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

arXiv:0910.5445 · Physical Review B

Formation dynamics of an entangled photon pair: A temperature-dependent analysis

Alexander Carmele, Frank Milde, Matthias‐René Dachner, M. Bagheri Harouni, R. Roknizadeh, Marten Richter, Andreas Knorr

Published May 26, 2010• 38 citations
arXivHTMLPDF

Abstract

We theoretically study the polarization entanglement of photons generated by the biexciton cascade in a GaAs/InAs semiconductor quantum dot (QD) located in a nanocavity. A detailed analysis of the complex interplay between photon and carrier coherences and phonons which occurs during the cascade allows us to clearly identify the conditions under which entanglement is generated and destroyed. A quantum state tomography is evaluated for varying exciton fine-structure splittings. Also, by constructing an effective multiphonon Hamiltonian which couples the continuum of the QD-embedding wetting layer states to the quantum confined states, we investigate the relaxation of the biexciton and exciton states. This consistently introduces a temperature dependence to the cascade. Considering typical Stranski-Krastanov grown QDs for temperatures around 80 K the degree of entanglement starts to be affected by the dephasing of the exciton states and is ultimately lost above 100 K.

DOI
10.1103/physrevb.81.195319

Related papers

Analytical solution of the quantum-state tomography of the biexciton cascade in semiconductor quantum dots: Pure dephasing does not affect entanglement

Alexander Carmele, Andreas Knorr

A fundamental approach to generate polarization-entangled photon pairs from solid-state devices is the biexciton cascade in semiconductor quantum dots. For efficient photon pair generation in the weak coupling regime, we present an analytical solution for the two-photon matrix elements (quantum-state tomography), including dephasing and relaxation mechanisms. In particular, we show that a pure dephasing mechanism does not affect the degree of entanglement for quantum dots with degenerated exciton levels.

Physical Review B•Aug 15, 2011•31 citations

Generation of C-band entangled photon pairs by biexciton-exciton cascade from symmetric InAs/InP quantum dots

Anna Musiał, Maja Wasiluk, Katarzyna Roszak +6 more

Hereby, we study the generation of pairs of polarization-entangled photons at telecom C-band by biexciton-exciton cascade from non-resonantly excited epitaxial InAs/InP quantum dots (QDs). It is realized without external tuning of the fine structure splitting (FSS), which does not exceed 10 $μ$eV in as-grown nanostructures, due to their high in-plane symmetry. Excitonic complexes are identified by means of excitation power-dependent and polarization-resolved magneto)microphotoluminescence. Their origin from different carrier configurations confined in the same QD is confirmed by time correlations of emitted photons. Experimental results are supported by 8-band kp calculations, followed by the configuration interaction method to include excitonic effects. This comparison reveals the structure of higher energy states, allowing for the reconstruction of the QD structural parameters. To verify and quantify the entanglement, we perform quantum state tomography and reconstruct the two-photon density matrix. Its diagonalization allows a detailed analysis of the entangled state and reveals an unfavourable interplay between phase accumulation and decoherence, pointing to a clear route for boosting entanglement by using a XX resonant, pulsed excitation scheme and shortening the radiative lifetimes.

arXiv:2509.24500•Sep 29, 2025•0 citations

Triggered polarization-entangled photon pairs from a single quantum dot up to 30 K

R. Hafenbrak, Sven M. Ulrich, Peter Michler +3 more

The radiative biexciton–exciton decay in a semiconductor quantum dot (QD) has the potential of being a source of triggered polarization-entangled photon pairs. However, in most cases the anisotropy-induced exciton fine structure splitting destroys this entanglement. Here, we present measurements on improved QD structures, providing both significantly reduced inhomogeneous emission linewidths and near-zero fine structure splittings. A high-resolution detection technique is introduced which allows us to accurately determine the fine structure in the photoluminescence emission and therefore select appropriate QDs for quantum state tomography. We were able to verify the conditions of entangled or classically correlated photon pairs in full consistence with observed fine structure properties. Furthermore, we demonstrate reliable polarization-entanglement for elevated temperatures up to 30 K. The fidelity of the maximally entangled state decreases only a little from 72% at 4 K to 68% at 30 K. This is especially encouraging for future implementations in practical devices.

New Journal of Physics•Sep 10, 2007•241 citations

Triggered polarization-entangled photon pairs from a single quantum dot up to 30 K

R. Hafenbrak, Sven M. Ulrich, P. Michler +3 more

The radiative biexciton-exciton decay in a semiconductor quantum dot (QD) has the potential of being a source of triggered polarization-entangled photon pairs. However, in most cases the anisotropy-induced exciton fine structure splitting destroys this entanglement. Here, we present measurements on improved QD structures, providing both significantly reduced inhomogeneous emission linewidths and near-zero fine structure splittings. A high-resolution detection technique is introduced which allows us to accurately determine the fine structure in the photoluminescence emission and therefore select appropriate QDs for quantum state tomography. We were able to verify the conditions of entangled or classically correlated photon pairs in full consistence with observed fine structure properties. Furthermore, we demonstrate reliable polarization-entanglement for elevated temperatures up to 30 K. The fidelity of the maximally entangled state decreases only a little from 72% at 4 K to 68% at 30 K. This is especially encouraging for future implementations in practical devices. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

•Jan 1, 2007•0 citations

Bell inequalities for polarization entangled photons out of a two-photon cascade in a single quantum dot

Matthieu Larqué, Isabelle Robert-Philip, A. Beveratos

We theoretically investigate the joint photodetection probabilities of the biexciton-exciton cascade in single semiconductor quantum dots and analytically derive the density matrix and the Bell's inequalities of the entangled state. Our model includes different mechanisms that may spoil or even destroy entanglement such as dephasing, energy splitting of the relay excitonic states and incoherent population exchange between these relay levels. We explicitly relate the fidelity of entanglement to the dynamics of these processes and derive a threshold for violation of Bell's inequalities. Applied to standard InAs/GaAs self-assembled quantum dots, our model indicates that spontaneous emission enhancement of the excitonic states by cavity effects increases the fidelity of entanglement to a value allowing for violation of Bell's inequalities.

•Jan 23, 2008•0 citations

Phonon impacts on entangled photon pair generation from the biexciton cascade in a quantum dot: phonon coherent state representation

M. Bagheri Harouni

A full quantum microscopic theory is developed to analyze a biexciton radiative cascade coupled to bulk acoustic phonons in a quantum dot. By considering the phonon sub-system in coherent state representation a new approach is proposed for investigating the phonon effects. Via this approach it is possible to obtain an exact analytical result for the phonon kernel in this system. This approach is introduced in the context of an example: the process of generating polarization-entangled photon pairs from the biexciton cascade in a quantum dot. We calculate the exact density matrix (using quantum state tomography) of photons and their concurrence. We show that the exchange interaction and temperature have remarkable effects on the degree of entanglement of the emitted photons. The approach introduced provides an exact analytical result for finite discrete electron states interacting with phonons.

Laser Physics•Sep 3, 2014•3 citations
We theoretically study the polarization entanglement of photons generated by the biexciton cascade in a GaAs/InAs semiconductor quantum dot (QD) located in a nanocavity. A detailed analysis of the complex interplay between photon and carrier coherences and phonons which occurs during the cascade allows us to clearly identify the conditions under which entanglement is generated and destroyed. A quantum state tomography is evaluated for varying exciton fine-structure splittings. Also, by constructing an effective multiphonon Hamiltonian which couples the continuum of the QD-embedding wetting layer states to the quantum confined states, we investigate the relaxation of the biexciton and exciton states. This consistently introduces a temperature dependence to the cascade. Considering typical Stranski-Krastanov grown QDs for temperatures around 80 K the degree of entanglement starts to be affected by the dephasing of the exciton states and is ultimately lost above 100 K.
A fundamental approach to generate polarization-entangled photon pairs from solid-state devices is the biexciton cascade in semiconductor quantum dots. For efficient photon pair generation in the weak coupling regime, we present an analytical solution for the two-photon matrix elements (quantum-state tomography), including dephasing and relaxation mechanisms. In particular, we show that a pure dephasing mechanism does not affect the degree of entanglement for quantum dots with degenerated exciton levels.
Hereby, we study the generation of pairs of polarization-entangled photons at telecom C-band by biexciton-exciton cascade from non-resonantly excited epitaxial InAs/InP quantum dots (QDs). It is realized without external tuning of the fine structure splitting (FSS), which does not exceed 10 μμμeV in as-grown nanostructures, due to their high in-plane symmetry. Excitonic complexes are identified by means of excitation power-dependent and polarization-resolved magneto)microphotoluminescence. Their origin from different carrier configurations confined in the same QD is confirmed by time correlations of emitted photons. Experimental results are supported by 8-band kp calculations, followed by the configuration interaction method to include excitonic effects. This comparison reveals the structure of higher energy states, allowing for the reconstruction of the QD structural parameters. To verify and quantify the entanglement, we perform quantum state tomography and reconstruct the two-photon density matrix. Its diagonalization allows a detailed analysis of the entangled state and reveals an unfavourable interplay between phase accumulation and decoherence, pointing to a clear route for boosting entanglement by using a XX resonant, pulsed excitation scheme and shortening the radiative lifetimes.
The radiative biexciton–exciton decay in a semiconductor quantum dot (QD) has the potential of being a source of triggered polarization-entangled photon pairs. However, in most cases the anisotropy-induced exciton fine structure splitting destroys this entanglement. Here, we present measurements on improved QD structures, providing both significantly reduced inhomogeneous emission linewidths and near-zero fine structure splittings. A high-resolution detection technique is introduced which allows us to accurately determine the fine structure in the photoluminescence emission and therefore select appropriate QDs for quantum state tomography. We were able to verify the conditions of entangled or classically correlated photon pairs in full consistence with observed fine structure properties. Furthermore, we demonstrate reliable polarization-entanglement for elevated temperatures up to 30 K. The fidelity of the maximally entangled state decreases only a little from 72% at 4 K to 68% at 30 K. This is especially encouraging for future implementations in practical devices.
The radiative biexciton-exciton decay in a semiconductor quantum dot (QD) has the potential of being a source of triggered polarization-entangled photon pairs. However, in most cases the anisotropy-induced exciton fine structure splitting destroys this entanglement. Here, we present measurements on improved QD structures, providing both significantly reduced inhomogeneous emission linewidths and near-zero fine structure splittings. A high-resolution detection technique is introduced which allows us to accurately determine the fine structure in the photoluminescence emission and therefore select appropriate QDs for quantum state tomography. We were able to verify the conditions of entangled or classically correlated photon pairs in full consistence with observed fine structure properties. Furthermore, we demonstrate reliable polarization-entanglement for elevated temperatures up to 30 K. The fidelity of the maximally entangled state decreases only a little from 72% at 4 K to 68% at 30 K. This is especially encouraging for future implementations in practical devices. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
We theoretically investigate the joint photodetection probabilities of the biexciton-exciton cascade in single semiconductor quantum dots and analytically derive the density matrix and the Bell's inequalities of the entangled state. Our model includes different mechanisms that may spoil or even destroy entanglement such as dephasing, energy splitting of the relay excitonic states and incoherent population exchange between these relay levels. We explicitly relate the fidelity of entanglement to the dynamics of these processes and derive a threshold for violation of Bell's inequalities. Applied to standard InAs/GaAs self-assembled quantum dots, our model indicates that spontaneous emission enhancement of the excitonic states by cavity effects increases the fidelity of entanglement to a value allowing for violation of Bell's inequalities.
A full quantum microscopic theory is developed to analyze a biexciton radiative cascade coupled to bulk acoustic phonons in a quantum dot. By considering the phonon sub-system in coherent state representation a new approach is proposed for investigating the phonon effects. Via this approach it is possible to obtain an exact analytical result for the phonon kernel in this system. This approach is introduced in the context of an example: the process of generating polarization-entangled photon pairs from the biexciton cascade in a quantum dot. We calculate the exact density matrix (using quantum state tomography) of photons and their concurrence. We show that the exchange interaction and temperature have remarkable effects on the degree of entanglement of the emitted photons. The approach introduced provides an exact analytical result for finite discrete electron states interacting with phonons.