# A Direct Coupling Coherent Quantum Observer for an Oscillatory Quantum Plant

## TL;DR

This paper introduces a direct coupling coherent quantum observer for oscillatory quantum plants, enabling accurate output estimation through averaging without disturbing the plant, with adjustable error bounds.

## Contribution

It presents a novel observer design for oscillatory quantum systems that achieves precise output estimation via finite time averaging and parameter tuning.

## Key findings

- Finite time averaging estimates quantum plant output accurately.
- Small averaging time and large gain reduce tracking error.
- Observer does not disturb the quantum plant signal.

## Abstract

A direct coupling coherent observer is constructed for a linear quantum plant which has oscillatory solutions. It is shown that a finite time moving average of the quantum observer output can provide an estimate of the quantum plant output without disturbing this plant signal. By choosing a sufficiently small averaging time and a sufficiently large observer gain, the observer tracking error can be made arbitrarily small.