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

World Congress on Intelligent Control and Automation

Boundary analysis in block schemes for control of some multi-level quantum systems

Ling Yang, Dewen Cao, Yaoxiong Wang, Feng Shuang, Fang Gao

Published Jun 1, 2016• 0 citations
Publisher

Abstract

Two-photon absorption (TPA) is an important quantum process in the light-matter interaction. When more than one TPA pathway exists in a quantum system, it is necessary to utilize the interference of these pathways to increase the sum TPA amplitude. A simple block scheme (Phys. Rev. A 2013, 88, 053427) is proposed to maximize the constructive interference of two TPA pathways in a four-level diamond-configuration quantum system. It can also be expanded to control multiple TPA pathways (Chin. J. Chem. Phys. 2015, 28, 426). The spectral boundaries in the scheme is related to the energy structure of the system. This work tries to give an analysis of the boundaries for general four-level and five-level quantum systems, which have two and three TPA pathways, respectively. How the boundaries and thus the number of blocks change with the energy structure will be explored.

DOI
10.1109/wcica.2016.7578281

Related papers

Controlling pathway dynamics of a four-level quantum system with pulse shaping

Dewen Cao, Ling Yang, Yaoxiong Wang +2 more

Abstract The dynamics of two two-photon absorption (TPA) pathways in a four-level quantum system driven by a laser pulse is investigated in this work. An analytical solution for pulse shaping is proposed to be globally optimal for constructive interference between the two pathways, and accurate spectral boundaries for phase modulation are obtained. The TPA rate can be enhanced by a factor of 8.33 with the optimal pulse instead of the transform limited pulse (TL pulse). Simple control strategies modulating both amplitudes and phases are also designed to increase the TPA amplitude along one pathway while decreasing that along the other simultaneously. The strategies are intuitive and the two pathway amplitudes can differ by two orders of magnitude.

Journal of Physics A Mathematical and Theoretical•Jun 6, 2016•4 citations

Quantum interference control of a four-level diamond-configuration quantum system

Han-gyeol Lee, Hyosub Kim, Jongseok Lim +1 more

We investigate coherent control of the two-photon transition pathways of a four-level atomic system in a diamond configuration. When an ultrashort laser pulse interacts with this system in the ground state $5{S}_{1/2}$ of rubidium, the two-photon transition probability amplitude of $5{D}_{3/2}$ is obtained by a summation of all possible resonant and nonresonant two-photon transition probability amplitudes via $5{P}_{1/2}$ and $5{P}_{3/2}$. Second-order perturbation theory predicts that the maximal constructive interference of the transition probability amplitudes occurs when the phases of eight different spectrum blocks satisfy four different phase relations. Experiments carried out with spectrally phase-coded laser pulses show good agreement with the theoretical prediction.

Physical Review A•Nov 27, 2013•18 citations

Double-control quantum interferences in a four-level atomic system

Jian Qi Shen, Pu Zhang

A new scheme is suggested to manipulate the probe transitions (and hence the optical properties of atomic vapors) via double-control destructive and constructive quantum interferences. The influence of phase coherence between the two control transitions on the probe transition is also studied. The most remarkable feature of the present scheme is that the optical properties (absorption, transparency and dispersion) of an atomic system can be manipulated using this double-control multi-pathway interferences (multiple routes to excitation). It is also shown that a four-level system will exhibit a two-level resonant absorption because the two control levels (driven by the two control fields) form a dark state (and hence a destructive quantum interference occurs between the two control transitions). However, the present four-level system will exhibit electromagnetically induced transparency to the probe field when the three lower levels (including the probe level and the two control levels) form a three-level dark state. The present scenario has potential applications in new devices (e.g. logic gates and sensitive optical switches) and new techniques (e.g. quantum coherent information storage).

Optics Express•Jan 1, 2007•36 citations

Photon Blockade Mediated by Two-Photon Absorption in an Optical Parametric Amplifier

Wei An, Jie Zhu

Photon blockade (PB) is a quantum effect in strongly nonlinear systems where a single photon prevents the system from being excited to a higher level, generating anti-bunched light fields. It enables the generation of single-photon sources for quantum information processing. Conventional photon blockade (CPB) leverages strong nonlinear interactions to generate an anharmonic energy spectrum. Unconventional photon blockade (UPB) utilizes destructive quantum interference between excitation pathways. Recently, environmentally induced photon blockade (EPB) has emerged as a novel approach, exploiting two-photon absorption (TPA) to realize photon blockade. In this work, we combine UPB and EPB together, considering the TPA effect in the optical parametric amplifier (OPA), thereby achieving a more stable PB with stronger suppression of multi-photon states.

arXiv:2509.15696•Sep 19, 2025•0 citations

Coherent Control of Multiple 2nd-Order Quantum Pathways

Fang Gao, Yao-xiong Wang, Dewen Cao +1 more

The manipulation of two 2nd-order quantum pathways has been successfully demonstrated experimentally in atomic Rubidium. This work would explore the coherent control of pathways in the quantum system with N intermediate states connecting the initial and target states. A 4N-block scheme is proposed to control the N 2nd-order pathways which are driven by a weak broadband pulse. The model with N=3 is given as an example to demonstrate our strategy. In this scheme, boundaries of the spectral blocks are functions of the resonant frequencies, and the resonant and non-resonant contributions interfere mutually to achieve the quantum pathway control effectively. The simple strategy may provide a practical choice for pathway manipulation experiments since there are only 2N phase variables to adjust.

Chinese Journal of Chemical Physics•Aug 1, 2015•3 citations

Temperature-Controlled Entangled-Photon Absorption Spectroscopy

Roberto de J. León‐Montiel, Jiŕí Svozilík, Juan P. Torres +1 more

Entangled two-photon absorption spectroscopy (TPA) has been widely recognized as a powerful tool for revealing relevant information about the structure of complex molecular systems. However, to date, the experimental implementation of this technique has remained elusive, mainly because of two major difficulties: first, the need to perform multiple experiments with two-photon states bearing different temporal correlations, which translates into the necessity to have at the experimenter's disposal tens, if not hundreds, of sources of entangled photons; second, the need to have a priori knowledge of the absorbing medium's lowest-lying intermediate energy level. In this work, we put forward a simple experimental scheme that successfully overcomes these two limitations. By making use of a temperature-controlled entangled-photon source, which allows the tuning of the central frequencies of the absorbed photons, we show that the TPA signal, measured as a function of the temperature of the nonlinear crystal that generates the paired photons, and a controllable delay between them, carries all information about the electronic level structure of the absorbing medium, which can be revealed by a simple Fourier transformation.

arXiv:1901.02605•Physical Review Letters•Jul 9, 2019•53 citations
Two-photon absorption (TPA) is an important quantum process in the light-matter interaction. When more than one TPA pathway exists in a quantum system, it is necessary to utilize the interference of these pathways to increase the sum TPA amplitude. A simple block scheme (Phys. Rev. A 2013, 88, 053427) is proposed to maximize the constructive interference of two TPA pathways in a four-level diamond-configuration quantum system. It can also be expanded to control multiple TPA pathways (Chin. J. Chem. Phys. 2015, 28, 426). The spectral boundaries in the scheme is related to the energy structure of the system. This work tries to give an analysis of the boundaries for general four-level and five-level quantum systems, which have two and three TPA pathways, respectively. How the boundaries and thus the number of blocks change with the energy structure will be explored.
Abstract The dynamics of two two-photon absorption (TPA) pathways in a four-level quantum system driven by a laser pulse is investigated in this work. An analytical solution for pulse shaping is proposed to be globally optimal for constructive interference between the two pathways, and accurate spectral boundaries for phase modulation are obtained. The TPA rate can be enhanced by a factor of 8.33 with the optimal pulse instead of the transform limited pulse (TL pulse). Simple control strategies modulating both amplitudes and phases are also designed to increase the TPA amplitude along one pathway while decreasing that along the other simultaneously. The strategies are intuitive and the two pathway amplitudes can differ by two orders of magnitude.
We investigate coherent control of the two-photon transition pathways of a four-level atomic system in a diamond configuration. When an ultrashort laser pulse interacts with this system in the ground state 5S1/25{S}_{1/2}5S1/2​ of rubidium, the two-photon transition probability amplitude of 5D3/25{D}_{3/2}5D3/2​ is obtained by a summation of all possible resonant and nonresonant two-photon transition probability amplitudes via 5P1/25{P}_{1/2}5P1/2​ and 5P3/25{P}_{3/2}5P3/2​. Second-order perturbation theory predicts that the maximal constructive interference of the transition probability amplitudes occurs when the phases of eight different spectrum blocks satisfy four different phase relations. Experiments carried out with spectrally phase-coded laser pulses show good agreement with the theoretical prediction.
A new scheme is suggested to manipulate the probe transitions (and hence the optical properties of atomic vapors) via double-control destructive and constructive quantum interferences. The influence of phase coherence between the two control transitions on the probe transition is also studied. The most remarkable feature of the present scheme is that the optical properties (absorption, transparency and dispersion) of an atomic system can be manipulated using this double-control multi-pathway interferences (multiple routes to excitation). It is also shown that a four-level system will exhibit a two-level resonant absorption because the two control levels (driven by the two control fields) form a dark state (and hence a destructive quantum interference occurs between the two control transitions). However, the present four-level system will exhibit electromagnetically induced transparency to the probe field when the three lower levels (including the probe level and the two control levels) form a three-level dark state. The present scenario has potential applications in new devices (e.g. logic gates and sensitive optical switches) and new techniques (e.g. quantum coherent information storage).
Photon blockade (PB) is a quantum effect in strongly nonlinear systems where a single photon prevents the system from being excited to a higher level, generating anti-bunched light fields. It enables the generation of single-photon sources for quantum information processing. Conventional photon blockade (CPB) leverages strong nonlinear interactions to generate an anharmonic energy spectrum. Unconventional photon blockade (UPB) utilizes destructive quantum interference between excitation pathways. Recently, environmentally induced photon blockade (EPB) has emerged as a novel approach, exploiting two-photon absorption (TPA) to realize photon blockade. In this work, we combine UPB and EPB together, considering the TPA effect in the optical parametric amplifier (OPA), thereby achieving a more stable PB with stronger suppression of multi-photon states.
The manipulation of two 2nd-order quantum pathways has been successfully demonstrated experimentally in atomic Rubidium. This work would explore the coherent control of pathways in the quantum system with N intermediate states connecting the initial and target states. A 4N-block scheme is proposed to control the N 2nd-order pathways which are driven by a weak broadband pulse. The model with N=3 is given as an example to demonstrate our strategy. In this scheme, boundaries of the spectral blocks are functions of the resonant frequencies, and the resonant and non-resonant contributions interfere mutually to achieve the quantum pathway control effectively. The simple strategy may provide a practical choice for pathway manipulation experiments since there are only 2N phase variables to adjust.
Entangled two-photon absorption spectroscopy (TPA) has been widely recognized as a powerful tool for revealing relevant information about the structure of complex molecular systems. However, to date, the experimental implementation of this technique has remained elusive, mainly because of two major difficulties: first, the need to perform multiple experiments with two-photon states bearing different temporal correlations, which translates into the necessity to have at the experimenter's disposal tens, if not hundreds, of sources of entangled photons; second, the need to have a priori knowledge of the absorbing medium's lowest-lying intermediate energy level. In this work, we put forward a simple experimental scheme that successfully overcomes these two limitations. By making use of a temperature-controlled entangled-photon source, which allows the tuning of the central frequencies of the absorbed photons, we show that the TPA signal, measured as a function of the temperature of the nonlinear crystal that generates the paired photons, and a controllable delay between them, carries all information about the electronic level structure of the absorbing medium, which can be revealed by a simple Fourier transformation.