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

Preservation of Energy-Time Entanglement in a Slow Light Medium

Curtis J. Broadbent, Ryan M. Camacho, Ran Xin, John C. Howell

Published Apr 4, 2008• 19 citations
Publisher

Abstract

We demonstrate the preservation of entanglement of an energy-time entangled biphoton through a slow light medium. Using the D(1) and D(2) fine structure resonances of Rubidium, we delay one photon of the 1.5 THz biphoton by approximately 1.3 correlation lengths and measure the fourth order correlation fringes. After the group delay the fringe visibility is reduced from 97.0+/-4.4% to 80.0+/-4.8%, but is still sufficient to violate a Bell inequality. We show that temporal broadening is the primary mechanism for reducing the fringe visibility and that smaller bandwidths lead to greatly reduced broadening.

DOI
10.1103/physrevlett.100.133602

Related papers

Preservation of entanglement in a slow light medium

Curtis J. Broadbent, Ryan M. Camacho, Ran Xin +1 more

We demonstrate the preservation of entanglement of an energy-time entangled biphoton through a slow light medium. After delay of one photon by ~1.3 correlation lengths, the 1.3 THz biphoton still violates a Bell inequality.

Conference on Lasers and Electro-Optics•May 4, 2008•0 citations

Slow Light with Fourth Order Fields

Curtis J. Broadbent, Praveen K. Vudyasetu, Ryan M. Camacho +2 more

We demonstrate experimentally the preservation of entanglement between delayed and non-delayed members of energy-time entangled biphotons, as well as the preservation of fourth order temporal coherence of thermal light with a delayed version of itself.

Slow and Fast Light (SL)•Jan 1, 2008•0 citations

Einstein-Podolsky-Rosen Energy-Time Entanglement of Narrow-Band Biphotons

Yefeng Mei, Yiru Zhou, Shanchao Zhang +5 more

We report the direct characterization of energy-time entanglement of narrow-band biphotons produced from spontaneous four-wave mixing in cold atoms. The Stokes and anti-Stokes two-photon temporal correlation is measured by single-photon counters with nanosecond temporal resolution, and their joint spectrum is determined by using a narrow linewidth optical cavity. The energy-time entanglement is verified by the joint frequency-time uncertainty product of 0.063±0.0044, which does not only violate the separability criterion but also satisfies the continuous variable Einstein-Podolsky-Rosen steering inequality.

arXiv:1911.00723•Physical Review Letters•Jan 10, 2020•36 citations

Nonlocality test of energy-time entanglement via nonlocal dispersion cancellation with nonlocal detection

Baihong Li, Feiyan Hou, Runai Quan +6 more

The energy-time entangled biphoton source plays a great role in quantum communication, quantum metrology, and quantum cryptography due to its strong temporal correlation and capability of nonlocal dispersion cancellation. As a quantum effect, nonlocal dispersion cancellation is further proposed as an alternative way for nonlocality testing of continuous variable entanglement via the violation of the Bell-like inequality proposed by Wasak et al. [Phys. Rev. A 82, 052120 (2010)]. However, to date there is no experimental report either on the inequality violation or on a nonlocal detection with single-photon detectors at a long-distance transmission channel, which is key for a true nonlocality test. In this paper, we report an experimental realization of a violation of the inequality after 62-km optical fiber transmission at telecom wavelengths with a nonlocal detection based on event timers and a cross-correlation algorithm, which indicates a successful nonlocal test of energy-time entanglement. This work provides feasibility for the strict test of the nonlocality for continuous variables in both long-distance communication fiber channel and free space.

arXiv:1906.03769•Physical Review A•Nov 4, 2019•29 citations

Applications of high-dimensional photonic entaglement

Curtis J. Broadbent

This thesis presents the results of four experiments related to applications of higher dimensional photonic entanglement. 1) We use energy-time entangled biphotons from spontaneous parametric down-conversion (SPDC) to implement a large-alphabet quantum key distribution (QKD) system which securely transmits up to 10 bits of the random key per photon. An advantage over binary alphabet QKD is demonstrated for quantum channels with a single-photon transmissionrate ceiling. The security of the QKD system is based on the measurable reduction of entanglement in the presence of eavesdropping. 2) We demonstrate the preservation of energy-time entanglement in a tunable slow-light medium. The fine-structure resonances of a hot Rubidium vapor are used to slow one photon from an energy-time entangled biphoton generated with non-degenerate SPDC. The slow-light medium is placed in one arm of a Franson interferometer. The observed Franson fringes witness the presence of entanglement and quantify a delay of 1.3 biphoton correlation lengths. 3) We utilize holograms to discriminate between two spatially-coherent single-photon images. Heralded single photons are created with degenerate SPDC and sent through one of two transmission masks to make single-photon images with no spatial overlap. The single-photon images are sent through a previously prepared holographic filter. The filter discriminates the single-photon images with an average confidence level of 95%. 4) We employ polarization entangled biphotons generated from non-collinear SPDC to violate a generalized Leggett-Garg inequality with non-local weak measurements. The weak measurement is implemented with Fresnel reflection of a microscope coverslip on one member of the entangled biphoton. Projective measurement with computer-controlled polarizers on the entangled state after the weak measurement yields a joint probability with three degrees of freedom. Contextual values are then used to determine statistical averages of measurement operations from the joint probability. Correlations between the measured averages are shown to violate the upper bound of three distinct two-object Leggett-Garg inequalities derived from assumptions of macro-realism. A relationship between the violation of two-object Leggett-Garg inequalities and strange non-local weak values is derived and experimentally demonstrated.

•Jan 1, 2010•0 citations

Flatband slow light in photonic crystals featuring spatial pulse compression and terahertz bandwidth

Michael Settle, Rob J. P. Engelen, M. S. Salib +3 more

Paradoxically, slow light promises to increase the speed of telecommunications in novel photonic structures, such as coupled resonators [1] and photonic crystals [2,3]. Apart from signal delays, the key consequence of slowing light down is the enhancement of light-matter interactions. Linear effects such as refractive index modulation scale linearly with slowdown in photonic crystals [3], and nonlinear effects are expected to scale with its square [4]. By directly observing the spatial compression of an optical pulse, by factor 25, we confirm the mechanism underlying this square scaling law. The key advantage of photonic structures over other slow light concepts is the potentially large bandwidth, which is crucial for telecommunications [5]. Nevertheless, the slow light previously observed in photonic crystals [2,3,6,7] has been very dispersive and featured narrow bandwidth. We demonstrate slow light with a bandwidth of 2.5 THz and a delay-bandwidth product of 30, which is an order of magnitude larger than any reported so far.

Optics Express•Jan 1, 2007•167 citations
We demonstrate the preservation of entanglement of an energy-time entangled biphoton through a slow light medium. Using the D(1) and D(2) fine structure resonances of Rubidium, we delay one photon of the 1.5 THz biphoton by approximately 1.3 correlation lengths and measure the fourth order correlation fringes. After the group delay the fringe visibility is reduced from 97.0+/-4.4% to 80.0+/-4.8%, but is still sufficient to violate a Bell inequality. We show that temporal broadening is the primary mechanism for reducing the fringe visibility and that smaller bandwidths lead to greatly reduced broadening.
We report the direct characterization of energy-time entanglement of narrow-band biphotons produced from spontaneous four-wave mixing in cold atoms. The Stokes and anti-Stokes two-photon temporal correlation is measured by single-photon counters with nanosecond temporal resolution, and their joint spectrum is determined by using a narrow linewidth optical cavity. The energy-time entanglement is verified by the joint frequency-time uncertainty product of 0.063±0.0044, which does not only violate the separability criterion but also satisfies the continuous variable Einstein-Podolsky-Rosen steering inequality.
The energy-time entangled biphoton source plays a great role in quantum communication, quantum metrology, and quantum cryptography due to its strong temporal correlation and capability of nonlocal dispersion cancellation. As a quantum effect, nonlocal dispersion cancellation is further proposed as an alternative way for nonlocality testing of continuous variable entanglement via the violation of the Bell-like inequality proposed by Wasak et al. [Phys. Rev. A 82, 052120 (2010)]. However, to date there is no experimental report either on the inequality violation or on a nonlocal detection with single-photon detectors at a long-distance transmission channel, which is key for a true nonlocality test. In this paper, we report an experimental realization of a violation of the inequality after 62-km optical fiber transmission at telecom wavelengths with a nonlocal detection based on event timers and a cross-correlation algorithm, which indicates a successful nonlocal test of energy-time entanglement. This work provides feasibility for the strict test of the nonlocality for continuous variables in both long-distance communication fiber channel and free space.
This thesis presents the results of four experiments related to applications of higher dimensional photonic entanglement. 1) We use energy-time entangled biphotons from spontaneous parametric down-conversion (SPDC) to implement a large-alphabet quantum key distribution (QKD) system which securely transmits up to 10 bits of the random key per photon. An advantage over binary alphabet QKD is demonstrated for quantum channels with a single-photon transmissionrate ceiling. The security of the QKD system is based on the measurable reduction of entanglement in the presence of eavesdropping. 2) We demonstrate the preservation of energy-time entanglement in a tunable slow-light medium. The fine-structure resonances of a hot Rubidium vapor are used to slow one photon from an energy-time entangled biphoton generated with non-degenerate SPDC. The slow-light medium is placed in one arm of a Franson interferometer. The observed Franson fringes witness the presence of entanglement and quantify a delay of 1.3 biphoton correlation lengths. 3) We utilize holograms to discriminate between two spatially-coherent single-photon images. Heralded single photons are created with degenerate SPDC and sent through one of two transmission masks to make single-photon images with no spatial overlap. The single-photon images are sent through a previously prepared holographic filter. The filter discriminates the single-photon images with an average confidence level of 95%. 4) We employ polarization entangled biphotons generated from non-collinear SPDC to violate a generalized Leggett-Garg inequality with non-local weak measurements. The weak measurement is implemented with Fresnel reflection of a microscope coverslip on one member of the entangled biphoton. Projective measurement with computer-controlled polarizers on the entangled state after the weak measurement yields a joint probability with three degrees of freedom. Contextual values are then used to determine statistical averages of measurement operations from the joint probability. Correlations between the measured averages are shown to violate the upper bound of three distinct two-object Leggett-Garg inequalities derived from assumptions of macro-realism. A relationship between the violation of two-object Leggett-Garg inequalities and strange non-local weak values is derived and experimentally demonstrated.
Paradoxically, slow light promises to increase the speed of telecommunications in novel photonic structures, such as coupled resonators [1] and photonic crystals [2,3]. Apart from signal delays, the key consequence of slowing light down is the enhancement of light-matter interactions. Linear effects such as refractive index modulation scale linearly with slowdown in photonic crystals [3], and nonlinear effects are expected to scale with its square [4]. By directly observing the spatial compression of an optical pulse, by factor 25, we confirm the mechanism underlying this square scaling law. The key advantage of photonic structures over other slow light concepts is the potentially large bandwidth, which is crucial for telecommunications [5]. Nevertheless, the slow light previously observed in photonic crystals [2,3,6,7] has been very dispersive and featured narrow bandwidth. We demonstrate slow light with a bandwidth of 2.5 THz and a delay-bandwidth product of 30, which is an order of magnitude larger than any reported so far.