Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review Letters

Partial Distinguishability in Femtosecond Optical Spontaneous Parametric Down-Conversion

Mete Atatüre, Alexander V. Sergienko, Bradley M. Jost, Bahaa E. A. Saleh, Malvin Carl Teich

Published Aug 16, 1999• 36 citations
Publisher

Abstract

Quantum interference is observed using femtosecond parametric down-conversion in the absence of spectral filtering of the down-converted light. The well-known symmetric dip observed in cw polarization-interferometry experiments becomes less pronounced and substantially asymmetric under such pulsed excitation. We show that this asymmetry arises from the partial distinguishability of contributions from space-time segments within the down-conversion crystal. We develop a theory that achieves agreement with experiment by coherently adding intrasegment contributions while incoherently adding intersegment contributions.

DOI
10.1103/physrevlett.83.1323

Related papers

Anticorrelation effect in femtosecond-pulse pumped type-II spontaneous parametric down-conversion

Yoon-Ho Kim, V. Berardi, Maria V. Chekhova +1 more

We report an experimental demonstration of an anticorrelation effect in femtosecond-pulse pumped type-II spontaneous parametric down-conversion. Our experimental data, which is different from that of Atat\"ure et al. [Phys. Rev. Lett. 83, 1323 (2000)], confirmed the shallow symmetric ``dip'' that is predicted theoretically by Keller and Rubin [Phys. Rev. A 56, 1534 (1997)] and Grice and Walmsley [Phys. Rev. A 56, 1627 (1997)]. We show in this paper that the asymmetric dip observed in the literature is an artifact, which is caused by the asymmetric optical elements introduced into the beam path after the down-conversion process. The ``partial distinguishability'' theory suggested by Atat\"ure et al. is therefore incorrect.

Physical Review A•Jun 1, 2001•17 citations

Quantum interference using ultrafast spontaneous parametric down-conversion

Mete Atatüre, Alexander V. Sergienko, Bradley M. Jost +2 more

Summary form only given. Pairs of entangled photons display a complex quantum state that cannot be represented through a product of single-particle states. The spontaneous parametric down-conversion (SPDC) process, that takes place when a laser pulse pumps a second-order nonlinear crystal has become recently a convenient source of such nonclassical states of light in quantum optics experiments. Nonstationary effects are mainly observed when the pump pulse temporal duration is significantly shorter than the characteristic interaction time in the nonlinear crystal. We introduce a nonstationary theory of SPDC to describe the results of fourth-order quantum-interference experiments when no spectral filtering is applied to the down-converted fields. Experiments involving nonlinear SPDC crystals with three different lengths were performed. The ultraviolet laser pulses were obtained from a Ti:sapphire femtosecond laser with a second-harmonic generator. These pulses were used to pump nonlinear crystals to initiate the process of nonstationary spdc and generate orthogonally-polarized photon pairs. These pairs then went into a polarization interferometer, and the coincidence counts of the detectors at the two output ports of the interferometer were recorded.

Quantum Electronics and Laser Science Conference•Jan 20, 2003•0 citations

Eliminating spectral distinguishability in ultrafast spontaneous parametric down-conversion

Hou Shun Poh, Jiaqing Lim, I. Marcikic +2 more

Generation of polarization-entangled photon pairs with a precise timing through down-conversion of femtosecond pulses is often faced with a degraded polarization entanglement quality. In a previous experiment, we have shown that this degradation is induced by spectral distinguishability between the two decay paths, in accordance with theoretical predictions. Here, we present an experimental study of the spectral compensation scheme proposed and first implemented by Kim and Grice [J. Mod. Opt. 49, 2309 (2002)]. By measuring the joint spectral properties of the polarization correlations of the photon pairs, we show that the spectral distinguishability between the down-converted components is eliminated. This scheme results in a polarization visibility of $97.9\ifmmode\pm\else\textpm\fi{}0.5%$ without any spectral filtering.

arXiv:0905.3849•Physical Review A•Oct 14, 2009•19 citations

Quantum interference and indistinguishability with femtosecond pulses

Giovanni Di Giuseppe, L. Haiberger, F. De Martini +1 more

The generation of entangled states of three or more photons through the nonlinear process of spontaneous parametric down-conversion requires the use of a femtosecond pump to provide an indistinguishability of photon pairs generated from different nonlinear crystals. We demonstrate experimentally that the quantum interference between two photons generated in each of the nonlinear crystals will degrade significantly as the duration of the femtosecond pump pulse becomes shorter than the coherence time of the signal and idler photons. Spectral postselection using narrow-band filters compensates this effect at the expense of the photon flux available for detection.

Physical Review A•Jul 1, 1997•91 citations

Multiparameter entanglement in quantum interferometry

Mete Atatüre, Giovanni Di Giuseppe, Matthew D. Shaw +3 more

The role of multiparameter entanglement in quantum interference from collinear Type-II spontaneous parametric down-conversion is explored using a variety of aperture shapes and sizes, in regimes of both ultrafast and continuous-wave pumping. We have developed and experimentally verified a theory of down-conversion which considers a quantum state that can be concurrently entangled in frequency, wavevector, and polarization. In particular, we demonstrate deviations from the familiar triangular interference dip, such as asymmetry and peaking. These findings improve our capacity to control the quantum state produced by spontaneous parametric down-conversion, and should prove useful to those pursuing the many proposed applications of down-converted light.

arXiv:quant-ph/0111024•Physical Review A•Aug 30, 2002•43 citations

Joint spectrum mapping of polarization entanglement in spontaneous parametric down-conversion

Hou Shun Poh, Chune Yang Lum, I. Marcikic +2 more

Polarization-entangled photon pairs can be efficiently prepared into pure Bell states with a high fidelity via type-II spontaneous parametric down-conversion (SPDC) of narrow-band pump light. However, the use of femtosecond pump pulses to generate multiphoton states with precise timing often requires spectral filtering to maintain a high quality of polarization entanglement. This typically reduces the efficiency of photon pair collection. We experimentally map the polarization correlations of photon pairs from such a source over a range of down-converted wavelengths with a high spectral resolution and find strong polarization correlations everywhere. A spectrally dependent imbalance between contributions from the two possible decay paths of SPDC is identified as the reason for a reduction in entanglement quality observed with femtosecond pump pulses. Our spectral measurements allow us to predict the polarization correlations for arbitrary filter profiles when the frequency degree of freedom of the photon pairs is ignored.

arXiv:quant-ph/0608009•Physical Review A•Apr 26, 2007•47 citations
Quantum interference is observed using femtosecond parametric down-conversion in the absence of spectral filtering of the down-converted light. The well-known symmetric dip observed in cw polarization-interferometry experiments becomes less pronounced and substantially asymmetric under such pulsed excitation. We show that this asymmetry arises from the partial distinguishability of contributions from space-time segments within the down-conversion crystal. We develop a theory that achieves agreement with experiment by coherently adding intrasegment contributions while incoherently adding intersegment contributions.
We report an experimental demonstration of an anticorrelation effect in femtosecond-pulse pumped type-II spontaneous parametric down-conversion. Our experimental data, which is different from that of Atat\"ure et al. [Phys. Rev. Lett. 83, 1323 (2000)], confirmed the shallow symmetric ``dip'' that is predicted theoretically by Keller and Rubin [Phys. Rev. A 56, 1534 (1997)] and Grice and Walmsley [Phys. Rev. A 56, 1627 (1997)]. We show in this paper that the asymmetric dip observed in the literature is an artifact, which is caused by the asymmetric optical elements introduced into the beam path after the down-conversion process. The ``partial distinguishability'' theory suggested by Atat\"ure et al. is therefore incorrect.
Summary form only given. Pairs of entangled photons display a complex quantum state that cannot be represented through a product of single-particle states. The spontaneous parametric down-conversion (SPDC) process, that takes place when a laser pulse pumps a second-order nonlinear crystal has become recently a convenient source of such nonclassical states of light in quantum optics experiments. Nonstationary effects are mainly observed when the pump pulse temporal duration is significantly shorter than the characteristic interaction time in the nonlinear crystal. We introduce a nonstationary theory of SPDC to describe the results of fourth-order quantum-interference experiments when no spectral filtering is applied to the down-converted fields. Experiments involving nonlinear SPDC crystals with three different lengths were performed. The ultraviolet laser pulses were obtained from a Ti:sapphire femtosecond laser with a second-harmonic generator. These pulses were used to pump nonlinear crystals to initiate the process of nonstationary spdc and generate orthogonally-polarized photon pairs. These pairs then went into a polarization interferometer, and the coincidence counts of the detectors at the two output ports of the interferometer were recorded.
Generation of polarization-entangled photon pairs with a precise timing through down-conversion of femtosecond pulses is often faced with a degraded polarization entanglement quality. In a previous experiment, we have shown that this degradation is induced by spectral distinguishability between the two decay paths, in accordance with theoretical predictions. Here, we present an experimental study of the spectral compensation scheme proposed and first implemented by Kim and Grice [J. Mod. Opt. 49, 2309 (2002)]. By measuring the joint spectral properties of the polarization correlations of the photon pairs, we show that the spectral distinguishability between the down-converted components is eliminated. This scheme results in a polarization visibility of $97.9\ifmmode\pm\else\textpm\fi{}0.5%$ without any spectral filtering.
The generation of entangled states of three or more photons through the nonlinear process of spontaneous parametric down-conversion requires the use of a femtosecond pump to provide an indistinguishability of photon pairs generated from different nonlinear crystals. We demonstrate experimentally that the quantum interference between two photons generated in each of the nonlinear crystals will degrade significantly as the duration of the femtosecond pump pulse becomes shorter than the coherence time of the signal and idler photons. Spectral postselection using narrow-band filters compensates this effect at the expense of the photon flux available for detection.
The role of multiparameter entanglement in quantum interference from collinear Type-II spontaneous parametric down-conversion is explored using a variety of aperture shapes and sizes, in regimes of both ultrafast and continuous-wave pumping. We have developed and experimentally verified a theory of down-conversion which considers a quantum state that can be concurrently entangled in frequency, wavevector, and polarization. In particular, we demonstrate deviations from the familiar triangular interference dip, such as asymmetry and peaking. These findings improve our capacity to control the quantum state produced by spontaneous parametric down-conversion, and should prove useful to those pursuing the many proposed applications of down-converted light.
Polarization-entangled photon pairs can be efficiently prepared into pure Bell states with a high fidelity via type-II spontaneous parametric down-conversion (SPDC) of narrow-band pump light. However, the use of femtosecond pump pulses to generate multiphoton states with precise timing often requires spectral filtering to maintain a high quality of polarization entanglement. This typically reduces the efficiency of photon pair collection. We experimentally map the polarization correlations of photon pairs from such a source over a range of down-converted wavelengths with a high spectral resolution and find strong polarization correlations everywhere. A spectrally dependent imbalance between contributions from the two possible decay paths of SPDC is identified as the reason for a reduction in entanglement quality observed with femtosecond pump pulses. Our spectral measurements allow us to predict the polarization correlations for arbitrary filter profiles when the frequency degree of freedom of the photon pairs is ignored.