Fundamental Quantum Limit to Multiphoton Absorption Rate for Monochromatic Light

TL;DR

This paper establishes a fundamental quantum limit on the multiphoton absorption rate for monochromatic light, showing that quantum entanglement does not enhance the absorption rate beyond coherent states.

Contribution

It proves an upper bound on the multiphoton absorption rate for arbitrary quantum states, demonstrating that entanglement cannot surpass coherent fields in this context.

Findings

Coherent fields reach the maximum multiphoton absorption rate.

Quantum entanglement does not provide an enhancement in absorption rate.

The bound applies to arbitrary quantum states considering photon degrees of freedom.

Abstract

The local multiphoton absorption rate for an arbitrary quantum state of monochromatic light, taking into account the photon number, momentum, and polarization degrees of freedom, is shown to have an upper bound that can be reached by coherent fields. This surprising result rules out any quantum enhancement of the multiphoton absorption rate by momentum entanglement.