to estimate the bulk contribution in any future application. A systematic degeneracy due to the molecular nature of the material is found which makes a subtle interpretation of transmission experiments necessary. Practical consequences for the analysis of typical SFG spectra are discussed.


Cabello's nonlocality and linear optics

Physical Review Letters 88 (2002) 989011-

AI Lvovsky

A study on the quantum nonlocality without inequalities and without probabilities for two observers was performed. Cabello's proposal for nonlocality was challenged and it was shown that nonlinear optics was required for a loophole-free demonstration of Cabello's nonlocality. Cabello had proposed a way of testing the inequality by means of linear optics and used the product of two observable quantities as a single quantum measurement.


Superfluorescence-Stimulated Photon Echoes

Physical Review Letters 89 (2002)

AI Lvovsky, SR Hartmann, F Moshary

Two closely spaced 778 nm, 4-ps pulses, two-photon resonant with the [Formula presented] transition in Rb vapor generate a ground state grating, which later is excited by a similar third pulse, producing conical yoked superfluorescence echo on the [Formula presented], 420-nm transition. The intensity of this emission as a function of the relative delay between the leading excitation pulses is governed by the dynamics of Doppler dephasing and rephasing. This is the first observation of an echo effect induced by a spontaneous relaxation process. © 2002 The American Physical Society.


Nonclassical character of statistical mixtures of the single-photon and vacuum optical states

Physical Review A - Atomic, Molecular, and Optical Physics 65 (2002) 1-6

AI Lvovsky, JH Shapiro

The electric-field-quadrature statistics of the ensembles of the vacuum state 0> are nonclassical according to the Vogel criterion. These states were synthesized and measured with an improved pair-production rate achieved by the pulse picking method. The Vogel criterion is generalized to apply to quadrature distributions obtained in interferometrically unstable settings. In addition, a quantitative analysis of statistical errors is given.


Quantum-optical catalysis by means of a single photon

Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series 74 (2002)

AI Lvovsky, J Mlynek

We convert coherent states of light into nonclassical coherent superpositions of the vacuum and the single-photon states via conditional measurements on a beamsplitter, employing single photons as "catalysts": they facilitate the conversion without being consumed.


Quantum-optical catalysis: Generating nonclassical states of light by means of linear optics

Physical Review Letters 88 (2002) 2504011-2504014

AI Lvovsky, J Mlynek

The preparation and characterization of a new quantum state of light, a coherent superposition of the single-photon and vaccum states was discussed. This state was generalized by a catalytic process in which the single photon state enabled the interaction without being affected. A transition between a highly classical and a highly nonclassical state of light occurred by changing the amplitude of the target coherent state.


Optical mode characterization of single photons prepared by means of conditional measurements on a biphoton state

European Physical Journal D 18 (2002) 237-245

T Aichele, AI Lvovsky, S Schiller

A detailed theoretical analysis of the spatiotemporal mode of a single photon prepared via conditional measurements on a photon pair generated in the process of parametric down-conversion is presented. The maximum efficiency of coupling the photon into a transform-limited classical optical mode is calculated and ways for its optimization are determined. An experimentally feasible technique of generating the optimally matching classical mode is proposed. The theory is applied to a recent experiment on pulsed homodyne tomography of the single-photon Fock state [A.I. Lvovsky et al., Phys. Rev. Lett. 87, 050402 (2001)]. © EDP Sciences, Springer-Verlag, Società Italiana di Fisica 2002.


Quantum tomography of the single-photon Fock state

Technical Digest - Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, QELS 2001 (2001) 238-239

AI Lvovsky, T Aichele, H Hansen, O Benson, J Mlynek, S Schiller

© 2001 Optical Soc. Of America. Summary form only given. The single photon Fock state is one of the most fundamental states of the light field. It is highly non-classical and reveals the wave-particle duality of light most strikingly. Its marginal distributions are of non-Gaussian shape and its Wigner function exhibits a strong negativity around the origin of phase space. Although the reconstruction of the Fock state has already been performed for the motional state of trapped beryllium ions, in the optical domain this task has not been resolved so far, the main difficulty being the lack of coherent single-photon sources. We present results of applying the technique of optical homodyne tomography to the single photon Fock state prepared by conditional measurements on a photon pair produced in parametric down conversion.


Ultrasensitive pulsed, balanced homodyne detector: Application to time-domain quantum measurements

Optics Letters 26 (2001) 1714-1716

H Hansen, T Aichele, C Hettich, P Lodahl, AI Lvovsky, J Mlynek, S Schiller

A pulsed, balanced homodyne detector has been developed for precise measurement of the electric field quadratures of pulsed optical quantum states. A high level of common mode suppression (>85 dB) and low electronic noise (730 electrons per pulse) provide a signal-to-noise ratio of 14 dB for measurement of the quantum noise of individual pulses. Measurements at repetition rates as high as 1 MHz are possible. As a test, quantum tomography of the coherent state was performed, and the Wigner function and the density matrix were reconstructed with 99.5% fidelity. The detection system can be used for ultrarsensitive balanced detection in cw mode, e.g., for weak absorption measurements. © 2001 Optical Society of America.


Quantum state reconstruction of the single-photon fock state

Physical Review Letters 87 (2001) 50402-1-50402-4-

AI Lvovsky, H Hansen, T Aichele, O Benson, J Mlynek, S Schiller

We have reconstructed the quantum state of optical pulses containing single photons using the method of phase-randomized pulsed optical homodyne tomography. The single-photon Fock state |1⟩ was prepared using conditional measurements on photon pairs born in the process of parametric down-conversion. A probability distribution of the phase-averaged electric field amplitudes with a strongly non-Gaussian shape is obtained with the total detection efficiency of (55 ± 1)%. The angle-averaged Wigner function reconstructed from this distribution shows a strong dip reaching classically impossible negative values around the origin of the phase space. © 2001 American Physical Society.


Nonlinear optical studies of surface structures of rubbed polyimides and adsorbed liquid crystal monolayers

Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals 364 (2001) 427-434

M Oh-E, AI Lvovsky, X Wei, D Kim, YR Shen

Sum-frequency generation (SFG) vibrational spectroscopy and second-harmonic generation (SHG) were used to probe rubbed polyimide (PI) surfaces and liquid crystal (LC) monolayers adsorbed on them. The results show that rubbing preferentially aligns PI backbones along the rubbing direction, but has little effect on the side chain orientation at the surface. However, adsorption of an LC monolayer well aligned by the rubbed PI surface can cause the side chains to tilt towards the rubbing direction. © 2001 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint, a member of the Taylor & Francis Group,.


Quantum state reconstruction of the single-photon Fock state

Physical Review Letters 87 (2001)

AI Lvovsky, H Hansen, T Aichele, O Benson, J Mlynek, S Schiller

The phase-averaged Wigner function and the density matrix diagonal elements of an optical single-photon Fock state |1> were reconstructed using the method of phase-randomized pulsed optical homodyne tomography. A total measurement efficiency of 55.3 ± 1.3% was obtained. The measurement technique and error analysis were checked by performing a simultaneous measurement on the vacuum state.


High-resolution Doppler-free molecular spectroscopy with a continuous-wave optical parametric oscillator

Conference on Lasers and Electro-Optics Europe - Technical Digest (2001) 539-

EV Kovalchuk, D Dekorsy, AI Lvovsky, C Braxmaier, J Mlynek, A Peters, S Schiller

A continuous-wave optical parametric oscillator was used for high-resolution Doppler-free molecular spectroscopy. The Doppler-free dispersive signal was obtained using the Pound-Drever-Hall frequency modulation technique and scanning the OPO frequency over a 5-MHz wide range. The observed linewidth of 500 kHz was attributed to medium-term OPO frequency jitter and pressure broadening.


Experimental evaluation of the surface specificity of sum-frequency vibrational spectroscopy

Conference on Quantum Electronics and Laser Science (QELS) - Technical Digest Series (2000) 261-262

X Wei, SC Hong, AI Lvovsky, H Held, YR Shen

Quantitative measurements and comparison of reflected and transmitted sum-frequency generation (SFG) spectra were carried out for a number of samples. The obtained data was used to determine whether the reflected SFG spectra of the samples are surface-dominated.

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