Notice Period for Resignation

The notice period is outlined in your employment contract, the "typical" notice in US employment is 14 days. so your contract will tell you this.
Some companies will want you to work the notice, some may send you home.

If you're dealing with private side information, you will be done the day you turn in your resignation, at least at a BB

you can quit immediately but you won't be able to work elsewhere during your notice period. your current firm will pay you during that period. 

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My BB doesn't have a length specified for analysts; it's up to the person leaving (typically 1-2 weeks). If you are going to a competitor however, it's a same day exit. 

I was on a low-tier BB IB team with a higher than usual turnover before/during COVID.

Notice period for juniors doesn’t vary too much. Two weeks' notice is considered respectable, anything less is frowned upon. Submit your notice to your staffer first and they’ll notify your HRBP to start the offboarding process.

You’ll be asked if you’re leaving for a competitor. Pre-COVID, if you answered “yes” then you’d be asked to immediately leave the building with no chance to pack your stuff (you’d have your coworkers grab your stuff). If not, they’ll most likely begin rolling you off your staffings / ask you to hand off to another analyst or associate.

I had to go to credit committee on my last day (for an MD who helped me get my job), so it’s not always just smooth sailing as soon as you send in your notice.