Publications by Alexander Lvovsky


Continuous-variable quantum-state tomography of optical fields and photons

in , (2007) 409-+

AI Lvovsky, MG Raymer


Electromagnetically-induced transparency with classical and nonclassical light

Optics InfoBase Conference Papers (2007)

J Appel, F Vewinger, E Figueroa, KP Marzlin, AI Lvovsky

We present our progress towards storage of squeezed light by means of electromagnetically-induced transparency as well as a family of protocols for routing, frequency conversion, and geometric steering of optical modes in atomic systems with multiple excited levels. © 2007 Optical Society of America.


Frequency conversion and routing of quantum information in atomic media

SIXTH SYMPOSIUM: OPTICS IN INDUSTRY 6422 (2007) ARTN 64221U

F Vewinger, J Appel, E Figueroa, AI Lvovsky


Electronic noise in optical homodyne tomography

PHYSICAL REVIEW A 75 (2007) ARTN 035802

J Appel, D Hoffman, E Figueroa, AI Lvovsky


Efficiency limits for linear optical processing of single photons and single-rail qubits

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 24 (2007) 189-197

DW Berry, AI Lvovsky, BC Sanders


Characterization of atomic coherence decay for storage of light experiments

SIXTH SYMPOSIUM: OPTICS IN INDUSTRY 6422 (2007) ARTN 64221T

E Figueroa, F Vewinger, J Appel, G Guenter, AI Lvovsky


Characterization of the atomic coherence decay for the storage of light

QUANTUM COMMUNICATIONS AND QUANTUM IMAGING IV 6305 (2006) ARTN 630514

E Figueroa, F Vewinger, J Appel, G Guenter, AI Lvovsky


Raman adiabatic transfer of optical states in multilevel atoms

Physical Review A - Atomic, Molecular, and Optical Physics 73 (2006)

J Appel, KP Marzlin, AI Lvovsky

We analyze electromagnetically induced transparency and light storage in an ensemble of atoms with multiple excited levels (multi- Λ configuration) which are coupled to one of the ground states by quantized signal fields and to the other one via classical control fields. We present a basis transformation of atomic and optical states which reduces the analysis of the system to that of electromagnetically induced transparency in a regular three-level configuration. We demonstrate the existence of dark state polaritons and propose a protocol to transfer quantum information from one optical mode to another by an adiabatic control of the control fields. © 2006 The American Physical Society.


Interconvertibility of single-rail optical qubits

Optics Letters 31 (2006) 107-109

DW Berry, AI Lvovsky, BC Sanders

We show how to convert between partially coherent superpositions of a single photon with the vacuum by using linear optics and postselection based on homodyne measurements. We introduce a generalized quantum efficiency for such states and show that any conversion that decreases this quantity is possible. We also prove that our scheme is optimal by showing that no linear optical scheme with generalized conditional measurements, and with one single-rail qubit input, can improve the generalized efficiency. © 2006 Optical Society of America.


Decoherence of electromagnetically induced transparency in atomic vapor.

Optics letters 31 (2006) 2625-2627

E Figueroa, F Vewinger, J Appel, AI Lvovsky

We report characterization of electromagnetically induced transparency (EIT) resonances in the D1 line of (87)Rb under various experimental conditions. The dependence of the EIT linewidth on the power of the pump field was investigated at various temperatures for the ground states of the lambda system associated with different hyperfine levels of the atomic 5S(1/2) state as well as magnetic sublevels of the same hyperfine level. Strictly linear behavior was observed in all cases. A theoretical analysis of our results shows that dephasing in the ground state is the main source of decoherence, with population exchange playing a minor role.


Pulsed squeezed light: Simultaneous squeezing of multiple modes

PHYSICAL REVIEW A 73 (2006) ARTN 063819

W Wasilewski, AI Lvovsky, K Banaszek, C Radzewicz


Single-qubit optical quantum fingerprinting

Physical Review Letters 95 (2005)

RT Horn, SA Babichev, KP Marzlin, AI Lvovsky, BC Sanders

We analyze and demonstrate the feasibility and superiority of linear optical single-qubit fingerprinting over its classical counterpart. For one-qubit fingerprinting of two-bit messages, we prepare " tetrahedrala" qubit states experimentally and show that they meet the requirements for quantum fingerprinting to exceed the classical capability. We prove that shared entanglement permits 100% reliable quantum fingerprinting, which will outperform classical fingerprinting even with arbitrary amounts of shared randomness. © 2005 The American Physical Society.


Classical and quantum fingerprinting with shared randomness and one-sided error

Quantum Information and Computation 5 (2005) 258-271

RT Horn, AJ Scott, J Walgate, R Cleve, AI Lvovsky, BC Sanders

Within the simultaneous message passing model of communication complexity, under a public-coin assumption, we derive the minimum achievable worst-case error probability of a classical fingerprinting protocol with one-sided error. We then present entanglement-assisted quantum fingerprinting protocols attaining worst-case error probabilities that breach this bound. © Rinton Press.


New results in optical homodyne tomography and their applications to quantum information technology

IQEC, International Quantum Electronics Conference Proceedings 2005 (2005) 1532-1533

AI Lvovsky, SA Babichev, J Appel


Continuous-variable experiments with optical qubits

Proceedings of SPIE - The International Society for Optical Engineering 5631 (2005) 42-50

SA Babichev, J Appel, AI Lvovsky

We present experimental homodyne tomography of an optical quantum bit represented by a single photon split into two optical modes. The reconstructed four-dimensional density matrix extends over the entire Hilbert space and thus reveals, for the first time, complete information about the dual-rail optical qubit as a state of the electromagnetic field. The experimental data violate the Bell inequality albeit with a loophole similar to the detection loophole in photon counting experiments. We also show that a homodyne measurement on just one of the modes leads to remote preparation of a single-rail optical qubit in the other mode.


Remote Preparation of a Single-Mode Photonic Qubit by Measuring Field Quadrature Noise

Physical Review Letters 92 (2004) 4-

SA Babichev, B Brezger, AI Lvovsky

An electromagnetic field quadrature measurement, performed on one of the modes of the nonlocal single-photon state [Formula presented], collapses it into a superposition of the single-photon and vacuum states in the other mode. We use this effect to implement remote preparation of arbitrary single-mode photonic qubits conditioned on observation of a preselected quadrature value. The preparation efficiency of the resulting qubit can be higher than that of the initial single photon. © 2004 The American Physical Society.


Remote Preparation of a Single-Mode Photonic Qubit by Measuring Field Quadrature Noise

Physical Review Letters 92 (2004) 479031-479034

SA Babichev, B Brezger, AI Lvovsky

Remote state preparation of single-mode photonic quantum bits in a counter intuitive scheme was discussed. An electromagnetic field quadrature measurement was performed. The measurements collapses the nonlocal single-photon state into a superposition of the single-photon and vacuum states in the other mode. It was found that the preparation efficiency of the resulting qubit can be higher than that of the initial single photon.


Conditionally prepared photon and quantum imaging

Proceedings of SPIE - The International Society for Optical Engineering 5551 (2004) 1-6

AI Lvovsky, T Aichele

We discuss a classical model allowing one to visualize and characterize the optical mode of the single photon generated by means of a conditional measurement on a biphoton produced in parametric down-conversion. The model is based on Klyshko's advanced wave interpretation, but extends beyond it, providing a precise mathematical description of the advanced wave. The optical mode of the conditional photon is shown to be identical to the mode of the classical difference-frequency field generated due to nonlinear interaction of the partially coherent advanced wave with the pump pulse. With this "nonlinear advanced wave model" most coherence properties of the conditional photon become manifest, which permits one to intuitively understand many recent results, in particular, in quantum imaging.


Iterative maximum-likelihood reconstruction in quantum homodyne tomography

Journal of Optics B: Quantum and Semiclassical Optics 6 (2004)

AI Lvovsky

I propose an iterative expectation maximization algorithm for reconstructing the density matrix of an optical ensemble from a set of balanced homodyne measurements. The algorithm applies directly to the acquired data, bypassing the intermediate step of calculating marginal distributions. The advantages of the new method are made manifest by comparing it with the traditional inverse Radon transformation technique.


Homodyne tomography characterization and nonlocality of a dual-mode optical qubit

Physical Review Letters 92 (2004)

SA Babichev, J Appel, AI Lvovsky

Homodyne tomography was used for analyzing a two-mode optical quibit with a reconstructed Wigner function and density matrix. A conditional measurement on a biphoton produced through parametric down-conversion aided in preparing the initial single-photon state. The dual-rail optical quantum bit was found to be a state of the electromagnetic field. A nonlocal character of the delocalized single photon that noncontextually violated the Bell inequality albeit was revealed.

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