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In this work, drawing inspiration from the type of noise present in real hardware, we study the output distribution of random quantum circuits under practical non-unital noise sources with constant noise rates. We show that even in the presence of unital sources like the depolarizing channel, the distribution, under the combined noise
channel, never resembles a maximally entropic distribution at any depth. To show this, we prove that the output distribution of such circuits never anticoncentrates — meaning it is never too "flat" — regardless of the depth of the circuit. This is in stark contrast to the behavior of noiseless random quantum circuits or those with only unital noise, both
of which anticoncentrate at sufficiently large depths. As consequences, our results have interesting algorithmic implications on both the hardness and easiness of noisy random circuit sampling, since anticoncentration is a critical property exploited by both state-of-the-art classical hardness and easiness results. This talk is based on arXiv:2306.16659.

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The existence of fermionic compact objects, such as neutron stars, is supported by a plethora of observational evidence — an intriguing idea is whether one can construct stars made up of the bosonic counterparts. Such theoretical objects are called boson stars, proposed to make up a fraction of the dark matter in our Universe and claimed to be promising horizonless black hole mimickers. In this talk I will discuss the state-of-the-art of numerical evolutions of boson star models in spherical symmetry. In particular, I will discuss how improper initial data construction can lead to spurious physical effects in the evolution of boson star mergers and introduce methods, necessary to remedy such spurious features. I will present our results on boson star head-on collisions of various mass ratios, highlighting the differences from the black hole mergers. Lastly, I will discuss our recent results on the high-precision numerical relativity simulations of quasi-circular boson star inspirals in pursuit of understanding the implications of boson star signatures on the LIGO-Virgo-KAGRA observations.

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