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1. Phononic bath engineering of a superconducting qubit

   https://doi.org/10.1038/s41467-023-39682-0  

   Kitzman, J. M.; Lane, J. R.; Undershute, C.; Harrington, P. M.; Beysengulov, N. R.; Mikolas, C. A.; Murch, K. W.; Pollanen, J. (July 2023, Nature Communications)

   Abstract Phonons, the ubiquitous quanta of vibrational energy, play a vital role in the performance of quantum technologies. Conversely, unintended coupling to phonons degrades qubit performance and can lead to correlated errors in superconducting qubit systems. Regardless of whether phonons play an enabling or deleterious role, they do not typically admit control over their spectral properties, nor the possibility of engineering their dissipation to be used as a resource. Here we show that coupling a superconducting qubit to a bath of piezoelectric surface acoustic wave phonons enables a novel platform for investigating open quantum systems. By shaping the loss spectrum of the qubit via the bath of lossy surface phonons, we demonstrate preparation and dynamical stabilization of superposition states through the combined effects of drive and dissipation. These experiments highlight the versatility of engineered phononic dissipation and advance the understanding of mechanical losses in superconducting qubit systems. 

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2. Page curves and bath deformations

   https://doi.org/10.21468/SciPostPhysCore.5.2.033  

   Caceres, Elena; Kundu, Arnab; Patra, Ayan; Shashi, Sanjit (January 2022, SciPost Physics Core)

   We study the black hole information problem within a semiclassicallygravitating AdS _d d black hole coupled to and in equilibrium with a d d -dimensionalthermal conformal bath. We deform the bath state by a relevant scalardeformation, triggering a holographic RG flow whose "trans-IR"region deforms from a Schwarzschild geometry to a Kasner universe. Thesetup manifests two independent scales which control both the extent ofcoarse-graining and the entanglement dynamics when counting Hawkingdegrees of freedom in the bath. In tuning either, we find nontrivialchanges to the Page time and Page curve. We consequently view the Pagecurve as a probe of the holographic RG flow, with a higher Page timemanifesting as a result of increased coarse-graining of the bath degreesof freedom. 

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3. Relativistic Semistochastic Heat-Bath Configuration Interaction

   https://doi.org/10.1021/acs.jctc.2c01025  

   Wang, Xubo; Sharma, Sandeep (February 2023, Journal of Chemical Theory and Computation)
4. Fast semistochastic heat-bath configuration interaction

   https://doi.org/10.1063/1.5055390  

   Li, Junhao; Otten, Matthew; Holmes, Adam A.; Sharma, Sandeep; Umrigar, C. J. (December 2018, The Journal of Chemical Physics)
5. Information transfer with a gravitating bath

   https://doi.org/10.21468/SciPostPhys.10.5.103  

   Geng, Hao; Karch, Andreas; Perez-Pardavila, Carlos; Raju, Suvrat; Randall, Lisa; Riojas, Marcos; Shashi, Sanjit (January 2021, SciPost Physics)

   Late-time dominance of entanglement islands plays a critical role in addressing the information paradox for black holes in AdS coupled to an asymptotic non-gravitational bath. A natural question is how this observation can be extended to gravitational systems. To gain insight into this question, we explore how this story is modified within the context of Karch-Randall braneworlds when we allow the asymptotic bath to couple to dynamical gravity. We find that because of the inability to separate degrees of freedom by spatial location when defining the radiation region, the entanglement entropy of radiation emitted into the bath is a time-independent constant, consistent with recent work on black hole information in asymptotically flat space. If we instead consider an entanglement entropy between two sectors of a specific division of the Hilbert space, we then find non-trivial time-dependence, with the Page time a monotonically decreasing function of the brane angle---provided both branes are below a particular angle. However, the properties of the entropy depend discontinuously on this angle, which is the first example of such discontinuous behavior for an AdS brane in AdS space. 

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