# What is a wavepacket without a photon?

There are a lot of questions on this site about photons and wavepackets.

Relation between radio waves and photons generated by a classical current

This one lists a lot of them as reference. None of them in detail specifically answers my question.

What happens when a photon hits a beamsplitter?

https://arxiv.org/ftp/arxiv/papers/1410/1410.3416.pdf

A wave.packet enters the beam splitter and breaks into two smaller wave.packets. The incident particle, shown as a dot in picture, emerges along path a accompanied by a wave packet. The wave packet in path b is empty.

I am not asking about the photon traveling as a wave, or a particle, or why the photon is delocalized when traveling and why it is taking all possible paths. I am not asking what happens when a photon hits a beam splitter.

I am asking if it is really possible what the paper suggests, that there can exist a wavepacket, without a photon, that is, where the photon number is 0.

In physics, a wave packet (or wave train) is a short "burst" or "envelope" of localized wave action that travels as a unit.

https://en.wikipedia.org/wiki/Wave_packet

The best definition of a wavepacket I found on this site is saying that a wavepacket is basically a localized excitation of the EM field. This is a contradiction, because the photon itself is usually defined as the excitation of the EM field. How could there be a wavepacket (a localized excitation), without a photon (excitation of the EM field)?

Question:

1. What is a wavepacket without a photon?
• It is telling that there should be no published version to the linked arxiv paper. – ZeroTheHero Jun 30 '20 at 21:33
• @ZeroTheHero can you please help where (which page) it says that? – Árpád Szendrei Jul 1 '20 at 3:49
• I do not understand your question. You can easily check this paper was never published. – ZeroTheHero Jul 3 '20 at 12:57