This open source project aims to facilitate versatile numerical tools to efficiently compute the dynamics of quantum systems that are possibly strongly coupled to structured environments. It facilitates the convenient application of several numerical methods that combine the conceptional advantages of the process tensor framework [1], with the numerical efficiency of tensor networks.

OQuPy includes numerically exact methods (i.e. employing only numerically well controlled approximations) for the non-Markovian dynamics and multi-time correlations of ...

• quantum systems coupled to a single environment [2-4],
• quantum systems coupled to multiple environments [5],
• interacting chains of non-Markovian open quantum systems [6], and
• ensembles of open many-body systems with many-to-one coupling [7].

Furthermore, OQuPy implements methods to ...

• optimize control protocols for non-Markovian open quantum systems [8,9],
• compute the dynamics of an non-Markovian environment [10], and
• obtain the thermal state of a strongly couled quantum system [11].

MAJOR CODE CONTRIBUTIONS

• Lead developer since 2020: Gerald E. Fux
• Co-lead developer since 2022: Piper Fowler-Wright

Version 0.5.0

• Aidan Strathearn: Gibbs state TEMPO [11].
• Eoin P. Butler, Eoin O'Neill, and Paul R. Eastham: Process tensor gradients and optimization [8,9]
• Ewen D.C. Lawrence and Peter Kirton: Degeneracy trick in TEMPO and PT-TEMPO.
• Roosmarijn de Wit: Multi-time system correlations.
• Piper Fowler-Wright: TEMPO parameter tutorial and automatic estimation.

Version 0.4.0

• Joel Beckles and Piper Fowler-Wright: Extension of mean-field evolution to multiple types of system.

Version 0.3.0

• Piper Fowler-Wright: Open quantum systems with mean-field evolution [7].

Version 0.2.0

• Gerald E. Fux: Chains of open quantum systems [6].
• Dainius Kilda: Precursor code for chains of open quantum systems [6].
• Dominic Gribben: Bath dynamics extension [10].
• Dominic Gribben: Multiple environments extension [5].

Version 0.1.2 (TimeEvolvingMPO)

• Gerald E. Fux: Improved memory cut-off [2].

Version 0.1.0 (TimeEvolvingMPO)

• Gerald E. Fux: Implement process tensor TEMPO (API and backend) [8].
• Gerald E. Fux: Implement core TEMPO functionality (API and backend) [3].
• Gerald E. Fux: Setup Project (CI, API design, project planning, etc.).

Bibliography

• [1] Pollock et al., Phys. Rev. A 97, 012127 (2018).
• [2] Strathearn et al., New J. Phys. 19(9), p.093009 (2017).
• [3] Strathearn et al., Nat. Commun. 9, 3322
  (2018).
• [4] Jørgensen and Pollock, Phys. Rev. Lett. 123, 240602 (2019).
• [5] Gribben et al., PRX Quantum 3, 10321 (2022).
• [6] Fux et al., Phys. Rev. Research 5, 033078 (2023).
• [7] Fowler-Wright et al., Phys. Rev. Lett. 129, 173001 (2022).
• [8] Fux et al., Phys. Rev. Lett. 126, 200401 (2021).
• [9] Butler et al., Phys. Rev. Lett. 132, 060401 (2024).
• [10] Gribben et al., Quantum, 6, 847 (2022).
• [11] Chiu et al., Phys. Rev. A 106, 012204 (2022).