Variational preparation of finite-temperature states on a quantum computer

R. Sagastizabal, B. A. Klaver, M. A. Rol, V. Negîrneac, X. Zou, N. Muthusubramanian, M. Beekman, C. Zachariadis, V. P. Ostroukh, N. Haider, A. Bruno, L. DiCarlo*, More Authors

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)
85 Downloads (Pure)


The preparation of thermal equilibrium states is important for the simulation of condensed matter and cosmology systems using a quantum computer. We present a method to prepare such mixed states with unitary operators and demonstrate this technique experimentally using a gate-based quantum processor. Our method targets the generation of thermofield double states using a hybrid quantum-classical variational approach motivated by quantum-approximate optimization algorithms, without prior calculation of optimal variational parameters by numerical simulation. The fidelity of generated states to the thermal-equilibrium state smoothly varies from 99 to 75% between infinite and near-zero simulated temperature, in quantitative agreement with numerical simulations of the noisy quantum processor with error parameters drawn from experiment.

Original languageEnglish
Article number130
Number of pages7
JournalNPJ Quantum Information
Issue number1
Publication statusPublished - 2021


Dive into the research topics of 'Variational preparation of finite-temperature states on a quantum computer'. Together they form a unique fingerprint.

Cite this