good suggestion but it might be tougher than that

Interviewers might ask you questions such as "do you need to give 2 weeks notice?", "Is it ok for you to speak? Are you working from home today?" , or even joking "how do you not let other people know that you are interviewing?" . There are so many chances that they would say something based on the assumption that you are still actively working, however you can't just tell them "by the way, I forgot to say that I am not working anymore". Simply tell the truth from the begining and it will give you a peace of mind.