と共に

と共に (とともに） is a phrase that means “with” either physically or temporally.
It is usually written in かな with the usages below.
You can think of it sort of like a longer version of the と particle.

Nouns

With
Noun + と共に

と共に（とともに） means with. With nouns it means physically with.
This has a tendency to be used with people. 

• 彼とともに来た。- Came a long with him. 
• その犬とともに死んだ – Died along with that dog.
• 雨とともに雹も降る – Rain, along with hail fell. 
• ケーキとともにコーヒーが出された – Cake, along with coffee were brought out.
  
  

Verbs

At the same time
Dictionary form verb + と共に

With verbs, と共に functions like とたん、or conditional と (immediate results). 
It means with in a temporal sense. 

• 雷鳴が鳴るとともに停電した – At the same time as the thunder rumbled, the power went out. 
• ドアを開けるとともに虫が入った – As the door opened, a bug came in.
• これを飲むとともに祈る – Pray as you drink this. 

Changes

Simultaneous Changes
Dictionary form change verb + と共に

When used with a change of some kind, と共に indicates something that changes with it.
When the change is proportional and occurs over a longer time span, につれて tends to be preferred.

• 季節が変わると共に、天気も寒くなっていく。- As the seasons change, the weather gets colder too. 
• 人口が増えると共に、町も大きくなる – As the population increases, the town gets bigger too.
• 音が大きくなるとともに、不安も募った – As the sound got bigger, so too did the uneasiness. 
  
  

Tense Mistakes

This pattern cannot be in the form of Past tense とともに Past tense/Future tense. Detailed explanation below.

• ドアを開けたとともに虫が入った✖ – As the door had been opened, a bug came in. 

Young Japanese people make this mistake as well. The reason is the last past tense verb sets the entire sentence in the past,
and another past tense verb in the same clause is even further in the past. Essentially, the past tense verbs add onto each other and make 2 different times:
「Past tense1 とともに」 Past tense 2 – Past tense verb 2 makes the part in「」past tense already. 
Past tense 2 (PT2) sets the entire sentence in the past, and Past tense 1 then sets itself even further in the past.

Source(Japanese)