Publications by Alexander Lvovsky

Tomography of a high-purity narrowband photon from a transient atomic collective excitation.

Physical review letters 109 (2012) 033601-

A MacRae, T Brannan, R Achal, AI Lvovsky

We demonstrate efficient heralded generation of high purity narrow-bandwidth single photons from a transient collective spin excitation in a hot atomic vapor cell. Employing optical homodyne tomography, we fully reconstruct the density matrix of the generated photon and observe a Wigner function reaching the zero value without correcting for any inefficiencies. The narrow bandwidth of the photon produced is accompanied by a high generation rate yielding a high spectral brightness. The source is, therefore, compatible with atomic-based quantum memories as well as other applications in light-atom interfacing. This Letter paves the way to preparing and measuring arbitrary superposition states of collective atomic excitations.

Note: a monolithic filter cavity for experiments in quantum optics.

The Review of scientific instruments 83 (2012) 066101-

P Palittapongarnpim, A MacRae, AI Lvovsky

By applying a high-reflectivity dielectric coating on both sides of a commercial plano-convex lens, we produce a stable monolithic Fabry-Perot cavity suitable for use as a narrow band filter in quantum optics experiments. The resonant frequency is selected by means of thermal expansion. Owing to the long term mechanical stability, no optical locking techniques are required. We characterize the cavity performance as an optical filter, obtaining a 45dB suppression of unwanted modes while maintaining a transmission of 60%.

Conservation of Vacuum in an Interferometer


DW Berry, AI Lvovsky, IEEE

On quantum efficiencies of optical states

Optics InfoBase Conference Papers (2011)

DW Berry, AI Lvovsky

We propose a universal measure of efficiency associated with a quantum-optical state and show that this efficiency cannot be improved by any linear-optical processing combined with destructive conditional measurements. © 2011 Optical Society of America.

Quantum-optical process tomography using coherent states


M Lobino, S Rahimi-Keshari, D Korystov, C Kupchak, E Figueroa, A Scherer, BC Sanders, AI Lvovsky

A balanced homodyne detector for high-rate Gaussian-modulated coherent-state quantum key distribution


Y-M Chi, B Qi, W Zhu, L Qian, H-K Lo, S-H Youn, AI Lvovsky, L Tian

Transverse multimode effects on the performance of photon-photon gates

PHYSICAL REVIEW A 83 (2011) ARTN 022312

B He, A MacRae, Y Han, AI Lvovsky, C Simon

Quantum process tomography with coherent states


S Rahimi-Keshari, A Scherer, A Mann, AT Rezakhani, AI Lvovsky, BC Sanders

Preservation of loss in linear-optical processing

PHYSICAL REVIEW A 84 (2011) ARTN 042304

DW Berry, AI Lvovsky

Conservation of vacuum in an interferometer

2011 Conference on Lasers and Electro-Optics: Laser Science to Photonic Applications, CLEO 2011 (2011)

DW Berry, AI Lvovsky

We provide a systematic method of quantifying the amount of loss a multimode optical state has experienced. We show that it is not possible to concentrate the non-vacuum components via linear optics. © 2011 OSA.

Quantum-optical state engineering up to the two-photon level

NATURE PHOTONICS 4 (2010) 243-247

E Bimbard, N Jain, A MacRae, AI Lvovsky

A bridge between the single-photon and squeezed-vacuum states.

Optics express 18 (2010) 18254-18259

N Jain, SR Huisman, E Bimbard, AI Lvovsky

The two modes of the Einstein-Podolsky-Rosen quadrature entangled state generated by parametric down-conversion interfere on a beam splitter of variable splitting ratio. Detection of a photon in one of the beam splitter output channels heralds preparation of a signal state in the other, which is characterized using homodyne tomography. By controlling the beam splitting ratio, the signal state can be chosen anywhere between the single-photon and squeezed state.

Linear-optical processing cannot increase photon efficiency.

Physical review letters 105 (2010) 203601-

DW Berry, AI Lvovsky

We answer the question whether linear-optical processing of the states produced by one or multiple imperfect single-photon sources can improve the single-photon fidelity. This processing can include arbitrary interferometers, coherent states, feedforward, and conditioning on results of detections. We show that without introducing multiphoton components, the single-photon fraction in any of the single-mode states resulting from such processing cannot be made to exceed the efficiency of the best available photon source. If multiphoton components are allowed, the single-photon fidelity cannot be increased beyond 1/2. We propose a natural general definition of the quantum-optical state efficiency, and show that it cannot increase under linear-optical processing.

Quantum Communication, Measurement and Computing (QCMC) Ninth International Conference on QCMC

American Inst. of Physics, 2009

A Lvovsky

The volume contains the proceedings of the 2008 International Conference on Quantum Communication, Measurement and Computing. This meeting has been the leading conference in the field for more than two decades.

A versatile digital GHz phase lock for external cavity diode lasers


J Appel, A MacRae, AI Lvovsky

Insight into the Spatiotemporal Mode-Selection Mechanism of Homodyne Detection via Quantum State Tomography of Weak Coherent Light


S-H Youn, N Jain, AI Lvovsky

Instant single-photon Fock state tomography.

Optics letters 34 (2009) 2739-2741

SR Huisman, N Jain, SA Babichev, F Vewinger, AN Zhang, SH Youn, AI Lvovsky

Heralded single photons are prepared at a rate of approximately 100 kHz via conditional measurements on polarization-nondegenerate biphotons produced in a periodically poled potassium-titanyl phosphate crystal. The single-photon Fock state is characterized using high-frequency pulsed optical homodyne tomography with a fidelity of (57.6+/-0.1)%. The state preparation and detection rates allowed us to perform on-the-fly alignment of the apparatus based on real-time analysis of the quadrature measurement statistics.

Memory for light as a quantum process.

Physical review letters 102 (2009) 203601-

M Lobino, C Kupchak, E Figueroa, AI Lvovsky

We report complete characterization of an optical memory based on electromagnetically induced transparency. We recover the superoperator associated with the memory, under two different working conditions, by means of a quantum process tomography technique that involves storage of coherent states and their characterization upon retrieval. In this way, we can predict the quantum state retrieved from the memory for any input, for example, the squeezed vacuum or the Fock state. We employ the acquired superoperator to verify the nonclassicality benchmark for the storage of a Gaussian distributed set of coherent states.

Optical quantum memory

Nature Photonics 3 (2009) 706-714

AI Lvovsky, BC Sanders, W Tittel

Quantum memory is essential for the development of many devices in quantum information processing, including a synchronization tool that matches various processes within a quantum computer, an identity quantum gate that leaves any state unchanged, and a mechanism to convert heralded photons to on-demand photons. In addition to quantum computing, quantum memory will be instrumental for implementing long-distance quantum communication using quantum repeaters. The importance of this basic quantum gate is exemplified by the multitude of optical quantum memory mechanisms being studied, such as optical delay lines, cavities and electromagnetically induced transparency, as well as schemes that rely on photon echoes and the off-resonant Faraday interaction. Here, we report on state-of-the-art developments in the field of optical quantum memory, establish criteria for successful quantum memory and detail current performance levels. © 2009 Macmillan Publishers Limited. All rights reserved.

Multimode electromagnetically induced transparency on a single atomic line


G Campbell, A Ordog, AI Lvovsky