How to type Ctrl-^?

The ^ character (which looks like an inverted V) is known as caret. It's also known as a hat, control or uparrow.

It's Shift+6 on my UK keyboard, and I think it's the same for US layouts as well, so you could try Ctrl+Shift+6

If you have a different layout you could have a look at this page on Wikipedia which has pictures of many different keyboard layouts.

If you're on Windows you can get a ^ by hold down Alt and typing 094 on your numeric keypad which will work for all layouts, but unfortunately this won't work if you're holding down Ctrl

According to Wikipedia:

Control characters are often rendered into a printable form known as caret notation by printing a caret (^) and then the ASCII character that has a value of the control character plus 64. Control characters generated using letter keys are thus displayed with the upper-case form of the letter. For example, ^G represents code 7, which is generated by pressing the G key when the control key is held down.

As "^" is ASCII 94 (decimal), "Ctrl-^" might represent ASCII 30. Hence, holding down Alt and typing 30 on the numeric keypad might do the trick to "type" Ctrl-^?