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:2109.12748 · Automatica

Stabilizing preparation of quantum Gaussian states via continuous measurement

Liying Bao, Bo Qi, Daoyi Dong

Published Mar 20, 2024• 5 citations
arXivHTMLPDF
DOI
10.1016/j.automatica.2024.111622

Related papers

Quantum State Preparation of Spin Ensembles by Continuous Measurement and Feedback

Ramon van Handel, John K. Stockton, Hideo Mabuchi +1 more

IMPERIAL COLLEGE PRESS eBooks•Feb 1, 2007•0 citations

Deterministic preparation of squeezed and non-Gaussian states in coupled qubit-boson systems

Fengquan Zhang, Xiaotong Liu, Yuping Mao +2 more

Deterministic preparation of bosonic resource states is a central task in continuous-variable quantum information processing and quantum metrology. Here we develop a measurement-based imaginary time evolution (MITE) protocol for preparing squeezed and non-Gaussian states. The protocol combines ancilla-mediated weak measurements of the Hamiltonian with a conditional phase rotation that suppresses excited state trapping and stabilizes convergence toward the ground state. The method is potentially applicable in hybrid discrete variable-continuous variable (DV-CV) platforms, where the qubit acts as the measurement readout. We demonstrate deterministic convergence over a broad range of parameters and show that the performance degradation near the stability boundary is governed by the shrinking Bogoliubov quasiparticle gap. The same framework also extends to non-Gaussian bosonic resource states, including Schrödinger cat states and excited states of the single-mode squeezing Hamiltonian, which display Wigner negativity. The squeezed states remain robust under bosonic loss over experimentally relevant regimes.

quant-pharXiv:2610.16207•Oct 13, 2026•0 citations

The logical set of Gaussian states under the stabilizer subsystem decomposition

Santiago Zamora, Kaustav Chatterjee, Ulrik Lund Andersen +4 more

Universal quantum computation requires non-Gaussianity in continuous-variable systems and non-stabilizerness in discrete-variable systems. Yet, mapping a Gaussian state into the Gottesman-Kitaev-Preskill logical subspace can yield a logical qubit with non-stabilizer resources. To understand how the continuous-variable structure determines logical resources, we characterize the image of single-mode Gaussian states under the corresponding extraction channel, known as the stabilizer subsystem decomposition. Specifically, we derive series expressions for the logical Bloch vector and characterize the resulting reachable set, enabling an analytical treatment of the robustness of magic of the logical states. We then turn this geometric framework into a certification tool: by mapping a discrete-variable qubit witness to a continuous-variable squeezing witness, we obtain lower bounds on the squeezing of prepared states. We also show that ensembles of Gaussian states can violate both stabilizer and classical bounds. Violation of the stabilizer bound certifies the relational resource known as "set-magic," while violation of the classical bound enables the certification of cryptographic randomness at moderate squeezing.

quant-pharXiv:2609.26898•Sep 24, 2026•0 citations

Unified approach to quantum engineering of non-Gaussian states

Mikhail S. Podoshvedov, Sergey A. Podoshvedov, S. P. Kulik

Physical Review A•Oct 26, 2026•0 citations

Gaussian States in Open System Dynamics and Continuous Measurements

Mikael Vartiainen

This thesis develops a comprehensive framework for the use of continuous variable (CV) Gaussian states under environmental interactions and continuous measurements. Gaussian states provide an experimentally relevant class of quantum states because they are fully described by their first and second statistical moments. This thesis begins by representing Gaussian operations as symplectic transformations on the statistical moments and formulates the evolution of a Gaussian state under both unconditional and conditional open system dynamics. Stochastic methods are introduced in a physicist-accessible manner by sacrificing mathematical rigor over physical intuition. These methods are necessary to model environmental noise and continuous measurements represented by a Wiener process. From stochastic principles, a stochastic version of the Schr\"{o}dinger equation and a master equation are derived that capture the measurement-induced back-action. From these principles a conditional equation of motion for the covariance matrix of a Gaussian state is derived, leading to the Riccati equation. Unconditional evolution always leads to diffusive dynamics when the noise is modeled by a Wiener process. The key difference between unconditional and conditional equations of motion is that monitoring always leads to a reduction of uncertainty because a measurement gains information about the system. At the same time, all correlations to the part of the system being measured are lost, which in many cases can lead to an impure quantum state. At some cases, a sufficient measurement scheme can even be used to stabilize the unconditional equation at all scales. The developed formalism is applied to a system of multiple parametric flux pumps based on spontaneous parametric down-conversion to analyze entanglement generation in a complex network of modes. A simple formula relevant to all symmetric pumping architectures, also relevant for asymmetric cases, is derived with graph theoretical tools. The investigation revealed fundamental challenges in entanglement-generation based on multiple two-mode squeezed modes. Overall, the thesis provides a complete framework of Gaussian state dynamics connecting symplectic geometry, open quantum systems, quantum measurement theory, and stochastic methods. The results highlight the importance of Gaussian states in modern quantum technologies and future improvements in quantum computation and communication.

Työväentutkimus Vuosikirja•Mar 16, 2026•0 citations

Gaussian Description of Continuous Measurements on Continuous Variable Quantum Systems

Lars Bojer Madsen, Klaus Mølmer

IMPERIAL COLLEGE PRESS eBooks•Feb 1, 2007•0 citations
Deterministic preparation of bosonic resource states is a central task in continuous-variable quantum information processing and quantum metrology. Here we develop a measurement-based imaginary time evolution (MITE) protocol for preparing squeezed and non-Gaussian states. The protocol combines ancilla-mediated weak measurements of the Hamiltonian with a conditional phase rotation that suppresses excited state trapping and stabilizes convergence toward the ground state. The method is potentially applicable in hybrid discrete variable-continuous variable (DV-CV) platforms, where the qubit acts as the measurement readout. We demonstrate deterministic convergence over a broad range of parameters and show that the performance degradation near the stability boundary is governed by the shrinking Bogoliubov quasiparticle gap. The same framework also extends to non-Gaussian bosonic resource states, including Schrödinger cat states and excited states of the single-mode squeezing Hamiltonian, which display Wigner negativity. The squeezed states remain robust under bosonic loss over experimentally relevant regimes.
Universal quantum computation requires non-Gaussianity in continuous-variable systems and non-stabilizerness in discrete-variable systems. Yet, mapping a Gaussian state into the Gottesman-Kitaev-Preskill logical subspace can yield a logical qubit with non-stabilizer resources. To understand how the continuous-variable structure determines logical resources, we characterize the image of single-mode Gaussian states under the corresponding extraction channel, known as the stabilizer subsystem decomposition. Specifically, we derive series expressions for the logical Bloch vector and characterize the resulting reachable set, enabling an analytical treatment of the robustness of magic of the logical states. We then turn this geometric framework into a certification tool: by mapping a discrete-variable qubit witness to a continuous-variable squeezing witness, we obtain lower bounds on the squeezing of prepared states. We also show that ensembles of Gaussian states can violate both stabilizer and classical bounds. Violation of the stabilizer bound certifies the relational resource known as "set-magic," while violation of the classical bound enables the certification of cryptographic randomness at moderate squeezing.
This thesis develops a comprehensive framework for the use of continuous variable (CV) Gaussian states under environmental interactions and continuous measurements. Gaussian states provide an experimentally relevant class of quantum states because they are fully described by their first and second statistical moments. This thesis begins by representing Gaussian operations as symplectic transformations on the statistical moments and formulates the evolution of a Gaussian state under both unconditional and conditional open system dynamics. Stochastic methods are introduced in a physicist-accessible manner by sacrificing mathematical rigor over physical intuition. These methods are necessary to model environmental noise and continuous measurements represented by a Wiener process. From stochastic principles, a stochastic version of the Schr\"{o}dinger equation and a master equation are derived that capture the measurement-induced back-action. From these principles a conditional equation of motion for the covariance matrix of a Gaussian state is derived, leading to the Riccati equation. Unconditional evolution always leads to diffusive dynamics when the noise is modeled by a Wiener process. The key difference between unconditional and conditional equations of motion is that monitoring always leads to a reduction of uncertainty because a measurement gains information about the system. At the same time, all correlations to the part of the system being measured are lost, which in many cases can lead to an impure quantum state. At some cases, a sufficient measurement scheme can even be used to stabilize the unconditional equation at all scales. The developed formalism is applied to a system of multiple parametric flux pumps based on spontaneous parametric down-conversion to analyze entanglement generation in a complex network of modes. A simple formula relevant to all symmetric pumping architectures, also relevant for asymmetric cases, is derived with graph theoretical tools. The investigation revealed fundamental challenges in entanglement-generation based on multiple two-mode squeezed modes. Overall, the thesis provides a complete framework of Gaussian state dynamics connecting symplectic geometry, open quantum systems, quantum measurement theory, and stochastic methods. The results highlight the importance of Gaussian states in modern quantum technologies and future improvements in quantum computation and communication.