The Slow spell affects spellcasting:
If the creature attempts to cast a spell with a casting time of 1 action, roll a d20. On an 11 or higher, the spell doesn’t take effect until the creature’s next turn, and the creature must use its action on that turn to complete the spell. If it can’t, the spell is wasted.
The description of the sorcerer's Metamagic option Quickened Spell states:
When you cast a spell that has a casting time of 1 action, you can spend 2 sorcery points to change the casting time to 1 bonus action for this casting.
If a sorcerer affected by Slow casts a spell using the Quickened Spell metamagic, does the spell always take effect on the same turn?