Harnessing environment effects for high-fidelity hybrid quantum devices: Prospects for a universal numerically exact approach to open quantum systems

This seminar will be held in DB113 and will also be streamed online - please join using the Teams link provided.

Abstract:

"With the tremendous progress in fabrication and control capabilities for quantum devices over the last decades, environment effects become increasingly important as they are a limiting factor for device functionality. However, a thorough understanding also makes it possible to utilise environments as resources. A prime example is the hybrid system of a semiconductor quantum dot coupled to an optical microcavity, whose qualities as a single-photon source can be drastically enhanced by a suitable phonon-assisted driving protocol[1]. Modelling such devices is particularly challenging as the simultaneous strong ultrafast driving and strong coupling to multiple structured environments brings approximate descriptions to their limits.
Here, I show how numerically exact techniques can be of use to predict the dynamics of open hybrid quantum systems to arbitrary precision without the need to invoke approximations with respect to interaction strengths, memory times, or system-environment correlation. Furthermore, I present the novel approach 'automated compression of environments' (ACE), which encapsulates environment influences in a tensor network structure, the so-called process tensor[2]. ACE calculates a process tensor directly from the microscopic Hamiltonian without requiring any specific derivation for the problem at hand, which makes it possible to use one and the same code to simulate the dynamics of open quantum systems with environments as diverse as photons, phonons, electrons, spins, and combinations of multiple environments numerically exactly.
These recent advances suggest that a universal numerically exact solver for arbitrary open quantum systems is within reach."

References:

[1]: M. Cosacchi, F. Ungar, M. Cygorek, A. Vagov, and V. M. Axt,
"Emission-frequency separated high quality single-photon sources enabled by phonons", Phys. Rev. Lett. 123, 017403 (2019)

[2]: M. Cygorek, M. Cosacchi, A. Vagov, V. M. Axt, B. W. Lovett, J. Keeling, and E. M. Gauger, "Simulation of open quantum systems by automated compression of arbitrary environments", Nat. Phys. (2022). https://doi.org/10.1038/s41567-022-01544-9