Started a job a month ago, now got an interview for a better job. Should I mention my current job to them?

I graduated college in May and started a new job in mid-July. This week, a recruiter reached out to me to schedule an interview for another job. I accepted the interview since the other job seems more interesting and suited to my skills than my current job. However, I haven't mentioned to the recruiter that I am already employed (and haven't updated my resume or LinkedIn) so they probably don't know I currently have a full-time job.

Should I mention to them that I am already employed but am willing to quit and switch, or just not talk about it at all? If they ask what I have been up to for the past three months after college, is it better to lie and say I've been unemployed, or to be honest?

The jobs are in different industries and belong to different fields, so I could be upfront about wanting to pursue a career in their field over my current one or how this job is a better fit for my skills. But I am also afraid of it looking bad that I am quitting my first full-time job out of college in a month because of a better offer.

usa jobs
usa jobs resume
usa hotel jobs
usajobs
usa jobs federal government
usa job in ksa
usa jobs
usa jobs login
usa jobs gov
usajobs.gov
www.usajobs.gov
usajobs.com
usajobs
usajobs.gov official