# Quantum Control through a Self-Fulfilling Prophecy

## TL;DR

This paper introduces a quantum control method called self-fulfilling prophecy, where feedback based on presumed states guides quantum systems to desired states or dynamics, even from arbitrary initial conditions.

## Contribution

It presents a novel feedback mechanism that can reliably prepare and control quantum states and trajectories, enhancing robustness against noise and imprecision.

## Key findings

- Self-fulfilling prophecy can prepare target quantum states from arbitrary initial states.
- The method protects quantum systems against noise and feedback imprecision.
- Arbitrary quantum trajectories can be deterministically driven using unsharp measurements.

## Abstract

Measurement combined with feedback that aims to restore a presumed pre-measurement quantum state will yield this state after a few measurement-feedback cycles even if the actual state of the system initially had no resemblance to the presumed state. Here we introduce this mechanism of {\it self-fulfilling prophecy} and show that it can be used to prepare finite-dimensional quantum systems in target states or target dynamics. Using two-level systems as an example we demonstrate that self-fulfilling prophecy protects the system against noise and tolerates imprecision of feedback up to the level of the measurement strength. By means of unsharp measurements the system can be driven deterministically into arbitrary, smooth quantum trajectories.