# Experimental investigation of quantum decay at short, intermediate and long times via integrated photonics

## TL;DR

This paper experimentally investigates quantum decay across different time regimes using integrated photonics, revealing the initial quadratic, exponential, and long-time power-law decay behaviors in a controlled optical setup.

## Contribution

It demonstrates the first direct observation of quantum decay regimes, including the elusive long-time power-law decay, using integrated photonic structures with high dynamic range measurements.

## Key findings

- Observation of exponential decay regime
- Detection of quadratic Zeno region
- Identification of long-time power-law decay

## Abstract

The decay of an unstable system is usually described by an exponential law. Quantum mechanics predicts strong deviations of the survival probability from the exponential: indeed, the decay is initially quadratic, while at very large times it follows a power law, with superimposed oscillations. The latter regime is particularly elusive and difficult to observe. Here we employ arrays of single-mode optical waveguides, fabricated by femtosecond laser direct inscription, to implement quantum systems where a discrete state is coupled and can decay into a continuum. The optical modes correspond to distinct quantum states of the photon and the temporal evolution of the quantum system is mapped into the spatial propagation coordinate. By injecting coherent light states in the fabricated photonic structures and by measuring light with an unprecedented dynamic range, we are able to experimentally observe not only the exponential decay regime, but also the quadratic Zeno region and the power-law decay at long evolution times.