*QSA scientists designed and demonstrated a novel NISQ-friendly algorithm for simulating real-world open quantum systems on quantum computers*

**The Science:** In the real world, quantum systems like materials, molecules and elementary particles interact with their environment. QSA Scientists developed an innovative algorithm capable of simulating such open quantum systems on quantum computers with polynomial scaling. The algorithm is built on the adaptive variational quantum dynamics approach and was demonstrated on IBM’s quantum processor by simulating the open-system quantum annealing dynamics, achieving good quantitative and qualitative agreement with the exact solution.

**The Impact: **In the real world, quantum systems like materials and elementary particles interact with their environment. QSA researchers developed an innovative algorithm with polynomial scaling that paves the way for effectively utilizing near-future quantum processors to simulate open quantum systems. They demonstrated the algorithm’s efficacy on real quantum hardware, marking a substantial advancement in quantum simulation.

**Summary:** Emerging quantum hardware provides new possibilities for quantum simulation. While research has mostly focused on simulating closed quantum systems, real-world quantum systems are mostly open. In different terms, quantum systems (materials, molecules, elementary particles) interact with their environment. Therefore, developing quantum algorithms that can effectively simulate open quantum systems is essential. QSA Scientists have developed a Noisy Intermediate-Scale Quantum (NISQ)-friendly algorithm using an unrestricted adaptive variational quantum dynamics (UAVQDS) algorithm that greedily builds resource-efficient ansätze through the dynamical addition of operators by maintaining the simulation accuracy, effectively handling the challenge of establishing a reasonable threshold for the McLachlan distance.

**Contact:** Bert de Jong – wadejong@lbl.gov

**Institutions:** Lawrence Berkeley National Laboratory

**Citation:** Chen, H. et al., Adaptive variational simulation for open quantum systems. *Quantum 8, 1252 (2024)*

**Funding Acknowledgement:** This work was supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Systems Accelerator (HC, WAdJ) and by DOE Office of Advanced Scientific Computing Research (ASCR) through the ARQC program (NG, SN).