Katy Perry has reportedly been talking about Riff Raff nonstop since they went out together.

The 29-year-old singer has been linked to the rapper since she split from John Mayer in February. Riff Raff - real name Horst Christian Simco - posted a photo on his Instagram of him and Katy after their evening together. He wrote: "ON A DATE WITH KATY PERRY SHE IS PURDY (sic)" alongside the sweet snap.

It is thought his fun personality is helping the quirky musician moving on from her ex-boyfriend.

"Riff has totally disarmed Katy, he's incredibly confident and isn't intimidated by her success," a source told British magazine Closer. "He's a bit bonkers and just what Katy needs to get over John. She's barely stopped talking about him since they went on a date!"

The pair met after being introduced by a mutual friend and Riff Raff has been treating Katy to a "holy trinity" of dates. These meet-ups include drinks, bowling and sushi.

While she is enjoying being back on the dating scene, Katy is said to be keeping things low-key and casual with her new beau.

"No one thinks things are serious between Katy and Riff, it's just a bit of fun. Katy is really taken with him, though," the source added.

In another bid to move on from John, the pop star is said to be "retraining" her brain from taking him back. It was recently reported Katy is relying on hypnotherapy to make her feel better.

"Katy was devastated when they broke up," a source told British magazine Grazia. "But Katy is a firm believer in alternative therapies and she wants to wipe him from her life for good, so she decided to see a hypnotherapist. She wants to retrain her brain to prevent John coming back."