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

Frontiers in Optics

Achieving High-Fidelity Bell States Through Interferometric Short-Pulsed Laser Techniques

Tomis, V. Narayanan

Published Jan 1, 2024• 0 citations
Publisher

Abstract

We present a method for creating Bell states by an interferometric approach with a short-pulsed laser. A Bell state was created by type-II spontaneous parametric down-conversion (SPDC), achieving a fidelity and visibility close to ~ 90%.
DOI
10.1364/fio.2024.jw5a.60

Related papers

Interferometric Bell-state preparation using femtosecond-pulse-pumped spontaneous parametric down-conversion

Yoon-Ho Kim, Maria V. Chekhova, S. P. Kulik +2 more

We present a theoretical and experimental study of preparing maximally entangled two-photon polarization states, or Bell states, using femtosecond-pulse-pumped spontaneous parametric down-conversion (SPDC). First, we show how the inherent distinguishability in femtosecond-pulse-pumped type-II SPDC can be removed by using an interferometric technique without spectral and amplitude postselection. We then analyze the recently introduced Bell-state preparation scheme using type-I SPDC. Theoretically, both methods offer the same results, however, type-I SPDC provides experimentally superior methods of preparing Bell states in femtosecond-pulse-pumped SPDC. Such a pulsed source of highly entangled photon pairs is useful in quantum communications, quantum cryptography, quantum teleportation, etc.

arXiv:quant-ph/0103168•Physical Review A•May 7, 2001•80 citations

Bell States Generation within the Bandwidth of Spontaneous Parametric Down-Conversion

G. Brida, Marco Genovese, Leonid A. Krivitsky +1 more

Summary form only given. Most works on Bell state generation via spontaneous parametric down-conversion (SPDC) do not consider the structure of its spectral line. However, we show that within the SPDC bandwidth, various Bell states can be produced.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2007•0 citations

High-visibility two-photon interference in femtosecond pulse pumped type-II SPDC

Yoon-Ho Kim, Maria V. Chekhova, S.P. Kulik +2 more

Summary form only given. By far the most efficient source of two-particle entangled state is spontaneous parametric downconversion (SPDC). Especially, cw laser pumped type-II SPDC has been widely treated as a good source of entangled photon pairs, since one can easily prepare a polarization Bell state. However, femtosecond pulse pumped type-II SPDC shows poor quantum interference visibility when a thick crystal is used. To restore the visibility, one has to use narrow-band spectral filters at the expense of available photon flux. We demonstrate a scheme for high-visibility two-photon interference with thick (3.4 mm.) type-II BaB/sub 2/O/sub 4/ (BBO) crystals in femtosecond pulse pumped SPDC. Polarization Bell states can be prepared using this method without spectral and amplitude post-selection.

Quantum Electronics and Laser Science Conference•Nov 13, 2002•0 citations

Automated Quantum State Tomography of Four Bell States Generated by Compact SPDC Source

Sondos R. Elsehimy, Khaled Kallaf, Hussein E. Kotb +2 more

The high fidelity of the four maximally entangled two-photon states, generated by a compact type-I SPDC source, is verified using automated quantum state tomography system.

Quantum 2.0 Conference and Exhibition•Jan 1, 2024•0 citations

Pure single photon generation

Peter J. Mosley, Christine Silberhorn, Alfred B. U’Ren +1 more

We propose a method of creating single photons in pure quantum states by parametric downconversion, along with the analysis of an experimental scheme for characterising their purity using multiple crystal interferometry.

Quantum Electronics and Laser Science Conference•Dec 10, 2005•0 citations

Nonlocal realism tests and quantum state tomography in Sagnac-based type-II polarization-entanglement SPDC-source

Ali Motazedifard, S.A. Madani, J.J. Dashkasan +1 more

We have experimentally created a robust, ultrabright and phase-stable polarization-entangled state close to maximally entangled Bell-state with %98-fidelity using the type-II spontaneous parametric down-conversion (SPDC) process in periodically-poled KTiOPO 4 (PPKTP) collinear crystal inside a Sagnac interferometer (SI). Bell inequality measurement, Freedman's test, as the different versions of CHSH inequality, and also visibility test which all can be seen as the nonlocal realism tests, imply that our created entangled state shows a strong violation from the classical physics or any hidden-variable theory. We have obtained very reliable and very strong Bell violation as S = 2.78 ± 0.01 with high brightness V HV = % \( 99.969 ± 0.003 \) and V DA = % \( 96.751 ± 0.002 \) and very strong violation due to Freedman test as δ F = 0.01715 ± 0.00001 . Furthermore, using the tomographic reconstruction of quantum states together a maximum-likelihood-technique (MLT) as the numerical optimization, we obtain the physical non-negative definite density operator which shows the nonseparability and entanglement of our prepared state. By having the maximum likelihood density operator, we calculate some important entanglement-measures and entanglement entropies. The Sagnac configuration provides bidirectional crystal pumping yields to high-rate entanglement source which is very applicable in quantum communication, sensing and metrology as well as quantum information protocols, and has potential to be used in quantum illumination-based LIDAR and free-space quantum key distribution (QKD).

arXiv:2012.04086•Heliyon•Jun 1, 2021•17 citations
We present a theoretical and experimental study of preparing maximally entangled two-photon polarization states, or Bell states, using femtosecond-pulse-pumped spontaneous parametric down-conversion (SPDC). First, we show how the inherent distinguishability in femtosecond-pulse-pumped type-II SPDC can be removed by using an interferometric technique without spectral and amplitude postselection. We then analyze the recently introduced Bell-state preparation scheme using type-I SPDC. Theoretically, both methods offer the same results, however, type-I SPDC provides experimentally superior methods of preparing Bell states in femtosecond-pulse-pumped SPDC. Such a pulsed source of highly entangled photon pairs is useful in quantum communications, quantum cryptography, quantum teleportation, etc.
Summary form only given. By far the most efficient source of two-particle entangled state is spontaneous parametric downconversion (SPDC). Especially, cw laser pumped type-II SPDC has been widely treated as a good source of entangled photon pairs, since one can easily prepare a polarization Bell state. However, femtosecond pulse pumped type-II SPDC shows poor quantum interference visibility when a thick crystal is used. To restore the visibility, one has to use narrow-band spectral filters at the expense of available photon flux. We demonstrate a scheme for high-visibility two-photon interference with thick (3.4 mm.) type-II BaB/sub 2/O/sub 4/ (BBO) crystals in femtosecond pulse pumped SPDC. Polarization Bell states can be prepared using this method without spectral and amplitude post-selection.
We have experimentally created a robust, ultrabright and phase-stable polarization-entangled state close to maximally entangled Bell-state with %98-fidelity using the type-II spontaneous parametric down-conversion (SPDC) process in periodically-poled KTiOPO 4 (PPKTP) collinear crystal inside a Sagnac interferometer (SI). Bell inequality measurement, Freedman's test, as the different versions of CHSH inequality, and also visibility test which all can be seen as the nonlocal realism tests, imply that our created entangled state shows a strong violation from the classical physics or any hidden-variable theory. We have obtained very reliable and very strong Bell violation as S = 2.78 ± 0.01 with high brightness V HV = % 99.969±0.003 99.969 ± 0.003 99.969±0.003 and V DA = % 96.751±0.002 96.751 ± 0.002 96.751±0.002 and very strong violation due to Freedman test as δ F = 0.01715 ± 0.00001 . Furthermore, using the tomographic reconstruction of quantum states together a maximum-likelihood-technique (MLT) as the numerical optimization, we obtain the physical non-negative definite density operator which shows the nonseparability and entanglement of our prepared state. By having the maximum likelihood density operator, we calculate some important entanglement-measures and entanglement entropies. The Sagnac configuration provides bidirectional crystal pumping yields to high-rate entanglement source which is very applicable in quantum communication, sensing and metrology as well as quantum information protocols, and has potential to be used in quantum illumination-based LIDAR and free-space quantum key distribution (QKD).