Multi-Agent Verification and Control with Probabilistic Model Checking -- Formal Controller Synthesis for Markov Jump Linear Systems with Uncertain Dynamics -- Jajapy: a learning library for stochastic models -- Introducing Asynchronicity to Probabilistic Hyperproperties -- A Bounded Model Checking Technique for Discrete-Time Nonlinear Systems -- An MM Algorithm to Estimate Parameters in Continuous-time Markov Chains -- STAMINA in C++: Modernizing an Infinite-State Probabilistic Model Checker -- Skipping and Fetching: Insights on Non-Convectional Product-Form Solutions -- On the Maximum Queue Length of the Hyper Scalable Load Balancing Push Strategy -- Data-driven Inference of Chemical Reaction Networks via Graph-based Variational Autoencoders -- Modeling uncertain biomass composition in genome-scale metabolic models with Flexible Nets -- On the Trade-off Between Efficiency and Precision of Neural Abstraction -- Equilibrium Analysis of Markov Regenerative Processes -- Max-entropy sampling for deterministic timed automata under linear duration constraints -- Quasi-Deterministic Burstiness Bound for Aggregate of Independent, Periodic Flows -- Matching Distributions under Structural Constraints -- Comparing Two Approaches to Include Stochasticity in Hybrid Automata -- Analysis of an epoch commit protocol for distributed processing systems -- Causal Reversibility Implies Time Reversibility -- Deductive Controller Synthesis for Probabilistic Hyperproperties -- Model Abstraction and Conditional Sampling with Score-Based Diffusion Model -- Probabilistic Counterexample Guidance for Safer Reinforcement Learning -- Symbolic Semantics for Probabilistic Programs -- Verification of Quantum Systems using Barrier Certificates.

This book constitutes the proceedings of the 20th International Conference on Quantitative Evaluation of Systems, QEST 2023, which took place in Antwerp, Belgium, in September 2023. The 23 papers included in this book were carefully reviewed and selected from 44 submissions. They deal with current topics in quantitative evaluation and verification of computer systems and networks, focusing on data-driven and machine-learning systems, case studies, and tool papers. The book also contains the extended abstract of the invited talk from David Parker. .