Getting two trinkets to talk to each other via the serial pins
1) you should use if (Serial.available()) before starting to read with readBytes. now you print random memory

2) readBytes is blocking. it waits for the next character until a timeout. default timeout is 1 second. after "hello" was received it waits a second. you could use readBytesUntil and some 'separator' character for example '\n' (new line)

3) readBytes returns the count of bytes read. you should use it to terminate the buffer

void loop()
{
  if (Serial.available()) {
    Serial.println("reading bytes");
    size_t l = Serial.readBytesUntil('\n', state, 10);
    state[l] = 0;
    Serial.println(state);
  }
}