Description
I will address the emergence of cooperative effects in driven-dissipative many-body quantum systems out of equilibrium, such as superradiant light emission, spin squeezing, phase transitions, and dark states [1-2]. The use of permutational symmetry allows one to efficiently solve the Lindblad dynamics with an exponential reduction in computational resources even accounting for local homogeneous dissipation channels [2]. Using the formalism of Dicke states, it is also possible to extend the study of the driven-dissipative dynamics also to the so-called “ultrastrong” coupling regime of light-matter interaction [2,3]. We crafted a tool in the form of an open-source software, the permutational invariant quantum solver (PIQS) and integrated it in the Quantum Toolbox in Python, QuTiP (www.qutip.org) [4], making it available to the research community for future investigations [5].
 
[1] Nathan Shammah, Neill Lambert, Franco Nori, and Simone De Liberato, Superradiance with local phase-breaking effects, Phys. Rev. A 96, 023863 (2017). https://arxiv.org/abs/1704.07066
 
[2] Nathan Shammah, Shahnawaz Ahmed, Neill Lambert, Simone De Liberato, and Franco Nori, Open quantum systems with local and collective incoherent processes: Efficient numerical simulation using permutational invariance, Phys. Rev. A 98, 063815 (2018). https://arxiv.org/abs/1805.05129
 
[3] Mauro Cirio, Nathan Shammah, Neill Lambert, Simone De Liberato, and Franco Nori, Multielectron ground state electroluminescence, Phys. Rev. Lett. 122, 190403 (2019) https://arxiv.org/abs/1811.08682
 
[4] J. Robert Johansson, Paul D. Nation, and Franco Nori, QuTiP: An open-source Python framework for the dynamics of open quantum systems, Comp. Phys. Comm. 183, 1760 (2012); QuTiP 2: A Python framework for the dynamics of open quantum systems, ibid. 184, 1234 (2013).
 
[5] Nathan Shammah and Shahnawaz Ahmed, The rise of open source in quantum physics research, http://blogs.nature.com/onyourwavelength/2019/01/09/the-rise-of-open-source-in-quantum-physics-research/
 
Biography
Dr. Nathan Shammah is a Postdoctoral Researcher in the Theoretical Quantum Physics Laboratory at RIKEN, Wako, Japan. He obtained his Ph.D. from the University of Southampton, U.K., with a thesis on light emission phenomena in solid state systems with flat electronic bands. He is a contributor to QuTiP and is interested in the physics of driven-dissipative many-body quantum systems. 
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