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

Observation of Simultaneity in Parametric Production of Optical Photon Pairs

David C. Burnham, Donald L. Weinberg

Published Jul 13, 1970• 1,111 citations
Publisher

Abstract

The quantum mechanical description of parametric fluorescence is the splitting of a single photon into two photons. This description has been verified by observing coincidences between photons emitted by an ammonium dihydrogen phosphate crystal pumped by a 325-nm He-Cd laser. The coincidence rate ${R}_{C}$ decreases to the calculated accidental rate [$<0.03{R}_{C}(max)$], unless the two detectors are arranged to satisfy energy and momentum conservation and have equal time delays.

DOI
10.1103/physrevlett.25.84

Related papers

Measurement of Time Delays in the Parametric Production of Photon Pairs

Stephen R. Friberg, C. K. Hong, L. Mandeļ

The spread in time intervals between the two photons produced in the process of spontaneous parametric down-conversion in a potassium dihydrogen phosphate crystal has been measured with a time resolution of the order of 100 psec. The correlation time is found to be independent of the coherence time of the pump photons or of the propagation time through the crystal, consistent with recent theoretical predictions.

Physical Review Letters•May 6, 1985•201 citations

Optical Absorption Measurements with Parametric Down-Converted Photons

Zhi Gao Zhao, Kent A. Meyer, William Barclay Whitten +1 more

It has been known for some time that correlated detection of pairs of photons generated by parametric down-conversion can eliminate several sources of error that occur in single-beam measurements. In the correlated photon measurements, the down-converted photons are separated into two beams with one photon of a pair in each beam. The absolute detection efficiency of a detector in one beam can be determined from the count rate of a detector in the other beam and the coincidence rate for the two detectors. These ideas can be used to measure the optical absorbance of a sample placed in front of one of the detectors. Errors due to stray light and dark counts are substantially reduced and fluctuations in pump intensity largely eliminated.

Analytical Chemistry•Aug 26, 2008•3 citations

Creating Entangled Photons by Spontaneous Parametric Down Conversion

Blake Savisky

The purpose of this project is to set up a system for creating entangled photon pairs for use in various quantum mechanical experiments, including the testing of Bell’s inequalities which demonstrates the fundamentally indeterministic nature of quantum mechanics. The photons are created by pumping a beta barium borate crystal with 405 nm laser light then, due to a process called type 1 spontaneous parametric down conversion, a single pump photon can be converted into two 810 nm photons in an entangled state. In the same lab, a similar set up has already been achieved using a 474 nm pump laser, but by using a shorter wave length, a higher detection rate can be achieved. Two collimators are set up to collect the down converted photons and send them to two photon counting modules. The collimators need to be positioned precisely to detect any down converted photons because they emerge from the crystal in a narrow beam that is at an angle with respect to the pump beam and only a miniscule fraction of pump photons are down converted. The angle at which the down converted photons emerge is a function of how the crystal is prepared and the polarization orientation of the pump beam. It was calculated using a program by National Institute of Standards and Technology.

•Jan 1, 2015•0 citations

Quadratic Coherence in Parametric Emission

Rama K. Raj, Izo I. Abram, J. L. Oudar +1 more

Optical parametric emission produces light in which photons are created in highly correlated pairs. This feature is formalized through the concept of quadratic coherence. We study the correlation between twin photons through a spectral and temporal analysis of the second-harmonic of the parametric light.

Physica Scripta•Jan 1, 1988•0 citations

Quantum Mechanics of a Two Photon State

Morton H. Rubin

We review the formalism for describing the two photon state produced in spontaneous parametric down conversion.

•Jan 1, 1996•0 citations

Broadband pumped polarization entangled photon-pair source in a linear beam displacement interferometer

Alexander Lohrmann, Chithrabhanu Perumangatt, Aitor Villar +1 more

We experimentally demonstrate a source of polarization entangled photon-pairs based on a single periodically poled potassium titanyl phosphate crystal pumped with a broadband, free running laser diode. The crystal is placed within a linear beam-displacement interferometer and emits photon-pairs based on type-0 spontaneous parametric downconversion. We observe pair rates of 0.56 Mpairs/s/mW in a single spatial mode with a polarization visibility of 97.7% over a spectral range of 100 nm. This experiment demonstrates a pathway toward observing gigacount rates of polarization entangled photon pairs by using high-power free-running laser diodes with fast multiplexed detectors.

arXiv:1908.09568•Applied Physics Letters•Jan 13, 2020•43 citations
The quantum mechanical description of parametric fluorescence is the splitting of a single photon into two photons. This description has been verified by observing coincidences between photons emitted by an ammonium dihydrogen phosphate crystal pumped by a 325-nm He-Cd laser. The coincidence rate RC{R}_{C}RC​ decreases to the calculated accidental rate [<0.03RC(max)<0.03{R}_{C}(max)<0.03RC​(max)], unless the two detectors are arranged to satisfy energy and momentum conservation and have equal time delays.
It has been known for some time that correlated detection of pairs of photons generated by parametric down-conversion can eliminate several sources of error that occur in single-beam measurements. In the correlated photon measurements, the down-converted photons are separated into two beams with one photon of a pair in each beam. The absolute detection efficiency of a detector in one beam can be determined from the count rate of a detector in the other beam and the coincidence rate for the two detectors. These ideas can be used to measure the optical absorbance of a sample placed in front of one of the detectors. Errors due to stray light and dark counts are substantially reduced and fluctuations in pump intensity largely eliminated.
The purpose of this project is to set up a system for creating entangled photon pairs for use in various quantum mechanical experiments, including the testing of Bell’s inequalities which demonstrates the fundamentally indeterministic nature of quantum mechanics. The photons are created by pumping a beta barium borate crystal with 405 nm laser light then, due to a process called type 1 spontaneous parametric down conversion, a single pump photon can be converted into two 810 nm photons in an entangled state. In the same lab, a similar set up has already been achieved using a 474 nm pump laser, but by using a shorter wave length, a higher detection rate can be achieved. Two collimators are set up to collect the down converted photons and send them to two photon counting modules. The collimators need to be positioned precisely to detect any down converted photons because they emerge from the crystal in a narrow beam that is at an angle with respect to the pump beam and only a miniscule fraction of pump photons are down converted. The angle at which the down converted photons emerge is a function of how the crystal is prepared and the polarization orientation of the pump beam. It was calculated using a program by National Institute of Standards and Technology.
We experimentally demonstrate a source of polarization entangled photon-pairs based on a single periodically poled potassium titanyl phosphate crystal pumped with a broadband, free running laser diode. The crystal is placed within a linear beam-displacement interferometer and emits photon-pairs based on type-0 spontaneous parametric downconversion. We observe pair rates of 0.56 Mpairs/s/mW in a single spatial mode with a polarization visibility of 97.7% over a spectral range of 100 nm. This experiment demonstrates a pathway toward observing gigacount rates of polarization entangled photon pairs by using high-power free-running laser diodes with fast multiplexed detectors.