In superconducting quantum computing one typically uses Josephson junctions (superconducting tunnel junctions) to make anharmonic resonators that act as qubits. Junctions are made by litography like classical CPUs. Such qubits are prepared by microwave pulses that correspond to rotations on the Bloch sphere. Entanglement between qubits is generated by variable coupling (in the simplest case adjusting current through a Josephson junction changes its inductance and thus coupling).
The Junctions are almost purely reactive so no loss is associated with them. Readout is usually done by reflecting a microwave pulse from a coupled microwave resonator and then determining the phase of the reflected pulse (which depends on the state of the qubit).
Losses etc. limit the coherence time within which one has to do all the operations. The actual arrangements tend to be a bit more complicated, but that’s the general idea. One gets pretty far with the experimental side of things by just doing classical circuit simulation. Understanding the many particle behavior between readouts maybe no so much.
A star collapsing gravitationally into a black hole emits a flux of radiation, knowns as Hawking radiation. When the initial state of a quantum field on the background of the star, is placed in the Unruh vacuum in the far past, then Hawking radiation corresponds to a flux of positive energy radiation travelling outwards to future infinity. The evaporation of the collapsing star can be equivalently described as a negative energy flux of radiation travelling radially inwards towards the center of the star.
Here, we are interested in the evolution of the star during its collapse. Thus we include the backreaction of the negative energy Hawking flux in the interior geometry of the collapsing star and solve the full 4-dimensional Einstein and hydrodynamical equations numerically. We find that Hawking radiation emitted just before the star passes through its Schwarzschild radius slows down the collapse of the star and substantially reduces its mass thus the star bounces before reaching the horizon. The area radius starts increasing after the bounce.
Beyond this point our program breaks down due to shell crossing. We find that the star stops collapsing at a finite radius larger than its horizon, turns around and its core explodes. This study provides a more realistic investigation of the backreaction of Hawking radiation on the collapsing star