Photon-added coherent states using the continuous-mode formalism

TL;DR

This paper models photon-added coherent states as pulses using a continuous-mode formalism, revealing their nonclassical properties and robustness under propagation loss, with implications for quantum sensing.

Contribution

It introduces a continuous-mode approach to photon-added coherent states, enabling pulse modeling and analysis of their properties with realistic loss effects.

Findings

PAC states exhibit sub-Poissonian photon distribution without perfect overlap.

Quadrature squeezing is observed in weak coherent states.

Propagation loss affects the fidelity but preserves nonclassical features.

Abstract

The addition of a photon into the same mode as a coherent state produces a nonclassical state that has interesting features, including quadrature squeezing and a sub-Poissonian photon-number distribution. The squeezed nature of photon-added coherent (PAC) states potentially offers an advantage in quantum sensing applications. Previous theoretical works have employed a single-mode treatment of PAC states. Here, we use a continuous-mode approach that allows us to model PAC state pulses. We study the properties of a single-photon and coherent state wavepacket superimposed with variable temporal and spectral overlap. We show that, even without perfect overlap, the state exhibits a sub-Poissonian number distribution, second-order quantum correlations and quadrature squeezing for a weak coherent state. We also include propagation loss in waveguides and study how the fidelity and other properties of PAC state pulses are affected.