Characterizing a non-equilibrium phase transition on a quantum computer

• Published in: Nature physics 2023-12, Vol.19 (12), p.1799-1804
• Main Authors: Chertkov, Eli, Cheng, Zihan, Potter, Andrew C., Gopalakrishnan, Sarang, Gatterman, Thomas M., Gerber, Justin A., Gilmore, Kevin, Gresh, Dan, Hall, Alex, Hankin, Aaron, Matheny, Mitchell, Mengle, Tanner, Hayes, David, Neyenhuis, Brian, Stutz, Russell, Foss-Feig, Michael
• Format: Article
• Language: English
• Subjects: 639/766/483/3926; 639/766/530/2795; Atomic; Circuits; Classical and Continuum Physics; Complex Systems; Computers; Condensed Matter Physics; Dissipation; Equilibrium; Error correction; Mathematical and Computational Physics; Mathematical models; Molecular; Optical and Plasma Physics; Optics; Percolation; Phase transitions; Physics; Physics and Astronomy; Quantum computers; Quantum computing; Quantum optics; Quantum theory; Qubits (quantum computing); Simulation; Statistical mechanics; System dynamics; Theoretical
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-023-02199-w

Quantum systems subject to driving and dissipation display distinctive non-equilibrium phenomena relevant to condensed matter, quantum optics, metrology and quantum error correction. An example is the emergence of phase transitions with uniquely quantum properties, which opposes the intuition that dissipation generally leads to classical behaviour. The quantum and non-equilibrium nature of such systems makes them hard to study with existing tools, such as those from equilibrium statistical mechanics, and represents a challenge for numerical simulations. Quantum computers, however, are well suited to simulating such systems, especially as hardware developments enable the controlled application of dissipative operations in a pristine quantum environment. Here we demonstrate a large-scale accurate quantum simulation of a non-equilibrium phase transition using a trapped-ion quantum computer. We simulate a quantum extension of the classical contact process that has been proposed as a description for driven gases of Rydberg atoms and has stimulated numerous attempts to determine the impact of quantum effects on the classical directed-percolation universality class. We use techniques such as qubit reuse and error avoidance based on real-time conditional logic to implement large instances of the model with 73 sites and up to 72 circuit layers and quantitatively determine the model’s critical properties. Our work demonstrates that today’s quantum computers are able to perform useful simulations of open quantum system dynamics and non-equilibrium phase transitions. Quantum computers may help to solve classically intractable problems, such as simulating non-equilibrium dissipative quantum systems. The critical dynamics of a dissipative quantum model has now been probed on a trapped-ion quantum computer.