© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

arXiv:2606.30424

Connecting Density Matrix Spectroscopy to Biexciton Entanglement Dynamics

Yusuke Masaki, Takashi Otaki, Hiroaki Matsueda

quant-phcond-mat.mes-hallcond-mat.str-elphysics.opticsSubmitted Jun 29, 2026• Announced Jun 30, 2026• 0 citations

Abstract

Quantum entanglement is one of the most intriguing features of quantum mechanics. To investigate the entanglement between two excitons in a biexciton, an experimental technique called density matrix spectroscopy (DMS) has recently been developed. DMS combines stimulated emission tomography and pump-probe techniques to obtain a time-resolved density matrix of the polarization state of a photon pair emitted from the biexciton. The reconstructed density matrix is expected to encode information about the biexciton state and its entanglement dynamics, but the precise nature of this connection has remained unclear. In this paper, we derive an analytical relationship between the density matrix obtained by DMS and the biexciton state. In addition, we perform numerical simulations to compare the entanglement dynamics obtained by DMS with the biexciton's entanglement dynamics in a two-dimensional electron-hole system using an extended ionic Hubbard model. We find that DMS can partially capture the entanglement in the biexciton, in particular, the dynamics of the difference $S_{\mathrm{bi}} - S_k$, where $S_{\mathrm{bi}}$ is the entanglement entropy of the biexciton and $S_k$ is the entanglement in terms of the wavevectors of the excitons that constitute the biexciton. These results demonstrate the validity of DMS for obtaining information about the entanglement dynamics of the biexciton.

Comments: 19 pages 10 figures

Related papers

Nonlinear polarization optical response to entangled state of biexciton

TETSUYA TSUJI, Goro Oohata, K Mizoguchi

Abstract We have investigated the nonlinear optical responses of biexcitons which show the polarization entanglement by using pump-probe spectroscopy. Measuring all polarization combinations of pump-probe signals and precise analysis using the idea of quantum tomography enable us to extract the specific property of the entanglement. The obtained results indicate the two kinds of the third-order nonlinear response, namely the photo-induced absorption and the optical Kerr effect. From the analysis with the optical Kerr effect signals, the polarization correlations of the optical responses are clearly derived.

Journal of Physics Conference Series•May 1, 2019•0 citations

Evaluation of two-photon polarization density matrix of polarization-entangled photon pairs generated through biexciton resonant hyper-parametric scattering

Yasuo Yamamoto, Goro Oohata, Kohji Mizoguchi

We have investigated the excitation-power dependence of polarization-entangled photon pairs generated from a CuCl single crystal using biexciton resonant hyper-parametric scattering. The two-photon polarization density matrix of photon pairs generated from a CuCl single crystal maintained at 10 K was measured under different excitation powers. The measured two-photon polarization density matrix, which corresponds to the two-photon polarization state, changes with an increase in the excitation power. The evaluations of the tangle and the linear entropy obtained from the measured density matrix indicate that the two-photon polarization density matrix can be expressed as the mixed state of an ideal state and a totally mixed state, and the mixture ratio of the totally mixed state increases as the excitation density increases. The variations of the density matrix and the mixture ratio with the excitation power originate from the generation of the multiple photon pairs. Furthermore, a numerical calculation considering simultaneous detection efficiency was able to reproduce the experimental results.

arXiv:1801.00596•Journal of the Optical Society of America B•May 22, 2019•0 citations

ANALYSIS OF CORRELATION FUNCTION AND POLARIZATION ENTANGLEMENT OF PHOTON PAIRS GENERATED FROM ANISOTROPIC SEMICONDUCTOR QUANTUM DOT

Shao‐Ding Liu, Mu-Tian Cheng, Xia Wang +1 more

The dynamics of the population density matrix and polarization density matrix of the biexciton system of single semiconductor quantum dots with pulse excitation were analyzed by using master equations and quantum regression theorem. A model based on the spectral distributions of the cascade photon emissions was proposed to calculate the polarization entanglement of the photon pairs emitted from the non-degenerate biexciton system with spectral filters. The influences of the spectral filter width and the exciton energy splitting between the two orthogonally polarized eigenstates on the entanglement were theoretically analyzed. The dependence of the polarization entanglement on the input pulse area was also discussed.

International Journal of Quantum Information•Aug 1, 2008•0 citations

Coherent Dynamics of Excitons and Biexcitons: Polarization and Intensity Dependence

Björn Haase, U. Neukirch, Juergen Gutowski +4 more

A systematic analysis of excitonic and biexcitonic contributions to four-wave mixing in dependence on the polarization state and on the intensity of the exciting beams is presented for ZnSe/Zn1—xMgxSySe1—iiy quantum wells. The relative signals of excitons and biexcitons for different polarization configurations are discussed in terms of a microscopic density matrix model revealing excellent correspondence to the complex experimental data. In configurations which do not allow for a third-order contribution of the biexciton of zero angular momentum higher-order correlations are shown to become important already at densities as low as 1010 excitons cm—2/pulse.

physica status solidi (b)•Mar 1, 1998•16 citations

Quantum Fourier transform spectroscopy of biexciton

Hiroya Seki, Kensuke Miyajima, Ryōsuke Shimizu

Fourier transform spectroscopy with classical interferometry corresponds to the measurement of a single-photon intensity spectrum from the viewpoint of the particle nature of light. In contrast, the Fourier transform of two-photon quantum interference patterns provides the intensity spectrum of the two photons as a function of the sum or difference frequency of the constituent photons. This unique feature of quantum interferometric spectroscopy offers a different type of spectral information from the classical measurement and may prove useful for nonlinear spectroscopy with two-photon emission. Here, we report the first experimental demonstration of two-photon quantum interference of photon pairs emitted via biexcitons in the semiconductor CuCl. Besides applying Fourier transform to quantum interference patterns, we reconstruct the intensity spectrum of the biexciton luminescence in the two-photon sum or difference frequency. We discuss the connection between the reconstructed spectra and exciton states in CuCl as well as the capability of quantum interferometry in solid-state spectroscopy.

arXiv:2109.03715•Sep 8, 2021•0 citations

Dynamics of excitons in individual InAs quantum dots revealed in four-wave mixing spectroscopy

Quentin Mermillod, Daniel Wigger, Valentin Delmonte +8 more

A detailed understanding of the population and coherence dynamics in optically driven individual emitters in solids and their signatures in ultrafast nonlinear-optical signals is of prime importance for their applications in future quantum and optical technologies. In a combined experimental and theoretical study on exciton complexes in single semiconductor quantum dots we reveal a detailed picture of the dynamics employing three-beam polarization-resolved four-wave mixing (FWM) micro-spectroscopy. The oscillatory dynamics of the FWM signals in the exciton-biexciton system is governed by the fine-structure splitting and the biexciton binding energy in an excellent quantitative agreement between measurement and analytical description. The analysis of the excitation conditions exhibits a dependence of the dynamics on the specific choice of polarization configuration, pulse areas and temporal ordering of driving fields. The interplay between the transitions in the four-level exciton system leads to rich evolution of coherence and population. Using two-dimensional FWM spectroscopy we elucidate the exciton-biexciton coupling and identify neutral and charged exciton complexes in a single quantum dot. Our investigations thus clearly reveal that FWM spectroscopy is a powerful tool to characterize spectral and dynamical properties of single quantum structures.

arXiv:1604.02262•Optica•Apr 1, 2016•60 citations

Quantum entanglement is one of the most intriguing features of quantum mechanics. To investigate the entanglement between two excitons in a biexciton, an experimental technique called density matrix spectroscopy (DMS) has recently been developed. DMS combines stimulated emission tomography and pump-probe techniques to obtain a time-resolved density matrix of the polarization state of a photon pair emitted from the biexciton. The reconstructed density matrix is expected to encode information about the biexciton state and its entanglement dynamics, but the precise nature of this connection has remained unclear. In this paper, we derive an analytical relationship between the density matrix obtained by DMS and the biexciton state. In addition, we perform numerical simulations to compare the entanglement dynamics obtained by DMS with the biexciton's entanglement dynamics in a two-dimensional electron-hole system using an extended ionic Hubbard model. We find that DMS can partially capture the entanglement in the biexciton, in particular, the dynamics of the difference

S_{\mathrm{bi}} - S_k

, where

S_{\mathrm{bi}}

is the entanglement entropy of the biexciton and

S_k

is the entanglement in terms of the wavevectors of the excitons that constitute the biexciton. These results demonstrate the validity of DMS for obtaining information about the entanglement dynamics of the biexciton.

Abstract We have investigated the nonlinear optical responses of biexcitons which show the polarization entanglement by using pump-probe spectroscopy. Measuring all polarization combinations of pump-probe signals and precise analysis using the idea of quantum tomography enable us to extract the specific property of the entanglement. The obtained results indicate the two kinds of the third-order nonlinear response, namely the photo-induced absorption and the optical Kerr effect. From the analysis with the optical Kerr effect signals, the polarization correlations of the optical responses are clearly derived.

We have investigated the excitation-power dependence of polarization-entangled photon pairs generated from a CuCl single crystal using biexciton resonant hyper-parametric scattering. The two-photon polarization density matrix of photon pairs generated from a CuCl single crystal maintained at 10 K was measured under different excitation powers. The measured two-photon polarization density matrix, which corresponds to the two-photon polarization state, changes with an increase in the excitation power. The evaluations of the tangle and the linear entropy obtained from the measured density matrix indicate that the two-photon polarization density matrix can be expressed as the mixed state of an ideal state and a totally mixed state, and the mixture ratio of the totally mixed state increases as the excitation density increases. The variations of the density matrix and the mixture ratio with the excitation power originate from the generation of the multiple photon pairs. Furthermore, a numerical calculation considering simultaneous detection efficiency was able to reproduce the experimental results.

The dynamics of the population density matrix and polarization density matrix of the biexciton system of single semiconductor quantum dots with pulse excitation were analyzed by using master equations and quantum regression theorem. A model based on the spectral distributions of the cascade photon emissions was proposed to calculate the polarization entanglement of the photon pairs emitted from the non-degenerate biexciton system with spectral filters. The influences of the spectral filter width and the exciton energy splitting between the two orthogonally polarized eigenstates on the entanglement were theoretically analyzed. The dependence of the polarization entanglement on the input pulse area was also discussed.

A systematic analysis of excitonic and biexcitonic contributions to four-wave mixing in dependence on the polarization state and on the intensity of the exciting beams is presented for ZnSe/Zn1—xMgxSySe1—iiy quantum wells. The relative signals of excitons and biexcitons for different polarization configurations are discussed in terms of a microscopic density matrix model revealing excellent correspondence to the complex experimental data. In configurations which do not allow for a third-order contribution of the biexciton of zero angular momentum higher-order correlations are shown to become important already at densities as low as 1010 excitons cm—2/pulse.

Fourier transform spectroscopy with classical interferometry corresponds to the measurement of a single-photon intensity spectrum from the viewpoint of the particle nature of light. In contrast, the Fourier transform of two-photon quantum interference patterns provides the intensity spectrum of the two photons as a function of the sum or difference frequency of the constituent photons. This unique feature of quantum interferometric spectroscopy offers a different type of spectral information from the classical measurement and may prove useful for nonlinear spectroscopy with two-photon emission. Here, we report the first experimental demonstration of two-photon quantum interference of photon pairs emitted via biexcitons in the semiconductor CuCl. Besides applying Fourier transform to quantum interference patterns, we reconstruct the intensity spectrum of the biexciton luminescence in the two-photon sum or difference frequency. We discuss the connection between the reconstructed spectra and exciton states in CuCl as well as the capability of quantum interferometry in solid-state spectroscopy.

A detailed understanding of the population and coherence dynamics in optically driven individual emitters in solids and their signatures in ultrafast nonlinear-optical signals is of prime importance for their applications in future quantum and optical technologies. In a combined experimental and theoretical study on exciton complexes in single semiconductor quantum dots we reveal a detailed picture of the dynamics employing three-beam polarization-resolved four-wave mixing (FWM) micro-spectroscopy. The oscillatory dynamics of the FWM signals in the exciton-biexciton system is governed by the fine-structure splitting and the biexciton binding energy in an excellent quantitative agreement between measurement and analytical description. The analysis of the excitation conditions exhibits a dependence of the dynamics on the specific choice of polarization configuration, pulse areas and temporal ordering of driving fields. The interplay between the transitions in the four-level exciton system leads to rich evolution of coherence and population. Using two-dimensional FWM spectroscopy we elucidate the exciton-biexciton coupling and identify neutral and charged exciton complexes in a single quantum dot. Our investigations thus clearly reveal that FWM spectroscopy is a powerful tool to characterize spectral and dynamical properties of single quantum structures.