How to implement IOS Siri for text to speech in IOS application?

Question

Is there any way to implement the IOS Siri's voice into my ios application for text to speech conversion? I want to implement the same voice as the Siri has.

Could be possible to convert text to voice with Siri using SWIFT language or anything?

I have already implement this one but the voice is not like Siri's has, its looking like computer's voice.

        import AVFoundation

        class ViewController: UIViewController {

            let synthesizer = AVSpeechSynthesizer()

            override func viewDidLoad() {
                super.viewDidLoad()

                let voice = AVSpeechSynthesisVoice(language: "en-US")

                let utterance = AVSpeechUtterance(string: "Hello, this is Siri's voice.")
                utterance.voice = voice

                synthesizer.speak(utterance)
            }
        }